676 



Fishery Bulletin 94(4), 1996 



ing the hours of darkness, lobsters (Jasus edwardsii) 

 feed more actively (Gunson, 1983) and can severely 

 damage fish. However, lobsters often become tangled 

 in nets while feeding on dead or dying fish in the 

 bottom region of the nets and were frequently caught 

 during nighttime sets in this study. Most intertidal 

 and subtidal marine isopods also peak in their activ- 

 ity rates during the hours of darkness (Jones and 

 Naylor, 1970; Fincham, 1973). Sea lice can completely 

 devour all but the skin and calcified structures of a 

 fish. The fact that both these predators feed predomi- 

 nantly at night means that damage incurred by fish 

 would be greater for overnight sets. 



In our study, few fish were damaged in the six hour 

 sets, but up to 40% of fish were damaged in the fif- 

 teen hour sets. Therefore, any increase in the num- 

 ber offish caught beyond six hours may be offset by 

 more fish being severely damaged. 



Gill nets do not representatively sample the fish 

 population at reef sites; none of the species in this 

 study was caught in its proportional occurrence in 

 nearshore habitats (Hickford and Schiel, 1995). Be- 

 havioral traits, such as swimming motion, and mor- 

 phological characteristics, such as spines or large 

 fins, act to make some species more vulnerable than 

 others to the fishing action of gill nets. The 2.5" mesh 

 is clearly the most effective at catching most species 

 of fish and is particularly effective at capturing ju- 

 venile and resident reef fish. Nets of this small mesh 

 size are commonly available to amateur fishermen 

 in New Zealand, who use them in nearshore waters. 

 Our study clearly shows that although commercially 

 valuable species, such as Odax pullus, Latridopsis 

 ciliaris, and Arripis trutta, can be caught in great 

 numbers around coastal reefs, the bycatch of resi- 

 dent species, such as Aplodactylus arctidens, 

 Notolabrus fucicola, and a broad range of others, is 

 considerable. Most of these species are of no com- 

 mercial value, but their removal from nearshore 

 waters may well have long-term consequences on 

 resident fish populations in areas where consider- 

 able gill netting occurs, such as around the Kaikoura 

 Peninsula. 



Acknowledgments 



We thank S. Nicholls, M. Davidson, A. Scott, C. 

 Clarke and G. Carbines for assistance with field 

 work. Logistic support was provided by the Univer- 

 sity of Canterbury's Edward Percival Field Station, 

 and we are grateful to J. van Berkel for his assis- 

 tance at all stages of our experiment. J. B. Jones and 

 the Ministry of Agriculture and Fisheries provided 

 equipment, logistic support, and expertise. We grate- 



fully acknowledge the financial support of the World 

 Wide Fund for Nature (New Zealand), through spon- 

 sorship from the Turanga Trust, and the New Zealand 

 Lotteries Fund for Scientific Research. Comments by 

 three anonymous reviewers were helpful in the devel- 

 opment of this manuscript. 



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