Testing a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska

O'Connell, Victoria; Straley, Janice M.; Liddle, Joe; Wild, Lauren; Behnken, Linda; Falvey, Dan; Thode, Aaron

doi:10.1093/icesjms/fsv014

Cited by 11 publications

(10 citation statements)

References 11 publications

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“…For example, sperm whales have been reported depredating on 18 to 25% of Patagonian toothfish longline sets in South Georgia (Moir Clark and Agnew, 2010; Purves et al, 2004;Söffker et al, 2015) and 35% of the sets in the Falklands (Goetz et al, 2011;Yates and Brickle, 2007). In Alaska, 10 to 35% of all longline sets were depredated by sperm whales on the sablefish fisheries (Hill et al, 1999;O'Connell et al, 2015;Peterson and Carothers, 2013;Straley et al, 2006Straley et al, , 2015Thode et al, 2015).…”

Section: Sperm Whale Depredation Levelsmentioning

confidence: 99%

“…Extensive efforts have been made by fishers and ship-owners to develop technological solutions to either deter marine mammals from fishing gear or to protect the fish caught on 6 hooks. However, most trials of such devices have showed limited efficacy (Dyb, 2006a;Hamer et al, 2012;Mooney et al, 2009;O'Connell et al, 2015;Tixier et al, 2015b). The development of fishing strategies for avoiding interactions has provided more promising insights into ways to reduce depredation levels.…”

Section: Introductionmentioning

confidence: 99%

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How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries?

et al. 2018

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Marine mammal depredation on fisheries (animals removing fish caught on fishing gear) is a worldwide issue involving socio-economic and ecological consequences. Longline fisheries are the most impacted by odontocete (toothed whales) depredation. While technological means have provided limited efficacy in reducing depredation, this study examined the fishing practices influencing both the proportion of depredated longline sets and the amount of fish removed by whales. We used an 8-year dataset from the Patagonian toothfish (Dissostichus eleginoides) longline fisheries operating in Crozet and Kerguelen Economic Exclusive Zones (EEZs) (South Indian Ocean) and GLMMs to investigate sperm whale (Physeter macrocephalus) depredation. Sperm whale depredation occurred on 61% of 5260 sets in Crozet and 41% of 16,902 sets in Kerguelen, and resulted in minimum estimated toothfish losses of 702 tons and 2649 tons, respectively, in the two areas. The probability of depredation decreased in winter months, increased with depth fished and decreased when vessels travelled over distances of >60 km from fishing grounds with encountering depredation. These findings suggest the natural spatio-temporal distribution of sperm whales and their ability to follow vessels over limited ranges influence the number of captured fish removals. The amount of depredated toothfish decreased with the speed at which longline sets were hauled and increased with the soaking time of sets suggesting that whales may depredate sets during both hauling and soaking operations. Together, these observations indicate that rates of depredation may be influenced by the conditions of fishing operations and could therefore be Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.employed to implement strategies of avoidance in all fisheries facing similar depredation impacts.

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Section: Sperm Whale Depredation Levelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries?

et al. 2018

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“…Several depredation mitigation measures have been or are being tested worldwide to mitigate this issue, including physical protection of the catch or acoustic devices, but this remains challenging work (Hamer, Childerhouse & Gales, ; Løkkeborg, ; O'Connell et al., ; Rabearisoa, Bach & Marsac, ; Rabearisoa, Sabarros et al., ; Straley et al., ; Tixier, Garcia, Gasco, Duhamel & Guinet, ; Tixier et al., ; Werner, Northridge, Press & Young, ). For this reason, it is important to know the mechanisms by which depredation episodes occur in pelagic longline fleets.…”

Section: Discussionmentioning

confidence: 99%

Depredation in pelagic surface longlines in the Atlantic and Indian Oceans

Muñoz‐Lechuga

Coelho

2018

Fisheries Management Eco

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Depredation has aroused great interest over the last few decades, mainly due to the expansion of distant fishing, in particular longlines. For this study, captures and depredation records were taken by scientific observers on board Portuguese commercial longline vessels in the Atlantic and Indian Oceans between 2011 and 2016. A total of 1,336 fishing sets were monitored, with a total of 86,183 fish captured, including 1,681 depredation events. The percentage of depredation tended to increase along the time series, except in the last year where a decrease was noted. Significant differences between sizes of swordfish Xiphias gladius damaged by predators were observed in the Indian Ocean but not in the Atlantic. The highest proportions of depredation were observed on tuna and small pelagic fishes in both oceans. For swordfish, the effects of spatial variables were significant on the rate of depredation events. The results provide an overview of the depredation patterns in the Portuguese pelagic longline fishery in the Atlantic and Indian Oceans, which can inform and improve fisheries management and contribute to the development of effective mitigation measures to reduce the impacts of depredation on fisheries.

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“…Given the specificities of the pole-and-line tuna fishing in the Azores, and the ecology of common dolphins and tuna, the only measure that could potentially reduce interaction would be to keep dolphins away from the fishing area using acoustic devices. However, the effectiveness of acoustic deterrents at decreasing cetacean interaction is still unclear [57, 59, 60]. Recently, Cruz et al .…”

Section: Discussionmentioning

confidence: 99%

Predicting Interactions between Common Dolphins and the Pole-and-Line Tuna Fishery in the Azores

et al. 2016

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Common dolphins (Delphinus delphis) are responsible for the large majority of interactions with the pole-and-line tuna fishery in the Azores but the underlying drivers remain poorly understood. In this study we investigate the influence of various environmental and fisheries-related factors in promoting the interaction of common dolphins with this fishery and estimate the resultant catch losses. We analysed 15 years of fishery and cetacean interaction data (1998–2012) collected by observers placed aboard tuna fishing vessels. Dolphins interacted in less than 3% of the fishing events observed during the study period. The probability of dolphin interaction varied significantly between years with no evident trend over time. Generalized additive modeling results suggest that fishing duration, sea surface temperature and prey abundance in the region were the most important factors explaining common dolphin interaction. Dolphin interaction had no impact on the catches of albacore, skipjack and yellowfin tuna but resulted in significantly lower catches of bigeye tuna, with a predicted median annual loss of 13.5% in the number of fish captured. However, impact on bigeye catches varied considerably both by year and fishing area. Our work shows that rates of common dolphin interaction with the pole-and-line tuna fishery in the Azores are low and showed no signs of increase over the study period. Although overall economic impact was low, the interaction may lead to significant losses in some years. These findings emphasize the need for continued monitoring and for further research into the consequences and economic viability of potential mitigation measures.

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Testing a passive deterrent on longlines to reduce sperm whale depredation in the Gulf of Alaska

Cited by 11 publications

References 11 publications

How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries?

How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries?

Depredation in pelagic surface longlines in the Atlantic and Indian Oceans

Predicting Interactions between Common Dolphins and the Pole-and-Line Tuna Fishery in the Azores

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