48 



Fishery Bulletin 93(1), 1995 



Righting times of juvenile crabs from all exposures 

 tended to decrease over time (Fig. 4). The righting 

 times of adult crabs exposed to <-2.2°h generally 

 showed little evidence of recovery. Median exposures 

 causing one-half the crabs to cease righting also gen- 

 erally declined, but 95% confidence bars overlapped. 



Pereiopod autotomy 



Exposure to cold air caused pereiopod autotomy. Ju- 

 venile pereiopod losses increased from to -2°h but 

 declined towards the most severe exposure (-8°h), 

 possibly because early mortality precluded autotomy 

 (Fig. 5A). Juvenile crabs often dropped legs or chela 

 during aerial exposure, but losses also continued af- 

 ter exposure (Fig. 5B), often during ecdysis (Fig. 6). 



Adult crabs autotomized fewer pereiopods than ju- 

 veniles; as with juveniles, loss was most frequent 

 immediately after exposure. Loss of pereiopods in 

 adults was directly related to severity of exposure 

 (P<0.001, r 2 =0.85, n=19; Fig. 5A). Autotomy was cor- 

 related with mortality in adult crabs (P<0.001, 

 r 2 =0.81, n=19) but not in juveniles (P=0.621, r 2 =0.07, 

 n=6). Autotomy was also correlated with the percent- 

 age of adult crabs not righting as measured immedi- 

 ately after exposure (P<0.001, r 2 =0.81, n=22). 



Ecdysis 



Juvenile crabs began molting 22 January and con- 

 tinued through 21 February. Molt timing was not 

 correlated with exposure (r 2 =0.09). Juveniles exposed 



-10 



8 



Degree-hours 



Figure 3 



Righting times of juvenile and adult female Chionoecetes bairdi capable 

 of righting (A), and percentage not righting (B) observed 32 days after 

 emersion as functions of exposure (°h). Percentages not righting were 

 100/(1 + e' 6235 + > 651 * ° h >) for adults and 100/(1 -h> (4701 * 2858 * ° h) ) for 

 juveniles. Error bars are ±1 standard error. The ability of the single 

 surviving -4.9°h adult crab improved over time; its righting time 32 

 days after exposure was similar to that of controls. 



