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The Prohibition of Keeping or Release of Live Fish (Specified Species) (Scotland) Order 2003

DescriptionThe Order will fulfil a proposal in last year's Green Paper 'Scotland's Freshwater Fish and Fisheries: Securing their Future'. It bans the keeping or release of non-native species without a licence.
ISBN
Official Print Publication Date
Website Publication DateDecember 20, 2002

CONSERVATION OF NATIVE FRESHWATER FISH STOCKS: THE PROHIBITION OF KEEPING OR RELEASE OF LIVE FISH (SPECIFIED SPECIES) (SCOTLAND) ORDER 2003

1. This consultation letter seeks your views on:

a) proposals to make a number of species and/or genera of non-native fish subject to licensing arrangements under the Prohibition of Keeping or Release of Live Fish (Specified Species) (Scotland) Order 2003;

b) the arrangements for licences to be made available; and

c) the direct and/or indirect costs that may arise from adoption of these proposals.

Background to the proposal

2. There is concern that existing controls, principally those under the Wildlife and Countryside Act 1981, might not be entirely successful in preventing the unauthorised introduction and spread of non-native freshwater fish which are considered to pose a risk to native flora and fauna and the environment, in inland waters in Scotland.

3. In England and Wales, arrangements exist under the Import of Live Fish Act 1980 to help curb unauthorised introductions. The Ministry of Agriculture, Fisheries and Food, now the Department of the Environment, Food and Rural Affairs (DEFRA) introduced the Prohibition of Keeping or Release of Live Fish (Specified Species) Order 1998, which came into effect on 1 November 1998. Under those arrangements it became an offence to keep or release any non-native fish or shellfish specified in the 1998 Order without a licence issued by DEFRA (for waters in England) or the National Assembly of Wales (for those in Wales). DEFRA is currently working on adding further species to the 1998 Order.

4. In the Green Paper, Scotland's Freshwater Fish and Fisheries: Securing Their Future (published August 2001), the Scottish Executive stated that it proposed to introduce similar measures in Scotland under the Import of Live Fish (Scotland) Act 1978. It is our intention to mirror the species listed in the amended DEFRA Order, as well as to include species which may be native to other parts of Great Britain, but which are not native to Scotland, where it is the general opinion that they should also be included.

5. There are currently three Orders made under the 1978 Act in force in Scotland: for coho salmon, pikeperch (zander) and crayfish other than of the species native to GB.

6. Anyone, including fish farmers and dealers/distributors, who wishes to keep or release such species must have a licence. Those wishing to buy and/or keep non-native fish subject to the licensing arrangements should be aware that granting of a licence cannot be guaranteed. It will be prudent, therefore, to apply for a licence before purchasing or agreeing to purchase any of the species contained in the Order. All introductions of non-native fish into the wild require a Wildlife and Countryside Act licence. For those species which are covered by both this Act and the 2003 Order a single joint application will be made and a single joint licence will be issued. All licences are issued free of charge.

7. The 2003 Order will apply only to selected genera or species rather than to all non-native fish. This reflects our aim to concentrate initially on those non-native fish that present the greatest and most immediate threat to native flora and fauna and the environment. However, it will be possible to extend the licensing scheme to include other species in the future should that prove necessary.

8. While it remains difficult to predict fully the effects that introduced species may have on native flora and fauna, it is accepted internationally that a cautious approach should be adopted. Rio Article 15 and other subsequent international agreements recognise formally the need for a precautionary approach in relation to species introductions. As demonstrated by the North American signal crayfish, non-native species can have far-reaching and undesirable ecological consequences and can lead to the displacement and/or collapse of other species through direct competition for food; through effects on the environment; or through disease. We believe action is needed if our native flora and fauna are not to be put at risk from potentially damaging introductions, especially in the light of growing evidence of climate change and the added uncertainty this carries regarding the potential for new species to become established.

9. It is proposed that enforcement be carried out by person's duly auhtorised by the Scottish Ministers. These officers, as empowered by the 1978 Act, may enter and inspect any land occupied by a person holding a licence and any other land upon which it is believed that fish of the species specified in an Order under Section 1 are being kept. In some circumstances, it may be necessary to attempt to remove species which have been illegally introduced and/or order a species' destruction.

10. Those species and genera we propose to include in the 2003 Order are listed in the Schedule to the draft Order. An assessment of the risks posed by these species is also included. This includes details of the characteristics and behaviour of these fish and summarises the potential impacts that they might have on our native flora and fauna if introduced. We would welcome your comments and views.

Legislation and timing

11. The existing controls and arrangements under the Wildlife and Countryside Act 1981 will remain in place. The proposed Order will not affect imports, or the existing prohibition of keeping and/or release Orders.

12. We will consider all comments carefully and, if necessary, shall consult again on any changes. Once Scottish Ministers have indicated that they are content, we intend to lay the Order for approval by the Scottish Parliament. We anticipate that the arrangements will come into effect in Spring 2003.

Licensing arrangments

13. Licences will specify the species and site for which they are valid and whether they permit a single or multiple introduction; the latter would normally be restricted to fisheries and to dealers. Licences could also impose conditions for the keeping of non-native fish, such as the provision and maintenance of screens and outfalls. It will be an offence to keep or release any non-native fish listed in the Order without a licence. In respect of fish specified in the Order that are already being kept when the Order comes into force, a 'grace' period of 6 months will apply to allow licences to be obtained. Thereafter, it is expected that those keeping any fish included in the Order will have obtained a licence.

14. Applications will be submitted to the Freshwater Fisheries Branch of SEERAD. After the necessary checks have been carried, out licences will be issued if appropriate. Suppliers and dealers will not be allowed to sell any of the listed species to anyone who does not hold a licence. The licence holder will be required to maintain records of all movements and these may be subject to periodic inspections

15. DEFRA's consultation has identified the need for a general licence for grass carp, sterlet/sturgeon and possibly ictalurid catfish (under review) due to the sizeable trade in these species in England and Wales. A general licence allows the keeping of these species without the need for a specific licence, by members of the public, in garden ponds and indoor aquaria. However, it is not our intention to issue general licences for any species included in this Order. We believe the potential threat to native stocks outweighs any argument for general licences to be issued in Scotland.

Burdens on industry

16. To measure the impact of the new regulations on businesses, we have produced a Regulatory Impact Assessment (RIA). A draft RIA is included at Annex B. This is based on our assessment of the impacts, and on experience of the system in England and Wales. However, it is a draft and we would welcome views. In particular, it would be helpful if you could identify and quantify any additional direct or indirect costs resulting from the adoption of the proposal outlined above that may impact on your business or sector. These will be taken into account in drafting the final version.

Comments

17. Comments on the proposed non-native list, the licensing arrangements and the draft RIA are invited from all interested parties and should be sent, to arrive no later than 14 March 2003, to Richard Gustar at the following address:

Scottish Executive Environment and Rural Affairs Department, Freshwater Fisheries Aquaculture and Marine Environment, Room 408A, Pentland House, 47 Robb's Loan, Edinburgh EH14 1TY

Comments may also be submitted in electronic format to richard.gustar@scotland.gsi.gov.uk

18. As is normal with all Scottish Executive consultations, all responses will be made available publicly unless the respondent specifically indicates that he or she wishes that it remain confidential. Copies of the consultation document and associated documents, together with responses, will be available in the Scottish Executive Library, Saughton House, Edinburgh.

19. An electronic copy of all the associated documents is also available on the Scottish Executive website at www.scotland.gov.uk/library4/ERADRA/FFAME/00015899.aspx.

Yours sincerely

GRAEME WAUGH

SEERAD: Freshwater Fisheries, Aquaculture and Marine Environment

LIST OF CONSULTEES

All DSFBs

All Fisheries Trusts

All ILF(S)A Licence Holders

All Protection Order Liaison Committees

All Registered Fish Farmers

All Scottish Local Authorities

Aberfeldy Angling Club

ACPOS

Action of Churches Together in Scotland

Allan Water Angling Improvement Association

Anglers Conservation Association

Angling For Change

Angling Foundation

Angling Trade Association

Association for the Preservation of Rural Scotland

Association of Inland, Navigation Authorities, C/o British Waterways

Association of Salmon Fishery Boards

Association of Scottish Stillwater Fisheries

Association of Stillwater Game Fishery Managers

Association of Waterways Cruising Clubs

Association of West Coast Fisheries Trusts

Assynt Angling Group

Atlantic Salmon Conservation Trust (Scotland)

Atlantic Salmon Trust

Barbel Society

Belhaven Trout Company

Bidwells Property Consultants

Bishops Conference Scotland

British Eel Anglers Club

British Finfish Farming Association

British Trout Association

British Trout Farmers Restocking Association

British Waterways

Busby Angling Association

Carlisle Angling Association

Carnie Consultancy

Carp Society

Catfish Conservation Group

Catholic Parliamentary Office

Central Scotland Anglers' Association

Church of Scotland

Clyde Fishermens Association

Commercial Coarse Fisheries Association

Consultative Committee on Protection Orders

Consumers Association

Consumers in the European Community Group (UK)

