Weinberg et al.: Capture probablity of a survey trawl for Parahthodes camtschaticus 



741 



trawl codend 



auxiliary codend 



trawl footrope 



wrapped wire 



chain hangings 



twine hangings 



fishing line 





auxiliary footrope 



Figure 1 



The 83/112 Eastern bottom trawl with auxiliary net used in the 2002 

 red king crab capture efficiency experiment (figure adapted from Munro 

 and Somerton, 2002, with permission from Elsevierl. 



formance and crab-behavioral variables to help us un- 

 derstand the escapement process. 



Materials and methods 



Description of trawl gear 



The 83/112 Eastern bottom trawl has been used by the 

 AFSC in annual surveys to assess EBS crab and shelf 

 groundfish stocks since 1982 (Armistead and Nichol, 

 1993). For the present experiment, an auxiliary net with 

 an independent footrope constructed of heavy chain-link 

 and a separate codend were attached to the bottom of 

 the survey trawl to capture epibenthic animals passing 

 beneath the trawl footrope (Fig. 1). Briefly, the 83/112 

 Eastern is a low-rise trawl that has a 25.3-m long hea- 



drope strung with 48 floats giving it approximately 102 

 kg of lift and a 34.1 m long, 5.2-cm diameter footrope 

 constructed of 1.6-cm stranded wire rope protected with 

 a single wrap of polypropylene line and split rubber hose. 

 The net is constructed with nylon twine: 10.1-cm stretch 

 mesh throughout the wing and throat sections; 8.9-cm 

 stretch mesh in the intermediate section; a double layer 

 of 8.9-cm stretch mesh in the codend; and a 3.1-cm 

 stretch mesh liner in the codend. It is fished with a pair 

 of 1.8x2.7-m steel V-doors weighing approximately 816 

 kg apiece. 



The auxiliary net attaches to the wingtips and to the 

 bottom of the survey trawl so that the bottom panel of 

 the trawl serves as the top panel of the auxiliary net 

 up to the beginning of the intermediate section. At this 

 point, the two nets part and the auxiliary net then has 

 a top panel of 8.9-cm stretch mesh and a double layer 



