Research Document - 2007/054

Review of data collected during the annual sea cucumber (Parastichopus californicus) fishery in British Columbia and recommendations for a rotational harvest strategy based on simulation modelling

By Humble, S.R., C.M. Hand, and W.K. de la Mare

Abstract

The sea cucumber (Parastichopus californicus) fishery in British Columbia is in Phase 1 of development, according to the nationally-adopted protocol for new or data-limited fisheries, wherein profit-based fisheries are held at conservative levels while the necessary stock assessment data are collected. Since 1997, the fishery has been restricted to 25% of the coast and management areas are harvested annually at 4.2% of estimated biomass. Commercial harvesters have expressed concern that the annual fishery is negatively impacting stocks.

A focussed review of research and fishery data was undertaken to evaluate the annual harvest regime and to identify any potential conservation concerns. The spatial distribution of harvest was examined to estimate localized harvest rates in this dive fishery. Harvest effort was found to be concentrated in approximately 12% of open areas, by shoreline distance, resulting in average local harvest rates of 30% of estimated biomass. Analysis of market sample, biological sample and survey density data failed to reveal significant impacts of annually-concentrated effort on sea cucumber populations, however sample regimes for estimating animal size distribution were found to be flawed.

A simulation model is presented, which uses estimated local harvest rates to evaluate risks and benefits of annual versus rotational harvest strategies. Model results suggest that at high local harvest rates, annual harvest leads to decline in animal size and population density while longer rotation periods result in larger animals and higher spawning densities. This paper describes a new program of experimental fishing designed to test rotational harvest and provide more informative data for management decisions in both the short-term and the long-term. Recommendations are provided for how a pilot rotational harvest could be conducted within a portion of the open fishery, including changes in data collection that would improve the ability to detect localised fishing effects.

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