In plane sight: a mark-recapture analysis of North Atlantic right whales in the Gulf of St. Lawrence

Abstract

North Atlantic right whales Eubalaena glacialis are most commonly observed along the eastern seaboard of North America; however, their distribution and occupancy patterns have become less predictable in the last decade. This study explored the individual right whales captured photographically from both dedicated and opportunistic sources from 2015 to 2019 in the Gulf of St. Lawrence (GSL), an area previously understudied for right whale presence. A total of 187 individuals, including reproductive females, were identified from all sources over this period. In years when more substantial survey effort occurred (2017-2019), similar numbers of individuals were sighted (mean = 133, SD = 1.5), and dedicated mark-recapture aerial surveys were highly effective at capturing almost all of the whales estimated in the region (2019: N = 137, 95% CI = 135-147). A high rate of inter-annual return was observed between all 5 study years, with 95% of the animals seen in 2019 sighted previously. Capture rates indicated potential residencies as long as 5 mo, and observed behaviors included feeding and socializing. Individuals were observed in the northern and southern GSL, regions divided by a major shipping corridor. Analyses suggest that individuals mostly moved less than 9.1 km d-1, although rates of up to 79.8 km d-1 were also calculated. The GSL is currently an important habitat for 40% of this Critically Endangered species, which underscores how crucial protection measures are in this area.

Using sonobuoys and visual surveys to characterize North Atlantic right whale (Eubalaena glacialis) calling behavior in the Gulf of St. Lawrence

“…The species' re covery has been further compromised by a recent unusual mortality event in which 32 individuals were found dead between 2017 and 2020, of which 16 were discovered in the Gulf of St. Lawrence (GSL), Canada (NOAA 2022a). The persistent right whale occupancy in the GSL since at least 2015 (Simard et al 2019, Crowe et al 2021, Johnson et al 2021, frequent observations of both socializing and foraging behavior (Crowe et al 2021 and this paper), and a dramatic increase in observed mortalities suggest that the GSL is an important high-risk habitat.…”

“…1). The surveys did not follow a typical systematic line transect approach but instead were directed to search areas with the intention to photograph as many individual right whales as possible (see Crowe et al 2021 for more details on these mark−recapture aerial surveys). The aircraft circled an aggregation long enough to collect sufficient photos for photo-identification, and as such, the number of photos per individual varied among deployments.…”

“…The images were taken using a Canon digital singlelens reflex camera with a fixed 300 mm lens. Visual survey protocols are described in detail in Cole et al (2013) and Crowe et al (2021).…”

“…A 30 km radius was chosen based on maximum observed acoustic detection distances measured in the Bay of Fundy (Laurinolli et al 2003) and modeled maximum detection distances in the southwestern region of the GSL (Simard et al 2019), the same general area as our study. Whale movement is unlikely to increase this range, as observations of right whales in the southern GSL suggest that 75% of daily distance between sightings of the same individual was less than 10 km (Crowe et al 2021), and movement simulations estimate that within a 6 h time frame (which is longer than the longest deployment duration in our study), both socializing and feeding whales would likely remain within approximately 30 km of the original point of the acoustic detection (Johnson et al 2020). Alternative space and time range combinations (20 and 60 km with 0.5 and 12 h) were considered and had little influence on the results.…”

Artificial intelligence for right whale photo identification: from data science competition to worldwide collaboration

“…Researchers take lateral photographs (from vessels, shore, cliffs) and aerial photographs (from aircraft, helicopters, uncrewed systems), and then match these images to existing photo identification catalogs. Individual photo identification is a crucial tool for estimating abundance and monitoring population trends over time (Calambokidis and Barlow 2006;Gormley et al 2012;Pace et al 2017;Koivuniemi et al 2019;Stamation et al 2020;Crowe et al 2021) and makes nuanced understanding of individuals possible, including distribution, age at first calving, calving interval, adult and juvenile survival, individual health, entanglement rates, social relationships, site fidelity, and migratory patterns (see Karczmarski et al 2022 for several relevant examples). The information gained from this research often has direct implications for the conservation and management of wild populations (e.g., in calculating Potential Biological Removal, drawing Seasonal and Dynamic Management areas, delineating Marine Protected Areas).…”