Celtic Sea Trout Project Follow-on Projects

The Celtic Sea Trout Project (CSTP) was a large EU funded international collaborative project looking into the status, distribution, genetics and ecology of sea trout around the Irish Sea. The main aims were to understand and describe sea trout stocks in the Irish Sea in order to enhance sea trout fisheries and strengthen their contributions to quality of life, to rural economies and to natural biodiversity, and to explore the use of sea trout life history variation as a tool to detect and understand the effects of climate change.

The CSTP produced a large data set on sea trout stocks and population characteristics that is unique in its spatial scale, covering 99 rivers draining into the Celtic and Irish Seas. It collected data from a very large number of sea trout (over 20,000 individuals), as well as a wide range of physical samples.

The Atlantic Salmon Trust funded two follow-on projects intended to make use of this material. These very different projects are good examples of the way the Trust is able to exploit opportunities of this sort, at relatively little cost, to add value to existing projects.

Population Dynamics Analysis of Sea Trout Populations around the Celtic and Irish Sea

The first of these projects made use of this data to develop life cycle models on 25 rivers intended to help judge the status of river-specific stocks and in essence to see how individual sea trout populations are doing from year to year. The approach used stage-based matrix projection modelling (thus, freshwater, maiden adults, spawners of different sea age etc), incorporating survivorship and fertility to derive key population variables such as growth rates, net reproductive rates (total eggs that females produce during their lifetime). These are indices of population fitness and determine features such as resilience and stability.  The models also help estimate how changes in key variables, such as fishing regulations and climate, are likely to alter a range of traits. The models illustrate the variability of sea trout/trout life cycle patterns, and contribute to the understanding of sea trout life cycles and stock dynamics. Overall, the project is an innovative useful exploration of the potential application of life cycle models to describe sea trout population which are otherwise notoriously difficult to characterise due to their complex life cycles, as well as of the limitations of this approach.  As with all models, these are critically dependent on the quality of the underlying data and of the ways that these are interpreted. The results have since been presented at the Fisheries Society of the British Isles Annual Conference, Bangor, July 2016 and the work has led to related collaborative studies with  French research groups.

Partners: Bangor University and the Atlantic Salmon Trust

AST Funding: £8,000 in 2014

 

Lipid concentrations as a measure of condition of Sea Trout in the Irish Sea

The second project explored a possible technique for assessing the condition of sea trout at sea. This pilot project used tissue samples collected from sea trout at sea as part of the Celtic Sea Trout project to assess whether lipid concentrations could provide a useful measure of condition. Lipids (fatty acids) provide high energy levels and are more prevalent in marine prey species, and hence marine fish and anadromous fish feeding at sea. Sea trout thus have higher lipid levels than resident trout, and the project aimed to test the thesis that thresholds of lipid status in sea trout in the sea may be a necessary precursor for maturation in any year and lipid status may be a useful index of condition for return migration. The results showed considerable variations in lipid levels between individual fish, and did not establish clear relationships between lipid levels, feeding areas, and maturation. However, it did provide useful guidance on how best to sample and test for lipid levels with suggestions for further work in this complex area.

Partners: Bangor University and the Atlantic Salmon Trust

AST Funding: £10,000 in 2014

LINKS:

Celtic Sea Trout Project