Abstract. A fishery for snow 



crab, Chionoecetes opilio, began in 

 1979 in a shallow water (<200 m) 

 area off the Avalon Peninsula of 

 southeastern Newfoundland and 

 developed rapidly with landings 

 peaking at 8609 metric tons (t) in 



1981. Landings began to decline in 



1982, and dropped to 74 t in 1985. 

 This fishery collapse coincided with 

 similar declines in catch per unit 

 of effort (CPUE) and abundance of 

 newly molted male snow crab. In 

 Bonavista Bay, a deep water (>200 

 m) fishing area north of the Avalon 

 Peninsula, CPUE declined less and 

 the proportion of newly molted 

 male snow crab remained rela- 

 tively constant during the same 

 period. Coincident with the decline 

 of the Avalon Peninsula fishery was 

 a pronounced drop in mean bottom 

 temperature on the commercial 

 fishing grounds, from -0.6° C to 

 -1.4°C, a phenomenon not observed 

 in Bonavista Bay. This decline in 

 water temperature appears to have 

 been the cause of the fishery col- 

 lapse because temperatures be- 

 came low enough to interrupt the 

 molting cycle of snow crab off the 

 Avalon Peninsula. If the potential 

 impact of the lower water tempera- 

 tures and subsequent long-term 

 cessation of growth and recruit- 

 ment within the snow crab popu- 

 lation had been recognized, the 

 available pool of commercial-sized 

 crab could have been harvested 

 more slowly over a period of years to 

 lessen the disruption of the fishery. 



A snow crab, Chionoecetes opilio 

 (Decapoda, Majidae), fishery 

 collapse in Newfoundland 



David M. Taylor 

 Paul G. O'Keefe 

 Charles Fitzpatrick 



Science Branch, Department of Fisheries and Oceans 

 P O. Box 5667. St. Johns, Newfoundland AIC 5X1 



Manuscript accepted 18 October 1993 

 Fishery Bulletin 92: 412-4 Hi 



412 



The Newfoundland snow crab, 

 Chionoecetes opilio, fishery began in 

 1968, and until 1978 was confined 

 to deep water (>220 m) bays and 

 areas within 30 km of the coast. In 

 1978, fishing effort in offshore ar- 

 eas east of the Avalon Peninsula 

 (Fig. 1 ) increased markedly, result- 

 ing in peak landings in 1981 (Fig. 

 2) of 8609 t (Taylor and O'Keefe 1 ). 



The Canadian Atlantic Fisheries 

 Scientific Advisory Committee 

 (CAFSAC) recommended that an- 

 nual exploitation rates for commer- 

 cially harvested snow crab stocks 

 not exceed 50-60% of annual pro- 

 ductivity in order to prevent 

 overexploitation (Anon. 2 ). The Com- 

 mittee adopted this guideline be- 

 cause the fishery targets males only 

 and most males have an opportu- 

 nity to mate at least once before 

 reaching the minimum legal size, 

 thereby ensuring adequate recruit- 

 ment into the fishery and the repro- 

 ductive integrity of the populations. 

 However, should there be a recruit- 

 ment failure, the reproductive po- 

 tential is maintained by sublegal 

 sexually mature males in the popu- 

 lation and females that can produce 

 at least two clutches of viable eggs 

 from one copulation using stored 

 sperm (Paul, 1984). 



The fishery occurs from April un- 

 til November each year. Typically, 

 catch per unit of effort (CPUE) de- 

 clines throughout the fishing sea- 

 son until July and August when a 



high level of molting activity results 

 in an increased abundance of newly 

 molted recruits. As fishermen are 

 discouraged by processors from 

 landing these low-yield soft-shelled 

 crabs, new-shelled animals of legal 

 size (>95 mm carapace width (CW)) 

 generally enter the fishery in the 

 following spring. Their recruitment 

 is evident by high CPUE values at 

 the beginning of the next fishing 

 season (Taylor and O'Keefe 1 ). 



Between 1979 and 1982, exploi- 

 tation rates off the Avalon Penin- 

 sula remained within recommended 

 levels, but beginning in 1982 catch 

 rates declined rapidly until 1984 

 when fishing became uneconomical 

 (Taylor and O'Keefe 3 ). Other areas 

 in Newfoundland, such as Bona- 

 vista Bay (Fig. 1 ), have consistently 

 had exploitation rates in excess of 

 recommended levels and conse- 

 quently have experienced reduc- 

 tions in catch rates. However, the 



1 Taylor, D. M., and P. G. O'Keefe. 1984a. 



Assessment of Newfoundland snow crab 



(Chionoecetes opilio) stocks, 1982. Can. Atl. 



Fish. Sci. Advis. Comm. CAFSAC Res. Doc. 



84/13, Dartmouth, Nova Scotia, 35 p. 

 'Anonymous, 1981. Advice on some 



invertebrate and marine plant stocks. Can. 



Atl. Fish. Sci. Advis. Comm. CAFSAC 



Advisory Document 81/1, Dartmouth, 



Nova Scotia, 6 p. 

 : < Taylor, D. M., and P. G. O'Keefe. 1986. 



Analysis of the snow crab, Chionoecetes 



opilio, fishery in Newfoundland for 1985. 



Can. Atl. Fish. Sci. Advis. Comm. CAFSAC 



Res. Doc. 86/57, Dartmouth, Nova Scotia, 



24 p. 



