Research Document - 2009/005
Assessment of the Exploratory Fishery for Sea Cucumber (Cucumaria frondosa) in Southwest New Brunswick
By S. Rowe, P. Comeau, R. Singh, S. Coffen-Smout, M. Lundy, G. Young, J. Simon, and H. Vandermeulen
Abstract
The southwest New Brunswick (SWNB) developmental sea cucumber fishery has evolved since 1999 to a Stage II Exploratory fishery under the New Emerging Fisheries Policy, with a recent 5 year average in landings of approximately 1200 t by 2 licence holders. A science review was requested of the sustainability and ecosystem effects of this fishery. Specifically, Department of Fisheries and Oceans (DFO) Maritimes Fisheries and Aquaculture Management Branch asked Science and Oceans, Habitat and Species at Risk branches: “What are the potential ecosystem (stock, habitat, and by-catch) impacts of the harvest of 1000-1300 t of sea cucumber in SWNB within the identified areas of recent fishing? Characterise and provide quantitive and/or qualitative information of the relative risk to the stock, habitat, and by-catch from this harvest.”
There is very limited information on life history and stock structure of sea cucumber in the Maritimes Region. Sustainable exploitation rates and other reference points are unknown, as are the consequences of removals on ecosystem structure and function.
Since 1999, more than 80% of the catch and 90% of the fishing effort was in a single fishing zone known as ‘The Passages’. Landings increased to a peak of approximately 1600 t in 2005 and have since remained around 1100 t, which may be a function of specified fishing zones and an overall Total Allowable Catch (TAC) of 1370 t being implemented prior to the 2006 fishing season. Effort peaked in 2005 and remained at lower levels during 2006-2008. Catch rates peaked at 4877 kg/hr in 2002 and remained similar to the long term average of 4292 kg/hr in 2007 and 2008. While catch rates have been maintained, there are uncertainties in whether catch rates in this fishery are reflective of population abundance.
A survey in 2004 revealed that large aggregations of sea cucumbers were relatively localized with highest catches found in the northern area of Deer Island, where the majority of the 2000-2004 fishing effort was directed. Because of the patchy nature of sea cucumber distribution and the lack of a systematic survey across the fishing area, it is not possible to establish a total population abundance estimate at this time.
There was an indication of a decrease in the size of animals landed over time, although the significance of these results has not been established and additional investigation is warranted. If the size of animals landed has decreased over time, this would result in an increase in the exploitation rate associated with the TAC of 1370 t.
The predominant by-catch species in the SWNB sea cucumber fishery was sea urchin, with catches estimated at 34 t during 2008. By comparison, 1028 t of sea urchin was landed in LFA 36 during the directed fishery in 2007-2008. The sea cucumber fishery returns all species other than sea cucumber to the water, although survival of by-catch has not been evaluated for this fishery. At-sea observers provided more detailed descriptions of by-catch than recorded in Sea Cucumber Science Logs and continued at-sea observer coverage is recommended.
The environment in which the SWNB sea cucumber fishery is conducted is considered to be productive and diverse, with very patchy distribution of benthic organisms and features. Immediate, localized impacts of the sea cucumber fishing gear on benthic habitat were observed (e.g., disturbance of periphyton layer), but the longer-term community implications and rates of recovery are not known and are worthy of further investigation. Risks of habitat impacts within the current fishing areas could be reduced by investigating the location/extent of any particularly sensitive habitat features and investigating the rates of recovery for known habitat types within these areas.
Given the number of uncertainties associated with this fishery, a cautious approach is advised.
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