Broadhurst et a I.: Evaluations of Nordmore grid and secondary bycatch-reduction devices 
21 I 
mm netting. They comprised two panels. The ante- 
rior panel was 100 meshes in circumference, 25 
meshes in length, and constructed of 400/36 ply, UV- 
stabilized, high-density polyethylene twine. The pos- 
terior panel was 150 meshes in circumference, 25 
meshes in length, and constructed of 3-mm diam- 
eter braided polyethylene twine. Two standard 
Nordmpre grids (each measuring 600 x 400 mm and 
weighing 1.9 kg, Fig. 2) were constructed and located 
in 2-m extension pieces (made from 400/36 ply, UV-sta- 
bilized, high-density polyethylene twine, mesh size = 
40 mm) immediately anterior to each codend (Fig. 3A, 
see also Broadhurst and Kennedy, 1996, for details). 
Experiment 1 (comparisons of secondary 
BRD's) 
Four designs of secondary BRD’s were constructed 
and installed into the codends described above, be- 
hind the Nordmpre grids. The first design (termed 
the fisheye) consisted of a stainless steel pyramid- 
shaped frame inserted 12 meshes to the left of the 
center of the top anterior section of the codend (Fig. 
3B, see also Watson and Taylor 2 ; Watson 3 ). The sec- 
ond design (termed the square-mesh panel) had a 
panel of 50-mm knotless netting, hung on the bar 
and inserted into the top anterior section of the 
codend (Fig. 3C). The third design (termed the ex- 
2 Watson, J. W., and C. W. Taylor. 1996. Technical specifica- 
tions and minimum requirements for the extended funnel, ex- 
panded mesh and fisheye BRDs. Mississippi Laboratory, 
NMFS, NOAA, P.O. Drawer 1207, Pascagoula, MS 39567. 
Watson, J. W. 1996. Summay report on the status of bycatch 
reduction devices development. Mississippi Laboratory, 
NMFS, NOAA, P.O. Drawer 1207, Pascagoula, MS 39567. 
tended mesh funnel or EMF) comprised a guiding 
funnel surrounded by larger square-shaped mesh (see 
Watson and Taylor 2 ; Watson 3 ) and was located in the 
anterior section of the codend (Fig. 3D). The fourth 
design (termed the Allerio Brothers grid, Watson 4 ) 
was constructed like the Nordmpre grid but included 
additional lateral fish escape windows posterior to 
the aluminium grid (Fig. 4). 
All four designs were compared against each other, 
one pair of each design on the outside nets of the 
triple-rigged gear (i.e. 6 separate paired compari- 
sons). The position and order of each secondary BRD 
was randomly determined, and during 6 days in the 
trawling season in the Hunter River, we completed 
a total of 12 replicate 30-min tows for each paired 
comparison. The location of each tow was randomly 
selected from the available prawn-trawl locations 
that were possible under the particular conditions. 
Prior to the trials, we rigged both nets with normal 
commercial codends to ensure that there were no 
differences in fishing characteristics. 
Experiment 2 (comparison of two secondary 
BRD's, standard Nora more grid and blubber 
chute) 
In this experiment, the fisheye and EMF, each at- 
tached to a Nordmpre grid, were compared against a 
standard Nordmpre grid (with no secondary BRD) 
and the commercially used blubber chute. The stan- 
dard Nordmpre grid and blubber chute were also com- 
pared against each other (providing a total of five 
4 Watson, J. W. 1995. Mississippi Laboratory, NMFS, NOAA, 
P.O. Drawer, 1207, Pascagoula, MS 39567. Personal commun. 
