Mitigation of incidental mortality of Australian sea lions in the west coast rock lobster fishery

Campbell, Richard A.; Holley, David; Christianopoulos, Dimitrios; Caputi, Nick; Gales, Nicholas J.

doi:10.3354/esr00155

Cited by 22 publications

(13 citation statements)

References 21 publications

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“…Gear modifications were designed either to (i) prevent ingress (Cole and Helser ; Campbell et al . ) or to (ii) promote escape (Tallack ; Rudershausen et al . ), especially of teleosts and turtles.…”

Section: Reviewmentioning

confidence: 99%

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Mitigating unaccounted fishing mortality from gillnets and traps

2013

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Gillnets and traps often are considered to have fewer holistic environmental impacts than active fishing gears. However, in addition to the targeted catches, gillnets and traps still cause unwanted mortalities due to (i) discarding, (ii) ghost fishing of derelict gear, (iii) depredation, (iv) escaping or dropping out of gear, (v) habitat damage, and potentially (vi) avoiding gear and predation and (vii) infection of injuries sustained from most of the above. Population‐level concerns associated with such ‘unaccounted fishing mortalities’ from gillnets and traps have been sufficient to warrant numerous attempts at mitigation. In this article, we reviewed relevant research efforts, locating 130 studies in the primary literature that concomitantly quantified mortalities and their resolution through technical modifications, with the division of effort indicating ongoing concerns. Most studies (85) have focused on discard mortality, followed by ghost‐fishing (24), depredation (10) and escape (8) mortalities. The remaining components have been poorly studied (3). All problematic mortality components are affected by key biological (e.g. species), technical (e.g. fishing mechanisms) and/or environmental (e.g. temperature) factors. We propose that these key factors should be considered as part of a strategy to reduce impacts of these gears by first assessing modifications within and then beyond conventional configurations, followed by changes to operational and handling practices. Justification for this three‐tiered approach is based not only on the potential for cumulative reduction benefits, but also on the likely ease of adoption, legislation and compliance.

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Section: Reviewmentioning

confidence: 99%

“…For example, changing the diameter of entrance openings impeded the entry of prospecting diamondback terrapin (Cole and Helser ; Butler and Heinrich ; Hart and Crowder ), Australian sea lion ( Neophoca cinerea, Otariidae; Campbell et al . ) and sea otter ( Enhydra lutris, Mustelidae; Hatfield et al . ).…”

Section: Reviewmentioning

confidence: 99%

Mitigating unaccounted fishing mortality from gillnets and traps

2013

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“…In contrast, modifications to fishing gear can provide a relatively low-cost method of reducing the incidental capture of non-target species, requiring a one-time expenditure on new gear (Watson et al 2005, Campbell et al 2008. To date, however, there have been only a limited number of trials of gillnet modifications that have demonstrated a significant decrease in cetacean bycatch.…”

Section: Introductionmentioning

confidence: 99%

“…When a high overlap between the distribution of the species and the fishery effort exists, time-area closures can be economically unsustainable. Due to the social and economic framework of the artisanal gillnet fishery in San Clemente del Tuyu, time-area closures are not considered a viable mitigation method for this fishery.In contrast, modifications to fishing gear can provide a relatively low-cost method of reducing the incidental capture of non-target species, requiring a one-time expenditure on new gear (Watson et al 2005, Campbell et al 2008. To date, however, there have been only a limited number of trials of gillnet modifications that have demonstrated a significant decrease in cetacean bycatch.…”

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confidence: 99%

Franciscana bycatch is not reduced by acoustically reflective or physically stiffened gillnets

Bordino¹,

Mackay²,

Werner³

et al. 2013

Endang. Species. Res.

