Stuart J. Middlemas

Accuracy of Assignment of Atlantic Salmon (Salmo salar L.) to Rivers and Regions in Scotland and Northeast England Based on Single Nucleotide Polymorphism (SNP) Markers.

Understanding the habitat use patterns of migratory fish, such as Atlantic salmon (Salmo salar L.), and the natural and anthropogenic impacts on them, is aided by the ability to identify individuals to their stock of origin. Presented here are the results of an analysis of informative single nucleotide polymorphic (SNP) markers for detecting genetic structuring in Atlantic salmon in Scotland and NE England and their ability to allow accurate genetic stock identification. 3,787 fish from 147 sites covering 27 rivers were screened at 5,568 SNP markers. In order to identify a cost-effective subset of SNPs, they were ranked according to their ability to differentiate between fish from different rivers. A panel of 288 SNPs was used to examine both individual assignments and mixed stock fisheries and eighteen assignment units were defined. The results improved greatly on previously available methods and, for the first time, fish caught in the marine environment can be confidently assigned to geographically coherent units within Scotland and NE England, including individual rivers. As such, this SNP panel has the potential to aid understanding of the various influences acting upon Atlantic salmon on their marine migrations, be they natural environmental variations and/or anthropogenic impacts, such as mixed stock fisheries and interactions with marine power generation installations.

What should I eat? Experimental evidence for prey selection in grey seals

Understanding the responses of predators, such as seals, to variations in prey availability is key to understanding their role in marine ecosystems. Individual variation in prey preference is likely to be important but we have little information on this aspect of predator behaviour. Operant conditioning techniques and an underwater feeding apparatus were used to test the prey species and size preferences of five captive grey seals, Halichoerus grypus, in a series of paired choice trials. The experimental procedure was designed to present simple foraging choices to remove as many potentially confounding variables as possible. Results suggest that individual grey seals exhibit prey preferences. When presented with different numbers of items of the same species, seals generally selected the larger number of prey items. When presented with choices between two species, seals apparently showed consistent preferences for particular species. However, the apparent species preferences may be simply explained in terms of size selection.

Identification of the farm of origin of Atlantic salmon smolt escapees in a freshwater Scottish loch using single-nucleotide polymorphic markers

Identification of the farm of origin of Atlantic salmon smolt escapees in a freshwater Scottish loch using single-nucleotide polymorphic markers John Gilbey*, Eef Cauwelier, James Sampayo, Iveta Matejusova, Charles Allan, Jennifer Graham, Lee Stradmeyer, and Stuart Middlemas Marine Scotland Science, Freshwater Fisheries Laboratory, Faskally, Pitlochry, Scotland PH16 5LB, UK Marine Scotland Science, Marine Laboratory, Victoria Road, Aberdeen, Scotland AB11 9DB, UK *Corresponding author: tel: þ44 (0)131 244 2408; e-mail: john.gilbey@gov.scot