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The influence of harvesting on maturation in female yellow perch

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Title: The influence of harvesting on maturation in female yellow perch
Author: Gislason, David
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: McLaughlin, RobertRobinson, Beren
Abstract: In wild fish populations, harvesting can reduce abundance, alter the distribution of phenotypes and drive changes in life history traits. Changes in maturation that influence adult fecundity are of concern when they reduce the productivity, yield and resilience of a population. Two hypotheses can account for earlier maturation of fish populations in response to harvest: individual compensatory growth responses to relaxed density-dependence and fisheries induced evolution (FIE). Plastic compensatory responses have received less attention in freshwater fish, while most prominent examples of FIE are for marine species. Independent of harvest, maturation may also respond to energy availability and mortality risk, and these may vary more in smaller freshwater compared to larger marine systems. I used 22 years of fisheries independent survey data from Lake Erie to assess the role of harvest on female age and length at maturation in yellow perch (Perca flavescens), walleye (Sander vitreus), white bass (Morone chrysops) and white perch (Morone americana). I asked whether, (i) changes in maturation were likely plastic; (ii) maturation schedule has evolved; and (iii) changes in maturation were more likely related to harvest or to other ecosystem factors. I tested a novel compensatory growth and life history model and found that adult yellow perch abundance was negatively related to harvest, but this had no effect on juvenile growth or on maturation. Nevertheless, the dynamic behaviour of maturation among cohorts strongly suggests plastic life history responses. I compared probabilistic maturation reaction norms for cohorts in the mid-1990s and late 2000s and found little evidence of evolutionary change in yellow perch maturation after accounting for plasticity in life history. Lastly, I evaluated the importance of harvest relative to the effects of large ecosystem scale factors on maturation dynamics for four fish species in Lake Erie. Analyses of compensatory growth and life history revealed no support for an influence of harvest on maturation within or among species. Instead, I found strong evidence of synchronous changes in maturity across species. My findings suggest that the maturation of Lake Erie’s fishes is not strongly influenced by recent harvest, but is instead responding to changes in ecosystem conditions.
Date: 2017-05
Rights: Attribution-NoDerivs 2.5 Canada
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Attribution-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NoDerivs 2.5 Canada