[MARMAM] New publication: Estimates of the relative abundance of long-finned pilot whales (Globicephala melas) in the Northeast Atlantic from 1987 to 2015 indicate no long-term trends

Solveig Enoksen solveig.enoksen at nammco.no
Wed Feb 13 04:47:31 PST 2019

Dear MARMAM members,

The North Atlantic Marine Mammal Commission is pleased to announce the early online publication of the first article of Volume 11 in our Scientific Publication Series, "Estimates of the relative abundance of long-finned pilot whales (Globicephala melas) in the Northeast Atlantic from 1987 to 2015 indicate no long-term trends" by Daniel G. Pike, Thorvaldur Gunnlaugsson, Geneviève Desportes, Bjarni Mikkelsen, Gísli A. Vikingsson & Dorete Bloch.

North Atlantic Sightings Surveys (NASS) and associated surveys, covering a large but variable portion of the North Atlantic, were conducted in 1987, 1989, 1995, 2001, 2007 and 2015. Previous estimates of long-finned pilot whale (Globicephala melas) abundance, derived using conventional distance sampling (CDS), are not directly comparable to one another because of differing survey coverage, field methods and, in the case of the 1989 NASS, different survey timing. CDS was used to develop indices of relative abundance to determine if pilot whale abundance has changed over the 28-year period from 1987 to 2015. The varying spatial coverage of the surveys is accommodated by delineating common regions that were covered by: i) all 6 surveys, and ii) the 3 largest surveys (1989, 1995, and 2007). These "Index Regions" were divided into East and West subregions, and post-stratification was used to obtain abundance estimates for these index areas only. Estimates are provided using the sightings from the combined platforms for surveys that used double platforms or the primary platform only.

Total abundance in the Index Regions, uncorrected for perception or availability biases, ranged from 54,264 (CV=0.48) in 2001 to 253,109 (CV=0.43) in 2015. There was no significant trend in the numbers of individuals or groups in either the 6 or 3 Survey Index Regions, and no consistent trend over the period. Power analyses indicate that negative annual growth rates of -3% to -5% would have been detectible over the entire period. The Index Regions comprise only a portion of the summer range of the species and changes in annual distribution clearly affect the results. Operational changes to the surveys, particularly in defining pilot whale groups, may also have introduced biases. Recommendations for future monitoring of the long-finned pilot whale population are provided.

The article is open access and available here: https://doi.org/10.7557/3.11.

Volume 11: North Atlantic Sightings Surveys - Counting whales in the North Atlantic 2002-2016 will consist of a series of articles dealing with the results of NASS, a series of internationally coordinated cetacean surveys that were conducted in the North Atlantic in 1987, 1989, 1995, 2001, 2007 and 2015.

Solveig Enoksen
Scientific & Communication Assistant
NAMMCO - North Atlantic Marine Mammal Commission
POB 6453, N-9294 Tromsø, Norway
+47 77 68 73 71, solveig.enoksen at nammco.no<mailto:solveig.enoksen at nammco.no>,
www.nammco.no<http://www.nammco.no/>, www.facebook.com/nammco.no/<http://www.facebook.com/nammco.no/> https://twitter.com/NAMMCO_sec

[NammRGB email]

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