Fitzpatrick KB, Weidel BC, Connerton MJ, Lantry J, Holden JP, Yuille M, Lantry B, LaPan S, Rudstam LG, Sullivan P, Brenden TO, Sethi SA. (2022) Balancing prey availability and predator consumption: a multispecies stock assessment for Lake Ontario. Canadian Journal of Fisheries and Aquatic Sciences 79:1529-1545.
Trophic interactions are drivers of ecosystem change and stability, yet are often excluded from fisheries assessment models. Incorporating predator-prey interactions directly into population models may improve estimates of species dynamics and predictions of future fishery sustainability. In Lake Ontario, popular recreational salmonine fisheries, including Chinook salmon (Oncorhynchus tshawytscha) and lake trout (Salvelinus namaycush), are dependent on a single prey species, alewife (Alosa pseudoharengus). To incorporate these tight predator-prey relationships into our assessment model, we built a multispecies population dynamics model that links, and simultaneously estimates, the dynamics of both predators and alewife. We found that prey availability has recently declined due to decreased alewife recruitment and a spike in Chinook salmon recruitment in 2016, leading to higher alewife mortality rates and lower predator growth rates. We then used the model to explore future predator-prey dynamics, specifically the impact of Chinook salmon stocking reductions on the potential for alewife population growth. Combined with other assessment tools, multispecies models can provide information on how trophic interactions and ecosystem dynamics may affect future fishery sustainability.