Archived DNA reveals fisheries and climate induced collapse of a major fishery.

Sara Bonanomi,Peter Grønkjær,Anja Retzel,Anders Nielsen,Dorte Meldrup,Loïc Pellissier,Christophe Pampoulie,Einar Eg Nielsen,Nina Overgaard Therkildsen,Steffen Malskær Olsen,Mary Susanne Wisz,Jakob Hemmer-Hansen,Rasmus Berg Hedeholm

doi:10.1038/srep15395

Abstract

Fishing and climate change impact the demography of marine fishes, but it is generally ignored that many species are made up of genetically distinct locally adapted populations that may show idiosyncratic responses to environmental and anthropogenic pressures. Here, we track 80 years of Atlantic cod (Gadus morhua) population dynamics in West Greenland using DNA from archived otoliths in combination with fish population and niche based modeling. We document how the interacting effects of climate change and high fishing pressure lead to dramatic spatiotemporal changes in the proportions and abundance of different genetic populations, and eventually drove the cod fishery to a collapse in the early 1970s. Our results highlight the relevance of fisheries management at the level of genetic populations under future scenarios of climate change.

Highlights

Fishing and climate change impact the demography of marine fishes, but it is generally ignored that many species are made up of genetically distinct locally adapted populations that may show idiosyncratic responses to environmental and anthropogenic pressures
Global change impacts the abundance and distribution of biodiversity in the worlds oceans, which in turn affects the services provided by marine ecosystems[1,2]
We used a large archive of fish earstones to study the population dynamics of Atlantic cod (Gadus morhua) during the historical commercial fishery in West Greenland, which displayed a dramatic collapse similar to a number of other cod fisheries[16,17,18,19]

Summary

Methods

The mixed stock individuals were assigned with the predict.dapc() function that projects multilocus genotypes onto discriminant functions (i.e. synthetic variables that maximize differences between and minimize differences within a priori defined reference groups), thereby deriving posterior membership probabilities to each reference group (spawning population) for each individual In both approaches, the baseline genetic signature (allele frequencies) of each spawning population was defined based on individual samples collected at the spawning time for a previous study[24], further details are outlined in Supplementary Information. N, the total number of investigated fish Ni was categorized into four genetically distinguished spawning groups: West Greenland offshore (1), West Greenland inshore (2), Iceland offshore (3), and Iceland inshore (4) (Supplementary Figure S1) These observations are naturally described by a multinomial distribution with sample size Ni. To describe the development of the stock proportions over time it is assumed that the probability vector: pt = (p1, p2, p3, p4) follows an unobserved process.

Author Contributions

Findings

Additional Information