WARM AND WANTED: EFFECTS OF CLIMATE CHANGE AND FISHERIES ON FISH GROWTH

Warming temperatures are hypothesized to accelerate the somatic growth of individual fish to smaller adult body sizes. Fisheries extract large fish from populations because of their high market value, and cause populations to adapt maturation to earlier ages and smaller fish sizes. This PhD research will test the response of the growth of Common sole (Solea solea) populations to these climate and fishing pressures. In a first step, biochronology of otoliths will be used to analyse the effects of extrinsic drivers like climate and fishing on changes in fish growth. Otoliths are ear bone structure holding growth information similar to tree rings used in dendrochronology. While extrinsic drivers stimulate changes in fish growth, it is the energy allocation within an individual fish that regulates whether a fish will grow or invest in reproduction. A biphasic growth model will estimate these intrinsic drivers to elucidate how warming temperatures change fish growth. In a third step, the PhD research will combine the individual-based biphasic growth model with information on fishing mortality at the population level. The effect of fishing and climate change on population biomass, its size structure and population growth will be hindcasted and simulated for various populations of sole in the North East Atlantic Ocean. As such, this PhD study will contribute to our understanding of how climate change and fishing pressure change the dynamics of fish populations.