Escape panels to reduce by-catch in the New South Wales demersal trap fishery

2002 ◽  
Vol 53 (8) ◽  
pp. 1179 ◽  
Author(s):  
John Stewart ◽  
Douglas J. Ferrell
Keyword(s):  
New South ◽  
New South Wales ◽  
Body Height ◽  
Mesh Size ◽  
Wire Mesh ◽  
Turn On ◽  
South Wales ◽  
Fish Traps ◽  
Trap Fishery ◽  
By Catch

Various sizes of wire mesh were tested as escape panels in fish traps in the New South Wales demersal trap fishery. The mesh selectivities of these escape panels were estimated using a 'parlour' trap, which is analogous to the 'covered codend' designs used to test selectivity in trawls. The results showed that we could estimate the selection size (l50) for most species based on their maximum body height and the maximum aperture of the escape panel mesh. This enabled us to make escape panel mesh that selected the main species in the fishery, snapper (Pagrus auratus), at a predetermined size. Placing the escape panel meshes with the longest axis orientated either vertically or horizontally showed that fish behaviour is important in determining mesh size selectivity. However, the selection size of some species was unaffected by the orientation of the mesh, suggesting that they were able to turn on their sides to escape. Silver trevally (Pseudocaranx dentex) formed tight schools within traps and were selected at smaller sizes when the meshes were oriented with the longest axis horizontally, suggesting that they do not turn on their sides to escape. Selectivity ogives were used with estimates of the sizes of retained and discarded fish captured in the fishery to estimate the impacts of using the escape panels tested on current landings. The results show the difficulty in designing effective escape panels in a multispecies fishery.

Variations in sex, length and age compositions of commercial catches of Platycephalus fuscus (Pisces : Platycephalidae) in New South Wales, Australia

2002 ◽  
Vol 53 (7) ◽  
pp. 1091 ◽  
Author(s):  
C. A. Gray ◽  
V. J. Gale ◽  
S. L. Stringfellow ◽  
L. P. Raines
Keyword(s):  
Average Length ◽  
New South ◽  
New South Wales ◽  
Total Mortality ◽  
Mesh Size ◽  
Growth Zone ◽  
Male Fish ◽  
Age Composition ◽  
South Wales ◽  
By Catch

Commercial landings of dusky flathead (Platycephalus fuscus) from four estuaries in New South Wales (NSW), Australia, were sampled for data on sex, length and age composition between February and July each year for 2–3 years between 1995 and 1997. Landings primarily contained female fish, ranging from 55% to 93% by number for different estuaries. Flathead sampled in commercial catches ranged from 30 cm to 96 cm total length (TL), but the majority were 33–50 cm TL. Fish >40 cm TL were primarily female and male fish >45 cm TL were uncommon. The length composition of catches differed between gillnets of different mesh sizes, with the average length of fish being least in the smallest allowed mesh size of 70 mm. Fish were aged by otolith interpretation and the analysis of marginal increments indicated that one opaque and one translucent growth zone was formed each year; the opaque zone being deposited in June–August (winter) and first observed in September–October (spring). Commercial landings included fish aged 2–11+ years, but fish aged 2–4+ years dominated landings in all estuaries. The total mortality of dusky flathead in each estuary was estimated by catch curve analysis and was relatively high, ranging from 0.45 to 1.64. The data indicate that dusky flathead may be heavily exploited in NSW.

Effects of an increase in mesh size on the catches of fish trawls off New South Wales, Australia

1995 ◽  
Vol 46 (4) ◽  
pp. 745 ◽  
Author(s):  
MK Broadhurst ◽  
SJ Kennelly
Keyword(s):  
New South ◽  
New South Wales ◽  
Mesh Size ◽  
The Body ◽  
South Wales ◽  
Large Numbers ◽  
By Catch ◽  
Species Specific ◽  
Trawl Fisheries ◽  
Future Management

In response to claims that fish trawls off New South Wales, Australia, caught excessive quantities of under-size fish, the catches of finfish by a conventional fish trawl (constructed of 90-mm mesh in the body) were compared with those by a fish trawl constructed of 100-mm mesh in the body. Catches by the 100-mm trawl showed a 27% reduction in all by-catch and a 28% reduction in the numbers of retained tiger flathead, compared with catches by the conventional trawl. The 100-mm trawl also showed a 48% and 47% reduction in the numbers and weights respectively of discarded tiger flathead and a 57% and 63% reduction in the numbers and weights respectively of discarded rubberlip morwong. For john dory, however, at a particular locality where large numbers occurred, the 100-mm trawl caught significantly more fish than did the conventional trawl (a mean increase in weight of 66%). There is a need to determine species-specific mesh selectivities and to study the behaviour of fish in trawls. The importance of the results for the future management and operational efficiency of trawl fisheries is discussed.

