ESTIMATES OF CETACEAN ABUNDANCE IN THE NORTH ATLANTIC OF RELEVANCE TO NAMMCO

The Scientific Committee of NAMMCO maintains a Working Group on Abundance Estimates, composed of invited experts in the field as well as some Committee members. This Working Group meets periodically to review new abundance estimates from recent surveys or, in some cases, re-analyses of older data. The reports of the Working Group are brought to the Scientific Committee at their annual meetings, and used to formulate advice on stock status, allowable removals or other matters. In most cases, the Scientific Committee will formally endorse estimates approved by the Working Group, and if so this is indicated on the Table. Some estimates have been endorsed by the Scientific Committee of the International Whaling Commission (IWC).


INTRODUCTION
The purpose of this table is to present the best available abundance estimates for cetacean species in areas of relevance to the work of NAMMCO. It is intended to be used as a starting point for researchers, and the original sources are provided if additional information is required.
The Scientific Committee of NAMMCO maintains a Working Group on Abundance Estimates, composed of invited experts in the field as well as some Committee members. This Working Group meets periodically to review new abundance estimates from recent surveys or, in some cases, re-analyses of older data. The reports of the Working Group are brought to the Scientific Committee at their annual meetings, and used to formulate advice on stock status, allowable removals or other matters. In most cases, the Scientific Committee will formally endorse estimates approved by the Working Group, and if so this is indicated on the Table. Some estimates have been endorsed by the Scientific Committee of the International Whaling Commission (IWC).
In some cases, estimates have been revised subsequent to their endorsement by the Scientific Committee. Publication of estimates generally occurs after their presentation to the Committee, and estimates may be revised due to reviewer suggestions, advances in analytical techniques or errors detected in the original analysis. In these cases, the published estimate is considered the most reliable and is presented even if it differs from the originally endorsed estimate. In most cases these differences are small. It is anticipated that these revised estimates will be endorsed by the Scientific Committee at some point.
A more complete version of the Table, published and regularly updated on the NAMMCO web site, includes all estimates which have been endorsed and used at some points by NAMMCO working groups. Some estimates have been superseded by newer estimates, as the analytical procedures have evolved and improved. This Table includes older estimates that have been superseded, newer analyses and published estimates. Reasons for the differences between estimates for the same species, year and area are explained under Comments. This "live" table, "North Atlantic -Abundance Estimates of relevance to NAMMCO // All cetacean species -All surveys", can be found https://nammco.no/marinemammals/.
In most cases, the survey areas vary between surveys, and estimate cannot be directly compared between survey years. Informed comparisons can usually be found in the published articles. Survey areas can be found here under the different survey headings.
When no abundance estimate for a species has ever been generated for an area because of paucity of sightings, this area is not included in this table for that species, even when a few sightings may have been made. For example, the NASS/TNASS series does not survey properly the geographical distribution of bowhead whales, i.e., does not cover an area large enough of their distribution range so they can be used to generate any abundance. Therefore, they are not indicated in this table for that species, although some bowhead whale sightings have been made during the surveys. These are indicated on the web Table though. A lack of sightings for a species in an area is only indicated when other abundance estimates exist for that species in that area, for example for blue whales in 2007 in the Iceland + Faroes area.
Narwhals are at present not included in the tables. The way abundance estimates for narwhal have been corrected for perception and availability biases have varied between surveys and raised concerns. The Joint NAMMCO/JCNB Working Group on Narwhal and Beluga, which is the scientific body providing advice to NAMMCO and the Canada-Greenland Joint Commission on Narwhal and Beluga (JCNB), decided at its last meeting in October 2020 (the report will become available here), that it needed to review these corrections and to agree on corrected estimates. Abundance estimates for narwhal, past and recent, will then become available on the updated web Mode SP -single platform; IO -double platform, independent observers; B-T -double platform, Buckland-Turnock mode (Buckland & Turnock 1992).

Uncorrected Abundance Estimate (UAE)
UAE Uncorrected Abundance estimate. Does not include corrections for perception or availability biases unless otherwise noted with a (p) CV Coefficient of variation.

Tfs
Too few sightings for generating an abundance estimate

Corrected Abundance Estimate (CAE)
Includes corrections for perception bias (Per), availability bias (Avail) or both as indicated.

Endorsed by
Organizational endorsement, usually NAMMCO or the International Whaling Commission (IWC). Committee meeting number and working group acronym are provided, the latest in '(…)'.
Square brackets around the organizational endorsement mean that an initial estimate has been previously endorsed by an organisation and was subsequently revised and represented and/or published.
In most cases the published is presented even if an earlier accepted estimate exists, as earlier estimates in working papers have been improved and adjustments made post review in the published versions. These changes are consistent with the advice provided.
On the NAMMCO live web version of the table, the comments include the explanation of the revisions made.

Publications
Citation to peer-reviewed publication if available. Citations to non-peer reviewed publications, generally meeting documents, are given in square brackets. All estimates of sei whales reported below are considered as partial estimates as the entire summer distribution and peak season are not covered by these surveys. The 1989 survey is considered the best survey for sei whales in term of coverage and timing, as its range extended far South and it was conducted on July and August, i.e., later in the summer compared with other NASS surveys.