ASPECTS OF THE BIOLOGY OF THE HAIR CRAB, 

 ERIMACRUS ISENBECKII, IN THE EASTERN BERING SEA 



Therese M. Armetta' and Bradley G. Stevens-^ 



ABSTRACT 



The distribution and relative abundance of the hair crab, Erimacrus isenbeckii . were determined from 

 data collected during annual summer trawl surveys conducted by the National Marine Fisheries 

 Service (NMFS) in the eastern Bering Sea, 1979-84. The estimated population was about 23 million 

 crabs from 1979 to 1981. but declined sharply to 4.4 million by 1984. The majority (67'-^) of the 

 population occurred in the Pribilof Islands area. Male crabs occurred at a mean temperature of 3.4°C 

 and depth of 66 m, whereas females occurred at a mean of 2.4°C and 64 m. Females comprised < W/r 

 of the catch in NMFS surveys. Over 99'^J of the females caught were mature, but only eight were 

 ovigerous with from 34,000 to 160,400 eggs. Length-width and length-weight relationships were 

 calculated for males and females. The majority (77*7^ ) of£ . isenbeckii caught during an independently 

 conducted study in May 1983 were found on a mixed sand and shell substrate. Scientific literature 

 (mostly Japanese) was reviewed to provide information on larvae, reproduction, molting, growth, 

 feeding habits, predation, migration, behavior, fishing, and marketing. 



The hair crab, Erimacrus isenbeckii (Brandt) 

 (Fig. 1 ). is a medium-sized brachyuran in the fam- 

 ily AtelecycHdae. Hair crab have been fished 

 in Japanese and Korean waters for over 60 years 

 (Kawakami 1934), and much hterature is avail- 

 able on the biology, distribution, and abundance 

 of the species in those waters. In contrast, fishing 

 for hair crab in U.S. waters began in 1979 (Griffin 

 and Dunaway 1985^). The recent development of 

 a U.S. fishery for hair crab and the substantial 

 decline of the eastern Bering Sea (EBS) popula- 

 tion from 1981 to 1984 prompted an analysis of 

 hair crab data collected by the National Marine 

 Fisheries Service (NMFS) during the summers of 

 1979-84. This report presents data on the distri- 

 bution and abundance of hair crab in the EBS 

 during those years, as well as aspects of ecology, 

 reproduction, molting, and growth. Additionally, 

 we have summarized the literature concerning 

 this species, since most of it is published in 



'Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 7600 Sand Point Wav NE, BIN 

 CI 5700, Seattle, WA 98115. 



-Kodiak Facilitv, Northwest and Alaska Fisheries Center, 

 National Marina Fisheries Service, NOAA, P.O. Box 1638, Ko- 

 diak. AK 99615. 



^GrifTin, K., and D. Dunaway. 1985. Bering Sea area shell- 

 fish management report to Alaska Board of Fisheries. In 

 Westward region shellfish report to the Alaska Board of Fish- 

 eries, p. 179-245. Alaska Department of Fish and Game, P.O. 

 Box 308, Dutch Harbor. AK 99692. 



Manu.scnpt accepted April 1987. 



FISHERY BULLETIN: VOL. 8.5, NO. 3, 1987. 



Japanese and not easily accessible to English- 

 speaking readers. 



REVIEW OF PUBLISHED LITERATURE 

 ON ERIMACRUS ISENBECKII 



The hair crab has a quadrangular carapace 

 slightly longer than it is wide, and is densely 

 covered with short bristles and sharp granular 

 projections; seven teeth are present on each lat- 

 eral margin. Chelipeds and walking legs are stout 

 and spiny. The epistome has a nearly straight 

 anterior margin. Rathbun (1930), Sakai (1939), 

 and Kobyakova (1955) described the morphology 

 of adult E . isenbeckii in detail. Five zoeal stages 

 and one megalopa stage in the development of 

 this crab are described by Kurata (1963). Accord- 

 ing to Kurata, the zoeae are relatively large, 

 ranging from 2.7 to 6.5 mm in body length (orbit 

 to midpoint of posterior edge of telson), depending 

 on zoeal stage, and are equipped with a long dor- 

 sal spine (1.2-2.8 mm) and prominent lateral 

 spines that are about one-fourth of the length of 

 the dorsal spine. Abdominal margins of the cara- 

 pace are fringed with setae; abdominal segments 

 possess knobs, spines, and spinules. The mega- 

 lopa is about 7.2 mm long. The rostrum is short 

 and wide and ends anteriorly in three short teeth. 

 Abdominal segments lack spines. 



In the EBS, hair crab occur from the northern 



523 



