Interim Report of the Working Group on Fisheries-induced Evolution (WGEVO). 12-14 June 2017, Laxenburg, Austria
|Ref.||ICES CM 2017/SSGEPD:15|
|Sponsor||ICES - International Council for the Exploration of the Sea|
The Working Group on Fisheries-induced Evolution (WGEVO) met thrice in 2017: twice remotely from 20 to 21 March 2017 and from 5 to 6 April 2017 and once in person at IIASA, Laxenburg, Austria from 12 to 14 June 2017.
WGEVO pursued its effort to assemble evidence of fisheries-induced evolution and its consequences for the conservation of biodiversity and sustainable exploitation of marine species. Specifically, it was demonstrated experimentally on a freshwater model species that hypoxia or reduced ambient oxygen can lead to plastic effects on growth, maturation and reproduction in a direction similar to that of genetic changes induced by size-selective fishing, thus acting as a potential confounding factor of fisheries-induced evolution (Diaz Pauli et al. 2017). A field study on gonad weight recorded since the late 70s in three populations of cod off Newfoundland supports the hypothesis that fisheries-induced evolution has occurred in gonadal investment in males, but not in females, and suggest that gonadal investment is more important for male reproductive success than expected in this lekking species (Baulier et al. 2017).
WGEVO continued the estimation of fisheries-induced Darwinian selection pressures exerted on exploited stocks’ life-history traits (somatic growth, maturation traits and reproductive effort). During the previous 3-year term, the group developed a general framework for assessing these fisheries-induced selection pressures and applied it to 44 stocks until last year. 13 new stocks were analyzed this year, bringing the grand total to 57. The estimation is still in progress for a few additonal stocks but WGEVO will complete the estimation part of the projet by the end of the year. The main findings of this large scale analysis of fisheries-induced selection pressures on life-histoy traits are that:
(i) Typically, fishing induces selection pressures towards earlier maturation at smaller size, reduced growth, and increased reproductive effort.
(ii) Across stocks, fisheries-induced selection pressures align along two nearly independent axes: a growth axis describing negatively covarying pressures on somatic and gonadic growth, and a maturation axis describing pressures on maturation.
(iii) Fisheries-induced selection pressures rise with fishing intensities for the main traits i.e. maturation propensity, growth and reproductive investment.
(iv) Fisheries-induced selection pressures show high sensitivity to a fishery’s size selectivity. For the main traits and across all examined life histories, selection pressures tend to be highest when the length at which fish become exposed to significant fishing is 1-2 times larger than their maturation length. Conversely, selection pressures tend to be more benign in fisheries with a peaked (permissive slot), rather than a sigmoidal size-selectivity pattern.
(v) Slow growing, long-lived species maturating late and large and having costly repoduction are more prone to fisheries-induced selection.
Statistical analyses to confirm these trends are in progress and a manuscript is being drafted to disseminate the results of this analysis as a peer-reviewed publication.