Convention of Scottish Local Authorities

Country Landowners Association

Crofters Commission

Crown Estate Commission

Dee Salmon Fishing Improvement Association

Department for Environment, Food and Rural Affairs

Dobbies Garden Centre plc

Dornoch & District Angling Association

Dumfries & Galloway Angling Association

English Nature

Environment Agency

European Research into Consumer Affairs

Federation of Border Angling Associations

Federation of Highland Angling Clubs & Associations

Firth of Clyde Forum

Fish Conservation Centre

Fisheries (Electricity) Committee

Forestry Commission

Forth Fisheries Foundation

Forum on the Environment

Friends of the Earth

FRS Freshwater Laboratory

FRS Marine Laboratory

Game Conservancy Trust

Game Fisheries Ltd

Garden Centre Association

General Assembly, Church of Scotland Offices

Grayling Society

Highlands and Islands Enterprise

Highlands and Islands Forum

Highlands of Scotland Tourist Board

HM Customs and Excise

Hon Lord Morison

Institute of Fisheries Management (Scottish Branch)

Institute of Freshwater Ecology

Institution of Water and Environmental Management (Scottish Branch)

Local Government Association

Loch Awe Improvement Association

Loch Lomond Angling Improvement Association

Magiscroft

National Association for Specialist Anglers

National Association of Fisheries & Angling Consultatives

National Consumers Council

National Farmers Union Scotland

National Federation of Anglers

National Federation of Consumer Groups

National Federation of Fishermen's Organisations

National Trust For Scotland

North Atlantic Salmon Conservation Organisation

North Atlantic Salmon Fund (UK)

Orkney Fish Farmers Association

Orkney Fisheries Association

Orkney Trout Fishing Association

Ornamental Aquatic Trade Association (OATA) Ltd

Parliamentary Office

Pet Care Trust

Pike Anglers Alliance

Pike Anglers Club of Great Britain

Piscatorial Society

Ralston McPherson

River Annan FIA

River Clyde Foundation

River Don Brown Trout Improvement Association

River Irvine Angling Improvement Association

River Kelvin Angling Association

River Tweed Commissioners

RICS in Scotland

Royal Society for Nature Conservation

Royal Society of Edinburgh

Royal Society for the Protection of Birds (Scotland)

Salmon and Trout Association (Scotland), C/o The National Game Angling Centre

Salmon Net Fishing Association of Scotland

Scottish Anglers National Association

Scottish Campain for Public Angling

Scottish Canoeing Association

Scottish Carp Group

Scottish Chambers of Commerce

Scottish Churches Parliamentary Office

Scottish Coastal Forum

Scottish Crofters Union

Scottish Enterprise

Scottish Environment LINK

Scottish Environment Protection Agency

Scottish Federation for Coarse Angling

Scottish Fisheries Co-ordination Centre, C/o FRS FL

Scottish Fisherman's Organisation

Scottish Fly Fishing

Scottish Landowners Federation

Scottish Natural Heritage

Scottish Quality Salmon

Scottish Society for the Preventation of Cruelty to Animals

Scottish Tourist Board

Scottish Water

Scottish Wildlife And Countryside Link

Scottish Wildlife Trust

Scottish Youth Parliament

Shetland Salmon Farmers Association

Skye Environmental Centre

Specialist Anglers Alliance

Specialist Anglers Conservation Group

Sportscotland

Tay Access Group

Tweed Foundation

Ultimate Discount Aquatics

United Clyde Angling Improvement Association

United Clyde Angling Protective Association

Water Research Centre

Welsh Federation of Coarse Anglers

West Sutherland Fisheries Trust

Wildlife and Countryside Link

WWF Scotland

Young Scot

Youth Link Scotland

DRAFT ORDER

SCOTTISH STATUTORY INSTRUMENTS

2003 No.

RIVER

SALMON AND FRESHWATER FISHERIES

The Prohibition of Keeping or Release of Live Fish (Specified Species) (Scotland) Order 2003

Made 2003

Laid before the Scottish Parliament 2003

Coming into force

The Scottish Ministers, in exercise of the powers conferred by section 1(1) of the Import of Live Fish (Scotland) Act 1978() and of all other powers enabling them in that behalf; and, in accordance with section 1(2) of that Act, after consultation with Scottish Natural Heritage and such other persons as the Scottish Ministers consider appropriate; and being of the opinion that the species of live fish to which this Order applies might compete with, displace, prey on or harm the habitat of any freshwater fish, shellfish or salmon in Scotland, hereby make the following Order:

Citation and commencement

1.-(1) This Order may be cited as the Prohibition of Keeping or Release of Live Fish (Specified Species) (Scotland) Order 2003.

(2) This Order shall come into force-

(a) in relation to fish first kept before ( date) on ( date); and

(b) in relation to fish first kept or released on or after ( date), on that date.

Prohibition of keeping or release of specified fish

2. No person shall keep or release in Scotland any live fish of the species specified in the Schedule to this Order, except under the authority of a licence granted by the Scottish Ministers.

A member of the Scottish Executive

St Andrew's House, Edinburgh, 2003

Article 2

SCHEDULE

SPECIES OF FISH WHOSE KEEPING OR RELEASE IN SCOTLAND IS PROHBITED EXCEPT UNDER AUTHORITY OF A LICENCE GRANTED BY THE SCOTTISH MINISTERS

COMMON NAME

SCIENTIFIC NAME

Asp

Aspius aspius

Barbel

species of the genus Barbus (excluding the native Barbus barbus)

Bass (including striped bass, white bass and their crosses e.g. hybrid striped bass)

species of the genus Morone

Big-head carp

Aristicthys nobilis

Bitterling

Rhodeus sericeus/Rhodeus amarus

Blacknose Dace

Rhinichthys atratulus

Blageon

Leuciscus souffia

Blue bream

Abramis ballerus

Blue Sucker

Cycleptus elongatus

Burbot

Lota lota

Catfish

species of the genera Ictalurus, Ameiurus and Silurus

Charr

species of the genus Salvelinus (excluding the native Salvelinus alpinus)

Chinese black or snail-eating carp

Myopharyngodon piceus

Chinese Sucker (also known as Zebra Hi Fin, banded shark/sucker)

Myxocyprinus asiaticus

Common White Sucker

Catostomus commersoni

Danubian bleak

Chalcalburnus chalcoides

Danubian Salmon & Taimen

species of the genus Hucho

Eastern Mudminnow

Umbra pygmaea

European Mudminnow

Umbra krameri

Fathead minnow (or Roseyreds)

Pimephales promelas

Freshwater minnow, Dragon Fish or Pale chub

Zacco platypus

Grass carp

Ctenopharyngodon idella

Landlocked salmon

non-anadromous varieties of the species Salmo salar

Large-mouthed black bass

Micropterus salmoides

Marbled trout

Salmo marmoratus

Nase

Chondrostoma nasus

Northern Redbelly Dace (common minnow

Phoxinus/Chrosomus eos

Pacific salmon and trout

species of the genus Oncorhynchus (excluding Oncorhynchus kisutch())

Paddlefish

species of the genera Polyodon and Psepherus

Perch

species of the genus Perca (excluding the native Perca fluviatilis)

Pike

species of the genus Esox (excluding the native Esox lucius)

Pike-perch

species of the genus Stizostedion (excluding Stizostedion luciopercaI())

Red shiner

Cyprinella/Notropis lutrensis

Rock bass

Ambloplites rupestris

Ruffe

Gymnocephalus cernuus

Schneider

Alburnoides bipunctatus

Silver carp

Hypophthalmichthys molitrix

Small-mouth bass

Micropterus dolomieu

Snakehead

species of the genus Channa

Southern Redbelly Dace (common minnow)

Phoxinus/Chrosomus ertythrogaste

Sturgeon or sterlet

species of the genera Acipenser, Huso, Pseudoscaphirhynchus and Scaphirhynchus

Sunbleak (Sundace), also known as Belica or Motherless Minnow

Leucaspius delineatus

Sunfish, including pumpkinseed (also basses, crapies & bluegills)

species of the genus Lepomis

Topmouth gudgeon

Pseudorasbora parva

Toxostome (or French nase)

Chondrostoma toxostoma

Vimba

Vimba vimba

Weatherfish

Misgurnus fossilis

Whitefish

species of the genus Coregonus (excluding the native Coregonus lavaretus and Coregonus albula)



EXPLANATORY NOTE

( This note is not part of the Order)

This Order, which is made under section 1(1) of the Import of Live Fish (Scotland) Act 1978 ("the Act"), and which comes into force, in relation to fish first kept before ( date) on ( date) and, in relation to all other fish, on ( date), prohibits the keeping or release in Scotland of any species of fish specified in the Schedule to the Order, except under authority of a licence granted by the Scottish Ministers.

Section 3 of the Act provides that any person who keeps or releases any of the species of fish listed in the Schedule to this Order without a valid licence or who contravenes the terms of a licence shall be guilty of an offence and liable on summary conviction to a fine not exceeding level 4 on the standard scale.

A regulatory impact assessment has been prepared in relation to this Order and placed in the Scottish Parliament Information Centre. Copies may be obtained from the Scottish Executive Environment and Rural Affairs Department, Pentland House, 47 Robb's Loan, Edinburgh, EH14 1TW.

DRAFT REGULATORY IMPACT ASSESSMENT (RIA)

1. Title of the Regulatory Proposal

The Prohibition of Keeping or Release of Live Fish (Specified Species) (Scotland) Order [2003]

2. Purpose and Intended Effect of Proposal

2.1 Identify the issue and objective

Issue

The unauthorised introduction and spread of non-native fish and shellfish species can have far-reaching and undesirable ecological consequences and can lead to the displacement and/or collapse of other native species and habitats.

Objective

The Order will seek to introduce new licensing arrangements to supplement existing controls to prevent the unauthorised introduction and spread of non-native fish and shellfish in Scotland. There is now increasing concern that other non-native temperate species also pose a threat to our native flora and fauna in the environment.

