Odontocete cetaceans foraging behind trawlers, worldwide

Bonizzoni, Silvia; Hamilton, Sheryl; Reeves, Randall R.; Genov, Tilen; Bearzi, Giovanni

doi:10.1007/s11160-022-09712-z

Cited by 26 publications

(35 citation statements)

References 238 publications

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“…The energetic benefit of depredation (Tixier et al, 2015) comes with an increased risk of injury for individuals, incidental capture (bycatch), and/or mortality during the interaction with the fishing gear, leading to a risk-reward trade-off that can modify individual behavior and social dynamics (Santana-Garcon et al, 2018;Buscaino et al, 2021). Several common bottlenose dolphin populations are known to interact with different fishing gears (e.g., Blasi and Boitani, 2014;Pennino et al, 2015;Buscaino et al, 2021), and a number of reports are related to trawling boats (e.g., Pace et al, 2012;Genov et al, 2019;Bonizzoni et al, 2021;Bonizzoni et al, 2022), with individuals intentionally entering the nets and actively take advantage of fisheries through depredation (i.e., injuries or removal of captured fish from a fishing gear; Chilvers and Corkeron, 2001;Hamer et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The interaction with trawling vessels highlights conservation issues and management implications as well (e.g., Chilvers and Corkeron, 2001;Pace et al, 2012;Bonizzoni et al, 2021;Vella et al, 2021;Bonizzoni et al, 2022). It clearly influences social dynamics and changes the pattern of interactions at the group level, possibly affecting demographic parameters such as survival and reproduction (Maldonado-Chaparro and Chaverri, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Information on the social structure of bottlenose dolphin units in the Mediterranean Sea is scattered and not fully reported yet (Blasi and Boitani, 2014). Some of the available data seem to suggest that sex composition (Blasi and Boitani, 2014) and operational trawlers (Pace et al, 2012;Genov et al, 2019;Bonizzoni et al, 2021;Bonizzoni et al, 2022) may play a pivotal role in shaping social structure and patterns of individual arrangements. Here, the social structure of the bottlenose dolphins living nearby the Tiber River estuary (central Mediterranean Sea, Italy) is reported, with the aim of providing an initial assessment of the relationships between individuals in this geographical unit under local conditions.…”

Section: Introductionmentioning

confidence: 99%

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Resources and population traits modulate the association patterns in the common bottlenose dolphin living nearby the Tiber River estuary (Mediterranean Sea)

et al. 2022

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Sociality and ecological drivers that can influence individual association patterns are infrequently considered in wildlife management, although they are essential aspects affecting animals’ responses to both human-related pressures and conservation strategies. In common bottlenose dolphins (Tursiops truncatus), sex-specific social dynamics and interactions with anthropogenic activities may affect grouping and induce changes in relationships between individuals. Out of a total of 347 individuals, we assessed the level of association among 68 bottlenose dolphins that have been sighted more than five times near the Roman coast (central Mediterranean Sea, Italy). The half-weight index (HWI) of dyadic associations, their network relations, and stability over time were investigated by using the SOCPROG software. Outcomes showed that females were more strongly associated than other individuals, with both preferred constant short-term associations and random long-term associations, possibly resulting in greater success in rearing young. Individuals interacting with the bottom trawl fishery showed weaker and short-term associations. Temporary disruption of individual associations during interaction with fishery and the relatively low number of females with calves participating in depredation seem to denote both the opportunistic nature of interactions with fishing vessels and the offspring-related protection strategy. The results show that the dolphins in this region maintain a complex but flexible social structure that varies with local biological requirements and is resilient to anthropogenic pressures.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Resources and population traits modulate the association patterns in the common bottlenose dolphin living nearby the Tiber River estuary (Mediterranean Sea)

et al. 2022

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“…Interactions between cetaceans and different types of fisheries have been described in many places (Lewison et al, 2014). Fishery discards constitute an important food source for cetaceans, attracting them to fishing grounds (Bonizzoni et al, 2022). In areas such as the Atlantic Ocean, bottom trawling entails a high number of cetacean accidental catches (Loṕez et al, 2003;Fernańdez-Contreras et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Assessment of the interactions between cetaceans and fisheries at the south of the Cetacean Migration Corridor and neighboring waters (Western Mediterranean)

