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Entangling gear can have very different configurations on North Atlantic right whales. A. EG 1427, showing a rostrum wrap with 82 m (269 ft) of trailing line. B. EG 2030, showing extensive body and flipper wraps, with little line trailing. Dashed lines are used to illustrate rope on the underside of the animal.
Source publication
Lethal and sublethal fishing gear entanglement is pervasive in North Atlantic right whales (Eubalaena glacialis). Entanglement can lead to direct injury and is likely to incur substantial energetic costs. This study (1) evaluates drag characteristics of entangled right whales, (2) contextualizes gear drag measurements for individual whales, and (3)...
Contexts in source publication
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... were followed dur- ing all transfers. Some gear sets had been altered to return components to their right- ful owner, or for use in other previous experiments. Gear sets were reassembled as needed, and towed in configurations that best replicated the entanglement scenario of each case as documented by the disentanglement team (see, e.g., Fig. 2) as ...
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... ET AL.: DRAG FROM ENTANGLING FISHING GEAR 10.08 across all measured depths and speeds for all gear sets. The median CV was 0.089; high CVs occurred at the lowest speeds, because CV approaches infinity as mean measured drag values approach zero. Drag coefficients (C d ) range from 9.2 9 10 -3 AE 0.0029 to 0.45 AE 0.13 across gear configurations (Fig. 4, S2). The meanAESD power relating drag and speed across all gear sets (n = 21) was 1.43 AE 0.52, less than the expected theoretical drag % speed 2 ...
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... and speed differentially affect the drag coefficients of gear sets in these five clusters (Fig. S2). Drag coefficients in clusters A, B, D, and E decrease with increasing speed, whereas the drag coefficient of cluster C (J092706) increases with speed. Drag coefficients of gear in clusters A and D increase with depth. In clusters C and E, drag coefficients are lower at greater depth at the lowest speeds, but become greatest at the ...
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... with depth on average (Fig. 4, S2), likely due to the increase in frontal area when lines are buoyed to the water surface (Fig. 1, orange line); those that did not follow this trend may have been neutrally buoyant, trailing at the same depth instead of being taut to the surface. Buoyancy will greatly affect the shape of gear underwater (Baldwin and Pickett 2009), as ...
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... absence of wraps of body parts and drag (at those body parts and to the whale as a whole). This study addresses some of the issues sur- rounding one of those factors: drag. By lessening the energy cost of swimming as well as the tension on entangled body parts, reducing drag certainly could benefit a whale with 300 m of line trapped in its baleen (Fig. 2A); however, drag reduction is unli- kely to save a whale with a rostrum or body wrap with only 10 m of line trailing (Fig. 2B), as trained responders need at least some trailing line to address body wraps in follow-up disentanglement attempts. Reducing drag, as seen in these results, can help in some whale entanglement cases, but will ...
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... sur- rounding one of those factors: drag. By lessening the energy cost of swimming as well as the tension on entangled body parts, reducing drag certainly could benefit a whale with 300 m of line trapped in its baleen (Fig. 2A); however, drag reduction is unli- kely to save a whale with a rostrum or body wrap with only 10 m of line trailing (Fig. 2B), as trained responders need at least some trailing line to address body wraps in follow-up disentanglement attempts. Reducing drag, as seen in these results, can help in some whale entanglement cases, but will not resolve those that involve wraps of body parts (e.g., Eg 3346 in ...
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... (A) and in situ photograph (B) of the satellite telemetry buoy used for tracking entangled whales for later disentanglement attempts. Figure S2. Groups of gear have similar drag coefficients and responses to depth and speed. ...
Citations
... Whale entanglement is a concern for animal welfare as well as conservation. During an entanglement, if unable to free itself, a whale may die of: asphyxiation through failure to reach the surface to breathe (Laist, 1987); an inability to forage (Cassoff et al., 2011;Moore and Van der Hoop, 2012); or in the case of larger whales, increased energy expenditure due to trailing gear ( Van der Hoop et al., 2016). Entanglement in creel lines can also cause severe injuries such as haemorrhaging, blood vessel lacerations, or the embedding of rope into bone, all of which can be fatal (Meyers et al., 2011). ...
