Using a stock assessment framework to examine circle hooks: exploring changes in catchability and implications for management.
- Autores: Shannon L. Cass-Calay, John F. Walter, Michael J Schirripa
- Localización: Bulletin of Marine Science, ISSN 0007-4977, Vol. 88, Nº. 3, 2012 (Ejemplar dedicado a: Proceedings of the International Symposium on Circle Hooks), págs. 745-754
- Idioma: inglés
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Resumen
A presumed conservation benefit of circle hooks is that they reduce catchability (q) and therefore bycatch of non-target species. While these changes may benefit a fish stock, they are difficult to incorporate in a stock assessment context, particularly for models that rely on fishery-dependent data, because few experiments exist that quantify the effects of circle hooks for a given species over appropriately large spatial scales. Consequently, to develop management advice, it may be necessary to model assumed changes in q within the adopted stock assessment model framework. Here we present a case study of bigeye tuna (Thunnus obesus lowe, 1839), a highly migratory species managed by the international commission for the conservation of atlantic tunas (iccat), and explore the management implications of changes in q within a multi-fleet, age-structured assessment context. This study demonstrates that changes in q on the order of ±30% are sufficient to cause notable differences in the magnitude of common management reference points estimated by stock assessment models. Relative to a base model that assumed a constant q, models that incorporated a theoretical reduction in q produced higher estimates of spawning stock biomass and maximum sustainable yield, and lower estimates of fishing mortality while a theoretical increase in q had the opposite effect. The magnitude of the change was dependent on the number of fisheries affected. We conclude that carefully designed studies are essential to quantify the effects of a proposed gear change and to inform the appropriate parameterization of stock assessment models.
