Managing Arctic predator harvest instability amplified by variable prey productivity and ocean temperature

Living marine resources are often managed for single target species under precautionary harvest policies to achieve socioeconomic and conservation objectives through a tradeoff between short-term yield stability and long-term sustainable harvest. However, not accounting for imperfect knowledge of how dynamic ecosystem processes modulate variability in fished populations (ecological uncertainty) may underestimate risks of missing management targets. We present an illustrative case study to test how constraining short-term fluctuation in catch quotas perturbs stock and yield stability of an apex predator, Northeast Arctic (NEA) cod (), when its primary food resource, capelin (), and climate vary over time. We use a stochastic multispecies model (STOCOBAR– ) to simulate the cod stock dynamics through life history processes under variable ocean temperatures. Capelin productivity influences cod biomass directly through consumption and indirectly through cannibalism by adult cod. We evaluate harvest strategy scenarios of varying levels (5% to 50%) of yield stability constraints under the current precautionary harvest control rule (target exploitation rate, , of 0.40 and threshold spawning stock biomass, , of 460 thousand tonnes). Analyses show that performance of constraining catch fluctuation is highly sensitive to how cod and capelin interact. When the constraints are tightened to 25 % or less, the stock abundance and catch are projected to rise while the year-to-year variation is amplified through variable cod cannibalism–capelin productivity. Our work reveals that muffling variance in catch forces cod to respond to capelin fluctuation faster, becoming increasingly unsynchronized with harvest intensity and, thus, increasing recruitment variability and facilitating stock depletion (higher probabilities of exceeding and falling below –21% and 15%, respectively). Our study demonstrates unintended consequences of stability control of fish catches, a commonly adapted harvest strategy in industrial capture fisheries. This policy can inadvertently destabilize stocks, amplify catch fluctuation, and ultimately increase overharvest risk when not accounting for compounded effects of ecologically connected processes in assessments, underscoring the need for an ecosystem approach to designing management strategies to safely harvest top predators in increasingly more dynamic oceans.