First estimates of Greenland shark (Somniosus microcephalus) local abundances in Arctic waters

Abstract

Baited remote underwater video cameras were deployed in the Eastern Canadian Arctic, for the purpose of estimating local densities of the long-lived Greenland shark within five deep-water, data-poor regions of interest for fisheries development and marine conservation in Nunavut, Canada. A total of 31 camera deployments occurred between July-September in 2015 and 2016 during joint exploratory fishing and scientific cruises. Greenland sharks appeared at 80% of deployments. A total of 142 individuals were identified and no individuals were observed in more than one deployment. Estimates of Greenland shark abundance and biomass were calculated from averaged times of first arrival, video-derived swimming speed and length data, and local current speed estimates. Density estimates varied 1–15 fold among regions; being highest in warmer (>0 °C), deeper areas and lowest in shallow, sub-zero temperature regions. These baited camera results illustrate the ubiquity of this elusive species and suggest that Nunavut’s Lancaster Sound eco-zone may be of particular importance for Greenland shark, a potentially vulnerable Arctic species.

Greenland Shark (Somniosus microcephalus) Stomach Contents and Stable Isotope Values Reveal an Ontogenetic Dietary Shift

“…Size distribution of Greenland sharks appears to vary spatially. While sharks <400 cm seem to dominate in the Canadian Arctic, northern Greenland and the Svalbard Archipelago (Norway), larger sharks >400 cm seem to be more common off southern Greenland, Iceland, and Newfoundland (Nielsen et al, 2014;Campana et al, 2015;Lydersen et al, 2016;Devine et al, 2018).…”

Advancing Research for the Management of Long-Lived Species: A Case Study on the Greenland Shark

“…Scar patterns and external markings may be used to identify individuals over short time periods (Devine et al, 2018), but these may also change or disappear with age (Robbins and Fox, 2012). External markers (e.g., Floy tags) facilitate identification (Section "Demographics and Life History"), however, studies should determine the average duration of tag retention by target species.…”

“…Scientific catch data suggest regional differences in the relative abundance of Greenland sharks by life stage/size and sex. For example, no adult females [>4 m total length (L T ), Yano et al, 2007] have been reported throughout the Canadian Arctic and in Svalbard (Norway) despite intense sampling (N > 300 individuals, Skomal and Benz, 2004;Fisk et al, 2002Fisk et al, , 2012Leclerc et al, 2012;Hussey et al, 2015aHussey et al, , 2018Devine et al, 2018).…”

“…Juvenile sharks, defined as individuals ≤200 cm L T , have been observed in both inshore and offshore waters (Hussey et al, 2015a), including animals within the birth size range (40-100 cm, MacNeil et al, 2012). Specifically, juveniles were observed in longline, trawl, and camera surveys within Scott Inlet, Baffin Island, and in offshore waters >1000 m depth (Fisk et al, 2002;Yano et al, 2007;Nielsen et al, 2014;Hussey et al, 2015a;Devine et al, 2018).…”

A framework to estimate the likelihood of species interactions and behavioural responses using animal‐borne acoustic telemetry transceivers and accelerometers

“…Greenland sharks are an ideal focal species to test interactions as they are known to cannibalize conspecifics (Idrobo & Berkes, 2012), can occur in high densities in localized regions (Devine, Wheeland, & Fisher, 2018;Hussey et al., 2014) and have been observed in pairs (Devine et al, 2018 (Jacoby, Fear, Sims, & Croft, 2014;Schilds et al, 2019). Teasing apart whether the interaction is passive, evasion or co-occurrence will require close examination of the individual triaxial acceleration data.…”