Abstract
The Trans-North Atlantic Sightings Survey (T-NASS) carried out in June-July 2007 was the fifth in a series of large-scale cetacean surveys conducted previously in 1987, 1989, 1995 and 2001. The core survey area covered an area of about 1.8 million nm² spanning from the Eastern Barents Sea at 34°E to the east coast of Canada, and between 52°N and 78°N in the east and south to 42°N in the west. We present design-based abundance estimates from the Faroese and Icelandic vessel survey components of T-NASS, as well as results from ancillary vessels which covered adjoining areas. The 4 dedicated survey vessels used a Buckland-Turnock (B-T) mode with a tracker platform searching an area ahead of the primary platform and tracking sightings to provide data for bias correction. Both uncorrected estimates, using the combined non-duplicate sightings from both platforms, and mark-recapture estimates, correcting estimates from the primary platform for bias due to perception and availability, are presented for those species with a sufficient number of sightings. Corrected estimates for the core survey area are as follows: fin whales (Balaenoptera physalus): 30,777 (CV=0.19); humpback whales (Megaptera novaeangliae): 18,105 (CV=0.43); sperm whales (Physeter macrocephalus): 12,268 (CV=0.33); long-finned pilot whales (Globicephala melas): 87,417 (CV=0.38); white-beaked dolphins (Lagenorhynchus albirostris): 91,277 (CV=0.53); and white-sided dolphins (L. acutus): 81,008 (CV=0.54). Uncorrected estimates only were possible for common minke whales (B. acutorstrata): 12,427 (CV=0.27); and sei whales (B. borealis): 5,159 (CV=0.47). Sighting rates from the ancillary vessels, which used a single platform, were lower than those from the dedicated vessels in areas where they overlapped. No evidence of responsive movement by any species was detected, but there was some indication that distance measurements by the primary platform may have been negatively biased. The significance of this for the abundance estimates is discussed. The relative merits of B-T over other survey modes are discussed and recommendations for future surveys are provided.
Highlights
The Trans-North Atlantic Sightings Survey (T-NASS) was the fifth in a series of large-scale cetacean surveys (NASS) conducted previously in 1987, 1989, 1995 and 2001 (Pike, 2009), and was coordinated through the Scientific Committee of the North Atlantic Marine Mammal Commission (NAMMCO)
We present results from associated extension surveys carried out from vessels conducting fisheries research outside of the core T-NASS survey area, in order to assess the distribution of cetacean species in areas that were not covered in the dedicated survey
The IC block around coastal Iceland was poorly covered, but this area was covered by a concurrent aerial survey (Pike et al, in press)
Summary
The Trans-North Atlantic Sightings Survey (T-NASS) was the fifth in a series of large-scale cetacean surveys (NASS) conducted previously in 1987, 1989, 1995 and 2001 (Pike, 2009), and was coordinated through the Scientific Committee of the North Atlantic Marine Mammal Commission (NAMMCO). The overall T-NASS project was the largest of the series, with 5 nations (Norway, Faroe Islands, Iceland, Greenland and Canada) participating directly with survey platforms, and Russia providing support in planning, logistics and personnel. A transAtlantic survey was achieved, adding areas to the west of Greenland and the eastern coast of Canada to the core NASS strata areas to the east (NAMMCO, 2016). Over 3,000 cetacean sightings of 18 species were made during the survey. By most measurements the 2007 T-NASS was the largest single wildlife survey ever conducted
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