et al. 2022

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The Cetacean Migration Corridor is an important marine protected area for cetacean species in the Western Mediterranean, and part of its waters constitute the main fishing grounds for the Valencia region (East Spain) fishing fleet. Here we aim to assess the interactions between all active fisheries operating in the waters of the Valencia region and the cetacean species inhabiting this area. A total of 282 face-to-face interviews (51.37% of the total fleet) to fishers were held on 20 ports at the study area to gather information about cetacean by-catch and all types of interactions between fisheries and cetaceans. The interviewed bottom trawlers (n = 148 boats) reported a monthly by-catch rate (C) of 0.01 dolphins per vessel. Bottom trawling vessels operating at neritic zones only reported by-catch of common bottlenose dolphin (C = 0.009), while those fishing at oceanic zones by-caught striped dolphin (C = 0.006) and common bottlenose dolphin (C = 0.003). The interviewed artisanal fishers (n = 114 boats), the second most important fishery in the study area, only reported one dolphin by-catch event, but 90 of these boats communicated continued negative interactions with the common bottlenose dolphin, causing gear damage and catch take. The interviewed vessels gave an estimation of their annual economic loss produced by this interaction (mean ± SD: 2,998.10 ± 2095.02 € per boat). Other fisheries operating in the Valencia region were purse-seiners (n = 15 boats) and pelagic longlines, a fishery that has almost disappeared in the study area (n = 5 boats). The first one had the highest estimated dolphin by-catch rate (C= 0.04) and mainly interacted with common bottlenose dolphin, but also with striped dolphin. The information gathered from interviews was complimented with long-term stranding data (1990–2020). Despite the fact that only 7.80% of all recorded stranded cetaceans showed fisheries interaction signs, 26.72% of the common bottlenose dolphins recorded showed evidence of this interaction, thus confirming that it is the cetacean species most affected by fisheries in the area. Records of stranded striped dolphin (6.45%) also showed evidence of fisheries interaction. Based on both dolphin by-catch and gear damage, management plans are needed in the area to ensure cetacean conservation and also fisheries sustainability in waters inside and around marine protected areas at the Spain’s Mediterranean.

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“…Bottom trawling accounts for 20% of global fisheries (Hiddink et al 2017), and interactions have been observed with a range of both odontocete and mysticete species of whale (Barros et al 2004; Bearzi et al 2003; Bonizzoni et al 2022; Chilvers and Corkeron 2001; Couperus 1997; Fertl and Leatherwood 1997; Hucke-Gaete et al 2004; Kovacs et al 2017; Leatherwood et al 1989; Lien 1994; Morizur et al 1999). In the western North Atlantic, the offshore habitat and diets of deep diving sperm whales ( Physeter macrocephalus ) and northern bottlenose whales ( Hyperoodon ampullatus ) are known to overlap with areas and species targeted by trawlers (Clarke et al 1993; Gaskin and Cawthorn 1967; Gowans et al 2000; Karpouzli and Leaper 2004; Northridge 1984; Wimmer and Whitehead 2004).…”

Section: Introductionmentioning

confidence: 99%

Sperm and northern bottlenose whale interactions with deep-water trawlers in the western North Atlantic

Oyarbide

Feyrer

Gordon

2021

Preprint

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Interactions between various cetacean species and fisheries are geographically widespread and diverse. Foraging in association with fishing activities may increase prey encounter rates and possibly increase the quantity and the quality of the food consumed. This paper describes interactions between benthic trawlers, targeting mainly Greenland halibut, and two whale species: sperm whales and northern bottlenose whales, in the eastern Grand Banks of the northwest Atlantic. Whale behaviors were compared during four trawling-related activities: preparing/ shooting the net, towing, hauling and transiting between fishing sites. Sperm whales and bottlenose whales were more likely to be observed during hauling. We observed probable feeding behavior of both species close to the surface at the end of hauling which suggests they are taking fish escaping from the cod end of the net when it is close to the surface. It is not clear whether feeding attempts are made during other phases of the trawling cycle. Ten sperm whales were photo-identified and six of these individuals were resighted on different days. Resights of individuals indicated that sperm whales could follow trawlers through several sets over of distances up to 234 km. While some individuals were observed to move between fishing grounds others remained within one fishing area for some time. By contrast, even though twenty-three bottlenose whales were photo-identified, there were no resights of individual whales. While northern bottlenose whales have been studied quite extensively in some adjacent areas, particularly off Nova Scotia, their behaviour and distribution within the Grand Banks fishing areas has not been well described. No matches were found between northern bottlenose whales in this study and photo-identification catalogues for the Scotian Shelf or the Arctic. Whether and how northern bottlenose whales found in this area are connected to other subpopulations remains unclear.

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Odontocete cetaceans foraging behind trawlers, worldwide

Cited by 26 publications

References 238 publications

Resources and population traits modulate the association patterns in the common bottlenose dolphin living nearby the Tiber River estuary (Mediterranean Sea)

Resources and population traits modulate the association patterns in the common bottlenose dolphin living nearby the Tiber River estuary (Mediterranean Sea)

Assessment of the interactions between cetaceans and fisheries at the south of the Cetacean Migration Corridor and neighboring waters (Western Mediterranean)

Sperm and northern bottlenose whale interactions with deep-water trawlers in the western North Atlantic

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