Limited conservation efficacy of large-scale marine protected areas for Pacific skipjack and bigeye tunas

Large-scale marine protected areas (MPAs) may not effectively conserve tropical tuna stocks, including skipjack and bigeye tunas. A study evaluating the Phoenix Islands Protected Area (PIPA) and hypothetical 33% MPAs in the western and central Pacific found minimal stock-wide conservation benefits for these species. Using the SEAPODYM model, researchers compared control and counterfactual simulations to assess population dynamics under different MPA scenarios. Results indicated weak to non-existent benefits for skipjack tuna (-0.1% to +5.8% change in spawning biomass) and modest gains for bigeye tuna (+4.8% to +12.0%). The limited efficacy is attributed to the species' wide larval dispersal and high mobility, which dissipate MPA protective effects. Additionally, fishing effort displacement from MPAs can negatively impact stocks outside these areas. This suggests that large oceanic MPAs may not be effective frontline management tools for tropical tunas with similar life history characteristics.

Hampton, J., Lehodey, P., Senina, I., Nicol, S., Scutt Phillips, J., & Tiamere, K. (2023). Limited conservation efficacy of large-scale marine protected areas for Pacific skipjack and bigeye tunas. Frontiers in Marine Science, 9. https://doi.org/10.3389/fmars.2022.1060943