2.2 Risk assessment

It is accepted that introductions of fish species have generally been harmful and national and international guidelines on the introduction and transfer of non-native species reflect this. However, it is impossible to predict precisely how non-native species will perform under novel conditions outside their native range, or the effects that introduced species may have on the native flora and fauna in their natural environment. It is thus difficult to distinguish introductions that might be relatively benign and have little impact on native species from those with the potential for being seriously damaging. A precautionary approach is therefore appropriate in relation to keeping and release of non-native species and international agreements reflect this.

All introductions of non-native fish species pose some threat. The introduction of novel species of fish or shellfish may have adverse effects upon resident fish populations either directly, or indirectly, through impacts on the aquatic ecosystem. There are a number of ways in which this might occur:

  • direct predation;
  • competition with indigenous fish for food, cover or spawning sites;
  • the introduction of new diseases or parasites (against which the resident populations have inadequate defences);
  • hybridisation with resident fish causing possible reduced viability and fecundity of stocks; and
  • potential adverse effects in the environment through habitat degradation.

Experience in Scotland and elsewhere has illustrated the problems that can occur and highlights just how difficult and expensive it is to eradicate such species once they have become established. The ecological damage that introduced species may cause to native species is wide and varied.

A number of species that are not native to Scotland, such as ruffe, are known to have become established in Loch Lomond. Concerns have been voiced about the impact of ruffe on the local fish populations, specifically on powan. Other species, including gudgeon, chub, dace, crucian carp, tench and bream, have also been introduced, and are liable to have posed some ecological impacts.

3. Options

3.1 Identify options

Three options have been identified:

Option 1 - Do nothing - continue to rely on present controls.

We are concerned with those species that pose the greatest and most immediate threat to native flora and fauna in Scotland. The Wildlife and Countryside Act 1981 applies only to the release into the wild of species not ordinarily resident in or not regular vistors to Great Britain, and species included in Part I of Schedule 9 of that Act. The 1981 Act does not provide protection from introductions of species that are ordinarily resident/regular visitors to Great Britain, but not native to Scotland. Nor does the 1981 Act regulate the keeping of any species of fish which could subsequently escape into the wild. Relying on present controls will not, therefore, provide protection from introductions of species not subject to the existinglicensing arrangements.

Option 2 - Increase awareness of the risks posed by unauthorised introduction of non-native fish and shellfish species.

We consider that further education on the potential risks of non-native fish will only prove effective if backed up by legislative controls, especially as illegal introduction of some non-native fish species can be highly profitable.

Option 3 - Compile a list of non-native fish and shellfish species which require a keeping/release licence.

Legislative backing, by proscribing the keeping or release of a list of non-native fish and shellfish, together with the appropriate dissemination of information, would provide the basis of an enforceable non-native fish and shellfish policy.

3.2 Issues of equity and fairness

It is perceived that the proposed measure should impact equally across the whole industry. The likely burden on small businesses is not considered to be any more onerous than for larger businesses, although we recognise that smaller businesses may have less administrative capacity.

4. Benefits

4.1 Identify the benefits of each option (to business, citizens and the environment)

Option 1

No perceived benefits in reducing the risk of further introductions of potentially damaging non-native fish and shellfish species.

Option 2

Limited benefit only as likely to have small impact on stopping unauthorised non-native introductions.

Option 3

This option provides for the greatest protection to native habitats from unauthorised introductions of non-native fish and shellfish species. It allows for easier investigation of offences and with other legislation makes it easier to trace fish movements in Scotland and the UK.

4.2 Qualify and value the benefits

Option 1

None.

Option 2

Limited impact; unlikely to affect unauthorised introductions.

Option 3

Creation of licensing controls and greater publicity will help to ensure accidental or deliberate introductions of non-native fish and shellfish are minimised and so protect the environment.

5. Compliance costs for business, charities and voluntary organisations

5.1 Business sectors affected

This Order will affect all those who wish to keep or introduce the scheduled non-native fish and shellfish in Scotland. There is no impact on importers unless they are also acting as dealers/wholesalers. Experience of ILFA in England and Wales since the introduction of their Order in 1998 has shown little, if any, impact on business sectors. We have no evidence to suggest the Scottish proposals will prove to be any more burdensome.

Those affected would be largely fish farmers, fisheries, dealers/wholesalers/retailers, but also some researchers, aquaria and also members of the public.

5.2 Compliance costs for a typical business

There is no cost to importers or those who wish to hold non-native fish which are not listed at in the schedule to the Order. Compliance costs will range from nil to negligible. The administrative costs of filling out the application form and postage will be minimal.

For fish farms and retailers - there will be a requirement to keep additional movement records but this should not be onerous.

For fisheries - successful applicants may need to install or upgrade facilities such as screens, grilles, or gravel beds. However, this would reflect good management practice (ie to ensure the fish do not escape).

5.3 Total compliance cost

Options 1 and 2

Nil.

Option 3

Minimal.

6. Consultation with small businesses

[The list of licensed non-native fish and shellfish has been fully and openly discussed with fish farmers, fishery owners/managers, dealers/wholesalers/retailers and their respective industry and trade associations. Their comments and concerns have been taken into account in determining the final list.]

7. Result of consultation

[Consultation has taken place with all interested parties, including industry and trade associations, government and conservation and environmental organisations.]

8. Summary and recommendation

It is recommended that Option 3 be adopted, to give legislative backing through the creation of an Order made under the Import of Live Fish (Scotland) Act 1978. Our preferred option is recommended because the potential ecological and environmental impacts are such that relying solely on education without some means of applying sanctions, if unwanted species are introduced, is felt to be insufficient to address an issue of this importance.

9. Enforcement, sanctions, monitoring and review

Enforcement will be carried out by those duly appointed by Scottish Minister, in accordance with Section 1 of the 1978 Act. SEERAD

December 2002

ASSESSMENT OF PROPOSED LIST OF SPECIES AND GENERA

Asp ( Aspius aspius)

The asp is a member of the carp family (Cyprinidae) the dominant family of freshwater fish in Europe, North America, Africa and Asia. However, it is one of the few members of this family to have a diet almost exclusively comprising fish.

Diet - Asp feed on invertebrates and planktonic animals for the first few weeks of life, but start eating young fish as early as 2 to 3 months of age. On reaching maturity, the asp feeds primarily on other cyprinid fish. Also known to consume small crustaceans and other animals (has been known to take frogs and ducklings).

Assessment - The asp occupies a range of habitat types and appears reasonably tolerant to environmental conditions. It would thus appear to be a potentially good coloniser. It is regarded as a valuable and popular sporting fish because of its large size and good fighting qualities. There is considered to be quite a high risk that this fish would be subject to transfer between waters (in the same way as zander), if present in the UK.

Likely impact from introduction

  • Direct predation on other fish;
  • competition with indigenous fish for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.

Barbel ( Barbus spp., excluding the native Barbus barbus)

There are a number of species of barbel resident in Europe, including the Mediterranean barbel ( Barbus meridonalis), the Italian barbel ( Barbel plebejus), the Iberian barbel ( Barbus comiza) and the Albanian barbel ( Barbus albanicus). Another species resident in Greece ( Barbus prespensis) has been shown to hybridise in the wild with our native barbel. The Iberian barbel is the largest of the species (able to exceed 1m) and is a popular sporting fish.

Diet - All species are bottom dwellers and feed on a mixture of insect larvae, crustaceans, annelids, plants and sometimes molluscs.

Assessment - Barbel species are tolerant of a wide range of environmental conditions, particularly salinity. Angler interest appears to be growing (regular reports in angling press).

Likely impact from introduction

  • Competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases;
  • hybridisation with native species; and
  • adverse effects on the environment through habitat degradation (e.g. effects on benthos, water turbidity changes due to feeding activity).

Bass (including striped bass, white bass and their crosses), species of the genus Morone

The striped bass ( Morone saxatilis) is native to the Atlantic coast of North America and spends most of its life in coastal salt water, migrating into freshwater to spawn. The white bass ( Morone chrysops) is also of North American origin and lives in both estuarine and fresh water. These species have been introduced outside their native range and have been used in aquaculture.

After declines in stocks of striped bass, the aquaculture industry produced (in 1967) the hybrid striped bass by crossing the anadromous striped bass with the white bass. The hybrid combined the attractive appearance and edibility of the striped bass with the hardier, faster-growing characteristic of the white bass. The hybrid is reported to withstand greater temperature ranges and overcrowding in confined environments and is therefore easier to farm.

Diet - The young are omnivorous feeding mainly on insect larvae, but when they reach 9 cm in length they begin to feed on fish. Adults feed on annelid worms, shrimps, crabs, squid, clams and fish.

Assessment - Interest both as a sporting fish and for farming purposes. Hybrid striped bass are also farmed for the table market. The hybrid striped bass may be sterile, but this has yet to be confirmed. It appears likely that these species could survive in UK coastal waters.

Likely impact from introduction

  • Direct predation ( feeds on many types of fish);
  • competition with indigenous fish for food cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. effects on benthos, water turbidity due to feeding activity).

Big-head Carp ( Aristichthys nobilis)

Small numbers of the fish have been imported into the UK. It favours rich lakes and slow flowing rivers.

Diet - The bighead carp is a filter feeder consuming plankton and detritus. This specialised diet has led to interest in the possible use of the fish for biofiltration.

Assessment - Bighead carp has a potential specialist role as a biological control agent in waters subject to problems with algal blooms. It is believed to be tolerant of a wide range of environmental conditions, although not as resistant to cold as the silver carp. It is unlikely to be a species highly favoured by anglers due to its specialised diet and possible difficulties of capture. However, it does grow to a large size.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat changes (e.g. water turbidity changes due to feeding activity).

