Fisheries Conservation Technology Unit

Coffs Harbour, Australia

Fisheries Conservation Technology Unit

Coffs Harbour, Australia
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Broadhurst M.K.,Fisheries Conservation Technology Unit
Fisheries Research | Year: 2011

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.

Dowling C.E.,University of New England of Australia | Hall K.C.,Fisheries Conservation Technology Unit | Broadhurst M.K.,Fisheries Conservation Technology Unit
Hydrobiologia | Year: 2010

The prevalence of catch-and-release factors known to adversely affect the mortality or physical condition of Australian bass Macquaria novemaculeata were surveyed across a range of anglers throughout impoundments and rivers in New South Wales. Subsamples of tournament-caught fish were also monitored in tanks for 1 h after being weighed to quantify immediate mortalities and sublethal physical damage. Most fish were caught on actively fished artificial baits, and were mouth hooked (96%), which resulted in no immediate mortality amongst monitored fish and a low frequency of mortality-causing factors in surveys. However, fish that were weighed-in during tournaments often had fin damage (52% of fish) and/or barotrauma (25% of fish, in impoundments only), and were held in live wells with poor water-quality. The prevalence of these sublethal effects varied considerably according to the specific seasons, locations, rules and procedures of each tournament; but could not be reliably attributed to any of the recorded catch-and-release variables (except for dissolved oxygen, which was significantly influenced by live-well volume). While these results validate the current release of angled Australian bass as a means of conserving their stocks, the potential for adverse effects could nevertheless be minimised via simple changes to conventional handling. © 2010 Springer Science+Business Media B.V.

Roberts L.W.,Fisheries Conservation Technology Unit | Butcher P.A.,Fisheries Conservation Technology Unit | Broadhurst M.K.,Fisheries Conservation Technology Unit | Cullis B.R.,University of Wollongong | Cullis B.R.,CSIRO
ICES Journal of Marine Science | Year: 2011

Yellowtail kingfish (Seriola lalandi) are angled throughout their global distribution and released in large numbers under the unsubstantiated assumption of few impacts. The validity of this supposition was tested for southeastern Australian stocks. In all, 54 fish were angled and released into cages with 36 controls and monitored for 5 d. Of the angled fish, 15% died, mostly as a consequence of gill-hooking and the associated physiological and mechanical damage. A biotelemetry experiment was then performed to determine if cutting the line on gill-hooked fish could improve their post-release fate. The attachment of transmitters was validated in an aquarium experiment before 12 jaw- and 10 gill-hooked fish were tagged, released, and tracked. One gill-hooked fish was detected motionless within 10 min, and another was last detected 7 min after release; both presumed dead. No jaw-hooked fish died within the first 24 h. The remaining fish were last detected between 3 and 49 d after release and, apart from subtle differences in their short-term responses, maintained similar wide-ranging movements and accelerations. The results justify cutting the line on deephooked fish to minimize post-release mortality and illustrate the utility of combining confinement and biotelemetry studies to assess the fate of released fish. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.

Butcher P.A.,Fisheries Conservation Technology Unit | Broadhurst M.K.,Fisheries Conservation Technology Unit | Hall K.C.,Fisheries Conservation Technology Unit | Cooke S.J.,Carleton University
ICES Journal of Marine Science | Year: 2011

The study was initiated in response to concerns about the post-release welfare of angled luderick (Girella tricuspidata) after protracted confinement in keeper nets. In all, 111 fish were angled and confined for 2-250 min before being released into holding cages (with 87 controls) and monitored for 4 d. Blood was taken from fish angled and brought on board immediately (n = 11), angled and held in keeper nets (n = 25), and angled and held in monitoring cages for 4 d (n = 12). Blood was also taken from controls held in monitoring cages for 4 d (n = 12). No controls and only one angled fish died. Compared with immediately sampled angled fish, those confined in keeper nets had significantly elevated cortisol, glucose, lactate, chloride, sodium, and aspartate aminotransferase. Most of the variables returned to pre-stress levels in caged fish after 4 d. Despite this recovery, the short-term stress associated with capture and keeper-net confinement has welfare implications and justifies avoiding such a practice and/or reducing the personal daily angling quota of the species. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.

Silva C.N.S.,Victoria University of Wellington | Broadhurst M.K.,Fisheries Conservation Technology Unit | Medeiros R.P.,Federal University of Paraná | Dias J.H.,Federal University of Paraná
Marine Policy | Year: 2013

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.

Broadhurst M.K.,Fisheries Conservation Technology Unit | Butcher P.A.,Fisheries Conservation Technology Unit | Cullis B.R.,Wagga Wagga Agricultural Institute
Fisheries Research | Year: 2011

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.

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 | Year: 2010

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.

Broadhurst M.K.,Fisheries Conservation Technology Unit | Millar R.B.,University of Auckland
Fisheries Management and Ecology | Year: 2011

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.

Broadhurst M.K.,Fisheries Conservation Technology Unit | Millar R.B.,University of Auckland | Brand C.P.,Fisheries Conservation Technology Unit
Fisheries Research | Year: 2010

This study was predicated by a recent management proposal to mandate square-mesh codends in an Australian estuarine squid trawl fishery, based on their improvements to the selectivity of penaeid trawls deployed across comparable temporal and spatial scales. The assumption of no impacts of a codend cover on the performance of a squid trawl was validated before it was used to quantify the size and species selection of a conventional codend made from 41-mm diamond-shaped mesh and two new designs made from 29- and 32-mm mesh hung on the bar (i.e. square shaped). Compared to the 41-diamond codend, both square-mesh designs incrementally and significantly reduced the catches of a small legally retained teleost (whitebait Hyperlophus vittatus), but had no significant effect on discarded catches (termed 'bycatch'). The 32-square codend also significantly increased the sizes at 50% probability of retention for the targeted squid (Luminous Bay squid Loliolus noctiluca and broad squid Photololigo etheridgei), across narrow selection ranges and, because all sizes are retained, consequently reduced their total landed catches. The results support the utility of square-mesh for consistently improving and maintaining lateral openings in codends, but the management of this fishery means that such configurations would result in economic loss, and for the 29- and 32-square codends, no concomitant reduction in bycatch. This study reiterates the need for bycatch issues to be clearly identified and defined on a fishery-specific basis, and prior to the implementation of mitigation measures. Crown Copyright © 2009.

Hall K.C.,Fisheries Conservation Technology Unit | Broadhurst M.K.,Fisheries Conservation Technology Unit | Butcher P.A.,Fisheries Conservation Technology Unit
Fisheries Management and Ecology | Year: 2012

Short-term (≤4days) post-release mortalities of two large, culturally and ecologically important Australian freshwater teleosts golden perch Macquaria ambigua (Richardson) and Murray cod Maccullochella peelii (Mitchell) were investigated. There was no angler-induced mortality among golden perch that were immediately released in winter and spring, but 24% of this species and 15% of Murray cod died after delayed release in summer. Significant predictors of mortality were limited to times caught and total length for golden perch, and restraint methods and recovery times for Murray cod, but other parameters were also implicated as cumulative influences. The estimated mortalities may be sufficient to produce population-level impacts for these two long-lived species but could be considerably reduced through revisions of tournament regulations. © 2011 State of New South Wales.

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