Scottish Marine and Freshwater Science Volume 6 Number 1: Loch Linnhe and Firth of Lorn MASTS Case Study Workshop Report

Report on a case study workshop on the Loch Linnhe and Firth of Lorn (LL&FL) system.

DOI: 10.7489/1539-1

The Loch Linnhe System: What do we know about it?

Three invited speakers provided a background to the physical environment (Dr Andy Dale), the aquatic ecosystem (Prof Mike Heath) and the management (Dr Ted Schlicke) of the Loch Linnhe system. These overviews were supplemented by contributed presentations from other attendees. All contributions have been listed on the agenda. A brief overview will follow, and there is a plan to publish a more comprehensive report in the near future.

The Physical Environment

Loch Linnhe has a fjordic nature where sea bed topography (with shallow sills), freshwater input and meteorological forcing drive the circulation. Freshwater inflows are a key control of the dynamics of the Loch Linnhe system through determining surface stratification and controlling deep water renewal. Pulsed releases of freshwater from Upper Loch Linnhe through the Corran Narrows travel along the northern side out of the loch (due to rotation) as a bore. Understanding entrainment and mixing is key to understanding the dynamics of the inflows of coastal water and deep-water renewal. Hydrodynamic models of the area perform reasonably well, although the accurate representation of salinity gradients, exchange at the open boundary, and local topographic steering of winds are important processes which need to be included in the models. Circulation patterns in the Firth of Lorn have been less well studied but freshwater influence is apparent in the upper and central parts of the Firth. Towards the seaward end Atlantic and Irish Sea origin waters become more influential. There are also important oceanographic features such as the Corryvreckan tidal race which leads to pulses of water exchange between the Firth of Lorn and the Sound of Jura.

The Aquatic Ecosystem

Studies have been conducted in the upper parts of the Loch into nutrients and algal production ( Grantham, 1981). More intense ecosystem studies were conducted in the early 1990s. Recent ecosystem research in LL& FL has largely focused on quantifying the potential impact of anthropogenic contributions to the nutrient cycle (from local factories and fish farms). The upper and outer loch can be considered distinct in their biogeography: significant differences have been observed in the nutrient cycles and plankton communities.

Benthic surveys have been limited in spatial extent within Loch Linnhe (focused on Loch Creran), although a survey of the Firth of Lorn has recently been completed. Several species of marine mega-fauna, including porpoise and seals, are often recorded in the Firth of Lorn but become less frequent moving up the loch. There is a Special Area of Conservation ( SAC) on Lismore for seals. Research at SAMS suggests there is a link between state of tide at the Great Race (Corryvreckan) and its use as a foraging site by seabirds and harbour porpoises (Andy Dale, SAMS).

Several ecosystem models have been developed for the area, focusing on representing the nutrient cycle through the loch and the contribution of fish farms and effluent to the nutrient budget ( Ross et al, 1993). More recently, connectivity modelling has been used to assess the potential of sea lice transmission and the impact of additional habitat provision from man-made structures (such as man-made reefs or local wind farm developments).

Uses and Management

The management of LL& FL focuses on supporting local aquaculture developments and regulating the disposal of waste via the system (industrial effluent and waste water). There are also local fisheries management issues, and a number of Marine Protected Areas ( MPAs) have been created in the region. Several legislative directives drive management initiatives in the region, focusing on reducing adverse impacts to the system from human pressures.

In total, there are approximately 20 active salmonid farms in the LL& FL region divided in to 2 disease management areas (or three industry-planned farm management areas). Sea lice ( Lepeophtheirus salmonis) are one of the industry's main parasite challenges. Recently, a large multi-disciplinary project has focused on quantifying potential farm connectivity and sea lice dispersal within the system. Several flooding events have occurred in the upper loch and new methods for flood forecasting have been developed for the region.

