Interim Report of the Working Group on Fisheries -induced Evolution (WGEVO). 18- 20 October 2016, Laxenburg, Austria
|Ref.||ICES CM 2016/SSGEPD:15|
|Sponsor||ICES - International Council for the Exploration of the Sea|
The Working Group on Fisheries-induced Evolution (WGEVO) met twice in 2016: once remotely from 27 to 29 September 2016 and once in person at IIASA, Laxenburg, Austria from 18 to 20 October 2016.
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, 2 individual-based eco-genetic models were developped for reconstructing the historical effect of fishing on the evolution of life-history traits describing growth, maturation and reproduction during the 20th century in 2 major exploited stocks, namely northeast Arctic cod (Eikeset et al. 2016) and North Sea plaice (Mollet et al. 2016a)
WGEVO applied Evolutionary Impact Assessment, a general framework developed during the previous 3-year term of the group for assessing the management implications of fisheries-induced evolution on stocks’ utilities in terms of ecosystem services, on North Sea plaice (Mollet et al. 2016b).
Finally, 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 31 stocks. 13 new stocks were analyzed this year, bringing the grand total to 44, and the calibration of the estimation algorithm is in progress for 13 additonal stocks. Although resuts can still be considered preliminary, 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 three maturation traits.
(iii) Fisheries-induced selection pressures rise superlinearly with fishing intensities.
(iv) Fisheries-induced selection pressures show high sensitivity to a fishery’s size selectivity. For all considered 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.
A manuscript is being drafted to disseminate the results of this analysis as a peer-reviewed publication.