Bitterling ( Rhodeus sericeus/Rhodeus amarus)

The Bitterling (also known as the Prussian Carp) is a member of the carp family (Cyprinidae). There are no closely related species in Europe. The preferred habitat of the Bitterling is still or slow-flowing water with plenty of weed growth and a sandy/silty bottom where freshwater mussels are present. In the British Isles, it is not present in either Ireland or Scotland. However, it has been introduced into England as an ornamental fish for use in ponds and aquaria. The Bitterling is listed under Schedule 9 of the Wildlife and Countryside Act, 1981, as a non-indigenous species recognised as being already established in the wild.

Diet - Bitterling feed on small invertebrates, especially planktonic crustaceans and small insect larvae (e.g. chironomids). They also eat filamentous and encrusting algae and detritus.

Assessment - Bitterling prefer still or slow-flowing water. The species is restricted to habitats containing the swan mussel ( Arodonta cygnea) or other related mussel species which it relies upon for reproduction. It is not a preferred species for angling. However, due to its small size it may be unwittingly transferred as part of a consignment of other coarse fish. It has considerable potential interest as an ornamental species.

Likely impact from introduction

  • Competition with indigenous fish for food or cover; and
  • the introduction of novel parasites or exotic diseases.

Blacknose Dace ( Rhinichthys atratulus)

The blacknose dace is a member of the Cyprinidae family and occurs in Canada and parts of the USA. The species has three distinct subspecies: southern black nose dace ( R. a. obtusus), eastern black nose dace ( R. a. atratulus) and central black nose dace ( R. a. meleagris). The black nose dace can be distinguished from other minnows by the black lateral band, which extends around the snout backward through the eye to the tail. It is a moderately small fish (averaging approx. 6-7cm, with a maximum size estimated to be around 10cm) and has a maximum reported age of 4 years. Often numerous black spots or bumps can be seen covering the body and fins. These spots are from the encysted stage of a larval parasitic worm found beneath the fish's skin.

Diet - The diet of the black nose dace consists primarily of aquatic chironomids, insect larvae, and diatoms. They are also known to eat fish eggs.

Assessment - Uncertain whether this species is currently present in the UK; interest likely to be confined to the ornamental trade. As a temperate species, appears to be capable of surviving under UK conditions.

Likely impact from introduction

  • Predation of eggs;
  • competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Blageon ( Leuciscus souffia)

The blageon is a member of the carp family. The blageon is found from the Rhône basin north to the headwaters of the Rhine, and eastwards to the Danube along the Alps, also in northern Italy in the Po catchment. It is not present in the British Isles.

The blageon favours small clear streams and mountain lakes where it occurs in shoals with trout, minnows and Mediterranean barbel, also the shallower reaches of larger rivers where it occurs with other coarse fish.

Diet - Blageon primarily feed on insect larvae, mayflies, sedges, worms and small crustaceans; may also eat algae.

Assessment - The habitat preference of Blageon is for clear streams or the shallower reaches of larger rivers. It is not a preferred species for angling due to its small size (although commonly used as a pike bait within Europe). There is a strong possibility of unwitting transfer as part of a consignment of other coarse fish.

Likely impact from introduction

  • Competition with indigenous fish for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.

Blue bream ( Abramis ballerus)

The blue bream is also a member of the carp family. Its current distribution extends from southern Finland and Sweden to northern Germany, south to the black and Caspian seas and along the lower Danube. The blue bream is not present in the British Isles. It is normally found in the lower reaches of rivers and lowland lakes, normally in freshwater, but is also found in brackish water in the Baltic, Black and Caspian Seas.

Diet - The blue bream is a plankton feeder, consuming zooplankton, and feeds in shoals in open water.

Assessment - Blue bream is regarded as an adaptable fish. It is unlikely to be highly prized by anglers.

Likely impact from introduction

  • Competition with indigenous fish for food, cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. water turbidity changes due to feeding activity).

Blue sucker ( Cycleptus elongatus)

The blue sucker is the only species of its genus. The fish can grow to a maximum size of 93 cm and has been reported to live for up to 13 years. The species is native to North America, where it is fairly widepsread, particularly in the Mississippi River basin from Pennsylvania south to Louisiana, and also in Alabama, Texas, New Mexico, and Mexico.

Blue suckers prefer deep, larger rivers with strong currents and high turbidity. However, they also survive in reservoirs as long as nearby tributary streams provide spawning habitat.

Diet - The diet of the blue sucker consists largely of aquatic insects and their larvae, crustaceans and plant material including algae. The fish feed on the bottom, sifting through the sediment in a typical vacuum-like manor.

Likely impact from introduction

  • Competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Burbot ( Lota Lota)

The burbot is the only European member of the cod family to live in freshwater. Burbot are bottom-dwelling fish, which mostly spend the day in concealment under stones or over-hanging banks, emerging to forage for food in the evening.

In the British Isles, their original distribution was restricted to larger rivers of eastern England where they were once very abundant. However, they are now thought to be extinct. Burbot are designated for special protection status under Schedule 5 of the WCA, which makes it an offence for fish to be intentionally killed, injured or taken.

Diet - Young burbot feed on invertebrates especially molluscs, crustaceans, and insect larvae, whereas older fish eat other fish and spawn, as well as crayfish, frogs and insect larvae. In some places they are regarded as potentially damaging to other more valuable fish stocks, for example aggregating to predate upon migrating salmon smolts.

Assessment - The decline of burbot to the point where it is probably extinct, indicates that current conditions in its former UK native range are no longer suitable for this species. Burbot are reported to be very hardy and easy to transport and maintain in aquaria. Popular with ice anglers in Scandinavia and North America, but not a popular sporting fish elsewhere.

Likely impact from introduction

  • Direct predation on other fish;
  • the introduction of new parasites or exotic diseases;
  • competition with indigenous fish for food cover or spawning sites; and
  • adverse effects on the environment (e.g. effects on community structure).

Catfish, species of the genera Ictalurus, Ameiurus and Silurus

Two species of the genera Silurus occur in Europe: the Wels catfish ( Silurus glanis) and Aristotles catfish ( Silurus aristotelis). The Wels is listed under Schedule 9 of the Wildlife and Countryside Act, 1981 (non-native species established in the wild). Owing to their large size, Wels catfish are highly regarded among anglers and the fish have now been introduced quite widely in the UK (often illegally) for use within specialist fisheries. The Ictalurid catfish is native to North America and north-eastern Central America, but was widely imported into Europe in the nineteenth century. At least three species are believed to have been imported into the UK for sale through the aquarist trade: American catfish or Black bullhead ( Ictalurus melas); brown bullhead ( Ictalurus nebulosus); and the Channel catfish ( Ictalurus punctatus).

Diet - Juvenile Wels catfish feed on small invertebrates; larger fish are predators and scavengers, mainly feeding on fish. They have also been known to feed on shellfish, amphibians, waterfowl and small mammals. Ictalurid catfish feed mostly on benthic items, such as worms and crustaceans.

Assessment - Catfish are highly esteemed as a sporting fish by some anglers (e.g. Catfish Conservation Group) and there is considerable interest in increasing distribution and availability within the UK. Species have been illegally transferred to sites within the UK. The Wels catfish is capable of spawning in the UK, but success of spawning is probably constrained by occurrence of suitable water temperatures. The species is farmed in parts of Europe for food. It has been imported regularly into the UK and readily available through dealers and garden centres.

Likely impact from introduction

  • Direct predation on other fish;
  • competition with indigenous fish for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment (e.g. effects on community structure).

Charr ( Salvelinus spp., excluding the native Salvelinus alpinus)

There are eight species in the genus, including the Great Lake trout, American Brook trout and Dolly Varden charr. Lake trout were introduced into ponds in Fife between 1928 and 1931, although none survived a pollution event in 1934. Brook trout were believed to have been first introduced into Britain in 1869, but have not become widely established in the wild.

Diet - Juveniles eat mainly insect larvae . Adult lake trout are the most piscivorous of the Salvelinus species; all species feed on insects, annelids, snails and small fishes, although brook trout are said to consume trout eggs as well.

Assessment - UK conditions (deeper, colder lakes) would appear to be potentially suitable for lake trout establishment. Dolly Varden charr have both freshwater and anadromous life-styles which enable the fish to adapt to a wide variety of habitats. It has similar spawning requirements to our native species. Salvelinus species are of interest to anglers as an alternative target species in put-and-take fisheries.

Likely impact from introduction

  • Direct predation on other fish;
  • competition with indigenous species for food, cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native salmonids.

Chinese black or snail-eating carp ( Mylopharyngodon piceus)

Diet - Black carp feed primarily on snails, mussels and clams. However, young fry initially feed on zooplankton, older fry on ostracods and aquatic insects and young of the year fish on chironomid larvae. At two years of age the diet changes, to include: molluscs, worms, aquatic macrophytes, larval insects and large zooplankton. Once an adult, it becomes more of a specialised feeder, the diet consisting, almost exclusively, of molluscs and snails.

Assessment - Natural spawning is likely to occur in only a few places (as with other Chinese carps). It is potentially of interest to anglers because of its large size.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. changes to benthos).

Chinese Sucker ( Myxocyprinus asiaticus)

The Chinese sucker (also known as the zebra hi fin, banded shark/sucker, and freshwater batfish) is a member of the family Catostomidae. The Chinese sucker is the only species of its genus, although there are 3 sub-species. It originates from the mountainous upper and also middle streams of the Yangtze River and the Hwang Ho drainage systems in Eastern China. It is a slow growing fish, although owing to a long life span (upwards of 25 years), can reach over 90 cm.

