SHAD GENETICS – EGG SAMPLING AND POPULATION STRUCTURE (2015)

Client: Natural England

The primary objective of this project, commissioned by Natural England during 2015, was to establish a baseline of spawning activity of twaite shad (Alosa fallax) on the River Teme; focussing on the reach between Powick Weir and the River Severn confluence. A secondary objective of the study was to quantify the spawning activity of sea lamprey (Petromyzon marinus) within the same reach.

Monitoring temporal and spatial recruitment trends of Alosa spp. using traditional sampling methods is difficult, due to their complex life history and the relatively limited time period during which larvae remain at natal sites. Accordingly, sampling of egg abundance and distribution has been demonstrated in this project to provide a cost-effective method to gather semi-quantitative data on spawning activity, distribution and habitat utilisation.

Genetic markers were used to A) validate whether collected eggs belonged to Alosa spp. and B) determine the relative proportion of A. fallax and A. alosa eggs. Analysis confirmed that the stock at the time of the survey was dominated by A. fallax, with a high frequency of hybridisation with A. alosa.

Results indicated that BUG field staff were more than 99 % accurate in their identification of shad eggs in the field. This confirms that, where budgets are constrained, cost-effective surveys to qualify and quantify shad spawning activity is achievable with a high degree of confidence.

“BUG has been one of the best consultancies I have worked with…Our project was completed to time, with excellent communication and the report was very clear and concise” (Natural England)

Sites

Samples collected

Shad eggs analysed

Satisfied client

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