Entanglement in static fishing gear is the largest cause of non-natural mortality for minke whales ( Balaenoptera acutorostrata ) in Scottish waters. To mitigate whale entanglement, one priority is to identify areas where the risk of entanglement is consistently high. Sightings data for minke whales and creel fleets were collected by the Hebridean Whale and Dolphin Trust, during vessel line transect surveys conducted between 2008 and 2014. Habitat modelling was used to relate survey, environmental, and temporal variables to the co-occurrence of minke whales and creels in coastal waters of western Scotland. This revealed that minke whale occurrence was related to depth, peaking around 70 m. Using predictive habitat modelling, the overlap between minke whale habitat and the creel fishery was measured as risk of entanglement. A method was developed to quantify the consistency of risk over the seven-year time period. This allowed for the identification of areas where there had been a consistently low, medium, or high risk of entanglement from 2008 to 2014. The three areas with a consistent high risk of entanglement were identified: Inner Sound and Sound of Raasay, east of North and South Uist, and north of The Small Isles. The method presented here could be used to guide management to areas where mitigation efforts will be the most consistently effective over time.
... Fisheries are expanding rapidly in Oman (Yousuf et al., 2009;Oman National Centre for Statistics and Information, 2020) and other parts of the known ASHW range, increasing the likelihood of entanglement. Entanglement, even when not lethal, may compromise feeding and swimming due to the drag created by gear (van der Hoop et al., 2016;van der Hoop et al., 2017), and should also be considered a serious health and welfare issue, given the severe injuries, pain and stress sustained by affected individuals (Cassoff et al., 2011;Moore and van der Hoop, 2012;Dolman and Moore, 2017;Dolman and Brakes, 2018). North Atlantic right whales with non-lethal entanglement histories were more likely to exhibit poor body condition than those without entanglement histories (Pettis et al., 2017). ...
The sub‐population of humpback whales inhabiting the Arabian Sea is a small and genetically distinct population that remains in low latitudes year‐round. Designated as Endangered on the IUCN Red list of Threatened Species, the sub‐population faces a number of threats throughout its range, including entanglement in fishing gear, ship strikes, disease and habitat degradation. Research conducted primarily off the coast of Sultanate of Oman over the past 20 years has contributed to understanding the population’s distribution, abundance, and conservation status. However, information on the population’s health and specific threats is limited. This study examines all available images of Arabian Sea humpback whales obtained between 2000 and 2018 for evidence of disease, predation, epizoites, ectoparasites, and human‐induced scars and wounds. Tattoo skin disease‐like lesions were detected in 41% of 93 whales, with a roughly equal distribution between males and females. Prevalence of the disease was significantly higher in 2012–2018 (51.7%) than in 2000–2011 (27.6%). Killer whale tooth rakes were detected on the ventral surface of the tail flukes of 12% (95% CI 4.5–18%) of 77 individuals. Roughly two thirds (66.6%: 95% CI 52–80%) of the 42 individuals represented by good quality photographs of the caudal peduncle region at the fluke insertion bore scarring patterns consistent with entanglement in fishing gear. At least two individuals showed severe injuries or deformations likely caused by interactions with fishing gear. Six individuals had injuries consistent with vessel strikes. Documented entanglement events from Oman and Pakistan involved large‐mesh nylon gillnets, known to be used extensively throughout the Arabian Sea. These findings indicate an urgent need to design effective measures for the management and mitigation of threats, and to continue monitoring Arabian Sea humpback whales, with an emphasis on methods that allow continued and expanded assessment of health, body condition, and anthropogenic interactions.
... Additionally, in northern right whales (Eubalaena glacialis) dive depth and duration is shown to be significantly shorter when entangled [73] as the cost of the whale towing heavy fishing gear was calculated as an increase in total power input from 1.6% to 120.9%, with locomotive power requirements increasing 60.0%-164.6% [74]. ...
