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Coffs Harbour, Australia

Broadhurst M.K.,Fisheries Conservation Technology Unit
Fisheries Research

Two experiments were done to assess and refine the Nordmøre-grid in a canoe-trawl fishery targeting Xiphopenaeus kroyeri off southern Brazil. During experiment 1, a codend containing a small (1881cm2) Nordmøre-grid (24-mm bar spaces) retained significantly less total bycatch (mean predicted weight reduced by 56%), brachyurids (by 79%) and teleosts (by 50%) than a conventional configuration (control), without significantly affecting the weights or numbers of X. kroyeri, although mean predicted weights were 12% lower. During experiment 2, the bar spaces were subsequently maintained, but the grid area was increased by 1.4 while the extension section mesh size was reduced by 1.3, and the impacts of different materials (hollow vs. solid aluminium rod), bar diameter (10 vs. 16mm) and presence/absence of a guiding panel were investigated. Most of these technical changes had minimal effects, with all grid configurations maintaining catches of X. kroyeri (at between -13 and +22% of the control) and significantly reducing total bycatch (up to 54%) and brachyurids (up to 90%). But, unlike the small grid, none of the large grids significantly reduced the catches of teleosts. This result was attributed to the increased distance required by fish smaller than the bar spaces to swim out of the escape exit. While ongoing refinements, including narrower bar spaces, could improve the performance of the Nordmøre-grid, the results justify the adoption of the generic configuration as a means for improving selectivity in this fishery. © 2011. Source

Silva C.N.S.,Victoria University of Wellington | Broadhurst M.K.,Fisheries Conservation Technology Unit | Medeiros R.P.,Federal University of Parana | Dias J.H.,Federal University of Parana
Marine Policy

Many conventional management strategies have been demonstrated to be ineffective in achieving sustainable fisheries, and new approaches are required to overcome existing environmental, social and economic problems. Adaptive co-management represents the combination of a learning-by-doing approach (adaptive management) involving all related and legitimate stakeholders in the decision-making process (collaborative management). In this study, the relevant experiences from a fishery in southern Brazil are reported. The first section of the paper summarizes the broad history of national fisheries and their management. Then the southern Brazilian artisanal penaeid-trawl fishery is briefly described and the three main problems associated with the common gears used are discussed, including their (1) poor size and species selectivities, (2) poor efficiencies, and (3) their mechanical impacts on benthic habitats. Finally, a framework is proposed to address the environmental and socio-economic issues in the fishery and its implementation discussed via an adaptive co-management approach. © 2013 Elsevier Ltd. Source

Broadhurst M.K.,Fisheries Conservation Technology Unit | Millar R.B.,University of Auckland
Fisheries Management and Ecology

The relationship between the amount of square mesh in codends and selectivity was investigated for an Australian penaeid stow-net fishery. Three lengths (3, 2 and 1 m) of square-mesh codend made from 27-mm mesh hung on the bar were alternately tested with a conventional 34-mm diamond-mesh design during two covered-codend experiments. Compared with the conventional codend, the square-mesh configurations incrementally selected school prawns, Metapenaeus macleayi (Haswell) across narrower selection ranges (SR) and mostly at greater sizes at 50% retention (L50), while retaining fewer fish. Irrespective of the mesh configuration or square-mesh codend length, there were significant differences between experiments (attributed to water flow) and impacts of catch weight on the selectivity of school prawns. Both variables had a negative relationship with L50, while water flow similarly affected SR. This study reaffirms the utility of square-mesh codends as a key input control for managing the selectivity of penaeid-catching gears. © 2010 Authors and Commonwealth of Australia. Source

Broadhurst M.K.,Fisheries Conservation Technology Unit | Butcher P.A.,Fisheries Conservation Technology Unit | Cullis B.R.,Wagga Wagga Agricultural Institute
Fisheries Research

Grey mullets (Mugilidae) are important to recreational fisheries throughout the developed world. In Australia, several species are angled and then released in large numbers; all with virtually unknown fate. In response to the need for such data to facilitate effective stock management, this study sought to quantify the post-release mortality and key causal factors for sand mullet (Myxus elongatus). A total of 125 fish were conventionally angled, and then released along with 50 controls into floating cages in a south eastern Australian estuary, where they were monitored for four days. Five treatment fish died, providing a non-significant mortality of 4%. The few fatalities were mostly explained by a significant positive relationship with the length of trace (between the float and hook) used, and bleeding during release. While sand mullet appear quite tolerant of catch and release, their welfare nevertheless could be improved through simple changes to fishing strategies. © 2010. Source

Butcher P.A.,Fisheries Conservation Technology Unit | Broadhurst M.K.,Fisheries Conservation Technology Unit | Orchard B.A.,Wagga Wagga Agricultural Institute | Ellis M.T.,Port Stephens Fisheries Institute
ICES Journal of Marine Science

Biotelemetry was used to test the hypotheses of few impacts to yellowfin bream (Acanthopagrus australis) released with ingested hooks. Sixteen sample fish were tagged and tracked (using 18 receivers), along with 32 controls (16 pre-tagged "C1" and 16 simultaneously tagged "C2" fish) for 112 d in Botany Bay, Australia. All fish survived initial release, but seven tags from two C1, four C2, and one hook-ingested fish remained motionless within the first 6 d, and another 23 fish were last detected near the release site (a fish farm). Most disappearances were attributed to recapture by anglers or predation. The latter fatalities were exacerbated among controls, and they possibly resulted from the confounding effects of confinement, including a loss of fitness. Such effects were limited to the first 4 d; after which all fish had similar movements. Most (98) subsequent detections were within 1 km of the fish farm, likely attributable to the associated habitat and abundant food. Although all fish remained near structures, 18 fish travelled farther. In addition to providing the first fine-scale information on the movements of yellowfin bream, the study validates releasing hook-ingested individuals with the line cut as a means for minimizing mortality. © 2010 United States Government, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center. Source

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