The Outcomes of Integrating Biological Interactions into Rebuilding Plans Depend on Prey Specialization
Ecosystem dynamics can lead to trade-offs between reaching harvest targets and protecting vulnerable species across fisheries management decisions. However, in the context of population rebuilding plans, considering predator-prey interactions might provide opportunities to minimize or reverse these trade-offs if harvest on predators can boost both fishery yields as well as prey recovery. To understand whether and under what conditions such opportunities might arise, we explore the effect of predator harvest on the rebuilding outcomes of a recovering prey that experiences bycatch mortality. We developed an age-structured model with predation and harvest to evaluate changes in the population dynamics of prey at steady state and in their rebuilding time under increasing harvest of predators. We parameterized our models based on yelloweye rockfish (Sebastes ruberrimus), a U.S. West Coast Groundfish stock under a rebuilding plan, and one of their known predators, lingcod (Ophiodon elongatus). We found that lingcod harvest reduced the long-term spawning biomass and increased rebuilding time of yelloweye rockfish regardless of their diet specialization; these negative effects were due to yelloweye bycatch in the lingcod fishery. However, predator diet specialization can influence the degree of effect from predator harvest during prey rebuilding, where the steady state dynamics of yelloweye rockfish were less affected by increasing lingcod harvest and rebuilding time was shorter when lingcod acted as a specialist compared to a generalist predator. As efforts to leverage ecosystem attributes in fisheries management are applied to rebuilding plans, we highlight the role that the nature and strength of biological interactions can play in shaping outcomes of recovery.