Diet - The Chinese sucker is reported to continually search for food, sifting and sucking the substrate for insects and other invertebrates.

Assessment - There is increasing interest in the Chinese sucker as an aquarium fish. In its native range, the species inhabits waters of around 15-30°C. This may limit its potential to become readily established in the UK, but it appears to be sufficiently tolerant of lower temperatures to be able to survive under UK conditions.

Likely impact from introduction

  • Competition with indigenous species for food, cover or spawning sites; and
  • introduction of new parasites or exotic diseases.

Common White Sucker ( Catostomus commersoni)

A member of the family Catostomidae, the white sucker is one of the most abundant and widely distributed freshwater fishes in North America, with a native range covering most of Canada and the USA. The species can dominate fish community biomass. While young these fish are considered important as food for trout and other game fish. However those that reach large size are considered serious competitors with these fish. When small, the fish has been commonly used as a bait fish and this, together with its ability to adapt to a wide range of habitats and changing environmental influences, has facilitated its widespread distribution in North America. White suckers grow most rapidly during their first year and can reach a length of 18 cm.

Diet - Primarily bottom feeders, with aquatic insect larvae, small molluscs, crustaceans, and various terrestrial worms preferred. However, the method of feeding is fairly indiscriminate and fish are likely to take almost any food available; this may include the eggs of other fish.

Assessment - There is one reported occurrence of a white sucker being captured by electro-fishing on the River Gade at Hemel Hempstead, Hertfordshire. The origin of the specimen was unknown but probably escaped from a fish farm just upstream. The fish farm in question has previously reported the presence of white suckers on the site to CEFAS (the fish were inadvertently imported with a consignment of other species). There are no other reports of white suckers from UK waters. Their adaptability to variable environmental conditions, across a temperate range, suggests that this species is likely to be able to survive and possibly thrive in UK waters. White suckers are of angling and commercial interest and are also as a popular bait fish.

Likely impact from introduction

  • Direct predation upon eggs;
  • competition with indigenous species for food cover or spawning sites; and
  • the introduction of new parasites or exotic diseases;

Danubian bleak ( Chalcalburnus chalcoides)

The Danubian bleak belongs to the carp family.

Diet - The Danubian bleak is typically a planktonic feeder principally consuming Crustaceans and insect larvae. However, it also feeds on insects at the surface, thus exhibiting an opportunistic feeding behaviour.

Assessment - A relatively small fish and thus at greater potential risk of accidental transfer within consignments of other fish species. Of possible interest to anglers.

Likely impact from introduction

  • Competition with indigenous fish for food, cover or spawning sites;
  • possible hybridisation with native species;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. water turbidity changes due to feeding activity).

Danubian Salmon & Taimen ( Hucho spp .)

The Danubian salmon (or Huchen) and the Taimen are related to the genus Salvelinus and are salmon-like in appearance, although much larger. Both freshwater and anadromous forms exist. Huchens are the largest of the salmonids and are among the biggest freshwater fish. There has been some debate about the status of the taimen, which is now regarded as a sub-species ( Hucho hucho taimen); this has been justified by a slight difference in colouration and an interruption in the area of distribution (although the morphology appears to be otherwise identical).

The native range of Hucho hucho extends from Northern Asia to Japan, but also includes the Danube basin of Europe. It has become very restricted in range in the Danube basin over recent years due to pollution and dams. Previous attempts to introduce this species into the Thames, Rhine and Elbe have all failed.

Diet - Juvenile diet consists mainly of benthic invertebrates, especially dipterous larvae. Adults are however, predatory and prey mainly on cyprinid fish (rarely salmonids).

Assessment - Could potentially survive under UK conditions. Popular sport fish with anglers, although previous attempts to introduce this species into the Thames have failed it is present the Danube basin of Europe.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous salmonids for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native salmonids.

Eastern Mudminnow ( Umbra pygmaea) & European Mudminnow ( Umbra krameri)

The mud minnows belong to the Umbridae, a family of five species containing only one species native to southeast Europe. Three species are found in North America while the fifth species, the Alaska blackfish ( Dallia pectoralis), is confined to Siberia and Alaska. The eastern mudminnow ( Umbra pygmaea) , which does not exceed 8 cm in length, is native to the Eastern USA, extending down the Atlantic and gulf slopes from south eastern New York (including Long Island) to St. Johns River drainage in Florida and Georgia. The species was introduced into the Netherlands in the 1920's and is now widespread in the south-eastern part of the Netherlands and in the province of Limburg in Belgium, where it is particularly abundant in acidified soft-water ecosystems, such as moorland pools.

The European mudminnow ( Umbra krameri) is confined to the Danube basin between Vienna and the Black Sea, and the lower reaches of the Dniester river. The fish attains a length of about 13cm.

Diet - Mudminnows are euryphagic carnivores that eat aquatic and terrestrial invertebrates and fish. They also feed in a variety of locations (benthic, midwater and surface) and organisms attached to vegetation are included in the diet. They are also known to be cannibalistic. Feeding activity patterns vary both daily and seasonally.

Assessment - Mudminnows often frequent quiet streams, swamps and other wetlands over sand, mud and under dense floating vegetation. They have a habit of burying themselves in the mud, digging in tail first. They can survive for days or weeks in sticky mud and can live successfully in water deficient in oxygen. They are also an extremely acid-tolerant species and can often be found living in waters with a pH as low as 3. The typical climate range of the eastern mudminnow is a temperate one of between 17 - 23°C. There is also a report of some mudminnows surviving in a jar of water that had frozen solid during an exceptionally cold spell. The eastern mudminnow has been widely classified as a pest wherever it has been introduced.

The European mudminnow has flourished in parts of Europe following introduction, but tends to occur in waters where no native fish can survive. It is therefore likely to be less of a threat than the eastern mudminnow.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Fathead minnow ( Pimephales promelas)

A small fish of not more than 6 cm, with a short life-span (seldom lives more than two years). The species is commonest in short muddy creeks connected with larger rivers; it has also been found in lowland lakes and ponds. The native range of this species extends through much of America and New Mexico. A yellow-red variety also exists which is commonly known as a rosey-red minnow.

Diet - The fathead minnows belong to group of mud-eating minnows which have a diet of algae and insects, partly of terrestrial species and partly aquatic larvae (e.g. Diptera).

Assessment - This species is popular as a bait fish in North America. It is also commonly used as a laboratory species. The ease with which it propagates, coupled with use as a bait, has led to widespread introductions across the USA and it has become established in most States where it has been introduced. It has also been identified as contributing to the decline of endangered species, having an adverse effect on young Colorado pikeminnow ( Ptychocheilus lucius) and young suckers. As a temperate species, appears to be capable of surviving under UK conditions.

Likely impact from introduction

  • Competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and possible hybridisation with native species.

Freshwater minnow, Dragon fish or Pale chub ( Zacco platypus)

The pale chub ( Zacco platypus) is one of the common freshwater fishes of middle and southern Japan, where it is more commonly known as the common or freshwater minnow. It is also found in Korea, Hong Kong and throughout China. It occurs in streams and rivers with rapid water flow (but not stagnant or deep waters) in a climate range of around 10 -22°C. It has a maximum size of around 20cm.

Diet - The main foodstuffs of pale chub are reported to be: zooplankton, small crustaceans, microscopic algae, small fish and detritus.

Assessment - Believed to be of some interest to the ornamental trade, but extent of existing trade uncertain. As a temperate species, appears to be capable of surviving under UK conditions.

Likely impact from introduction

  • Predation of eggs & larvae;
  • competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Grass carp ( Ctenopharyngodon idella)

The grass carp (also known as the White Amur) is a member of the carp family (Cyprinidae), the dominant family of freshwater fish in Europe, North America, Africa and Asia. The fish's diet of aquatic vegetation has led to widespread interest in the possible use of this fish for controlling weed growth. The fish has been introduced widely in the British Isles.

Diet - The grass carp predominantly consumes aquatic macrophytes, although it will also consume invertebrates and other items.

Assessment - The grass carp has a potential specialist role as a biological control agent in waters subject to problems with aquatic vegetation. It is tolerant of a wide range of environmental conditions, but is very unlikely to breed under UK conditions. The species is favoured by anglers due to its potential large size and is widely available as an ornamental fish for use in aquaria and small garden ponds.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish (and other animals) for food, cover or spawning sites;
  • the introduction of novel parasites or exotic diseases;
  • adverse effects on the environment through habitat degradation (e.g. water turbidity changes due to feeding activity, ecosystem effects); and
  • loss of biodiversity (e.g. loss of aquatic plants of high conservation interest due to selective grazing).

Landlocked salmon ( Salmo salar sebago)

The landlocked salmon ( Salmo salar sebago) is a sub-species of the Atlantic salmon ( Salmo salar) which is native to North America. It is virtually identical to the Atlantic salmon, however, as its name suggests, it is non-anadromous. A small number of releases of landlocked salmon have been authorised under the Wildlife and Countryside Act for use in specialist put-and-take fisheries.

Diet - Juvenile fish feed on insects. Adults are largely piscivorous, feeding on small species such as sticklebacks and rainbow smelt ( Osmerus mordax) in their native range.

Assessment - Interest in the stocking of this fish for angling purposes is likely to be the main factor controlling distribution and possible spread of this fish in the UK. Given its similarity to the native Atlantic salmon it is anticipated that landlocked salmon could spawn successfully in our rivers and become established in Scotland. There is also a high possibility that these fish could hybridise with native salmon.

