Plankton Production, Fish Catch, and the Potential for Sharp Regional Catch Trends Under Climate Change
Charles A Stock1, Jasmin G John1, Vicky Lam2, Ryan R Rykaczewski3, William W.L. Cheung4, John P Dunne1, Rebecca G Asch5 and Jorge L Sarmiento6, (1)Geophysical Fluid Dynamics Laboratory, Princeton, NJ, United States, (2)University of British Columbia, Fisheries Centre, Vancouver, BC, Canada, (3)University of South Carolina, Columbia, SC, United States, (4)The University of British Columbia, Institute for the Oceans and Fisheries, Vancouver, BC, Canada, (5)East Carolina University, Greenville, NC, United States, (6)Princeton University, Program in Atmospheric and Oceanic Sciences, Princeton, NJ, United States
Abstract:
Fish catch has been related to diverse plankton metrics with often ambiguous mechanistic linkages to fish and varying degrees of spatial and temporal robustness. Proposed fish catch indicators also exhibit different patterns of variability and projected change, hindering fisheries assessments and the formulation of resilient marine resource management strategies. We combine 1) a new catch reconstruction featuring improved estimates of illegal and under-reported catch, 2) a novel high-resolution global Earth System Model (GFDL-ESM2.6) featuring ~10 km ocean resolution and regionally robust patterns of carbon flow through the planktonic food web, and 3) simple fish trophodynamic considerations, and revisit the relationship between catch and planktonic food web fluxes in a more mechanistic context. Realized 20-year peak catches across globally distributed coastal regions could be well explained by the estimated planktonic production available to fish (via mesozooplankton and the flux of carbon to the benthos) after accounting for the catch trophic level (r = 0.64, r = 0.74 after removing lightly fished Australian systems). Similar skill, however, could result from models invoking high trophic efficiencies within the fish food web and a modest fraction of energy available to fish taken as catch, or low trophic efficiencies and a high fraction. Projections using either parameter combination suggest that projected regional changes in fish yields may be considerably larger than those implied from primary production.