Humans have been altering wildlife habitatsHabitat and wildlife behavior worldwide at an accelerated pace in recent decades. While it is well-understood how human-induced behavioral changes affect infectious disease risk in terrestrial wildlife, less is known in marine life. Here we examine this link in marine mammalMarine mammals populations by (1) conducting a systematic literature review to determine how human disturbancesDisturbance change marine mammal behavior in ways that can impact disease spread, and (2) using a mathematical modeling framework to examine how these behavioral changes might influence potential epidemics. Human disturbances can influence marine mammal behavior in ways that increase their exposure and susceptibility to pathogens, as well as their infectivity, or ability to effectively shed pathogens and infect conspecifics. When these changes to exposure, susceptibility, and infectivity are applied in four different marine mammal case studies (California sea lionsSea lion, Zalophuscalifornianus; Australian humpback dolphinsHumpback dolphin, Australian, Sousa sahulensisSousa sahulensis; killer whalesKiller whale, Orcinus orcaOrcinus orca; Indo-Pacific bottlenose dolphinsBottlenose dolphin, Indo-Pacific, Tursiops aduncusTursiops aduncus), epidemics are predicted to be larger and more likely to occur. Considering the rate at which human disturbanceDisturbance is increasing in the marine environmentEnvironment and the large number of marine mammal species and populations that are endangeredEndangered or on the verge of extinctionExtinction, we advocate for the careful consideration of the direct and indirect impact of human disturbance on marine mammalMarine mammalshealthHealth.
... Studies on the U.S. East Coast demonstrate that drag from fishing gear can be energetically costly and physiologically stressful for individual whales [19]. [95,181], and can have population-level impacts by reducing reproductive capacity of female whales and increasing the impact of parasites and the likelihood of disease [24,182]. ...
Whales serve important biological and cultural functions in the California Current ecosystem (CCE). Due to concerns regarding anthropogenic impacts on whales, the California Ocean Protection Council articulated a goal to achieve zero mortality for CCE whales, with a target of creating a statewide plan by 2022. Achieving zero mortality is a laudable but difficult goal as success depends on understanding the existing sources of mortality, the opportunities for policy change, and coordination of activities across the entire CCE. This review synthesizes the available research on drivers of mortality for nine whale species in the CCE and existing policy that addresses those drivers. Five main threats contribute to whale mortality in the CCE and are currently targeted through relevant policy responses: entanglement, vessel strikes, noise, water quality, and marine debris. Three threats remain largely unaddressed in management, despite their contribution to lethal and sublethal impacts on whales: nutritional stress, disease, and predation. Ultimately, sources of whale mortality are interconnected and their impacts span both geographic and jurisdictional boundaries, necessitating a holistic approach to managing whale mortality in the CCE.
... • Minimize ALDFG production and adverse consequences [6,20,26,109,120,121,172,133,74,195,19,89,126,143,168,181,186,54,69,76,78,85,132,161,162,179] b May be more appropriately categorized as an underlying, indirect driver of ALDFG production [1,175]) reduces gear loss rates. o Securely stowing gear onboard and managing waste produced when repairing and making up new gear reduces the risk of gear being swept or discarded overboard [126]. ...
There has been increasing recognition of the need to address adverse ecological and socioeconomic effects of abandoned, lost and discarded fishing gear (ALDFG). This component of marine debris has been progressively problematic over recent decades with the rapid expansion of global fisheries’ footprint and effort, and the transition to synthetic and more durable materials for gear components. ALDFG drivers and consequences vary substantially by gear type, region, scale and individual fishery within these and other broad categories, including by the robustness of the fisheries management framework and influence of market-based incentives. Therefore, relevant interventions to avoid, minimize and remediate ALDFG depend on the fishery-specific context. This study compiled comprehensive, cross-referenced databases of causes of ALDFG production, and mitigation methods and enabling conditions for effective ALDFG management. Management interventions were categorized within a sequential mitigation hierarchy, where approaches to avoid and minimize ALDFG production and adverse consequences are considered before potentially less effective and more costly interventions for remediation and offsets. The linked databases enable discovery of the most promising ALDFG mitigation methods and priority fisheries management improvements so that a broader range of ALDFG policy interventions can be tapped. Illustrative case studies of ALDFG drivers and interventions were explored for gillnet, pelagic longline, trap and anchored fish aggregating device fisheries. By enabling stakeholders to identify the subset of alternative interventions that are relevant to fishery-specific ALDFG drivers and enabling conditions, the cross-referenced databases guide the allocation of resources to mitigate this especially problematic component of global marine litter.
