Research Document - 2010/002
Assessment of the Bay of Fundy sea urchin fishery, Lobster Fishing Area 36
By David Robichaud
Abstract
The green sea urchin (Strongylocentrotus droebachiensis) commercial fishery was initiated along the coast of southwestern New Brunswick, in the Bay of Fundy, in 1989. The sea urchin fishery was separated into 2 management areas. These 2 areas were assigned the same boundaries as Lobster Fishing Areas (LFAs) 36 and 38. In LFA 36, the existing sea urchin fishery is based on a total allowable catch (TAC) system. The sea urchins are harvested mainly by diving and to a lesser extent by dragging. Presently, there are 14 diver based licence operators and only 4 licensed dragging operators. It is currently managed using a minimum legal size limit of 51 mm test diameter (TD) and by a fishing season. A TAC of 900 t was established in 1996 and it has been in place since. In this assessment, fishing effort, landings trends and catch rates were evaluated using logbook information. In addition, sea urchin size structure, densities and biomass were re-evaluated using diver based survey information. The traditional fishing grounds around Campobello Island, Deer Island, and Letete to Pocologan area were resurveyed in 2002-03 and the results compared with the previous survey results from the 1992-94 surveys. In addition, the expansion area from Maces Bay to Chance Harbour, where no previous surveys had been done, was surveyed in 2002. The TAC and harvesting rates were revised.
Since the establishment of a 900 t TAC in 1996, landings remained below 800 t. However, during the last 4 fishing seasons, urchin landings have exceeded the TAC twice and remained the highest since 1996. There has been a increasing trend in catch per unit effort (CPUE) for both the dive and drag fisheries since 1991-92. The proportion of the catch harvested by divers has fluctuated between 65% (1997-98) and 88% (2003-04). With the exception of Deer Island, where legal size sea urchin densities have decreased, all other areas show no significant differences in densities between the 1992-94 and 2002-03 survey periods. With the exception of immature urchins (< 25 mm TD), the density of urchins was significantly higher in the shallow depth strata (0 - 10 m) during both survey periods. Total biomass has changed little between the 2 survey periods. Estimated fishable biomass appears to have declined, but is not significantly different between the 2 surveys due to a high degree of variability. Based on the established TAC of 900 t, the harvesting rate is estimated to be 7.9%-1.1% higher than the harvesting rate of 6.8% that was approved in 1996. However, the Passamaquoddy Bay area is also fished, but has never been surveyed and, therefore, no biomass estimate for this area is available. For that reason, the 7.9% harvesting rate is an overestimate. A review of the survey design and another survey in the next 2-3 years is recommended.
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