Utility of morphological data for key fish species in southeastern Australian beach‐seine and otter‐trawl fisheries: Predicting mesh size and configuration

Broadhurst, Matt K.; Dijkstra, Koenraad K. P.; Reid, Dennis; Gray, Charles A.

doi:10.1080/00288330.2006.9517419

Cited by 39 publications

(51 citation statements)

References 22 publications

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“…Like most gillnets, the 80 mm configurations examined in this study selected the key teleosts across discrete ranges of sizes that were closely correlated to their maximum girth in relation to the mesh perimeter (i.e. 160 mm; Broadhurst et al 2006b). Further, nearly all fish penetrated multiple meshes along their anterior bodies, with some completely wrapped in netting, which presumably occurred after they entered the first mesh and then struggled to escape (Hamley 1975).…”

Section: Discussionmentioning

confidence: 99%

Mitigating discard mortality from dusky flathead Platycephalus fuscus gillnets

Broadhurst

Millar²,

Brand³

2009

Dis. Aquat. Org.

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The mortalities and contributing parameters were estimated for key species discarded during commercial gillnetting (80 mm mesh) targeting dusky flathead Platycephalus fuscus in a southeastern Australian estuary. Bycatches (1470 individuals from 16 species over 11 deployments) were assessed for their immediate mortalities onboard the gillnetter, before subsamples (570 individuals from 11 species) were discarded into cages and monitored for their short-term fate over 4 d. Appropriate controls were concurrently caged and monitored. Blood samples were taken from some live meshed-and-discarded yellowfin bream Acanthopagrus australis and luderick Girella tricuspidata and analysed for plasma cortisol and glucose. Concomitantly angled fish were similarly sampled (to provide baseline estimates of blood physiology). The immediate mortalities of the abundant species ranged between 0 (undersize blue swimmer crab Portunus pelagicus < 6 cm carapace length) and 70% (undersize P. fuscus < 36 cm total length [TL]). Water temperature had a statistically significant positive relationship with the immediate mortality of G. tricuspidata and large-tooth flounder Pseudorhombus arsius, and TL had a significant negative relationship with the immediate mortality of black sole Synaptura nigra. Compared to baseline estimates, mean plasma cortsiol concentrations in meshed-and-discarded G. tricuspidata and A. australis were significantly greater, and approached levels comparable to most teleosts after peak stress. Mean glucose concentrations were not concomitantly elevated, possibly reflecting limited time between stress and sampling for some individuals. Short-term mortalities occurred throughout the entire 4 d monitoring period for most species and ranged from 0 (yellowfin leatherjacket Meuschenia trachylepis) to 29% (A. australis). Water temperature and TL were identified as having significant impacts similar to those described above on the delayed fate of A. australis and G. tricuspidata. The partitioned mortalities were combined to provide estimates of overall mortality (± SE) for the main species that ranged between 5.9 ± 3.3% (P. pelagicus) and 76.9 ± 7.8% (undersize P. fuscus). Discard mortality in this fishery could be mitigated by allowing fishers to retain a small percentage of undersize P. fuscus, restricting the deployment of nets in water temperatures >16 to 17°C, and encouraging the careful removal of catches from meshes.KEY WORDS: Gillnet · Bycatch · Discards · Mortality · Unaccounted fishing mortality Resale or republication not permitted without written consent of the publisherDis Aquat Org 85: [157][158][159][160][161][162][163][164][165][166] 2009 factors (such as twine diameter -∅, material and hanging ratios) according to the species being targeted (Gray 2002, Gray et al. 2004, 2005a, 2005b. While there are considerable differences among the types and designs of gillnets used in NSW, most can nevertheless be separated into 4 broad categories according to their deployment and the main species sought. These c...

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Section: Discussionmentioning

confidence: 99%

Mitigating discard mortality from dusky flathead Platycephalus fuscus gillnets

Broadhurst

Millar²,

Brand³

2009

Dis. Aquat. Org.