Mesh selectivity in the New South Wales demersal trap fishery

2003 ◽  
Vol 59 (3) ◽  
pp. 379-392 ◽  
Author(s):  
John Stewart ◽  
Douglas J Ferrell
Keyword(s):  
New South ◽  
New South Wales ◽  
South Wales ◽  
Trap Fishery

scholarly journals Developing a beam trawl for sampling estuarine fish and crustaceans: assessment of a codend cover and effects of different sizes of mesh in the body and codend

2008 ◽  
Vol 65 (4) ◽  
pp. 687-696 ◽  
Author(s):  
Douglas Rotherham ◽  
Matt K. Broadhurst ◽  
Charles A. Gray ◽  
Daniel D. Johnson
Keyword(s):  
Experimental Approach ◽  
New South ◽  
New South Wales ◽  
Mesh Size ◽  
The Body ◽  
Estuarine Fish ◽  
Beam Trawl ◽  
South Wales ◽  
The Mean ◽  
Selection Of

Abstract Rotherham, D., Broadhurst, M. K., Gray, C. A., and Johnson, D. D. 2008. Developing a beam trawl for sampling estuarine fish and crustaceans: assessment of a codend cover and effects of different sizes of mesh in the body and codend. – ICES Journal of Marine Science, 65: 687–696. An experiment was carried out in the Clarence River (New South Wales, Australia) to test the hypotheses that fish and crustacean catches in an experimental beam trawl were affected by a codend cover and the sizes of mesh in the body and codend. The cover had no obvious effects on the catches retained in the codend. Similarly, in comparisons between trawl bodies made from 26- and 41-mm diamond-shaped mesh, there were no differences in the assemblages of fish caught, or in the mean numbers entering the codends. For one species of fish (Acanthopagrus australis), however, there were differences in the proportions caught between the trawl bodies across different size classes. There was also some evidence to suggest that mesh size in the body of the trawl influenced the size selection of school prawns (Metapenaeus macleayi). For most finfish, there were no differences in catches between codends made from 20-mm and from 29-mm mesh hung on the bar (i.e. square-shaped mesh). In contrast, mesh size in the codend was important for the size selectivity of school prawns, with smaller carapace lengths at 50% retention in the 20-mm codend. We conclude that use of a 41-mm mesh in the body and a 20-mm square mesh in the codend of the beam trawl would be appropriate for future sampling with this gear in estuaries of New South Wales. A similar experimental approach to ours is needed in adapting the beam trawl to estuaries in other parts of the world, or in developing other types of research trawl.

Retained and discarded by-catch from oceanic prawn trawling in New South Wales, Australia

1998 ◽  
Vol 36 (2-3) ◽  
pp. 217-236 ◽  
Author(s):  
S.J Kennelly ◽  
G.W Liggins ◽  
M.K Broadhurst
Keyword(s):  
New South ◽  
New South Wales ◽  
South Wales ◽  
By Catch

By-catch from Praen trawling in the Hawkesbury River, New South Wales: Species Composition, distribution and Abundance

1990 ◽  
Vol 41 (1) ◽  
pp. 13 ◽  
Author(s):  
CA Gray ◽  
VC McDonall ◽  
DD Reid
Keyword(s):  
Species Composition ◽  
New South ◽  
New South Wales ◽  
Spatial And Temporal Variability ◽  
Composition Distribution ◽  
Number Of Species ◽  
South Wales ◽  
By Catch ◽  
Autumn And Winter ◽  
Number Of Individuals

This study examined spatial and temporal variability in the composition, distribution and relative abundance of by-catch from prawn trawl sampling in the Hawkesbury River, New South Wales. It also determined whether there were differences in the fauna between sections of the river that are open and closed to prawn trawling. By-catch was sampled monthly between March 1986 and February 1988 in three areas along the river that differed in distance from the mouth of the estuary and in salinity. The total incidental catch comprised 75 species of fish, 13 species of crustaceans and 5 species of molluscs: 42 species were commercially and/or recreationally important. Classification and ordination analyses showed that the species composition of the by-catch differed between the area closest to the mouth of the estuary and that furthest upstream, and that this difference was relatively consistent throughout time. The number of species in the by-catch decreased with increasing distance upstream. Annual and seasonal changes in the number of species were similar in all areas along the river: more species were caught in 1987 than in 1986, and in autumn and winter each year. In contrast, the number of individuals caught differed among areas and these differences varied between years. Similarly, seasonal fluctuations in the numbers of individuals caught varied between years, but these variations were similar in all areas. In the area furthest upstream there were no apparent differences in the numbers of species and individuals caught by prawn trawl sampling in sections of the river open or closed to prawn trawling.

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