Understanding the impacts of climate change on population connectivity
Species can cope with changing climates by colonizing new territories, but their ability to do so depends upon their dispersal capabilities. For marine species in particular, patterns of dispersal remain poorly understood, including how these patterns change through time to allow or constrain climate-driven shifts in species distributions. DNA from natural populations can provide insight into dispersal patterns and, when combined with historical collections, changes in dispersal over time. Especially for economically important species, it is crucial to understand the role of shifting climate on population sizes and distributions, and incorporate these new knowledges into current management strategies.
Summer flounder (Paralichthys dentatus) remains an economically important and popular species for commercial and recreational fishermen along the United States’ eastern shore. Overfishing resulted in a steep population decline in the late 1980s to early 1990s, marked fishing restrictions, and conservation measures to improve stock abundance. Today, the summer flounder stock has been successfully rebuilt, but is managed as a single population with state allocations based off of the population distribution in the 1980s. With genetic material from long-term collections of larval summer flounder and recently caught adult specimens along the U.S. East Coast, we are using double digest RAD sequencing to map genotypes across time and space, enabling an understanding of summer flounder population substructure and movement over the past 26 years.
With summer flounder population structure and dispersal unresolved, best management of the stock is a contentious issue. Being able to distinguish between putative subpopulations and illuminate dispersal patterns is a first step towards a more sustainable fisheries management plan for summer flounder. DNA from 428 larval summer flounder and 306 adults from sites throughout its species range were extracted, processed and analyzed to determine the degree of larval connectivity and historical movement of genotypes as sea surface temperatures have warmed over the past 26 years. As part of a larger collaborative project, the connectivity matrix from our genetic analysis is being replicated using otoliths from the same individual larvae. Both connectivity matrices will be used to develop population and economic models that will benefit fisheries managers, summer flounder and the fishermen who depend upon them.