Harvest Control for Schooling Fish Stocks under Cyclic Oceanographic Regimes: A Case for Precaution and Gathering Auxiliary Information
M. Vasconcellos and T. Pitcher
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Description
This paper examines the influence of three aspects of the population dynamics of small pelagic fish stocks on fisheries harvest control: (1) the non-stationarity in productivity driven by cyclic environmental regimes; (2) the collapse in distribution range following stock collapse; and (3) the consequent change in catchability with stock size. The suitability of three harvest control options, including effort limitation, minimum age in the catch, and constant escapement, was evaluated with a simulation model and according to contrasting levels of uncertainty on population parameters. Harvest control by constant effort is particularly inadequate in avoiding catchability-lead stock collapse for populations which exhibit cyclic annual production. Overall, minimum escapement policies offer the best tradeoff between mean catch, catch variability, and rebuilding capacity of the stock. In cases of highly uncertain production rates, the estimation of harvest control measures can be hampered by the non-stationarity of population parameters and by the lack of contrast in catch rates. Resolution of complications from variable catchability requires auxiliary information on abundance trends and, more important, demands the adoption of more cautious harvest control policies. For pelagic stocks dominated by environmental regimes, the protection of the first spawning age classes seems to be an appropriate measure to increase resilience to overfishing.
Item details
- Item number: AK-SG-98-01au
- Year: 1998
- DOI: https://doi.org/10.4027/fsam.1998.47
