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Lochead J.,Shellfish Stock Assessment Section | Gillespie D.,Sclerochronology Laboratory | Hand C.,Shellfish Stock Assessment Section
Journal of Shellfish Research | Year: 2012

Samples of live geoducks and intact dead geoduck shells were collected from sites near Tofino, on the west coast of Vancouver Island, British Columbia, in 2004, 2006, and 2008. Shells were aged by the Sclerochronology Laboratory at the Pacific Biological Station using the dendrochronological technique of cross-dating. The year of death of the dead shells was determined by using the novel technique of overlapping the synchronous growth patterns of the live and dead shells. Results indicate that most of the geoducks in the sample, regardless of age, died in 1991 and 1992. We investigated possible causes of their deaths. We conclude that the mass mortality of geoducks on the exposed west coast of Vancouver Island may be the result of wave-induced anastrophic (localized catastrophic) burial. Copyright © 2013 BioOne.

Hajas W.,Shellfish Stock Assessment Section | Hand C.,Shellfish Stock Assessment Section | Duprey N.,Shellfish Stock Assessment Section | Lochead J.,Shellfish Stock Assessment Section | Deault J.,Shellfish Stock Assessment Section
Fisheries Research | Year: 2011

Data from four experimental sea cucumber (Parastichopus californicus) fishing areas in British Columbia are used to estimate productivity that has occurred during the experiments. The estimates are made by incorporating the data into a Bayesean model describing both productivity and survey-error. The Bayesean nature of the analyses enables the estimated productivity to be expressed probabilistically.The estimated productivities that have occurred in the data can serve as a guide for managing commercial sea cucumber fisheries for stocks with similar characteristics to those in the experiment. Since productivities are presented probabilistically, they can, under certain conditions, be used to generate a level of confidence that a particular harvest-management strategy is sustainable.Thus far, the applicability of the analyses is limited by the range of data that has occurred during the experiment. All the stocks began the experiment in a near-virgin state. The lowest level of abundance that has occurred so far is approximately 28% of the virgin-value. To estimate productivity for lower levels of abundance would rely on mathematical models to extrapolate the current results. As the experiments continue, it is expected that data for stocks that are more depleted will be collected and that the revised analyses will be applicable over a wider range of conditions. © 2011 .

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