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

Abstract

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.

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

“…Datasets used for modelling trends in observed encounters are available as part of the open access data repository for this publication [ 25 ].…”

Identifying important habitat for northern bottlenose and Sowerby's beaked whales in the western North Atlantic

“…Climate change‐induced sea‐ice retreat is also increasing both human activity and the temporal persistence of seasonally resident species in the Arctic (Moore & Huntington, 2008). NBW associations with fishing vessels in the Davis Strait region (Johnson et al, 2021; Oyarbide et al, 2023) highlight how behavioural differences among populations may challenge broad‐scale, species‐level habitat assessments and require recognition of spatial and temporal variability of populations in future conservation efforts (Laidre et al, 2015; Torres et al, 2015).…”

Navigating the unknown: assessing anthropogenic threats to beaked whales, family Ziphiidae

“…Entanglements have been documented globally for at least 15 beaked whale species (figure 1, electronic supplementary material, table S1); however, many incidents probably go unreported, due to low rates of self-reporting by fishers, few at-sea fisheries observers in offshore areas, and potential misidentification (e.g. [115], but see [116]). Entanglement of beaked whales appears to be relatively less common than coastal cetaceans [117]; however given the challenges, differences in reporting may be biased by effort.…”

“…Depredation behaviour has been documented in at least 19 species of odontocetes across the globe, and commonly occurs with long-line fishing activities (e.g. 110,124,125); however, depredation on trawl and purse seine fisheries has also been observed [116,126,127]. Despite the potential for negative consequences, reduced foraging costs associated with depredation led to survival benefits and growth in some cetacean populations [125,128].…”

“…Beaked whale depredation behaviour has primarily been documented for northern bottlenose whales in trawl, gillnet and long-line fisheries [116,129–131], and there is some evidence of long-line depredation interactions (e.g. hooked in the mouth or stomach) occurring with Sowerby’s beaked whales [132], Shepherd’s beaked whales ( Tasmacetus shepherdi ) [133], Blainville’s beaked whales [134] and unidentified mesoplodonts [134].…”