Likely impact from introduction

  • Direct predation on other fish;
  • competition with indigenous fish for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native salmon.

Large-mouthed black bass ( Micropterus salmoides)

The largemouth bass (or black bass) is the largest member of the North American sunfish family (Centrarchidae). The species are of North American origin, but have been introduced widely in Europe and other parts of the world. Several members of this family (6) are now established in Europe, with 2, or possibly 3, in the British Isles. The largemouth bass is listed under Schedule 9 of the Wildlife and Countryside Act, 1981 (non-native species established in the wild).

Diet - Juvenile fish eat mainly insects and larvae. Older fish feed on a range of items: crustaceans, rotifers, oligochaetes, small fish, frogs and even aquatic weeds. However, adult fish are predominantly piscivorous and feeding intensity is correlated with temperature.

Assessment - The largemouth bass is a highly prized fish amongst anglers, both for its sporting quality and good eating. Fishing for the species, in many warmer countries, is given the same coveted status as salmon fishing in cooler countries. Levels of submerged vegetation and the substrate type have been suggested as important factors in regulating the abundance of largemouth bass. Predator foraging success can be affected at high levels of plant stem density. Largemouth bass are warm water species, preferring a water temperature of 20 to 24 oC.

Likely impact form introduction

  • Direct predation on other fish;
  • competition with indigenous fish for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment (e.g. effects on community structure).

Marbled Trout ( Salmo marmoratus)

The native range of Salmo marmoratus extended across Northern Italy, the Adriatic basin of Slovenia and Croatia, Montenegro and Albania. However, its present range has been significantly reduced by pollution, habitat destruction and the introduction of other species (notably brown trout). There is some debate about the taxonomy of this species and some authors suggest it is a sub-species of the brown trout ( Salmo trutta marmoratus). It appears that brown trout and marbled trout are able to hybridise, producing fertile hybrid descendants.

The marbled trout is a long-lived species that can reach up to 25kg. The name originates from the olive-brown or olive-green and white pattern of its skin. It utilises sandy and gravely bottoms in both running or standing water to spawn.

Diet - Smaller marbled trout feed mainly on bottom dwelling organisms and aquatic insects while larger ones mostly eat other fish.

Assessment - Although it is a popular sport fish with anglers, its increasing rarity within its natural geographical distribution may make it unlikely that any fish would be removed and transferred elsewhere for stocking purposes. However, may now be being farmed. U.K. climatic conditions would seem to be suitable for this species.

Likely impact from introduction

  • Predation;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species (particularly brown trout).

Nase ( Chondrostoma nasus)

The nase is a member of the carp family. There are several species of nase which occur in Europe. In addition, the nase is known to hybridise with other species such as the toxostome and, less frequently, the chub.

Diet - The nase is a specialised benthic grazer and feeds mainly on the algae which grows on the rocky and stony bottoms of the river. Its thick lips are adapted for scraping algae, such as cyanophyta from the stones. Larger species may have more varied diet.

Assessment - Chondrostomes are sensitive to anthropogenic changes in the river habitat. The development of eggs is adversely affected in stillwater areas with organic sedimentation. Being a specialised benthic grazer it is restricted to areas containing algae. It requires well-oxygenated water. Nase are not usually fished for or caught by anglers because of their specialised diet.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.

Northern Redbelly Dace/Common minnow ( Phoxinus/ Chrosomus eos)

The northern redbelly dace which closely resembles its southern counterpart has a life span of about 3 years. The overall range of the northern redbelly dace is from Nova Scotia and Prince Edward Island, west in a rather curving band through southern Canada and the Northern and north central United States.

Diet - The diet of the northern redbelly dace includes much plant material, including diatoms and filamentous algae, as well as zooplankton, insects and occasionally fish.

Assessment - Possibly present in the UK; interest likely to be confined to the ornamental market, where it may already be in trade. As a temperate species, appears to be capable of surviving under UK conditions.

Likely impact from introduction

  • Competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Pacific salmon and trout ( Oncorhynchus spp.)

The Pacific salmon are a group of mainly anadromous, but some freshwater, migratory fish found in northern Pacific coastal areas from Japan to California and in adjacent parts of the Arctic ocean. There are a number of species: Pink (or Humpback) salmon ( O. gorbuscha); Chum salmon ( O. keta); Coho salmon ( O. kisutch); Chinook salmon ( O. tshawytscha); Sockeye salmon - ( O. nerka); Masu salmon ( O. masou); and Amago salmon ( O. rhodurus). The Pacific trout are a group of freshwater and anadromous species occupying the North Pacific basin and south Mexico and Arizona. There are possibly six species, two of which are of particular significance from a fisheries perspective: Rainbow trout ( O. mykiss) and Cutthroat troat ( O. clarki). There are also thought to be a number of potential sub-species and there is believed to be considerable hybridisation between the various species. The two species named above have both freshwater and anadromous forms. Unlike Pacific salmon, anadromous Pacific trout do not necessarily die after spawning.

Diet - Pacific salmon juveniles feed largely on invertebrates. Adults become predatory, consuming crustaceans, squid, sand eels and other fishes. Adult Pacific trout eat winged insects, freshwater shrimps and other invertebrates and also consume fish. Sea-run fish eat sand eels, shrimps and prawns.

Assessment - The anadromous life-cycle of many species may allow an extension of their range through straying. All species support valuable commercial and sport fisheries and have been introduced fairly widely for both aquaculture and release into the wild. Many fish farms currently rear rainbow trout in Scotland, and many introductions have already taken place. Potential angler interest in further introductions of these species is therefore high. Some species of Pacific salmon and trout have subsequently become established in some areas outside their native range. Conditions in Scotland are likely to be suitable for the survival of these species and may also be suitable for their breeding. All waters which currently contain rainbow trout as a result of their deliberate introduction to them will require a licence.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous salmonids for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Paddlefish ( Polyodon and Psepherus spp.)

There are only two species of paddlefish, the American paddlefish ( Polyodon spathula) and the Chinese paddlefish (sometimes called the swordbill sturgeon, Psephurus gladius). The paddlefish belong to the family Polyodontidae and are large freshwater fish in the same Order (Acipenseroiformes) as the sturgeons.

Diet - American paddlefish are primarily filter feeders, principally consuming zooplankton. However, they also consume a variety of benthic items including crustaceans and worms. There are some reports of fish being recorded in the diet (e.g. shad have been found in their stomachs). The Chinese paddlefish is piscivorous.

Assessment - There is possible interest in the species for both ornamental and angling purposes.

Likely impact from introduction

  • Predation (in the case of Psephurus);
  • competition with indigenous fish for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. effects on benthos, water turbidity changes due to feeding activity).

Perch ( Perca spp., excluding the native Perca fluviatilis))

The genus Perca contains three species: the Eurasian perch ( Perca fluviatilis), the yellow perch ( P. flavescens) and the Balkhash perch ( P. schrenki). The yellow or North American perch ( P. flavescens) and the Eurasian perch are biologically equivalent and almost identical. Yellow perch are found in North America, east of the Rocky Mountains; P.schrenki occurs in parts of Asia.

Diet - Juvenile perch feed on zooplankton, switching to benthic invertebrates as they grow. Perch are versatile feeders and feed on whatever is available; fish are often the primary component of the diet in adults and cannibalism is common.

Assessment - The introduction of yellow perch into a small lake resulted in changes in biomass and size structure of the benthic community. There was an approximate 60% reduction in total benthic biomass and a 50% reduction in mean weights in the littoral zone after perch introduction.

Deleterious impacts caused by the introduction and establishment of yellow perch have been demonstrated on salmonids. Competition with yellow perch for available food supply resulted in a drastic change in the food habits of salmonids and a reduction in their growth rates in excess of 50%

Likely impact from introduction

  • Direct predation;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Pike ( Esox spp., excluding the native Esox lucius)

The genus Esox consists of five species, four of which are non-native. Esox niger, the chain pickerel grows up to 35 cm long and is smaller than the native pike; Esox americanus, the grass pickerel (reaches a length of 60 cm); Esox masquinongy, the Muskellunge is the largest pike species and can reach up to 240 cm in length and up to 110lb in weight; Esox reicherti Amur or black spotted pike (very little is known of this species). Three species (chain pickerel, grass pickerel and muskellunge) are restricted to North America, while the Amur pike occurs only in Siberia.

Diet - Predatory / piscivorous.

Assessment - All the Esocids are popular sport fish; only the northern pike ( Esoxlucius) is resident in the UK. The tiger muskellunge is a hybrid of the northern pike and muskellunge (possibly sterile), and this species is frequently stocked for sport fishing in North America. When muskellunge occurs with northern pike, the latter species is reportedly competitively superior.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases;
  • hybridisation with native species; and
  • adverse effects on the environment through a change in community structure (due to piscivory).

Pike-perch ( Stizostedium spp.)

There are three predaceous pike-perches of the genus Stizostedion resident in Europe (including the Caspian and Aral Seas): Stizostedion lucioperca (Zander); Stizostedion volgensis (Volga zander); Stizostedion marinum; and two [the sauger ( Stizostedion canadense) and walleye ( Stizostedion vitreum)] in North America.

Several species of pike-perch are native to eastern Europe and western Asia, but they have been introduced into southern Scandinavia and most other parts of Europe. Zander are now quite widespread in England. The fish has been spread by illegal introductions; in 1976 fish were discovered in the River Severn catchment. Fish have also been stocked into a number of stillwater fisheries. The zander is listed under Schedule 9 of the Wildlife and Countryside Act, 1981 (non-native species established in the wild).

