North Norfolk Sea Trout Project
The rivers Stiffkey & Glaven in North Norfolk have abundant, though patchy distributions of brown trout. Sea trout have been caught in both rivers, but their contribution to river and offshore fisheries is unknown. The objectives of this project are to:
- quantify the origin, distribution and migration characteristics of sea trout within North Norfolk rivers and associated coastal waters
- determine the contribution of sea trout from small streams to the wider stocks
- provide key information on fish movements including: a) temporal patterns of sea trout runs, b) migration rate, c) delay caused by water control structures, and d) habitat use during freshwater and estuarine phases.
There are three elements to the project.
A combination of PIT and acoustic telemetry is being used to generate time-stamped positions of individual fish as they move through the study area, enabling individual movements to be mapped. Telemetry at structures such as flow gauging weirs and tide gates will indicate if fish are delayed, and the physical and environmental conditions delays occur under. Expansion of the acoustic telemetry array into estuaries and surrounding coastal waters will make it possible to study sea trout movements in these waters and to identify feeding areas.
Genetic analysis undertaken as part of the Living North Seas project has shown that the North Norfolk stocks have a distinct genetic signature. The project will build on this work to establish whether the trout in these streams constitute a genetically distinct population, and, if they do, the extent to which they are taken in the Anglian Drift Net Fishery. This fishery targets sea trout, most of which originate in North Eastern English and South Eastern Scottish rivers, but a recent review of the fishery identified a need for a greater understanding of the origins of the fish taken.
The final element of the project will make use of stable isotope analysis to determine the maternal parentage of trout fry in the rivers Stiffkey and Glaven, and so establish the relative importance of the anadromous and non-anadromous elements in the population
Overall, the study will enhance our knowledge not only of the genetic distinctiveness of the trout in these rivers, but also contribute to our understanding of the significance of small streams for sea trout production, and the factors influencing the life histories and movements of resident (brown) and sea going trout. It will also provide managers and regulators with information that will improve the management of both trout stocks in rivers and coastal sea trout fisheries.
The AST is covering the costs of genetic and stable isotope analyses
As yet, there are no results from this project. Samples were collected in 2015, but the number fell below the threshold needed to provide statistically significant results, so analysis was delayed until further samples could be collected.
Partners: Environment Agency, Zoological Society of London, Wild Trout Trust, Norfolk Rivers Trust, Buxton Conservation Trust, University College London and Atlantic Salmon Trust
AST Funding : £5,000 a year in 2015 and 2016