52 



Fishery Bulletin 93(1). 1995 



-2- 



T" 

 -5 



-4 



~ i ' r~ 



-3 -2 



Degree hours 



Figure 7 



Feeding rates (milligram food/gram crab weight/day) of 

 adult female Chionoecetes bairdi before (F =4.556 + 1.071 



pre 



x °h) and after (F pos ,=12.161 + 1.255 x °h) zoeal hatching 

 as a functions of exposure (°h). Error bars indicate 95% CI. 



100- 



80- 



60- 



S 40- 



20 



0- 



-20- 



did not molt 



-3 -2 



Degree- hours 



Figure 8 



Changes in wet weight of juvenile Chionoecetes bairdi as a 

 function of exposure. Weights of crabs that molted versus 

 those that did not were treated separately. Error bars are 

 ±1 standard error. 



Mortality and injury due to aerial exposure have 

 been reported for other commercially harvested de- 

 capod crustaceans. For example, king crabs were af- 

 fected by exposure to cold air, but were less sensitive 

 than Tanner crabs (Carls and O'Clair, 1990). The 

 western rock lobster, Panulirus cygnus, was signifi- 

 cantly affected by >15 minutes exposure to warm air 

 (27-35°C); recapture rates were lower than for un- 

 exposed controls, and the probability of mortality due 

 to predation rose (Brown and Caputi, 1983). 



We do not know what physiological mechanism(s) 

 caused the abnormal events during ecdysis that of- 

 ten resulted in death. O'Brien et al. (1986) induced 

 apolysis (the separation of integumentary tissues 

 from the exoskeleton during proecdysis) in several 

 species of brachyurans by packing crabs in ice. 

 Apolysis occurred within one hour in most cases and 

 was not caused by death (O'Brien et al., 1986). 

 O'Brien et al. (1986) did not observe ecdysis in their 

 experimental crabs; therefore, the effect of apolysis 

 on the timing, duration, and success of ecdysis in 

 crabs is not known. In the present experiment, al- 

 though mortality occurred during ecdysis in juvenile 

 crabs, the timing of ecdysis was not affected. 



Evaporative water loss during exposure probably 

 did not contribute significantly to the effects we ob- 

 served. The fact that warmer exposures, such as the 

 32-minute exposure at +5°C, caused little or no ef- 

 fect supports this supposition. Similar observations 

 were made for king crab (Carls and O'Clair, 1990). 

 In a study by Taylor and Whiteley (1989), the lob- 



ster Homarus gammarus vulgaris, which rarely 

 comes in contact with air in its natural environment, 

 was exposed to air at 15°C for up to 14 hours. Water 

 loss, inferred from the constancy of most hemolymph 

 ion concentrations, was minimal (Taylor and 

 Whiteley, 1989). Oxygen delivered to H. gammarus 

 tissues was substantially reduced, and C0 2 accumu- 

 lated, but levels returned rapidly to normal after a 

 14-hour exposure. Lactate levels increased, but el- 

 evation of bicarbonate ions increased the buffering 

 capacity of the hemolymph. Because exposures did 

 not exceed 32 minutes, it is unlikely that reduced 

 oxygen directly caused Tanner crab mortality in our 

 experiment. However, at low air temperatures, gills 

 may have been damaged by frost, thus impairing 

 respiratory gas, metabolite, and ion exchange after 

 the crabs were returned to the water. 



The ability of crabs to right themselves proved to be 

 a sensitive measure of crab viability. Righting response 

 data collected immediately after exposure correlated 

 strongly with less-immediate responses such as mor- 

 tality and growth. Pereiopod loss also impaired righting. 



Pereiopod autotomy in adult crabs was a function 

 of exposure. Mortality may have influenced the au- 

 totomy response curve for juvenile crabs: during se- 

 vere exposure, crabs apparently died before autotomy 

 could take place. 



Aerial exposure reduced weight gain in juvenile 

 crabs and caused weight loss in juveniles that did 

 not molt. However, wet weights of the adult crabs 

 (all anecdysial) did not vary with exposure. This ab- 



