Distribution and abundance of West Greenland humpback whales (Megaptera novaeangliae)

Abstract

Photo-identification surveys of humpback whales Megaptera novaeangliae were conducted at West Greenland during 1988–93, the last 2 years of which were part of the internationally coordinated humpback whale research programme YoNAH, with the primary aim of estimating abundance for the West Greenland feeding aggregation. The area studied stretched from the coast out to the offshore margin of the banks, determined approximately by the 200 m depth contours, between c. 61°70′N and c. 66°N. The surveys were conducted between early July and mid-August and 993 h were expended on searching effort. A total of 670 groups of humpback whales was encountered leading to the identification of 348 individual animals. Three areas of concentration were identified: an area off Nuuk; an area at c. 63°30′N; and an area off Frederikshåb. Sequential Petersen capture–recapture estimates of abundance were calculated for five pairs of years at 357 (1988–89), 355 (1989–90), 566 (1990–91), 376 (1991–92), and 348 (1992–93). Excluding the anomalously high estimate in 1990–91, the simple mean is 359 (SE = 27.3, CV = 0.076) and the inverse CV-squared weighted mean is 356 animals (SE = 24.9, CV = 0.070). These calculations lead us to conclude that between 1988 and 1993 there were 360 humpbacks (CV = 0.07) in the West Greenland feeding aggregation. Using the Cormack–Jolly–Seber model framework non-calf survival rate was estimated at 0.957 (SE = 0.028). Our data have low power (P < 0.3) to detect a trend of 3.1%, assuming the probability of a type I error was 0.05.