418 



Fishery Bulletin 94(3). 1996 



stimuli from the trawl and to the hanging configura- 

 tions of the codends. Fish were apparently herded 

 together at the taper of the codend, invoking an es- 

 cape response to the sides and top of the net. The 

 attachment of an anterior panel of 100-mesh circum- 

 ference to a posterior panel constructed of heavy 

 twine and 200-mesh circumference, presumably cre- 

 ated a back pressure of water that was directed out 

 through the open anterior square meshes, facilitat- 

 ing the escape of fish. This sequence of events was 

 assumed to occur continually throughout the dura- 

 tion of the trawl. The response of prawns to this 



stimuli appeared fairly limited; other studies have 

 shown that prawns are not capable of maintaining 

 active escape responses to the trawl and are quickly 

 forced against the meshes and towards the back of 

 the codend (Lochhead, 1961; Main and Sangster, 

 1985; Newland and Chapman, 1989). 



The two square-mesh codends used in experiment 

 1 were designed to take advantage of the theory dis- 

 cussed above by incorporating a panel of square mesh 

 on top of the anterior section only, so that small fish 

 might escape without a reduction in the catch of 

 prawns or of larger commercially important bycatch 