A Meta-Data Catalogue for LL& FL

Presentations in the first two sessions of the workshop highlighted that LL& FL is a relatively data-rich region. As datasets are held by a number of different institutions/individuals, a meta-data catalogue of these data would be beneficial. An initial listing was drafted during the workshop (see Table 1 below) although attendees agreed that a more thorough overview should be collected after the meeting.

One particular application of data in LL& FL could be to provide a test-bed of ecosystem function assessment criteria: if ecosystem assessment tools do not work for relatively confined, data-rich ecosystems such as LL& FL, then can they be expected to work in larger regional assessments (such as North Sea scale)? However, LL& FL are clearly not fully self-contained systems and so their status will be linked to that of the wider Irish Sea and West of Scotland. The degree to which the LL& FL systems could be evaluated in isolation requires further discussion.

Table 1

Initial listing of available data within LL& FL.

Physical Environment
  • Observed quantities unlikely to change (change typically over a decadal scale).
  • The outer part of Firth of Lorn well surveyed ( INIS Hydro and MAREMAP), although substrate type not well known due to lower data quality. LL to be surveyed soon.
  • Information on sill depths and side lochs from the Sea Loch Catalogue ( Edwards & Sharples, 1986) (recent update by Marine Scotland Science ( MSS) from digitised charts)
Freshwater Inputs (nutrients/suspended matter)
  • Scottish Environment Protection Agency ( SEPA) have river gauge observations
  • Catchment models: grid2grid model (2007-2012; MSS), eHYPE (1980-2012; SMHI; available online)
  • FW temperature data - FFL data/Strontium data.
  • Marine Optics data on organic and inorganic suspended particulates and coloured dissolved organic matter (U. Strathclyde, CEFAS and SEPA)
  • Survey data from MSS, SEPA and SAMS
  • Tiree buoy oceanographic mooring (future uncertain).
  • Glider observations from a number of deployments in LL& FL
Atmospheric inputs (hydrodynamic modelling)
  • NOC have the mesoscale model outputs.
  • SAMS has model outputs from WRF simulation; and Met Office from the Unified Model.
  • Weather station data from a number of field campaigns ( MSS and SAMS).
  • Tidal diamonds and tidal models ( e.g. OTPS)
  • Number of current meter deployments ( MSS/ SAMS)
  • Existing models based on POLCOMS, FVCOM case study, and several SAMS FVCOM models
  • Tidal asymmetry for predicting sediment movement, used in Clyde by SEPA.
Aquatic Ecosystem
  • This was a gap in expertise during the workshop (esp. pore water chemistry, speciation etc.).
  • Observations of contaminants, nitrogen, phosphate and silicate mainly.
  • Gather relevant data after workshop (Tim Brand, SAMS)
  • Paul Tett has some digitised 1970's Loch Creran data available (Keystones?) 100% PP and ~90% nutrient data digitised.
  • Microplankton (anything that does not have an embryo in its live cycle - Paul Tett). Extensive data from Creran, some from Etive and Spelve but a lot less from further up the loch system. Taxonomic data from U Strathclyde. Food Standards Agency collects water samples every fortnight for toxic algae monitoring but the non-toxic species are not routinely counted.
  • Zooplankton - 1991 Loch Linnhe Project ( LLP) and SAMS has a big archive from last couple of years and a lot of taxonomic analysis of Etive by Pond and Brierley. MSS have taken samples for sea lice which are still held. Need to collect annual and multi annual data sets. CPR survey data further offshore.
  • Icthyoplankton - some data from 1990 and SAMS jellyfish surveys, recent SAMS report on the ichthyoplankton suggests Firth of Lorn is not so important as a spawning area but acts as a nursery to larvae which are transported in from further offshore (this is in line with earlier suggestions in the literature). Mike Heath has a large collection of otoliths somewhere (1970's Da Silva looking at juvenile herring in loch Creran).
  • Jellyfish monitored over two years ( C. Fox, Davidson, & Beveridge, 2014)
  • Distribution of cirripede larvae has been studied in the Firth of Lorn (Raeanne Miller, PhD, SAMS).
  • Not a huge amount available for the main loch, depth restrictions on benthic surveys on the outer loch (contact Dave Hughes at SAMS)
  • LLP 1991 - infaunal biomass data from core samples (muddy sites only). Some rock/sand samples from 1991 but these have been lost.
  • British Geological Survey has conducted inshore surveys ( MSS may have some LL data). SEPA - grab samples, benthos report document/s to be uploaded (possibly for successive years). Quite a lot of benthic surveys conducted in the wider Firth of Lorn by Scottish Natural Heritage ( SNH) in relation to Marine Protected Areas. SAC sites in the Firth of Lorn and Loch Creran will need monitoring on a regular basis.
  • Rocky shore and sandy beach surveys conducted over a number of years at several sites within the Firth of Lorn (Mike Burrows, Clive Fox from SAMS). Autumn beam-trawl surveys at Tralee (2009 onwards)
Fish & Shellfish
  • Juvenile herring assessment survey up to the mid 1980's.
  • Data from a number of trawl surveys conducted by SAMS ( SMBA as it then was) in the 1980s (John Gordon reports in SMBA Internal Reports series).
  • Summary of early studies relevant to use of Firth of Lorn by juvenile fish ( C. J. Fox & Lappalainen, 2014) Inshore fisheries data on Loch Creran (1960's through to mid-90's?) -now only a single vessel active in this area as far as we know.
  • No commercial fisheries operating in the LL system, was a spurdog fishery in Loch Etive which is connected to the Firth of Lorn but this was fished out in 70's.
  • More recent fisheries activity data from Scotmap inshore commercial fisheries shows activity in the Firth of Lorn and Loch Linnhe (mainly crab and lobster pots and Nephrops creeling; Nephrops trawling in outer Firth of Lorn but also some scallop dive activity.
  • Amateur angling also quite popular in the area and a possible source of data - common skate known to occur in the Sound of Mull, spurdog throughout Firth of Lorn and Loch Etive. Scottish Sea Angling Conservation Network ran a spurdog tagging program in the area.
  • Salmon - aggregated by region so not specific for each river.
  • Wild fisheries trust - North, South and West banks of the Linnhe, some association with Lochaber Fisheries Trust.
  • MSS data on wild fish populations from rod catch information, and tracking reared fish.
  • This was a gap in expertise during the workshop.
  • National ringing survey (Clive Craik at SAMS)

