| Summary: | The identification of stocks and quantifying their relative contribution to recruitment are major objectives toward improving the management and conservation of marine exploited species. Next-generation sequencing allows to analyze thousands of genomic markers which provide the resolution needed to address these questions in marine species with weakly differentiated populations. Greenland Halibut (Reinhardtius hippoglossoides) is one the most important exploited demersal species throughout the North Atlantic, and in particular in the Gulf of St. Lawrence, Canada. There, two nurseries are known, the St. Lawrence Estuary and the northern Anticosti Island, but their contribution to the renewal of stocks remains unknown. The goals of this study were i) to document the genetic structure and ii) to estimate the contribution of the different identified breeding stocks to nurseries. We sampled 100 juveniles per nursery and 50 adults from seven sites ranging from Saguenay fjord to offshore Newfoundland, with some sites sampled over two consecutive years in order to evaluate the temporal stability of the contribution. Our results show that after removing of sex-linked markers, the Estuary/Gulf of St. Lawrence represent a stock which is genetically distinct from the Atlantic around Newfoundland (Fst = 0.00146, p-value = 0.001). Population assignment showed that recruitment in both nurseries is largely predominantly associated with the St. Lawrence stock. However, we found that the relative contribution of both stocks to the nurseries is temporally variable with 1% contribution of the Newfoundland stock one year but up to 33% for the second year, which may hypothetically be caused by year-to-year variation in larval transport into the Gulf of St. Lawrence. This study serves as a model for the identification of stocks for fisheries resources in a context where few barriers to dispersal occurs, in addition to demonstrating the importance of considering sex-linked markers and temporal replicates in studies of population ...
|
|---|