ARMETTA and STEVENS; BIOLOGY OF THE HAIR CRAB 



against premolt carapace lengths (L„) and de- 

 rived the following equations (not converted to 

 CD: 



Both sexes 



(<50 mm RL) 

 Males 



O50 mm RL) 

 Females 



(>50 mm RL) 



L„+i = -0.40+ 1.336 (L„) 

 Ln^i = 1L68 + L036 (L„) 



L„ + i = 9.49 + 0.998 (L„) 



Abe (1982) plotted the regression of percent 

 growth per molt on length, and estimated maxi- 

 mum lengths to be 125 mm RL (116 mm CL) for 

 females and 177 mm RL (162 mm CL) for males. 

 The largest hair crabs observed by NMFS in the 

 EBS (Table 5) were smaller than these projec- 

 tions, as were those caught near Hokkaido by Abe 

 (1982), who reported maximum lengths of 152 

 mm RL (139 mm CL) for males and 105 mm RL 

 (97 mm CL) for females. Reportedly, female hair 

 crabs from Hokkaido rarely reach a carapace 

 length >80 mm RL (73 mm CL) (Sakurai et al. 

 1972). In contrast, over 20*^/^ of the females caught 

 in the EBS were >80 mm CL. However, NMFS 

 trawl gear caught few hair crab <40-50 mm CL, 

 and juvenile and female crabs may occupy rocky 

 nearshore habitat which cannot be adequately 

 sampled by such gear. 



The mean age of hair crab in the fishable popu- 

 lation can be estimated from available data. Abe 

 ( 1982) concluded that male crabs mature in their 

 10th postlarval instar, about 33 months after 

 hatching, at about 60 mm RL (54 mm CL; Fig. 3). 

 According to Yamamoto (1971), they would re- 

 quire one more annual molt to reach stage Cll in 

 their fourth year. At this size, crabs may molt 

 annually or biennially. Male crabs landed in 

 the EBS fishery averaged 106 mm CL (116 mm 

 RL) in 1984, or about stage C14 (Tables 1, 7). To 

 attain this size would require 3 molts from Cll, 

 and these crabs would range in age from 7 to 10 

 years depending upon whether their last 3 molts 

 were annual or biennial. If any failed to molt 

 more than 1 year in a row, they would be age 11 

 at this size. Abe (fn. 13) (Fig. 3) indicated that 

 male hair crab in Hokkaido waters reach similar 

 sizes at the age of 6 years (assuming none skip 

 molted). 



Resource Potential and 

 Management 



Because of the great declines in abundance of 



the Bering Sea populations of E. isenbeckii from 

 1979 to 1984, this fishery will probably not be of 

 great economic importance in the near future. If 

 abundance increases in the future and prices re- 

 main adequate, this fishery might become lucra- 

 tive, albeit on a small scale relative to other 

 Bering Sea crab fisheries. The species could then 

 probably support a small boat fishery in the Pri- 

 bilof Islands. Hair crab are still in high demand in 

 Japan. 



The EBS hair crab fishery is not intensively 

 managed. Fishing may occur year-round and is 

 not limited by quotas. However, only males may 

 be landed and gear is restricted to crab pots. 

 There is no minimum size limit since the mar- 

 ketable size is large relative to the probable size 

 of male maturity (about 54 mm CL), although the 

 latter has not been adequately determined. 



As a result of distribution and habitat differ- 

 ences as well as gear selectivity, the size- 

 frequency distributions of NMFS collections have 

 been largely unimodal with few juveniles and fe- 

 males in the catch. Thus, a thorough study of EBS 

 hair crab reproduction and recruitment has not 

 been feasible. Much useful information could 

 probably be gained by systematic, year-round 

 sampling of rocky heterogeneous habitats around 

 the Pribilof Islands with appropriate gear such as 

 rock dredges and beam trawls. Some data of this 

 sort have already been collected by Armstrong et 

 al. (fn. 11) and during other NMFS surveys, but 

 are too limited to allow an improved understand- 

 ing of growth rates, or the seasonality of molting 

 and spawning of hair crab in the EBS. Further 

 information on maturity, growth, and mortality 

 is critical for informed management and will be 

 necessary if this fishery gains importance. 



ACKNOV^XEDGMENTS 



This research would not have been possible 

 without the cooperation and assistance of the 

 masters and crews of the vessels used, including 

 the RV Alaska, RV Chapman, RV Miller Free- 

 man, RV Oregon, FV Paragon II, FV Discovery 

 Bay , FV Ocean Harvester, and FV Pat San Marie. 

 We must also acknowledge the significant efforts 

 of the biological staff at the Kodiak Research Lab- 

 oratory, who collected most of this data, and the 

 secretarial and graphics staffs at the Kodiak and 

 Seattle NMFS offices who assisted in the prepara- 

 tion of this manuscript. We thank R. S. Otto, 

 NMFS, Kodiak, AK, for reviewing the manu- 



543 



