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The Celtic Sea Trout Project

The Celtic Sea Trout Programme aims are:

  • To understand and describe sea trout stocks in the Irish Sea and thereby to enhance sea trout fisheries and strengthen their contributions to quality of life, to rural economies and to national biodiversity. 
  • To explore the use of sea trout life history variation as atool to detect and understand the effects of climate change. 

The sea trout is the sea migratory form of the brown trout and is a popular target of rod and net fisheries of rivers and coastal waters around the Irish Sea.  Adult sea trout lay their eggs in river gravels, the young stages live for 1 to 3 years in freshwater before emigrating (as smolts) to sea where they feed hard and return after  varying periods as mature adults, homing to the rivers of their birth to repeat the cycle. Thus the sea trout life cycle requires good environmental quality in freshwater, estuaries and at sea. Moreover, current understanding suggests that the incidence of sea trout and the composition and status of their stocks is sensitive to changes in the environments in which they live. These life history features and the sea trout’s widespread occurrence, makes it a unique and potentially sensitive indicator of environmental change. 
However, there are major unanswered questions in the understanding of sea trout, namely:

  • where do they go at sea and how are their stocks structured and interlinked?
  • what is their marine ecology (feeding, growth, survival and life history variation)?
  • what environmental and other pressures are they exposed to?
  • how do their life histories (and thus fishery quality) respond to environmental variation?

Sea trout fisheries in parts of Western Britain, including the Irish Sea, are suffering decline; but the pattern is mixed and in most cases the causes of change and thus the solutions are poorly understood. So we need answers to the question outlined above
The CSTP intends to provide this missing knowledge and to translate it into fishery and conservation benefits for countries bordering the Irish Sea. 
The programme content

In summary the programme involves collection of sea trout samples from 80 rivers (of which 20 have been targeted for detailed sampling), estuaries, coastal waters and further offshore, over three years. The samples will be mostly of fin clips and scales accompanied by accurate size information; but whole fish will also be taken to examine feeding and other aspects of biology. The samples will be processed to describe stock structures and distributions (using micro-chemistry and genetics), life histories, growth and survival (from scale analysis) and feeding. From these data and reviews of the fisheries and freshwater trout production a picture will be assembled of the quality and quantity of sea trout stocks and fisheries around the Irish Sea. Various modelling approaches will be used to pull this information together to show the interactions between stocks, fisheries and the environment at sea and in freshwater, and thus to help to explore management options.

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