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“…In particular, by combining the partitioned estimates of mortality, it is apparent that like many similarly handled small teleosts discarded from active gears worldwide (Broadhurst et al 2006a), the majority (between 72 and 100%) of Gerres subfasciatus and Herklotsichthys castelnaui died after discarding, mostly within 24 to 48 h. In comparison, the total discard mortalities of trawled Acanthopagrus australis and seined Rhabdosargus sarba generally were more protracted (over up to 120 h) and ranged from 3 to 35% and from 24 to 100%, respectively. For A. australis, the percentages dying were comparable to those recorded for individuals released from capture by hook and line (e.g.…”

Section: Discussionmentioning

confidence: 99%

Damage and partitioned mortality of teleosts discarded from two Australian penaeid fishing gears

Uhlmann

Broadhurst²

2007

Dis. Aquat. Org.

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“…At the end of the experiment, all surviving hook-ingested/-ejected and control fish were removed from their tanks and sampled for plasma cortisol and glucose before being euthanized in a solution of benzocaine (100 mg l -1 in seawater). The euthanized hook-ingested/-ejected and control fish were immediately weighed (to the nearest 0.01 g), sexed where possible, and measured for TL, maximum height (MH) maximum width (MW) and maximum girth (MG) (all to the nearest 1 mm) according to descriptions provided by Broadhurst et al (2006). Those fish that still contained ingested hooks were lat- erally X-rayed before all individuals were dissected.…”

Section: Methodsmentioning

confidence: 99%

Ingestion and ejection of hooks: effects on long-term health and mortality of angler-caught yellowfin bream Acanthopagrus australis

Broadhurst¹,

Butcher²,

Brand³

et al. 2007

Dis. Aquat. Org.

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Ninety juvenile yellowfin bream Acanthopagrus australis were angled from holding tanks, allowed to ingest nickel-plated, carbon-steel J-hooks and released (with their lines cut) into individual experimental tanks during 2 experiments in order to assess their (1) long-term (up to 105 d) health, mortality and rate of hook ejection and (2) short-and medium-term (< 42 d) temporal changes in health during hook ingestion. Equal numbers of control fish were scooped from holding tanks and similarly monitored in experimental tanks. Of 20 hook-ingested fish released during Expt 1, 3 died within 8 d, providing a non-significant mortality of 15%. Between Day 6 and Day 56 post-release, 13 of the surviving individuals ejected their hooks, which were typically oxidized to about 94% of their original weight and often broken into 2 pieces. At Day 105, there were no significant differences between the 20 control and 17 hook-ingested/-ejected fish in terms of their ability to digest and assimilate food (measured as changes in apparent digestibility coefficients), stress (measured as concentrations of plasma cortisol and glucose) or of morphological parameters that included weight (Wt) and maximum height (MH), maximum width (MW) and maximum girth (MG). During Expt 2, 3 individuals that still contained ingested hooks and 3 controls were sampled on each of 9 occasions between Day 3 and Day 42 post-release. All fish were sampled for blood cortisol and glucose and were then euthanized before being weighed and measured for total length (TL), MH, MW and MG. Hook-ingested individuals were also X-rayed to determine the position and orientation of hooks. There were no significant differences in plasma glucose between hook-ingested and control fish. Irrespective of the treatment of fish, concentrations of cortisol were elevated on some sampling occasions, indicating variable, acute stress. The MH and MG of fish were not significantly different between groups. Significant differences were detected for MG and Wt, with hook-ingested fish having weights similar to those of the control fish but a relatively greater MW (owing to stomach distension from ingested hooks) until 2 wk post-release, after which both morphological parameters generally declined. There was no significant temporal progression of hooks in the stomach of treatment fish; however, some hooks reorientated to positions that may have precluded passage along the digestive tract. We conclude that, for the J-hooks examined, cutting the line is an appropriate strategy that results in the greater majority of released hook-ingested yellowfin bream surviving with minimal negative long-term effects. KEY WORDS: Acanthopagrus australis · Catch-and-release · Hook mortality · Hook ingestionResale or republication not permitted without written consent of the publisher

show abstract

Utility of morphological data for key fish species in southeastern Australian beach‐seine and otter‐trawl fisheries: Predicting mesh size and configuration

Cited by 39 publications

References 22 publications

Mitigating discard mortality from dusky flathead Platycephalus fuscus gillnets

Mitigating discard mortality from dusky flathead Platycephalus fuscus gillnets

Damage and partitioned mortality of teleosts discarded from two Australian penaeid fishing gears

Ingestion and ejection of hooks: effects on long-term health and mortality of angler-caught yellowfin bream Acanthopagrus australis

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