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



51 



B 



juveniles only 



-10 



-8 -6 -4 



Degree-hours 



-2 



-2.0 °h 



-4.0 °h 



-1.5 °h 



-10 °h 



I ' I 

 24 



Days after exposure 



50 



40 



30 



■20 = 



-10 



control 



l -1 — T 

 32 



Figure 5 



Percent of total pereiopod loss by juvenile and adult female Tanner crabs as a function of exposure 

 I A) and as a function of time for juveniles (B). Error bars are ±1 standard error. 



dieted by mortality after exposure-induced death 

 ceased. 



Mortality of adult Tanner crabs was significantly 

 greater below -3°h and vigor was reduced below 

 -2°h compared with control crabs. Exposures that 

 are this severe probably occur infrequently on the 

 fishing grounds except during winter in the north- 

 ern Gulf of Alaska and the Bering Sea. Data are 

 lacking on the time incidentally captured crabs 

 remain on deck before being released, but dura- 

 tion probably varies widely. Larger vessels employ- 

 ing assembly-line techniques may process crabs 

 more rapidly than do smaller vessels. Poor handling 

 of culls combined with prolonged exposure may fur- 

 ther reduce survival of incidentally caught crabs. 



Crabs captured incidentally during trawling are 

 probably stressed more than those caught in pots. 

 Stevens ( 1990) reported trawl tows ranging up to 

 6.4 hours and retention times of Tanner crabs up 

 to 17 hours; the median lethal holding time for 

 Tanner crabs was 8.3 hours. Net type influenced 

 survival, and injuries were present in a greater pro- 

 portion of dead than of live crabs (Stevens, 1990). 



100- 



-e -4 



Degree- hours 



Figure 6 



Limb loss by juvenile Chionoecetes bairdi at ecdysis as a func- 

 tion of exposure: percent loss=-8.856 + 4,756.960 e"° 629 * (0h * 

 10) . Error bars are ±1 standard error. Numbers molting in each 

 group were 4, 4, 2, 6, 1, and 1 for controls through -8°h, re- 

 spectively. 



