Functional genetic diversity in an exploited marine species and its relevance to fisheries management

The timing of reproduction influences key evolutionary and ecological processes in wild populations. Variation in reproductive timing may be an especially important evolutionary driver in the marine environment, where the high mobility of many species and few physical barriers to migration provide limited opportunities for spatial divergence to arise, and where many species synchronize their reproduction to seasonal cycles of planktonic productivity. Using genomic data collected from spawning aggregations of Pacific herring (Clupea pallasii) across 1,600 km of coastline, we show that reproductive timing drives population structure in these pelagic fish. Within a specific spawning season we observed isolation by distance, indicating that gene flow is limited over our study area. These results emphasize the importance of considering both seasonal and spatial variation in reproductive timing when delineating management units for Pacific herring. On several chromosomes we detected linkage d...