The walleye ( Stizostedion vitreum) has also been introduced to the UK. However, this species is not believed to be currently present in the UK.

Diet - Pike-perch are primarily piscivorous and feed on fish of all kinds. They are also known to eat their own young. Juvenile fish feed initially on invertebrates and zooplankton. Zander tend to consume smaller fish than pike of the same size.

The impact of zander on prey stocks can be substantial (e.g. zander living in the fens are alleged to have caused a massive reduction in stocks of Cyprinids following their introduction).

Assessment - Highly regarded as a sporting fish and have been subject to repeated illegal transfers between waters. UK conditions are suitable for spawning and colonisation; populations rapidly become established in a suitable habitat. Predation by adult fish on their own young may be a factor in stabilising fish communities following introductions. Pike-perch are capable of utilising a range of habitat types.

Likely impact from introduction

  • Direct predation - pike-perch consume many kinds of small fish.
  • competition with indigenous fish for food cover or spawning sites; and
  • the introduction of new parasites or exotic diseases;

Red Shiner ( Notropis lutrensis)

This little fish is distinguished among other cyprinids by the brilliance of its colour and by the depth and thinness of its body. It is short-lived (few fish survive beyond 3 years of age), at which time they could have attained a maximum length of up to 9 cm. The native range of the species is largely concentrated around the Mississippi River basin, although it is also found in New Mexico. It is found mainly in running water, but also in lowland lakes, and prefers temperatures between 15-25°C.

Diet - It is reported to feed on small crustaceans, aquatic insects, larvae and algae, although plant leaves, detritus and larval fish have also been noted.

Assessment - The red shiner has a high tolerance of extreme environmental conditions and has the ability to rapidly colonise new habitats. They are also known to hybridise with other cyprinids. Evidence of impacts on indigenous species includes the displacement of spikedace in the Colorado River and the introduction of Asian tapeworm in the River Utah. In the USA, it has been described as the second greatest threat to the welfare of indigenous south-western fishes after the mosquito fish.

Likely impact from introduction

  • Direct predation on eggs and larvae;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Rock bass ( Ambloplites rupestris)

The rock bass is a member of the North American sunfish Family (Centrarchidae). This family is exclusively North American but has been widely distributed in Europe and other parts of the world.

Several members of this family (6) are now established in Europe, with 2, or possibly 3, in the British Isles. The rock bass is listed under Schedule 9 of the Wildlife and Countryside Act, 1981 (non-native species established in the wild). However, it is uncertain whether it is still present in this country.

Diet - Juveniles feed on small invertebrates such as mayflies and chironomids. After 3 months their diet switches to crustaceans (e.g. crayfish), the larvae of aquatic insects and fish.

Assessment - The rock bass requires a high water temperature for successful spawning. Thus, the relatively cool climate in the UK is unlikely to be suitable for widespread colonisation. Its distribution is also constrained by suitable habitat, particularly cover. Rock bass is quite an important 'pan' fish in North America, being cropped by both anglers and commercial fishermen

Likely impact from introduction

  • Direct predation on other fish;
  • competition with indigenous fish for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment or local flora and fauna.

Ruffe ( Gymnocephalus cernuusea)

This is a small member of the perch family, seldom exceeding 15 cm in length. Native to parts of Europe and Asia, and found in shoals in lakes and slower flowing stretches of river, sometimes in high densities.

Diet - Insect larvae and crustaceans are major food items, and fish fry and amphibian tadpoles may also be taken. In some waters, heavy predation on fish eggs, including those of coregonids, can occur.

Assessment - In the UK, native only to some rivers of eastern England, but has readily colonised new waters, through anglers discarding unused livebait, inadvertent introductions during stocking of other coarse fish, and via the canal network. A similar spread into central and western France has taken place. Formerly entirely absent from Scotland, in recent years it has become established in Loch Lomond and the Forth and Clyde Canal, and probably Loch Ken. Following colonisation, very high densities can be attained.

Likely impact from introduction

  • Pertubation of natural fish communities;
  • predation on eggs or fry of other fish species;
  • competition with other fish for food, space or spawning sites; and
  • the introduction of new parasites or diseases.

Schneider ( Alburnoides bipunctatus)

The schneider or spirlin occurs in eastern France across central Europe to Russia and the Danube basin, and as far as the Caspian and Aral seas. The species is usually resident in small clear streams, but is also found in lakes; and lives in shoals close to the bottom, often in association with minnows and trout.

Diet - Schneider feed mainly on small bottom-dwelling animals, including: insect larvae and crustaceans; also feeds on flying insects.

Assessment - Schneider has a habitat preference for shallow clear streams; requiring well oxygenated water. It is not a preferred species for angling due to its small size, but could be used as bait. It can be kept in aquaria.

Likely impact from introduction

  • Competition with indigenous fish (e.g. trout) for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.

Silver Carp ( Hypophthalmichthys molitrix)

The silver carp is native to China and the Amur basin, but has been widely introduced. It is now found in Asia, the USSR and Europe, particularly eastern Europe. Small numbers have also been introduced into the British Isles.

Diet - The silver carp is a filter feeder consuming phytoplankton. This specialised diet has led to interest in the possible use of the fish for controlling algal blooms.

Assessment - The silver carp has a potential specialist role as a biological control agent in waters subject to problems with algal blooms. The species is very unlikely to breed under UK conditions, although it is tolerant of a wide range of environmental conditions. It is unlikely to be a species favoured by anglers due to its specialised diet.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat changes (e.g. water turbidity changes due to feeding activity).

Small-mouth bass ( Micropterus dolomieu)

The small-mouth bass is a member of the sunfish family (Centrarchidae) and resembles the large-mouth bass. The small-mouth bass is native to eastern central North America, but it has been widely redistributed in America and Europe, where it occurs sporadically in Western Europe. Since 1878, attempts have been made to introduce this species into the British Isles, but none are thought to have become established.

Diet - Juvenile smallmouth bass feed on aquatic insects and crustaceans; adults are piscivorous feeding on fish and crayfish.

Assessment - The smallmouth bass is a highly prized sport fish within its native range. It has been successfully introduced beyond its native range, mainly for its angling potential and has previously been introduced into the UK. It is an adaptable species, but reportedly does best in warmer water.

It is uncertain whether or not smallmouth bass adversely affect salmonids; there are some suggestions that the species might enhance salmonid production by foraging on species that compete with salmonids. However, high levels of predation of salmonids and other species by these fish have been reported for various water bodies in the USA.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Snakehead ( Channa spp.)

Also known as murrels, snakeheads belong to the Family Channidae. There are approximately 30 named species, all members of the genus Channa, although some still erroneously use the genus Ophicephalus.

Snakeheads are air-breathing freshwater fish native to tropical freshwaters of Asia and Africa, although temperate species also occur in Northern China. Thanks to their air-breathing habit and to their ability to aestivate under harsh conditions, they can be found in almost any habitat where there is water, including lowland and upland streams, canals, lakes, ponds and marshland. They have been widely translocated, especially in the Americas, where they have become established, even in areas outside their reported temperature optima.

Snakeheads have long cylindrical bodies with long dorsal and anal (ventral) fins, and large mouths with a protruding lower jaw. The lower jaw may contain canine-like teeth. Coloration and size are variable with some species attaining 1m in length. Some of the species have a brown mottled appearance while others can be quite colourful.

Diet - Juveniles eat zooplankton, insect larvae, small crustaceans, and the fry of other fish. As adults they feed mostly on other fishes, with crustaceans, frogs, small reptiles, and some times small birds and mammals comprising the remainder of their diet.

Assessment - Some half-a-dozen snakehead species are thought to have been imported into the UK by the aquarium trade, including C. striata, C. micropeltes and C. melasoma. Despite having established in many North American environments, where they are reportedly causing widespread impacts on the indigenous fish fauna, temperatures in Scotland are too dissimilar from their optima to become established.

Likely impact from introduction

  • Unlikely to become established, given temperature optima; and
  • introduction of diseases.

Southern Redbelly Dace/Common minnow ( Phoxinus/Chrosomuserythrogaster)

The southern redbelly dace which reaches a maximum size of approximately 6 cm (2 1/ 2 inches), is a common fish where suitable habitat is present. It can be found in the Mississippi-Ohio River system with distinct populations in Kansas, Colorado and New Mexico.

Diet - This species is considered a herbivore, which takes mainly algae and diatoms. However, they are also known to take some microcrustaceans and those kept in aquariums will feed on bloodworm and mosquito larvae.

Assessment - Possibly present in the UK; interest likely to be confined to the ornamental market, where it may already be in trade. As a temperate species, appears to be capable of surviving under UK conditions.

Likely impact from introduction

  • Competition with indigenous species for food, cover or spawning sites;
  • introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Sturgeon or sterlet (Family Acipenseridae)

Sturgeons (Family Acipenseridae) are only found in the Northern Hemisphere. The family contains about 25 species (Genera Acipenser, Huso, Pseudoscaphirhynchus and Scaphirhynchus) and is unique among vertebrates in that all members can hybridise in the wild if their spawning grounds overlap. The species most commonly introduced into the UK is the sterlet ( A. ruthenus). Concerns about the status of stocks in its native range, due to factors such as pollution, over-fishing and barriers to migration, led to farming of the species.

Sterlet (imported and presumably of farmed origin) are now widely available through aquarists and garden centres in the UK and are increasingly reported from fisheries.

