Research Document - 2000/051
Exploratory Fisheries for Rock Crab, Cancer irroratus, and Jonah Crab, Cancer borealis, in Canadian Lobster Fishing Areas 34, 35, 36 and 38.
By D.A. Robichaud and P. Lawton
Abstract
This document describes the evolution of inshore exploratory rock and Jonah crab fisheries in the Gulf of Maine, in LFA's 34, 35, 36 & 38, since 1995. Trends in landings, effort and catch rates (kg per trap haul) were analyzed to assess the potential impact that the fishery has had on the rock and Jonah crab resources in each LFA.
Commercial concentrations of Jonah crabs have been found off southwestern Nova Scotia in the midshore (LFA 34) and off southern Grand Manan (LFA 38). Commercial concentrations of rock crabs were found in the St. Marys Bay area (LFA 34), in the Annapolis Basin area (LFA 35), and in several areas situated between Passamaquoddy Bay and Point Lepreau, N.B. (LFA 36). In 1995 some rock crabs were found in LFA 38, off Grand Manan. However the search for a viable concentration of rock crab in LFA 38 was abandoned as effort was diverted to the more lucrative Jonah crab fishery.
The mean size of male Jonah crab was greater in LFA 34 (139 to142 mm carapace width, CW) than in LFA 38 (131 to 136 mm CW). The mean sizes of male rock crabs (111 to 122 mm CW) were similar in all areas, though different trap types were used. The annual catch rates for Jonah crab were similar in LFA 34 (4.1 to 6.3 kg/th) and LFA 38 (4.8 to 6.5 kg/th). Rock crab annual catch rates, were higher in LFA 35 (5.6 to 8.1 kg/th) compared to LFA 34 (2.4 to 4.3 kg/th) and LFA 36 (2.3 to 3.1 kg/th). By-catch of lobsters did not seem to be a problem in both crab fisheries.
With the limited information gathered during the last five years, it is premature to predict the sustainability of this fishery. However there is still some room for limited expansion in unexplored areas. Data gathered in this report indicates that the current level of effort is not having any obvious impact on the resource such as a reduction in average catch size or reduction in catch rates. The economic feasibility of this fishery is marginal and very dependant on the value and the demand for the product.
Jonah crabs and rock crabs are also fished as a by-catch in the lobster fishery. The potential effort, which can be exerted by the lobster fishery, is far greater than the current directed fishery. Removals by the lobster fishery are a fundamental piece of missing information needed for the assessment of rock and Jonah crab stocks. The by-catch issue should be reviewed on an LFA by LFA basis since in some LFA's these issues could be more easily resolved than in others.
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