... For example, foraging ability can be significantly impaired when fishing gear damages, or is attached to, a cetacean's mouth, and has led to starvation in some cases (Andersen et al., 2008;Cassoff et al., 2011). Increased drag from carrying fishing gear can incur considerable energetic costs (Moore and Van der Hoop, 2012;Van der Hoop et al., 2016), while severe tissue damage can result in haemorrhage or debilitation (Cassoff et al., 2011;Moore and Van der Hoop, 2012), and open, unresolved wounds can lead to serious infection (Borucinska et al., 2002;Cassoff et al., 2011). Injured whale sharks (Rhincodon typus) exhibit less evasive behaviours toward tourists and boats than non-injured individuals (Quiros, 2007;Haskell et al., 2015), which suggests that injuries may reduce their agility, or that individuals are choosing warmer surface waters, where tourism activities are concentrated, to aid wound healing (Womersley et al., 2021). ...
Manta ray populations worldwide are vulnerable to sublethal injuries resulting from human activities, e.g., entanglement in fishing line and boat strikes, which have the potential to impact an individual’s health, fitness, and behaviour. Sublethal injuries and physical abnormalities also occur naturally from predation events, deformity, parasites, and disease. To determine the type and frequency of anthropogenic and natural originated injury events affecting Mobula alfredi and M. birostris in the Maldives, we examined data from the Manta Trust’s Maldivian Manta Ray Project (MMRP) database, which contains 73,638 photo-identification (photo-ID) sightings of the two manta ray species from 1987 to 2019. The likely origin of each injury or physical abnormality was determined based on visual assessment of the photo-ID images. Multiple injuries to an individual originating from the same event were grouped for analysis. Generalised linear mixed models (GLMM) were used to investigate the relationship between the occurrence of injury events and the explanatory variables sex and maturity status for both species, with the additional variable site function (cleaning, feeding, cruising) investigated for M. alfredi. Spatial and temporal variations in M. alfredi injury events, and their origin and type, were investigated by calculating the percentage of injury events per sighted individual at each Maldivian atoll, and per re-sighted individual in each year from 2005 to 2019. For both species, injury events were predominantly of natural origin, with predatory bites being the most frequent type. The most common anthropogenic injury type was entanglement in fishing line. Injuries to M. alfredi were significantly more likely to be observed on juveniles than adults, males than females, and at cleaning stations as opposed to feeding or cruising sites. Neither sex nor maturity status were significant explanatory variables for the occurrence of injuries to M. birostris. Highest percentages of anthropogenic injuries per sighted M. alfredi were recorded in North Malé, South Malé, Baa, Addu, and Laamu Atolls, where boat traffic, fishing, and tourism activities are concentrated. Overall, this work greatly improves understanding of the sublethal threats faced by manta rays in the Maldives; identifying focus areas where conservation management actions are required to ensure more effective protection of this threatened species group.
... Nine of these whales had marine debris in their gastro-intestinal tract, with up to 25 kg of debris collected from a single individual (Unger et al. 2016). A study of North Atlantic right whales by van der Hoop et al. (2016), demonstrated how entanglement in fishing gear increases the energy requirements of an entangled whale by up to 102%. This substantial energetic cost has detrimental effects, possibly causing severe emaciation and mortality. ...
Litter in the marine environment, in particular plastic, is a significant threat to marine megafauna. Cetaceans are known to ingest or become entangled in marine debris, likely impacting individuals and populations. Southeast Asia is a biodiversity hotspot and harbours a diverse cetacean assemblage. However, there are key knowledge gaps relating to the impact of litter in this region due the lack of experts to survey its vast coastlines. This study aims to address such gaps by using social media, gathering data from Facebook posts relating to cetacean strandings and litter across Southeast Asia between 2009 and 2019. Results show that at least 15 cetacean species have been negatively affected by litter, with ingestion most commonly affecting deep-diving species. Epipelagic and mesopelagic foragers were most vulnerable to entanglement. Davao in the Philippines was identified as a litter-related stranding hotspot. The Irrawaddy dolphin ( Orcaella brevirostris ) and pygmy sperm whale ( Kogia breviceps ) are particularly vulnerable to litter. The combination of social media and peer reviewed literature can help build a more complete picture of the spatial distribution of marine litter and the scale of the impact it has on cetacean populations. In this study we provide details of a valuable online tool for helping to understand the impact of marine litter on cetaceans and other charismatic species that are a focus of community engagement.
