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.

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.

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.

Observer-based survey of by-catch from prawn trawling in Botany Bay and Port Jackson, New South Wales

1996 ◽  
Vol 47 (7) ◽  
pp. 877 ◽  
Author(s):  
GW Liggins ◽  
SJ Kennelly ◽  
MK Broadhurst
Keyword(s):  
New South ◽  
Recreational Fisheries ◽  
Fishing Season ◽  
South Wales ◽  
Large Numbers ◽  
Commercially Important ◽  
The Mean ◽  
By Catch ◽  
Species Specific ◽  
Port Jackson

Catches and by-catches were surveyed in the commercial prawn trawl fleets of Botany Bay and Port Jackson, two estuaries in the Sydney metropolitan area (NSW, Australia). Catches were surveyed in all tows during replicate fishing trips in each month during the 1990-91 and 1991-92 prawn trawl seasons in each estuary. Significant species-specific variabilities in abundances were detected between estuaries, between years, and between early and late in the fishing season. The mean annual ratio of by-catch to catch of prawns (by weight) was 2.5 : 1 for Botany Bay and 1.8 : 1 for Port Jackson. A mean annual by-catch (� 1 s.e.) of 142 � 14 t was taken from the Botany Bay fishery and 38 � 3 t from Port Jackson. These by-catches included large numbers of small recreationally and commercially important finfish: a mean annual by-catch of 1.52 �0.20 million fish from Botany Bay and 219� 23 thousand fish from Port Jackson. Despite uncertainties about the impacts of such by-catches on interacting commercial and recreational fisheries, it is recommended that strategies for the reduction of such by-catches be considered.

Reducing the mortality of discarded undersize sand whiting Sillago ciliata in an estuarine seine fishery

2000 ◽  
Vol 51 (8) ◽  
pp. 749 ◽  
Author(s):  
Steven J. Kennelly ◽  
Charles A. Gray
Keyword(s):  
Field Experiment ◽  
Laboratory Experiment ◽  
New South ◽  
New South Wales ◽  
Mesh Size ◽  
Beach Seine ◽  
South Wales ◽  
Large Numbers ◽  
Significant Mortality

A field experiment was done to determine the effects of mesh size in the bunt and codend of an estuarine beach-seine net on the meshing (gilling) and discarding of undersize sand whiting Sillago ciliata (Sillaginidae). Four mesh sizes were examined: 45 mm, 50 mm, 57 mm and 64 mm, in an alternate-haul experiment in the Clarence River, New South Wales, Australia. A laboratory experiment was also done to determine the mortality of sand whiting after becoming meshed in seine nets. The currently allowed mesh size (50 mm) catches a large proportion of undersize sand whiting that become meshed in the netting and are subsequently discarded. The laboratory experiment showed that ~40% of these fish may die within a few weeks whereas no unmeshed fish die. In contrast, the 57 mm mesh size meshed few undersize sand whiting yet retained almost the same number of legal-sized fish as the 50 mm mesh. Hence, the maximum mesh size allowed in the bunts of nets used in this fishery should be raised to 57 mm to allow the escape of large numbers of undersize sand whiting that are currently being caught, meshed and discarded in a condition that leads to significant mortality.

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.

Prehistoric aboriginal occupation of the rangelands: Interpreting the surface archaeological record of far western New South Wales, Australia.

2000 ◽  
Vol 22 (1) ◽  
pp. 44 ◽  
Author(s):  
SJ Holdaway ◽  
PC Fanning ◽  
DC Witter
Keyword(s):  
Arid Regions ◽  
Aboriginal People ◽  
New South ◽  
New South Wales ◽  
Landscape Archaeology ◽  
South Wales ◽  
Large Numbers ◽  
Different Parts ◽  
Stone Artefact

Recent erosion in arid regions of western NSW has exposed large areas that are scattered with stone artefacts manufactured by Aboriginal people in prehistory. These exposures offer an opportunity for archaeologists to study the artefacts abandoned by Aboriginal people through time and to compare those artefacts that accumulate in different parts of the landscape. To reconstruct the nature of prehistoric behaviour in the rangelands, two approaches are needed. First, the geomorphological context of the artefacts needs to be considered since exposure of the artefacts is a function of landscape history. Second, large areas (measured in thousands of square metres) and large numbers of artefacts need to be considered if patterns reflecting long-term abandonment behaviour by Aboriginal people are to be identified. This paper reports on the Western New South Wales Archaeological Program (WNSWAP) which was initiated in 1995 to study surface archaeology in the rangelands. Geomorphological studies are combined with artefact analysis using geographic information system software to investigate Aboriginal stone artefact scatters and associated features such as heat retainer hearths, in a landscape context. Results suggest that apparently random scatters of stone artefacts are in fact patterned in ways which inform on prehistoric Aboriginal settlement of the rangelands. Key words: Aboriginal stone artefacts; rangelands; landscape archaeology; geomorphology; GIs

Biology of angel sharks (Squatina sp.) and sawsharks (Pristiophorus sp.) caught in south-eastern Australian trawl fisheries and the New South Wales shark-meshing (bather-protection) program

2017 ◽  
Vol 68 (2) ◽  
pp. 207 ◽  
Author(s):  
V. Raoult ◽  
V. Peddemors ◽  
J. E. Williamson
Keyword(s):  
New South ◽  
Growth Curves ◽  
Commercial Fishing ◽  
South Eastern ◽  
Total Length ◽  
South Wales ◽  
Large Numbers ◽  
Eastern Australia ◽  
Trawl Fisheries ◽  
South Eastern Australia

Two species of angel shark (Squatina australis, S. albipunctata) and two species of sawshark (Pristiophorus nudipinnis, P. cirratus) are frequently caught in south-eastern Australia. Little is known of the biology of these elasmobranchs, despite being caught as secondary target species in large numbers. The present study collected morphometric and reproductive data from sharks caught in shark-control nets, commercial fishing trawlers and research trawlers in south-eastern Australia. All four species had female-biased sexual size dimorphism, but growth curves between sexes did not differ. Male S. australis individuals were fully mature at ~800-mm total length, male P. nudipinnis at ~900mm, and male P. cirratus at ~800mm. Anterior pectoral margins could be used to determine total length in all species. No morphometric measurement could reliably separate Squatina spp. or Pristiophorus spp., although S. albipunctata over 1000-mm total length had larger eyes than did S. australis.

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