Using bycatch data to understand habitat use of small cetaceans: lessons from an experimental driftnet fishery

Abstract

Stenson, G. B., Benjamins, S., and Reddin, D. G. 2011. Using bycatch data to understand habitat use of small cetaceans: lessons from an experimental driftnet fishery. – ICES Journal of Marine Science, 68: 937–946. Many marine mammals inhabit offshore areas where it is difficult to determine distribution and abundance. Historical bycatch data of marine mammals in the Northwest Atlantic obtained from the Canadian experimental Atlantic salmon (Salmo salar) driftnet fishery were examined to obtain information on seasonal distribution and relative abundance. From 1965 to 2001, 47 cruises were undertaken totalling 12 566.5 km-h of fishing effort; four species of small cetacean and two species of pinniped were caught. Harbour porpoises (Phocoena phocoena) were the most frequently caught species in all areas except the Labrador Sea, where Atlantic white-sided dolphins (Lagenorhynchus acutus) were more common. Long-finned pilot whales (Globicephala melas), common dolphins (Delphinus delphis), harp seals (Pagophilus groenlandicus), and harbour seals (Phoca vitulina) were also taken occasionally. Although typically considered an inshore species, harbour porpoises were regularly reported in deep water (>2000 m), in the Newfoundland Basin and Labrador Sea. Atlantic white-sided dolphins were often caught along the edge of the continental shelf and appeared to prefer relatively warm water. Finally, catch records indicate that waters of the Newfoundland Basin and Southern Grand Banks may contain important winter habitat for several small species of cetacean.

Multiple-colony winter habitat use by murres Uria spp. in the Northwest Atlantic Ocean: implications for marine risk assessment

“…2). Relative presence is based on a literature review of anthropogenic activities in subregions (Bakken & Falk 1998, Wiese et al 2001, Merkel et al 2002, Bakken & Mehlum 2005, Benjamins et al 2008, Merkel & Barry 2008, Wilhelm et al 2009, AMAP 2010, C-NLOPB 2010, Carstens 2010, Stenson et al 2011 Table 3. Proportional Use by tracked thick-billed murres and common murres, as determined by proportion of individual 50% kernel home ranges (KHRs) per colony that intersected with nearshore, shelf, and oceanic marine zones in the Northwest Atlantic Study Area (Fig.…”

“…5). In addition, given the spatial contraction of the Newfoundland gillnet fishery in winter (Benjamins et al 2008, Stenson et al 2011 and the distribution of both murre species on the northern edges of the Grand Bank, bycatch is not expected to be a major source of adult winter mortality. In contrast, risks encountered in shelf and offshore areas are likely to be more significant for birds from our study colonies.…”

“…Energetic stress is compounded by a complex range of anthropogenic pressures. In winter, murres are extremely vulnerable to marine oil pollution , Votier et al 2005, Burke et al 2012, are hunted for subsistence in nearshore areas throughout the high and low arctic (Elliot 1991, Donaldson et al 1997, Bakken & Mehlum 2005, Merkel & Barry 2008, and occasionally drown in gillnets (Benjamins et al 2008, Stenson et al 2011. The risks associated with these activities depend on their spatiotemporal overlap with murre distributions.…”