UW Aquatic & Fishery Sciences Quantitative Seminar

Ray Hilborn

UW School of Aquatic & Fishery Sciences

Evaluating the role of fishing and environment in driving fish productivity



While it is generally now accepted that the productivity of fish stocks is driven by abundance (as influenced by fishing) and by environmental factors, the influence of environment has not been systematically incorporated into population dynamics, and has primarily been concerned with finding co-variates that explain year-to-year variation in recruitment. An alternative hypothesis is that productivity (recruitment, growth and natural mortality) comes in distinct temporal regimes.

This talk will describe work that Katyana Vert Pre and I have been doing to try to evaluate the extent to which surplus production can be explained by changes in stock biomass, as opposed to simply changing in regimes over time. We used the data from the North Sea, using AIC mutli-model weighting to evaluate the relative explanatory power of alternative hypotheses. None of the hypotheses explained the pattern of surplus production for two of the stocks. Of the remaining stocks, overall we found that the total amount of support was 20% for population abundance, 40% for temporal changes, and 40% for a mixed model.

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