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Appendix 3: Research Priorities
Management of fisheries for Atlantic salmon and brown trout in Scotland is underpinned by a strong base of scientific understanding. However, there are significant deficiencies in our knowledge that need to be addressed. In comparison, research into the biology of grayling and non-salmonid fishes in Scotland, notably cyprinids, pike and eels, is less well advanced, and in these cases the research needs are very substantial in almost all areas. A main priority is for the development of tools for assessing numbers and distribution of species in relation to habitat, particularly pike and eels. The generally-agreed research priorities for salmon and brown trout are outlined below.
For salmon and trout in the freshwater environment, there is a need to quantify the numbers of fish of different sizes and age classes that can be supported in various types of local habitat, the factors that limit this production, and the influence of potential mortality agents on dynamics of the populations. There is particular interest in establishing how growth and survival of salmon and trout is affected by the presence of predators, non-native species, notably signal crayfish, other fish species, escaped farmed fish of the same species, and disease agents. Research is needed into methods for minimising the spread and impact of diseases and parasites in wild fish populations.
There is also keen interest in establishing the influence on fish at all life stages of land use, thermal regime, water quality, climate change and water flow, especially as influenced by abstraction and generation of electricity. In this regard, there is particular requirement for research into practical tools for de-compaction of substratum, sediment transport processes, re-instatement of natural substratum throughout the river course, and for transfer of fish past dams and associated lochs. Particular concerns associated with land use and atmospheric deposition are the effects of agri-chemicals (including fertilisers and pesticides) and changes in those factors that limit production of fish and the direction of such change, for example nitrification, acidification and stripping of phosphorus from upland catchments through man's activities. Studies of the behaviour of fish are important in many contexts, including assessment of the impacts of potential obstructions to migration, understanding how habitat is used across a range of spatial scales, and investigation of the coastal phase of migration, which is perceived to be a time when the fish are particularly vulnerable to predation.
Research is required into the interactions between the different forms of leisure activities that utilise water bodies. In particular, there is a need to investigate concerns that rafting and canoeing reduce angling efficiency and influence the use of refuge areas and spawning of fish, particularly in wider rivers. Furthermore, there is concern over the influence of motorised craft on the general ecology of lochs, including populations of fish.
There is requirement for research into mortality and growth of salmon at sea. There is particular concern regarding the effects of aquaculture on populations of wild fish, through proliferating sea lice and disease and through the influence of escaped farmed fish distorting the gene frequencies of the wild stocks by in-breeding. There is also concern about the possible effects of seals and piscivorous birds and of reduced food supplies on the high seas. Further research is required in each of these areas.
Management of salmon and trout and recommendation of exploitation levels is supported by continuous stock assessment. Research is required to develop and improve such assessments and to explore opportunities for applying genetic tools to differentiate stocks into population components to enhance management and conservation. Further work is also required to determine the impacts of angling and netting on populations of fish. For all species of fish, there is a need for improved methods for assessing populations in wide rivers and standing waters.
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