Abstract. Female and 



sublegal-size male Tanner crabs, 

 Chionoecetes bairdi, are often 

 caught incidentally in the males- 

 only fishery for this species. Effects 

 of low air temperature during the 

 winter fishery on juvenile and fe- 

 male adult crabs and on the devel- 

 oping eggs brooded by the females 

 were simulated in the laboratory by 

 exposing crabs to cold air (-20 to 

 +5°C) up to 32 minutes; controls 

 were not exposed. Exposure was 

 expressed as degree-hours (°h), the 

 product of temperature (°C) and 

 time (hours). Severe exposure 

 caused death: median lethal expo- 

 sure stabilized at -3.3 + 0.8°h for 

 juveniles and —4.3 ± 0.5°h for adults 

 after 16 days. Exposure also re- 

 duced vigor (measured by righting 

 ability), caused pereiopod auto- 

 tomy, and depressed adult feeding 

 rates and juvenile growth. Expo- 

 sures causing one-half the crabs to 

 cease righting were —1.2 ± 0.3°h for 

 juveniles and -2.1 ± 0.3°h for 

 adults (measured immediately af- 

 ter exposure). Mean pereiopod au- 

 totomy ranged up to 44% for juve- 

 niles exposed to -2°h, and up to 

 10% for adults exposed to -10.6°h. 

 Ecdysis of juveniles was not af- 

 fected, but exposed juveniles fre- 

 quently shed additional pereiopods 

 with the molt. Prompt return of 

 incidentally caught Tanner crabs to 

 the sea when temperatures are be- 

 low freezing should reduce adverse 

 effects of cold aerial exposure. 



Responses of Tanner crabs, 

 Chionoecetes bairdi, 

 exposed to cold air 



Mark G. Carls 

 Charles E. O'Clair 



Auke Bay Laboratory, Alaska Fisheries Science Center 

 National Marine Fisheries Service, NOAA 

 1 1305 Glacier Highway 

 Juneau, Alaska 99801-8626 



Manuscript accepted 23 May 1994. 

 Fishery Bulletin 93:44-56 (1995). 



Tanner crabs, Chionoecetes bairdi 

 Rathbun, 1893, are the target of a 

 large commercial pot fishery and 

 are an important commercial spe- 

 cies in Alaskan waters (Otto, 1989). 

 Landings of C. bairdi rose to a peak 

 of 57,923 metric tons (t) in 1978, then 

 declined to 5,390 t in 1987; landings 

 increased to 23,507 t in 1990. 1 



Current Alaska fishing regula- 

 tions require release of small (<139- 

 mm carapace width) male and all 

 female C. bairdi. Commercial fish- 

 ery openings in recent years have 

 generally ranged from November 

 through April, 2 when minimum 

 daily air temperatures can drop to 

 -21°C. 3 The amount of time inciden- 

 tally captured crabs remain on deck 

 varies, ranging from a few minutes 

 during pot fishing to hours in some 

 trawling operations (Stevens, 1990). 

 Exposure to cold air during fishing 

 operations may be detrimental to 

 individual crabs (Carls and O'Clair, 

 1990), exposed egg clutches, and 

 possibly — with sufficient fishing 

 pressure — to the population. Regu- 

 lations also require that Tanner 

 crabs caught incidentally by multi- 

 species trawling operations in the 

 eastern Bering Sea be returned to 

 the sea, but these regulations may 

 be ineffective because of poor survival 

 (22 + 3.6% for C. bairdi) of the culled 

 crabs (Stevens, 1990). 



Here we report the responses of 

 juvenile and adult female Tanner 

 crabs and their offspring exposed to 



cold air. Our objectives were to 

 determine the effects (immediate 



1 Kruse, G. Alaska Dep. Fish and Game, Div. 

 Commer. Fish., Juneau, AK 99802. Pers. 

 commun., July 1992. 



2 ADF&G (Alaska Department of Fish and 

 Game). 



1989a. Report to the Alaska Board of Fish- 

 eries. Southeast Alaska and Yakutat (Re- 

 gion 1) 1988/89 shellfish fisheries. Regional 

 Information Rep. No. 1J89-01. ADF&G, 

 Div. Commercial Fisheries, Juneau, AK. 



1989b. Westward region shellfish report to 

 the Alaska Board of Fisheries. ADF&G 

 Regional Information Rep. No. 4K89-3. 

 ADF&G, Div. Commercial Fisheries, 

 Westward Regional Office, 211 Mission 

 Rd., Kodiak, AK 99615, 325 p. 



1989c. Prince William Sound management 

 area shellfish report to the Alaska Board 

 of Fisheries. ADF&G Regional Informa- 

 tion Rep. No. 2C89-03. ADF&G, Div. 

 Commercial Fisheries, Central Region, 

 333 Raspberry Rd., Anchorage, AK 

 99581, 55 p. 



1989d. Cook Inlet area shellfish manage- 

 ment report to the Alaska Board of Fish- 

 eries, 1988-89. Regional Information 

 Rep. No. 2H89-03. ADF&G, Div. Com- 

 mercial Fisheries, 333 Raspberry Rd., 

 Anchorage, AK 99581, 75 p. 



1989e. Synopsis of the Montague Strait ex- 

 perimental harvest area 1985-1988. 

 ADF&G Regional Information Rep. No. 

 2C89-04. ADF&G, Div. Commercial Fish- 

 eries, Central Region, 333 Raspberry Rd., 

 Anchorage, AK 99581, 21 p. 



1989f. Report to the Board of Fisheries 

 Norton Sound red king crab fishery (sum- 

 mer fishery only). ADF&G Regional In- 

 formation Rep. No. 3N89-05. ADF&G, 

 Div. Commercial Fisheries, Central Re- 

 gion, Juneau, AK, 14 p. 



3 NOAA. 1987. Local climatological data, 

 monthly and annual summaries with com- 

 parative data. U.S. Dep. Commer., Na- 

 tional Climatic Data Center, Asheville, NC 

 28801. 



44 