Seal data Sea Mammal Research Unit and SNH (not much in way of cetacean activity although increasing numbers of harbour porpoise have been observed by wildlife tour operators in Firth of Lorn in recent years, David Ainsley pers. comm.)

Could be supplemented by data holdings at SMRU and MS Licensing (seal shooting)

Uses and Management
Urban input
  • SEPA has monitoring information on discharges
  • Marina construction/invasive species (Liz Cook, SAMS; Lyndsay Brown, MSS). SAMS have been conducting research into whether marinas form habitat for benthic stages of jellyfish - data have been collected from a number of marinas in the FL (Clive Fox, SAMS).
  • Offshore structures as habitat/stepping stones (Tom Adams, SAMS)
  • Documented on website, including monthly biomass/feed and chemical use by individual farm.
  • Sea lice work over the last few years - have trawl data, settlement phase data, Scottish Salmon Producers Organisation data ( ), wild captures ( , footprint/chemical residues from seabed (
  • Marine analytical unit commissioned - economic value of aquaculture and fisheries to local community.
  • Shellfish cultivation +40 sites in greater LL area location on website, SAMS have done some assessment of mussel farm impacts on benthos - Scottish Aquaculture Research Forum ( SARF) project report.
  • CAR licence applications held by SEPA
Human Pressures
  • Scottish Marine Atlas ( MS)
  • Sound of Mull Planning Pilot; Loch Etive spatial management plan
  • Loch Creran and Firth of Lorn SAC documents.
  • Scotmap data
  • SAMS may be able to contribute information on economic benefits of ecosystem in future (Jaspar Kenter)


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