Broadhurst et al.: Effects of square-mesh panels in codends and of haulback delay on bycatch reduction 42 1 



fore, result in further loss of commercial red spot 

 whiting and possibly some reduction in the catch of 

 prawns. 



The square-mesh codends tested in these experi- 

 ments provide further evidence of the effectiveness 

 of this type of exclusion device in reducing the bycatch 

 of unwanted species, while maintaining the catch of 

 prawns and other species of commercial size. Fur- 

 ther, for a fishery that retains a range of species, these 

 designs offer a relatively simple and inexpensive 

 method for eliminating a large part of the incidental 

 catch. It is evident from the results, however, that 

 not all species to be excluded behave in a similar 

 manner and that the effects of operational procedures 

 such as haulback delay can significantly influence 

 the rate of exclusion of some species. Therefore, it is 

 imperative that future research into exclusion de- 

 signs, such as square-mesh panels, include an as- 

 sessment of such operational factors so that the full 

 impact of bycatch excluders on reducing the mortal- 

 ity of incidentally caught juveniles can be assessed. 



Acknowledgments 



This work was funded by the Australian Fishing In- 

 dustry Research and Development Corporation 

 (Grant 93/180). The authors are grateful to Gary 

 Anderson for the use of his vessel, the Valerie Dawn, 

 to Brad McCarthy for his technical support, and to 

 John Watson and Ian Workman for providing help- 

 ful discussions. Thanks are extended to Nick Otway, 

 Neil Andrew, John Stewart, and Geoff Gordon for 

 critically reading the manuscript. 



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