Abstract
Worldwide fisheries supply 16% of the total human consumption of animal protein and employ over 35 million people. But with 47% of fish stocks fully exploited and 28% overexploited or depleted, the need for sustainable fisheries is widely acknowledged. Recent work questions the sustainability of currently adopted management plans based on the concept of ‘maximum sustainable yield’ because it ignores two basic features of the exploited populations: (1) harvesting-induced, rapid evolutionary change; and (2) population feedback on realized life history. In particular, the simultaneous action of both features conceivably increases the vulnerability of exploited fish stocks to catastrophic collapses, given the likelihood of alternative stable states in size-structured communities. This means that a theory of life history evolution in an ecological setting with population feedback is indispensable for determining sustainable harvesting strategies. Such a theory is currently lacking, as existing theory of life history evolution, and of the effect of harvesting in particular, do not explicitly account for the ecological role of individual life history. The proposed research aims at filling this gap by starting from recently developed ecological theory on the community consequences of size-dependent life histories and extending it to account for evolution. I will develop models of a tri-trophic food chain, using structured population models that explicitly account for individual life history and its influence on the ecology of individual organisms. These ecologically mechanistic models will be studied within the framework of adaptive dynamics, which allows for studying evolutionary processes under influence of population feedback. I will study the implications of harvesting-induced life history evolution for sustainable exploitation of fish populations, addressing the following questions: 1. Does harvesting-induced evolution of exploited fish stocks increase or decrease their vulnerability to catastrophic collapses? 2. Is it possible, by manipulating directional selection, to induce evolution towards ‘catastrophic recovery’?
Netherlands