Fighting for fish

For the Trinity Term 2021 Alumni Newsletter, Katrina Davis writes about the Marine Conservation Ecology and Management group (, which uses ecological and economic models to assess the trends and dynamics of marine resource use and conservation. Recently, they have been investigating the prevalence and impacts of marine human–wildlife conflict.

As apex predators, marine mammals like sea lions and seals (e.g., pinnipeds) play important regulatory roles in marine systems. However, for much of human history, marine mammals have been exploited for meat, their pelts, or to stop them ‘stealing’ from fisheries or damaging fishing gear. This exploitation pushed many marine mammal populations to the edge of extinction during the 18th and 19th centuries. Thankfully, in the 20th century, protective legislation around the world has allowed many marine mammal populations to recover. Unfortunately, recovery has brought unexpected complications. Where marine mammal populations have increased, the spatial overlap of their foraging areas with fisheries has also increased, which means a renewal of conflict between marine mammal and fisheries worldwide.

One of the research questions my group at the Department of Zoology is assessing is the prevalence and impact of these conflict on global fisheries. We are conducting a meta-analysis, with an initial focus on pinnipeds, to estimates their impact on the amount of fish that fisheries catch, and damage to fishing gear. We are also evaluating whether the characteristics of fisheries or pinniped populations influence the extent of these effects. Relevant characteristics include gear type and taxon.

Beyond a broad understanding of the global impacts of conflicts between marine mammal and fisheries, our research also focuses on understanding the mechanisms causing these interactions. To do this, we develop detailed population and fisheries models that allow us to evaluate the dynamics of marine human–wildlife interactions. For example, marine mammal predation of fish and damage to fishing gear often affects fishers with the least secure incomes, such as small-scale coastal fisheries in lower or middle income countries like Peru and Chile in South America. My group uses unmanned-aerial vehicles (UAVs, e.g., drones) to collect population data for pinnipeds like the South American sea lion (Otaria flavescens) and South American fur seal (Arctocephalus australis) on the west coast of South America. We combine demographic and bioeconomic modelling approaches estimates the impact of conflict on fisheries catch, as well as pinniped population dynamics.

Our findings help us understand how pinniped populations will respond to management interventions, like targeted population culls, or to changes in environmental conditions—as are expected under future climate change. We also use discrete choice experiments to understand and predict fishers' response to human-wildlife conflict, or preferences for management actions. Our overall aim is to ensure the long-term future of marine mammals, and minimise negative impacts on human populations who depend on fishing.