Research Document - 2013/057
Assessment of Rock crab (Cancer irroratus) stock status in the coastal waters of Québec in 2012<
By L. Gendron and G. Savard
Abstract
In Quebec, the commercial exploitation of rock crab began in 1988, but did not really begin to take off until 1995. The rock crab is a key species in the ecosystem, and represents an important prey for lobster and several species of fish. The fishery is managed by a conservation plan which aims to protect the trophic links, particularly with the lobster. The management measures currently in place are intended to protect the reproductive potential by keeping harvesting rates low or moderate. The fishery is managed by controlling fishing effort, and by controlling catches as well in the Magdalen Islands and the Gaspé Peninsula. Harvesting is also limited spatially through fishery closures in certain areas. The minimum catch size is 102 mm (carapace width), creating an exclusively male-directed fishery.
The present document describes the data and analyzes that were used to determine stock status for the years 2009 to 2012 and provide recommendations for the 2013 to 2015 fishing seasons (DFO 2013). Stock status assessment is based primarily on indicators of abundance (landings and catch per unit effort, CPUE) and demographic indicators (size of crabs landed) from commercial fishing, but also on a trawl survey for the Magdalen Islands. The analysis of the indicators is based on the evolution of temporal trends and recommendations for reducing fishing pressure are issued in the case of important or continuous declines in one or more indicators.
In 2012, stock status indicators suggest that, to date, harvesting levels are not causing any major disruptions for populations in most areas. However, a decrease in rock crab abundance was observed in the Magdalen Islands and the possibility that it could be linked to the increase in lobster abundance, an important predator of the rock crab has put forward as a hypothesis. A quota reduction was recommended for this area. The introduction of quotas in 2010 in the Gaspé has eliminated the problem of latent effort. However, it was not possible to determine whether the established quotas allowed to maintaining the stock at a moderate level of exploitation as fishing effort declined since 2009 and the quotas have not been met. It was therefore recommended to maintain current levels of harvest, except for a specific area where there has been a significant decrease in the size of crabs, suggesting that fishing pressure was too high. A decrease in the quota has been recommended for this specific area. On the North Shore, the stability observed in the indicators since the start of the fishery in 2004 suggests that the current harvest levels are sustainable. The introduction of a catch limit for this area was recommended. Finally, regardless of the status of stocks, in the absence of a better control of lobster vessel rock crab by-catches it was agreed not to recommend an increase in the intensity of the directed fishery.
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