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The incidental capture of franciscana Pontoporia blainvillei in gillnet fisheries of Argentina, Uruguay and Brazil represents a major conservation threat to this species. We report on an experimental trial that compared franciscana bycatch rates in standard gillnets to gillnets with 1 of 2 modifications: increased acoustic reflectivity by infusion of barium sulphate (BaSO 4 ) or increased flexural stiffness of the nylon twine. Field trials were conducted in association with artisanal fishermen at San Clemente del Tuyu in Bahia Samborombon, Argentina, between October 2009 and March 2010. Depth sensors were used to record the underwater fishing behaviour of the 3 net types. Seventy-seven dolphins were observed incidentally captured in 807 monitored gillnet hauls, with similar fishing effort observed for each net type. There was no significant difference in franciscana bycatch rates (p > 0.05) or target fish catches (p > 0.05) among the 3 net types. The stiff net twine had a slightly but significantly higher flexural stiffness (FS) than the reflective or control net twine. The FS of the dry stiff twine was similar to that previously reported for BaSO 4 twine with a similar diameter; in contrast, the FS of the reflective nylon was, unexpectedly, much lower. However, the difference in the FS between wet, submerged stiff twine and control twine used in the field was estimated at 19.4%. The BaSO 4 net fished with a significantly lower mean float line height than either the control or stiffened net. These results show that the use of reflective or stiff nets does not lead to a reduction in franciscana bycatch rates; therefore, other management strategies need to be developed to reduce the impact of incidental captures of this species. KEY WORDS: Bycatch · Gillnet · Franciscana · Artisanal fishery Resale or republication not permitted without written consent of the publisher FREE REE ACCESS CCESS Contribution to the Theme Section 'Techniques for reducing bycatch of marine mammals in gillnets'Endang Species Res 21: [1][2][3][4][5][6][7][8][9][10][11][12] 2013 species is listed as Vulnerable by the IUCN (Reeves et al. 2008) and is considered to be the most threatened cetacean in the Southwest Atlantic (Secchi 2010). In coastal waters of Buenos Aires Province, Argentina, an estimated 650 dolphins are bycaught annually (Bordino & Albareda 2004). The most recent population estimate for this species in Argentinean waters is 14 000 individuals (Crespo et al. 2010), so it is unlikely that current bycatch levels are sustainable, and management measures are, therefore, urgently required to reduce the incidental bycatch of the species.The use of acoustic alarms has been shown to significantly reduce the bycatch rates of franciscana (Bordino et al. 2002) and other cetaceans in gillnets (Kraus et al. 1997, Carretta et al. 2008), but the financial cost of implementation and enforcement of pinger use limits their applicability in many smallscale fisheries (Read 2008). Concerns that the widespread use of acoustic alarms cou...

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“…The ASL has a 14 mo gestation period and a 15–18 mo lactation period that are among the longest for an otariid (Higgins and Gass 1993, Gales et al 1994). This nonannual breeding cycle translates into a lower lifetime reproductive potential for this species, the result of which is a high vulnerability to minor changes in survival rates due to environmental variability and anthropogenic factors (Page et al 2004, Goldsworthy and Page 2007, Campbell et al 2008 b ).…”

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confidence: 99%

Survival estimates for the Australian sea lion: Negative correlation of sea surface temperature with cohort survival to weaning

McIntosh

Arthur

Dennis³

et al. 2012

Marine Mammal Science

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The Australian sea lion (Neophoca cinerea) population at Seal Bay Conservation Park, South Australia, is estimated to be declining at a rate of 1.14% per breeding season. To better understand the potential causes of this decline, survival rates were examined to 14 yr of age for eight cohorts marked as pups (aged 0.17 yr) between 1991 and 2002. Apparent yearly survival rates ( ) varied by cohort for pups from marking to weaning at 1.5 yr ( = 0.30-0.67). Postweaning juvenile survival (1.5-3 yr) was 0.89 and survival from 3 to 14 yr was constant ( female:male = 0.96:0.89). of pup cohorts was negatively correlated to local sea surface temperature where the sea lions forage (SST) and was especially low for cohort 7 in 2000 (0.30). It is possible that periods of unusually warm oceanographic conditions may be limiting primary production and inhibiting maternal provisioning to pups. Pup survival to weaning is relatively low compared to other otariid species, is likely to limit recruitment, and may be contributing to the decline in pup abundance observed in the colony.

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Mitigation of incidental mortality of Australian sea lions in the west coast rock lobster fishery

Cited by 22 publications

References 21 publications

Mitigating unaccounted fishing mortality from gillnets and traps

Mitigating unaccounted fishing mortality from gillnets and traps

Franciscana bycatch is not reduced by acoustically reflective or physically stiffened gillnets

Survival estimates for the Australian sea lion: Negative correlation of sea surface temperature with cohort survival to weaning

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