744 



Fishery Bulletin 88(4). 1990 



policy of reducing bycatch mortality as much as pos- 

 sible. To that end, the most useful results of this study 

 were, first, that crab mortality increased with CAP- 

 TIME, so reduction of CAPTIME should be a high 

 priority. Second, reduction of king (and probably Tan- 

 ner) crab mortality could be achieved by conducting the 

 trawl fishery during periods of the year when molting 

 activity is at a minimum. 



Summary 



1 Over 50000 crabs were measured during the study. 

 Vitality was recorded for over 10000, injuries for 3353, 

 and delayed mortality for 691. 



2 Overall survival was estimated to be 21% ( ± 2.0%) 

 for king crabs and 22% (±3.6%i) for Tanner crabs. 



3 Overall survival of king crabs declined at sizes 

 above 120 mm CL. Overall survival could not be deter- 

 mined for Tanner crabs, but immediate survival showed 

 a slight increase with size. 



4 Immediate mortality of king and tanner crabs in- 

 creased in direct proportion to time in captivity, but 

 was poorly related to weight of the catch. 



5 Immediate survival odds for king crabs increased 

 significantly with shell age. 



6 No clear difference in survival was apparent be- 

 tween the net types for either king or Tanner crabs. 



7 Delayed mortality was shown to be dependent on 

 both vitality and injuries, with vitality being the best 

 predictor. Observation of injuries did not contribute 

 substantial additional information concerning future 

 (48-hour) survival. 



8 Leg and body injuries contributed about the same 

 amount to immediate mortality, but mortality in- 

 creased with number of legs injured, and injuries to leg 

 segments proximal to the autotomy plane were more 

 serious for king crabs but not for Tanner crabs. 



Acknowledgments 



This research project was conducted in conjunction 

 with research funded by NOAA grant 86-ABH-00042 

 to the Highliners Association and Natural Resources 

 Consultants. I owe a great deal of praise to J.E. Munk, 

 of the NMFS Kodiak Lab, for conducting a large por- 

 tion of the injury assessment and survival data collec- 

 tion under very difficult conditions. A number of biol- 

 ogists worked diligently aboard the Sulak to recover 

 and measure crabs, and I wish to express appreciation 

 to all of them, but particularly to Pam Goddard for 

 organizing and supervising their efforts. 



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