Abstract
A ship-based mosaic survey of Northeast Atlantic cetaceans was conducted over a 5-year period between 2014–2018. The area surveyed extends from the North Sea in the south (southern boundary at 53oN), to the ice edge of the Barents Sea and the Greenland Sea. Survey vessels were equipped with 2 independent observer platforms that detected whales in passing mode and applied tracking procedures for the target species, common minke whales (Balaenoptera acutorostrata acutorostrata). Here we present abundance estimates for all non-target species for which there were sufficient sightings. We estimate the abundance of fin whales (Balaenoptera physalus) to be 11,387 (CV=0.17, 95% CI: 8,072–16,063), of humpback whales (Megaptera novaeangliae) to be 10,708 (CV=0.38, 95% CI: 4,906–23,370), of sperm whales (Physeter macrocephalus) to be 5,704 (CV=0.26, 95% CI: 3,374–9,643), of killer whales (Orcinus orca) to be 15,056 (CV=0.29, 95% CI: 8,423–26,914), of harbour porpoises (Phocoena phocoena) to be 255,929 (CV=0.20, 95% CI: 172,742–379,175), dolphins of genus Lagenorhynchus to be 192,767 (CV=0.25, 95% CI: 114,033–325,863), and finally of northern bottlenose whales (Hyperoodon ampullatus) to be 7,800 (CV=0.28, 95% CI: 4,373–13,913). Additionally, our survey effort in the Norwegian Sea in 2015 contributed to the 6th North Atlantic Sightings Survey (NASS) and the survey was extended into the waters north and east of Iceland around Jan Mayen island. This NASS extension, along with our Norwegian Sea survey in 2015, was used to estimate the abundance of fin whales, humpback whales, and sperm whales. All estimates presented used mark-recapture distance sampling techniques and were thus corrected for perception bias. Our estimates do not account for additional variance due to distributional shifts between years or biases due to availability or responsive movement.
Highlights
Norwegian shipboard line-transect surveys of the Northeast Atlantic have been ongoing since 1987 as part of a program to estimate abundance of common minke whales (Balaenoptera acutorostrata acutorostrata) as input to the Revised Management Procedure (RMP) of the International Whaling Commission (IWC, 1994)
This paper presents new abundance estimates from the 2014–2018 mosaic survey for all cetacean species for which there were a sufficient number of sightings
This is similar to past surveys (Øien, 2009; Leonard & Øien, 2020) and should not have a large effect on overall abundance, as these species are not expected to aggregate in ice covered areas
Summary
Norwegian shipboard line-transect surveys of the Northeast Atlantic have been ongoing since 1987 as part of a program to estimate abundance of common minke whales (Balaenoptera acutorostrata acutorostrata) as input to the Revised Management Procedure (RMP) of the International Whaling Commission (IWC, 1994). Abundance estimates of non-target species have been published from surveys conducted in 1988, 1989, 1995 (Christensen et al, 1992; Øien 1990, 2009), and the mosaic surveys in 1996–2001, 2002–2007 and 2008–2013 (Øien 2009; Leonard & Øien, 2020). This paper presents new abundance estimates from the 2014–2018 mosaic survey for all cetacean species for which there were a sufficient number of sightings. This includes fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), sperm whales (Physeter macrocephalus), killer whales (Orcinus orca), harbour porpoises (Phocoena phocoena), northern bottlenose whales (Hyperoodon ampullatus), and dolphins (Lagenorhynchus spp). Throughout this paper, the term Lagenorhynchus spp. refers collectively to white-sided dolphins (Lagenorhynchus acutus) and white-beaked dolphins (Lagenorhynchus albirostris), which are estimated to genus, rather than species level
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