Diet - Sterlet are opportunistic and consume a wide variety of benthic items. Their diet consists of: Chironomidae, Trichoptera, other insect larvae, molluscs, worms and crustaceans (e.g. crayfish). Eggs laid by certain cyprinid fish such as bream, roach & white bream have also been recorded in the sterlet's diet.

Assessment - Sterlet will not survive where oxygen concentrations are low. The fish has been widely introduced and is readily available from dealers and garden centres as an ornamental species for use in tanks and small ponds. Given their growth potential it is very likely that these fish will outgrow such facilities and are thus quite likely to be released to the wild. It is not certain whether the fish would successfully spawn in the UK. Due to its large size, it is likely to be regarded as a novel sporting fish and therefore of considerable potential interest to anglers. Illegal introductions and transfer between waters may therefore occur.

Likely impact from introductions

  • Direct predation (e.g. reported consumption of fish eggs);
  • competition with indigenous fish for food, cover or spawning sites;
  • the introduction of novel parasites or exotic diseases (the nematode parasite Contracaecum bidenatum has been recorded in sterlet); and
  • adverse effects on the environment through habitat degradation (e.g. effects on benthos, or water turbidity changes due to benthic feeding activity).

Sunbleak or Sundace ( Leucaspius delineatus) (also known as Belica or Motherless minnow)

The sunbleak, which inhabits ponds, lakes and slow stretches of rivers is a member of the carp family (Cyprinidae) the dominant family of freshwater fish in Europe, North America, Africa and Asia. It is widely distributed in Europe from the Caspian Sea westwards to the rivers of Belgium and Holland. It is native to: Germany, Southern Denmark, the southern tip of Sweden, Holland, Belgium and northern France. Three other Leucaspius species have been recorded in southern Europe: two in Greece and one in western Turkey.

Average size is 6 - 8 cm (2 ½ - 3 in), although fish can grow up to 12 cm (5 in).

Diet - Sunbleak feed on small aquatic invertebrates, crustaceans and delicate plants. Also thought to consume fish eggs and possibly very small fish.

Assessment - The sunbleak, which can tolerate high temperatures and low oxygen levels; is thought to possess many characteristics that would favour successful colonisation in the UK. The sunbleak is already established in several waters in southern England, having been introduced inadvertently (it is not favoured by anglers due to its small size). It is known to be present at sites in Hampshire (e.g. Broadlands Lake and River Test) and in Somerset (e.g. Kings Sedgemoor Drain and the Taunton and Bridgewater canal). In the Taunton and Bridgewater canal, it has been claimed that the sunbleak is adversely affecting coarse fish populations (possibly due to its predation of eggs) and is regarded as something of a pest.

Likely impact from introduction

  • Competition with indigenous fish for food, cover or spawning sites;
  • predation on eggs of other fish species;
  • introduction of new parasites or exotic diseases; and
  • possible hybridisation with native species.

Sunfish, including pumpkinseed ( Lepomis spp.)

The sunfish species are part of the North America freshwater family Centrarchidae, and are sometimes referred to as basses, crappies and blue gills. There are several species: the long-eared sunfish ( Lepomis megalotis) ; the redbreast sunfish ( Lepomis auritus); the bluegill ( Lepomis macrochirus) ; the green sunfish ( Lepomis cyanellus); the orange spotted Sunfish ( Lepomis humili) and the pumpkinseed ( Lepomis gibbosus). The latter has been introduced widely in Europe and other parts of the world. The pumpkinseed is listed under Schedule 9 of the Wildlife and Countryside Act 1981 (non-native species established in the wild).

Diet - Sunfish feed at all levels in the water column but rarely eat benthic organisms, instead feeding primarily on adult insects and larvae, molluscs and crustaceans. All sunfishes are, however, opportunistic feeders and will even exhibit piscivorous habits.

Assessment - Generally, sunfishes have a broad ecological tolerance and both the green and redbreast sunfish have been successfully introduced into areas outside of their native range. The green sunfish are reported to feed heavily on juvenile fish and consequently to suppress populations of native fish. All species are sensitive to sudden changes in temperature; the extent to which UK conditions might affect the establishment of viable sunfish populations is unknown. The bluegill is an important sports fish and has also been used extensively in experimental work. Pumpkinseed is a popular ornamental aquarium species and is widely available; there does not appear to be much trade in the other Lepomis species, although other ornamental species are sometimes sold under the name sunfish (e.g. Elassoma evergladei). Despite its small size, pumpkinseed is popular among both anglers and commercial fishermen in North America; this may influence interest in the species in Scotland.

Likely impact from introduction

  • Direct predation;
  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases;
  • hybridisation with native species; and
  • adverse effects on the environment or local flora and fauna (e.g. effects on community structure).

Topmouth gudgeon ( Pseudorasbora parva)

The topmouth gudgeon is a member of the carp family.

Diet - The topmouth gudgeon feeds on benthic crustaceans, zooplankton and insect larvae, although it is also reported to eat pond snails. It has been seen to attack young (1+) grass carp, silver carp and bighead carp when kept in captivity and to inflict wounds on the sides and towards the tail of these fish. The fish has also been recorded to predate on fish eggs.

Assessment - The topmouth gudgeon combines many characteristics that are likely to favour successful colonisation in many environments, as evident from its rapid spread across Europe. It has a wide physiological tolerance to extremes of temperature, it grows fast, attains sexual maturity early, spawns repeatedly over a long period, and exhibits some parental care of its offspring; and it also has a broad dietary spectrum. It is unlikely to be a favoured species among anglers given its small size (unless possibly as a pike bait). However, there is a strong possibility of unwitting transfer within consignments of other coarse fish. Further spread through the UK is likely, particularly if sold via the ornamental trade.

Likely impact from introduction

  • The introduction of novel parasites or exotic diseases. Topmouth gudgeon have been shown to be carriers of pike fry rhabdovirus (PFR) and also to act as a new host for the trematode parasite Clinostomum complanatum;
  • competition with indigenous fish for food, cover or spawning sites. Given its ability to spread rapidly, there is considered to be a risk that P. parva will compete with native species and will cause problems as its population expands;
  • topmouth gudgeon have been observed to attack fish causing injuries to the skin and musculature; such damage is likely to promote infectious diseases. This suggests topmouth gudgeon would be an undesirable component of fish communities in ponds; and
  • direct predation - there are reports that topmouth gudgeon have been observed to feed on the eggs of zander.

Toxostome or French Nase ( Chondrostoma toxostoma)

The toxostome is a member of the carp family. The fish prefers clear stony streams and the shallow parts of upland rivers. It lives in small shoals in pools, behind stones or rocks, and in quieter water at the margins.

Diet - The toxostome, like the nase, feeds mainly on the algae which grows on aquatic plants and on the rocky and stony bottom of the river.

Assessment - Being a specialised benthic grazer it is restricted to areas containing algae. Nase require well-oxygenated water. Nase are not usually fished for or caught by anglers because of their specialised diet, relatively small size and the fact that they occupy similar habitat to more sought after species such as trout.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.

Vimba ( Vimba vimba)

The Vimba is a member of the carp family. The vimba is not present in the British Isles.

Diet - Vimba are benthic feeders and feed on worms, insect larvae and molluscs.

Assessment - Vimba are tolerant of a wide range of environmental conditions, particularly salinity. It is a popular species with anglers.

Likely impact from introduction

  • Direct or indirect competition with indigenous fish for food, cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • adverse effects on the environment through habitat degradation (e.g. water quality changes through benthic grazing).

Weather fish ( Misgurnis fossilis)

The weather fish, or pond loach, is the largest representative of the loach family ( Cobitidae), attaining a length of 35 cm or more. It is strictly confined to freshwater and can be found in eastern and central Europe from the River Rhine to the Caspian Sea basin.

Diet - Feeds primarily on molluscs, chironomids and insect larvae.

Assessment - Weather fish, at all life stages, are well adapted to oxygen-poor environments. It has previously attracted some interest as an ornamental species, and is thought to feature in the current ornamental trade.

Likely impact from introduction

  • competition with indigenous species for food cover or spawning sites;
  • the introduction of new parasites or exotic diseases; and
  • hybridisation with native species.

Whitefish ( Coregonus spp., excluding the native Coregonus lavaretus and albula)

This genus includes the various whitefishes of Europe, Asia and North America. All are typically salmonid in appearance, but with large scales. There is substantial variety in their form and life style, with both autumn and spring spawners, lake and stream spawners, and large, fast-growing fish and stunted fish. Many are lake dwelling, but sea-run and stream-resident forms also occur. They are good eating, and the populations are often dense and occur as shoals. In many countries, lakes are fished by net for whitefish, and extensive stocking has been carried out. The variety of forms found reflects the success of the genus, the repeated disruption of the cool fresh waters of the northern hemisphere through the ages by glaciation, and gene introgression by hybridisation.

Included in the order is the pollan ( Coregonus autumnalis), which occurs in Irish lakes. However, the forms of the two species which occur in the UK ( Coregonus lavaretus of Loch Lomond and Loch Eck in Scotland, Ullswater, Haweswater, Red Tarn and Brotherswater in the English Lake District, and Llyn Tegid in Wales, with various local names, and the vendace Coregonus albula of Bassenthwaite Lake and Derwentwater in the English Lake District) are not subject to the Order.

Diet - Typically planktonic or bottom feeding throughout life, but varies with species and life history form.

Assessment - Many of the forms could potentially survive and breed under UK conditions. The planktivorous or bottom feeding habits of most whitefish limit their interest to anglers.

Likely impact from introduction

  • hybridisation with native salmonids;
  • competition with indigenous salmonids for food, cover or spawning sites; and
  • the introduction of new parasites or exotic diseases.