The effects of fishing on stability of a food web under climate warming

Abstract: Predicting the effects of fishing in a warmer environment caused by climate change requires knowledge of what trophic level is fished on, the physiological effects of temperature on fish, and how these two affect ecological interactions. Both temperature and fishing are known to affect the stability of food webs in several ways. Still, we know little of the effects on stability when fishing on different trophic levels in a warmer environment. Using a stage-structured biomass model, I analyse how fishing on adult consumers and/or predators in a warmer environment affects the stability of the community. I find that predators go extinct at a lower fishing pressure in a warmer environment while fishing on adult consumers in a warmer environment instead stabilises the community by reducing cyclic dynamics. Combined fishing on both adult consumers and predators can reduce the risk of predator extinction and negate for the negative effects of high temperature on the stability of the food web. I also find that fishing at the level corresponding to the maximum sustainable yield (MSY) of predators is unsustainable, since if the fishing pressure is raised slightly from the MSY the predator goes extinct, especially in a warmer environment. My results indicate that restricting the fishing pressure in warmer environments or fishing on the adult consumer simultaneously to avoid predator extinction might be recommended. In general, it is important to be aware of the complexity of ecological systems when managing fisheries, as climate change can result in unintuitive and unexpected results depending on what trophic level is fished.