US 



Abstract. -Populations of the 

 grooved Tanner crab, Chionoecetes 

 tanneri, and the triangle Tanner crab, 

 C. angulatus, were surveyed along the 

 continental slope of the eastern Bering 

 Sea with a bottom trawl. Over the 

 depth range sampled 1 100-1,000 m), 

 the relative abundance of the two spe- 

 cies was about equal. Mature male and 

 female C. tanneri occurred at the same 

 depths, but for C. angulatus. males 

 were found at significantly shallower 

 depths than were females. Carapace 

 widths at 50 r < maturity for males and 

 females were 118.7 mm and 79.2 mm 

 for C. tanneri and 91.4 mm and 57.8 

 mm for C. angulatus. Fecundity of C. 

 tanneri did not increase with carapace 

 width (CW, mm) and averaged 86,500 

 eggs over the sizes sampled. Fecundity 

 of C. angulatus increased with carapace 

 width according to the following for- 

 mula: eggs = -65,600 + 1660  CW. 

 Mean egg diameter was 0.75 mm for C. 

 tanneri and 0.74 mm for C. angulatus. 

 The relationship between body weight 

 (gml and carapace width did not differ 

 between species: weight = 1.219 /10 4 x 

 CW* 1M 



Contribution to the biology of the 

 grooved and triangle Tanner crabs, 

 Chionoecetes tanneri and 

 C. angulatus, in the 

 eastern Bering Sea 



David A. Somerton 



Alaska Fisheries Science Center 



National Marine Fisheries Service. NOAA 



7600 Sand Point Way NE. Seattle. Washington 98 1 I 5 



William Donaldson 



Alaska Department of Fish and Game 

 21 1 Mission Road, Kodiak. Alaska 99615 



Manuscript accepted 17 November 1995. 

 Fishery Bulletin 94:348-357 i 1996). 



The continental slope of the North 

 Pacific Ocean is inhabited by sev- 

 eral species of crabs in the genus 

 Chionoecetes that are similar in size 

 to their shallower, commercially 

 harvested relatives C. bairdi and C. 

 opilio but are immediately distin- 

 guishable by their brilliant orange 

 or red color and slender legs. In the 

 eastern North Pacific Ocean there 

 are two species: the grooved Tanner 

 crab, C. tanneri, ranging from north- 

 ern Mexico to Kamchatka, and the 

 triangle Tanner crab, C. angulatus. 

 ranging from Oregon to the Sea of 

 Okhotsk (Hart, 1982). In the west- 

 ern North Pacific there is a single 

 species, C. japonicus, which occurs 

 in the Sea of Japan (Sinoda, 1982). 

 Although the potential for commer- 

 cial fisheries for C. tanneri has been 

 recognized for quite some time 

 (Pereyra, 1967), commercially suc- 

 cessful fishing ventures have oc- 

 curred only recently (Jamieson, 

 1990). In contrast, C. japonicus has 

 been commercially fished since the 

 mid-1960's (Sinoda, 1982). The pri- 

 mary impediment to the develop- 

 ment of commercial fisheries for C. 

 tanneri and C. angulatus has been 

 that the large supply of other Chi- 

 onoecetes species on the world mar- 



ket has kept the price too low to off- 

 set the high costs of fishing in deep 

 water. Fisheries for other slope- 

 dwelling species, however, have de- 

 veloped when the catches of shal- 

 lower, related species have declined. 

 For example, in Japan the fishery for 

 C. japonicus developed after the lo- 

 cal stocks of C. opilio declined (Sin- 

 oda, 1982). In Alaska, the fishery for 

 the slope-dwelling king crab Lith < « /< <s 

 aequispina developed after the de- 

 cline in abundance of the shelf-dwell- 

 ing king crabs Paralithodes camt- 

 sckaticus and P. platypus (Somerton 

 and Otto, 1986). This pattern may be 

 reflected in Alaskan Chionoecetes be- 

 cause as C. bairdi and C. opilio popu- 

 lations in the Bering Sea have de- 

 clined, landings of C. tanneri have in- 

 creased from a negligible amount in 

 1992 to 360 metric tons in 1993, and 

 to 414 metric tons in 1994. ' 



Although aspects of the biology of 

 ('. tanneri have been documented in 

 areas off Oregon (Pereyra, 1966, 

 1968; Tester and Carey, 1986) and 

 British Columbia (Jamieson et al., 

 1990), only information on size dis- 



1 1995. Alaska Department of Fish and 

 Game, 211 Mission Road, Kodiak, AK 



I I Unpubl. data. 



