Scientific update
Fisheries-induced evolution of metamorphosis
Introduction
Fishing is often size-selective, especially when larger individuals of a population are targeted. Because of this selective removal, fishing will alter the genetic composition of the exploited population. Many fish species that are of commercial interest undergo metamorphosis, changing diet and habitat during their life. Metamorphosis decouples traits between life stages, allowing these traits to evolve independently from each other [1]. At the same time, metamorphosis is costly. The aim of this project is to understand the balance of these benefits and costs, to discern the ecological conditions favoring the evolution of metamorphosis, and thereby, to predict how size-selective fishing affects the evolution of metamorphosis.
Methods
We extend the consumer-resource model by [2]. All individuals have access to a shared resource, while large individuals also have access to an alternative resource. It is assumed that the two resources require different morphologies to be effectively utilized. On this basis, we use the framework of adaptive dynamics to investigate when metamorphosis can evolve.
Results
Metamorphosis can evolve when the alternative resource is in high supply. A population that has evolved metamorphosis will keep metamorphosing even when the alternative resource becomes scarce, resulting in an evolutionary hysteresis. When a population of fish with metamorphosis is being harvested, it will adapt by decreasing the extent of their metamorphosis and start their metamorphosis later in life. When the alternative resource is in high supply, this evolutionary response does not strongly affect yield or the maximum harvesting rate the population can tolerate before collapsing. However, when the alternative resource is scarce, the evolutionary response makes the population more robust against high exploitation levels, sustaining high yields even in populations that would have collapsed from overexploitation in the absence of evolution.
Conclusions
Size-selective harvesting of fish populations will lead to an evolutionary change in the extent and timing of metamorphosis. In particular, the morphology of individuals after metamorphosis becomes more similar to the morphology before metamorphosis. Furthermore, a smaller fraction of the population will undergo metamorphosis. This fisheries-induced evolutionary response can allow for a higher exploitation level of the harvested population.
References
[1] Moran NA (1994). Adaptation and constraint in the complex life cycles of animals. Annual Review of Ecology and Systematics 25: 573-600
[2] Persson L, Leonardsson K, de Roos AM, Gyllenberg M & Christensen B (1998). Ontogenetic scaling of foraging rates and the dynamics of a size-structured consumer-resource model. Theoretical Population Biology 54: 270-293
Supervisor
Ulf Dieckmann, Evolution and Ecology Program, IIASA
Note
Hanna ten Brink, of the University of Amsterdam, the Netherlands, is a citizen of the Netherlands. She was funded by the IIASA Dutch National Member Organization and worked in the Evolution and Ecology Program during the YSSP.
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.
Further information