This theme and the research objective questions reflect the necessity to develop a greater understanding of specific interactions of diadromous fish with OMRE developments. The overall aim of this theme is to address the research knowledge gaps in the interactions of diadromous fish with OMRE developments. Addressing these research knowledge gaps will directly contribute to sustainable development of OMRE.
The priority research objectives of Theme 1 are summarised below.
1. What routes and depths do salmon smolts use as they leave Scotland?
Malcolm et al, 2013 highlight that within the Scottish context there is a lack of information on the migration behaviour and coastal spatial distribution of Atlantic salmon post smolts. Assessment of smolt migration behaviour from East Coast Rivers is important as previous modelling work using particle tracking models has identified the need for behavioural data to parameterise particle models (Guerin et al, 2014).
This research objective question is most readily addressed by combining models of water currents (hydrographic models) and wind effects with information on swimming vectors of smolts. It is proposed that predictions from such models could then be tested by surface trawling to capture smolts at sea. A number of distinct work packages can be identified to facilitate this approach.
Evaluate timing of smolt migrations and sizes of smolts to determine where experimental tracking work may be possible
Current action: a contract has been allocated by Marine Scotland Science (MSS) to the Scottish Fisheries Co-ordination Centre to compile existing smolt trap data held by Fisheries Boards and Trusts. Available data has now been compiled and a meta-data report produced.
Future actions: An analysis of existing data needs to be carried out to determine whether smolt migration timing can be generalised from an understanding of geographic location and catchment characteristics. It may be necessary to collect further data on sizes and riverine migration timings of smolts at strategic locations. This consideration is subject to the outcome of the current action.
Track the coastal and marine movements of emigrating smolts to determine swimming vectors in relation to geographic location
Current action: MSS have scoped the deployment of acoustic receiving stations at an initial series of coastal locations.
Future actions: Further develop the existing scoping document into a detailed project specification, compile a field team and ensure adequate budget. This will require purchase of necessary equipment. Capture, tag and track fish and measure local currents, wind speeds and direction. Compile a series of studies around the Scottish coast that can be generalised.
Model smolt distributions combining swimming vectors with local currents and wind
Current action: existing particle tracking models are being re-coded by MSS for application to the Scottish East Coast, to be run using a range of notional smolt swimming vectors as an exploratory exercise.
Future actions: the Scottish Shelf Seas Model will be applied to develop a framework that will enable incorporation of empirical data regarding smolt movements and environmental variables.
Empirical evaluation of smolt distributions
Current action: designs and costs for construction of a video trawl have been scoped by MSS and plans for test deployments in the North Sea have been drafted. Work is underway in the broader context to establish whether single nucleotide polymorphisms (SNPs) can be used to distinguish the river of origin of smolts.
Future actions: subject to results of current actions, deploy video trawls on MSS vessel Scotia for specific surveys. As required, commission cruises to fill gaps in trawl coverage. If and when general smolt distributions are established from video footage, strategically sample fish to determine rivers of origin from genetics (subject to results of current work regarding SNPs). Consider incorporating a Passive Integrated Transponder (PIT) detector in the video trawl frame and tag smolts from strategic locations around Scotland with PITs.
2. What routes and depths do adult salmon use in Scottish coastal waters on their return to spawning rivers?
Both stakeholder groups specified that this research objective question was of high importance. As Malcolm et al identified, if spatial overlap and depth usage could be assessed within development areas of MORE then the potential interactions between OMRE developments and diadromous fish could be identified at a project development conception stage.
Depth use and spatial location
Current actions: MSS is deploying pop-up satellite transmitters on salmon captured on the N. Coast to record their depths, associated water temperatures and light levels during subsequent coastal migration. Tags are programmed to pop-off after a broad range of time delays to determine diving behaviour throughout homeward migrations, and to obtain some locational information.
Future actions: subject to the results of current actions, extend satellite tracking work to include a range of tagging locations; consider scoping deployment of an acoustic tracking system to record locations with time as salmon migrate around the Scottish coast.
3. Potential impacts of noise from installation and operation of OMRE generators on salmon
This research objective question aims to facilitate a greater understanding of the hearing characteristics of diadromous fish and the potential physiological and behavioural responses to OMRE construction and operational noise.
Current actions: MSS has worked with the University of Exeter to establish sound detection threshold curves in wild post-smolts, captive post-smolts and captive adults using the established auditory-evoked potential technique for comparison with existing data from behavioural methods. Models have been prepared of the acoustic outputs of operational offshore wind turbines mounted on jackets, monopiles and gravity bases, and their dispersion in the sea. These outputs will be compared with acoustic frequency-hearing threshold curves for salmon.
Future actions: to observe behavioural (avoidance, swimming behaviour) and physiological (ventilation rate, metabolic rate) responses of salmon to playback of pile driving noise in laboratory tanks. These observations will be validated by measuring physiological responses of fish caged at a range of distances from pile driving in the wild.
4. What are the likely effects of electromagnetic fields from generators and associated cabling on salmon?
There is little information on effects of alternating current electromagnetic fields on salmon. Salmon may be exposed to such fields, particularly near wave generators where cabling traverses the water column. The SNH review on the potential impacts of EMF on diadromous fish (Gill & Bartlett, 2010) published in the peer reviewed literature (Gill et al., 2012) has identified that diadromous fish would be able to detect electromagnetic fields however the potential biologically significant response on detection are not yet clear.
Current action: MSS has constructed a Helmholtz coil system in an annular tank to test effects of alternating current EMFs on behaviour of adult and post-smolt salmon.A series of experiments has been undertaken and will be reported in 2014 after detailed analysis.
Future actions: the need for further work will be subject to findings of current work and consideration of the relevance of the findings extending to other species.
5. How many fish might be struck or otherwise disabled by blades of sub-sea generators?
Malcolm et al identified that the risk of collision or strike which leads to mortality, either directly or indirectly, of diadromous fish is an important issue to be addressed.
Current actions: MSS is exploring the effects of fish size and swimming speed, and the size and rotation speed of simulated tidal turbines on the risk of collision.
Future actions: depending on the outcome of current work, there may be need for in situ observations of the responses of salmon to turbines. These might include active tracking of fish and observations using Didson or similar acoustic cameras.