533 



Abstract— Three experiments were 

 performed in an estuarine squid- 

 trawl fishery in New South Wales, 

 Australia, to test modifications to 

 trawl nets. Lateral mesh openings 

 were experimentally increased and 

 physical bycatch reduction devices 

 (BRDs) were placed in codends. 

 These modifications aimed to reduce 

 nontargeted catches of fish, while 

 maintaining catches of the targeted 

 broad squid [PhotoloUgo ethcridgei) 

 and bottle squid tLoliolus noctihica). 

 Compared to conventional codends 

 made with 41-mm diamond mesh, 

 codends made with different posterior 

 circumferences and larger 45-mm 

 mesh had no significant effect on 

 the catches of any species. The best 

 performing configurations involved 

 the installation of BRDs designed 

 to separate organisms according to 

 differences in behavior. In particular, 

 versions of a composite square-mesh 

 panel reduced the total weight of 

 bycatch by up to 71'7f and there was 

 no significant effect on the catches of 

 squid. The results are discussed in 

 terms of the probable differences in 

 behavior between fish and squid in 

 codends. After this study, a square- 

 mesh panel BRD was voluntarily 

 adopted throughout the fishery. 



Experiments in gear configuration to reduce 

 bycatch in an estuarine squid-trawl fishery 



James P. Scandol (contact author) 



Tony J. Underwood 



Centre for Research on Ecological Impacts of Coastal Cities 



Marine Ecology Laboratories, All 



University of Sydney 



Sydney. New South Wales 2006, Australia 



Present address for J, P, Scandol, NSW Department of Primary Industries 



PO Box 21 



Cronulla New South Wales 2230, Australia 

 Email address for J. P Scandol: James.Scandol.S'dpi. nsw.gov.au 



Matt K. Broadhurst 



NSW Department of Primary Industries 



Fisheries Conservation Technology Unit, 



POBoxJ321 



Coffs Harbour, New South Wales 2450, Australia 



Manuscript submitted 26 April 200,5 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



6 December 2005 by the Scientific Editor. 



Fish. Bull. 104:533-541 (2006). 



The incidental catch of nontarget 

 organisms (termed "bycatch") by com- 

 mercial fishing gears will remain an 

 important issue in the management 

 of fisheries. Article 7.6.9 of the Food 

 and Agriculture Organization's Code 

 of Conduct for Responsible Fisher- 

 ies (FAO, 1995) notes "States should 

 take appropriate measures to mini- 

 mize waste, discards, catch by lost or 

 abandoned gear, catch of non-target 

 species, both fish and non-fish species, 

 and negative impacts on associated 

 or dependent species, in particular 

 endangered species," Several options 

 are available for achieving these aims 

 (Hall, 1996), but the most common 

 strategy involves technological 

 improvements to fishing gears that 

 reduce unwanted mortality due to 

 fishing (Kennelly and Broadhurst, 

 2002), 



Much research into gear design to 

 reduce bycatch has been undertaken 

 in demersal trawl fisheries and espe- 

 cially those targeting shrimp (for re- 

 views see Kennelly, 1995; Broadhurst, 

 2000), This research reflects the se- 

 riousness of bycatch issues in these 

 fisheries and, in particular, the inci- 

 dental mortality of key species such 

 as marine turtles and juveniles of 

 commercially and recreationally im- 

 portant fish. Considerably less work 



has been done on bycatch in other 

 fisheries, including those targeting 

 cephalopods. 



The global catch of squid has been 

 estimated at 2,8 million tonnes (t) 

 per year (FAO^), Squid are harvested 

 with highly-selective jigs or less 

 selective gill nets, seines and, more 

 commonly, trawls (Rathjen, 1991; 

 Morals da Cunha and Moreno, 1994; 

 Simon et al,, 1996), Large-scale use 

 of pelagic gill or drift nets has been 

 restricted because of concern about 

 incidental catches (e.g., Burke et al,, 

 1994; Piatt and Gould, 1994), Despite 

 their widespread use, very little work 

 has been done to modify towed gears 

 so that they selectively harvest squid. 

 In one of the few studies relevant to 

 this issue. Glass et al. (1999) attached 

 video cameras to the anterior sections 

 of trawls targeting longfin squid (Lo- 

 ligo pealeii) in the Atlantic Ocean 

 and observed that squid positioned 

 themselves considerably higher in the 

 trawl than fish. It was suggested that 

 this difference in behavior could be 

 used to separate catches. 



' Food and Agriculture Organization 

 (FAO). 2005. FAO Fisheries Global 

 Information System, www.fao.org/fi/ 

 figis laccessed on 23 Nov 2005]. Aver- 

 age annual global production of all squid 

 species for 2000 to 200.3. 



