Carls and O'Clair: Responses of Chionoecetes bairdi to cold air 



45 



and long-term) of exposure to cold air on 1) survival; 

 2) sublethal responses, including righting response, 

 limb autotomy, feeding rate, ecdysis (juveniles), and 

 growth; and 3) reproductive responses including egg 

 survival, zoeal production, zoeal viability, and subse- 

 quent egg extrusion and viability of the extruded clutch. 



Methods 



Experimental crabs were collected with crab pots. 

 Juvenile crabs (both sexes) were collected in Auke 

 Bay, Alaska (lat. 58°21'N, long. 134°41'W) on 14 and 

 19 January 1988. Ovigerous females were captured 

 near Eagle River (lat. 58°31'N, long. 134°48'W) and 

 Lena Point (lat. 58°24'N, long. 134°47'W) in Favorite 

 Channel, Alaska, on 11 February 1988. 



In the laboratory, carapace length (distance from 

 the posterior margin of the right ocular orbit to the 

 midpoint of the posterior margin of the cara- 

 pace) was measured to the nearest millime- 

 ter. Carapace width was subsequently esti- 

 mated by regressing carapace widths and 

 lengths of Tanner crabs measured at a later 

 date. 4 Live weight was measured to the near- 

 est 0.1 g. Juvenile crab weights ranged from 

 26 to 229 g (* = 109 ±14 g), and carapace 

 lengths ranged from 35 to 64 mm (3c=49 

 ±2.3 mm) (Fig. 1). Estimated juvenile cara- 

 pace widths (for both sexes) ranged from 46 

 to 74 mm (width=-0.237 + 1.318 x length, 

 r 2 =0.994, rc=145). The immature condition of 

 males was determined solely by body size. 

 Adult female crab weights ranged from 182 

 to 553 g ( x = 329 ± 8 g), and carapace lengths 

 ranged from 65 to 96 mm (x=80 ±1.0 mm) 

 (Fig. 1). Estimated female carapace widths 

 ranged from 85 to 124 mm (width=1.746 x 

 1.274 x length, r 2 =0.995, n=70). 



Crabs were maintained in 500-L tanks at 

 ambient seawater temperatures (6.0-6.9°C 

 for juveniles, 5.3-6.0°C for adults) until ex- 

 posure to test air temperatures; after expo- 

 sure they were returned to the same tanks 

 for 32-35 days of observation (4.7-6.7°C for 

 juveniles, 4.7-5. 2°C for adults). A subset of 

 40 female crabs was retained for an addi- 

 tional three months of observation. 



Crabs were exposed in a modified chest 

 freezer divided by a vertical baffle into two 

 compartments of unequal size (Carls and 

 O'Clair, 1990). Infrared heat lamps were 



placed in the smaller compartment for temperature 

 control. To ensure uniform temperatures, a small fan 

 (in the center bottom of the baffle) drew air from the 

 exposure chamber into the small chamber at 45 ± 

 5 cm/sec. Return air circulated over the baffle into 

 the exposure chamber. Temperatures were measured 

 with a thermistor located in the exposure area near 

 the fan and were regulated manually by switching 

 the heat lamps on or off. Temperatures were con- 

 trolled to ±0. 1°C after the chamber had cooled to the 

 desired temperature. Crabs were exposed to cold air 

 on the plywood bottom of the exposure chamber. 



Juvenile crabs were randomly placed in six groups 

 with 10 crabs per group and were exposed to cold air 

 on 21 and 25 January (about one week after capture). 

 Exposure temperatures ranged from -5.0 to -20.0°C; 

 exposure durations were 0, 12, 16, or 24 minutes to 

 yield 0, -1.0, -1.5, -2.1, -4.0, and -8.0°h exposures 

 (Table 1). The lengths (F 5 54 =0.06, P>0.99) and 



25 



r 





~n 



~\ 



20 



T 

 200 260 320 380 



Wet weight (grams) 



Ik 



_ r _r 

 500 



40- 



30- 



10- 



Adult females 

 Juveniles 



dcuxi 



30 



17/ 



Tilm rl 



i i 



50 60 70 



Carapace length (mm) 



n 



Figure 1 



Chionoecetes bairdi length and weight frequencies. Adult female 

 frequencies may not be directly comparable to juvenile frequencies 

 because they were taken from a different locality. 



4 r^O.99. Stone, R. NMFS Auke Bay Lab., Juneau, AK 

 99801-8626. Unpubl. data, May 1992. 



