The genomics of spawning seasonality and seascape in commercially harvested herring (Clupea harengus) in the Northwest Atlantic

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Our objective is to identify the geographic and temporal (seasonal) genetic structure in herring (Clupea harengus) in the NW Atlantic. Herring, a widely distributed marine pelagic fish of economic importance exhibits a high degree of biocomplexity, i.e., a complex pattern of diversity associated with differences in spawning time and location, and life history. Some populations reproduce in the spring and others in the fall and their relative abundance has changed in recent years likely in response to latitudinal shifts in ocean temperature. Fishery management in general does not consider such a degree of biocomplexity, yet disregard for how diversity is distributed within management units is likely to lead to overexploitation of the weaker population components, ultimately leading to the loss of biodiversity. Our goal is to understand how such diversity is distributed in space and time. Most previous studies found little evidence of genetic structure in herring at all but the largest geographic scales. Renewed attempts to understand population structure in this species are justified because of the following three recent developments, which make this project unique: First the herring genome has recently been completely sequenced and annotated. Second, we recently found not only genomic differences between fall and spring spawning herring but also found the same differences occurring in Canadian and European herring populations, with some differences located near genes linked to photoperiodic regulation of reproduction. We thus identified the genomic regions likely underlying spawning seasonality, with autumn spawners differing from spring spawners in allele frequencies at a number of single nucleotide polymorphic sites (SNPs) some of which are linked to genes of known function. This is evidence of local adaptation. These achievements were possible because of the recent explosive development of Next Generation Sequencing technology. We plan to take advantage of these major breakthroughs to examine the geographic and seasonal structure of herring in the NW Atlantic. The proposed work is of interest to Fisheries and Oceans Canada (DFO), the collaborating institution responsible for the management of the herring fishery in Canada.