The importance of including predation in fish population models: Implications for biological reference points

A suite of applications utilizing various fisheries models have demonstrated that natural mortality due to predation is: (1) temporally and ontogenetically variable and (2) especially for forage species, generally higher than assumed in traditional single species stock assessments. Here we demonstrate that biological reference points generated by explicitly incorporating predation mortality into population dynamic models are generally more conservative (e.g., recommend higher standing biomass) than those produced using traditional assessment methods. Because biological reference points are the benchmark against which fisheries management decisions are made, they should reflect the ecological realities faced by each species to the fullest extent possible. We suggest much broader consideration of the more conservative biological reference points produced by explicitly incorporating predation mortality as a component of natural mortality to population models. This approach could implement a powerful yet tractable facet of ecosystem based fisheries management and is especially important for those stocks where predation mortality is known or suspected to be important.

Research highlights▶ Predation can be an important factor determining the dynamics of fish populations. ▶ Methods exist to estimate the magnitude of the effects of predation. ▶ Predation mortality should be appropriately incorporated into determination of stock status, via Biological Reference Points (BRPs), for many fish stocks, particularly forage species. ▶ Calculating BRPs without including predation in instances where it can be important can and has led to erroneous management advice.