Characteristics of genetic factors that influence gender in Atlantic salmon

Abstract

Very little is currently known about how gender is established in Atlantic salmon, and environmental and commercial matters have increased interest in the life history strategies of this ancient fish. It is necessary to assess the sex ratios in populations of Atlantic salmon both before they head out to oceanic feeding grounds and when they return to spawn, before we can begin to understand the mechanisms that govern gender in this species. Much of the challenge faced by those studying gender in the Atlantic salmon lies in the problem of sexing juvenile salmon. It is currently not possible to sex Atlantic salmon without the need to sacrifice the individual. The principle aim of this project was to establish such a method. To this end, several approaches were taken to attempt to develop a non-destructive method of sexing juvenile salmon. The first comprises a PCR-based test to assess whether the Sox9a gene, known to be involved in vertebrate sex determination, is gender-specific in Atlantic salmon. The second strand of work involved the use of genetic markers identified as gender-specific in Pacific salmon to reveal whether any of these sequences segregated with gender in Atlantic salmon. In the final part of the study, a suppressive subtractive hybridisation technique was used to compare male and female Atlantic salmon cDNA, and isolate sequences unique to each. Results from the Sox9a study showed that the Sox9a gene is present in both males and females, and therefore not gender-specific in Atlantic salmon. One of the sequences identified from Pacific salmon showed female-specificity in one of the three strains of Atlantic salmon tested. The suppressive subtractive hybridisation technique successfully yielded two populations of differential sequences from male and female cDNA. The work done in this study thus partially achieved the aim of establishing a non-destructive gender test and lays the foundations of further work exploring gender in Atlantic salmon.

Date of Award	Oct 2011
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	Colin Peter Waring (Supervisor) & James McLellan (Supervisor)