... This phenomenon follows Bernoulli's principle (outside of the boundary layer): lower pressure is accompanied by higher flow speed and the fluid velocity vanishes at the stagnation point.4 | DISCUSSIONPrevious studies have shown the value in evaluating drag on free-swimming and entangled NARWs to understand the effects of entanglement in fishing gear on this species(Cassoff et al., 2011;Knowlton et al., 2012Knowlton et al., , 2016Moore & van der Hoop, 2012;van der Hoop et al. 2014van der Hoop et al. , 2016van der Hoop, Corkeron, Henry, et al., 2017;van der Hoop, Nowacek, et al., 2017). However, drag predictions under various circumstances are fragmentary. ...
Accurate estimates of drag on marine animals are required to investigate the locomotive cost, propulsive efficiency, and the impacts of entanglement if the animal is carrying fishing gear. In this study, we performed computational fluid dynamics analysis of a 10 m (length over all) right whale to obtain baseline measurements of drag on the animal. Swimming speeds covering known right whale speed range (0.125 m/s to 8 m/s) were tested. We found a weak dependence between drag coefficient and Reynolds number. At a swimming speed of 2 m/s, we analyzed the boundary layer thicknesses, the flow regimes, and drag components. We found the thickest boundary layer at the lateral sides of the peduncle, whereas the boundary layer thickness over the outer part of the flukes was less than 1.7 cm. Laminar flow occurred over the anterior ~0.6 LoA and turbulent flow from ~0.8 LoA to the fluke notch. On the surfaces of the flukes outside of the body wake region, flow was laminar. Our most significant finding is that the drag coefficient (0.0071–0.0059) of a right whale for swimming speeds ranging from 0.25 m/s to 2 m/s is approximately twice that of many previous estimates for cetaceans.
... Chronically entangled NARWs may carry fishing gear for months to years, and often show signs of considerable loss in energy reserves over that time period, as evidenced by emaciation. Drag measured from gear that was removed from entangled NARWs (van der Hoop et al. 2013Hoop et al. , 2016 was combined with other measured parameters, allowing estimation of drag on new entanglement cases at the time of their observation (van der Hoop et al. 2017a). Drag measurements enabled estimation of the energetic cost of entanglement using biomechanics and physical models, and blubber thickness and body condition measurements (van der Hoop et al. 2017b). ...
Whaling has decimated North Atlantic right whales Eubalaena glacialis (NARW) since the 11th century and southern right whales E. australis (SRW) since the 19th century. Today, NARWs are Critically Endangered and decreasing, whereas SRWs are recovering. We review NARW health assessment literature, NARW Consortium databases, and efforts and limitations to monitor individual and species health, survival, and fecundity. Photographs are used to track individual movement and external signs of health such as evidence of vessel and entanglement trauma. Post-mortem examinations establish cause of death and determine organ pathology. Photogrammetry is used to assess growth rates and body condition. Samples of blow, skin, blubber, baleen and feces quantify hormones that provide information on stress, reproduction, and nutrition, identify microbiome changes, and assess evidence of infection. We also discuss models of the population consequences of multiple stressors, including the connection between human activities (e.g. entanglement) and health. Lethal and sublethal vessel and entanglement trauma have been identified as major threats to the species. There is a clear and immediate need for expanding trauma reduction measures. Beyond these major concerns, further study is needed to evaluate the impact of other stressors, such as pathogens, microbiome changes, and algal and industrial toxins, on NARW reproductive success and health. Current and new health assessment tools should be developed and used to monitor the effectiveness of management measures and will help determine whether they are sufficient for a substantive species recovery.
... entanglement, ship strike, gull harassment, other) may delay parous females from reaching energetic levels needed for reproduction (e.g. van der Hoop et al. 2016). Lesions from gull harassment has increased in southern right whales in Argentina and is known to cause mortality and impact nursing behaviour (Marón et al., 2015). ...
