218 
Fishery Bulletin 95(2), 1 997 
escaped at the standard Nordmpre grid. While the 
relatively small bar spacings (20 mm) may have been 
sufficient to exclude a large number of individuals 
simply because of their size, it is also possible that 
smaller fish were able to escape passively. For ex- 
ample, in a previous paper (Broadhurst et al., 1996) 
we provided evidence that some small bream 
( Acanthopagrus australis ) detected the grid in ad- 
vance (either visually or by means of their lateral 
lines). These fish may have then orientated away 
from the grid into an area of reduced water flow be- 
hind the guiding panel. The geometric attitude of the 
grid possibly directed some of these fish out of the 
codend without mechanical separation through the 
bars. 
Whatever the mechanism of escape, we conclude 
that, given the effectiveness of the Nordmpre grid in 
excluding large quantities of bycatch, there appears 
to be little advantage in attaching secondary BRD’s 
behind grids in the HR prawn-trawl fishery. Because 
of this, the additional labor and time involved in the 
manufacture, maintenance, and deployment of these 
secondary BRDs is clearly unwarranted. 
Like several recent studies, this study has shown 
that there is great utility for the Nordmpre grid in 
many of NSW estuarine prawn-trawl fisheries. The 
increases in prawn catches and reductions in bycatch 
shown in our work in these fisheries have already 
led many commercial fishermen to use the standard 
Nordmpre grid in preference to the traditional blub- 
ber chute. Such independent and voluntary adoption 
of the Nordmpre grid by industry may eventually lead 
to further refinements in design and should facili- 
tate widespread acceptance of this bycatch-reduction 
gear throughout most of NSW’s estuarine prawn- 
trawl fisheries. 
Acknowledgments 
This work was funded by the Australian Fishing In- 
dustry Research and Development Corporation 
(Grant No. 93/180). The authors are grateful to Gerry 
O’Doherty for his valuable expertise and for construc- 
tion of the BRD’s, Chris Hyde for the use of his ves- 
sel, the Diane Mildred , and Chris Paterson and 
Daniel Foster for providing technical support. 
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