Trends in bowhead whales in West Greenland: Aerial surveysvs. genetic capture‐recapture analyses

Abstract

We contrast two methods for estimating the trends of bowhead whales (Balaena mysticetus) in West Greenland: (1) double platform visual aerial survey, corrected for missed sightings and the time the whales are available at the surface; and (2) a genetic capture-recapture approach based on a 14-yr-long biopsy sampling program in Disko Bay. The aerial survey covered 39,000 km 2 and resulted in 58 sightings, yielding an abundance estimate of 744 whales (CV = 0.34, 95% CI: 357-1,461). The genetic method relied on determining sex, mitochondrial haplotypes and genotypes of nine microsatellite markers. Based on samples from a total of 427 individuals, with 11 recaptures from previous years in 2013, this resulted in an estimate of 1,538 whales (CV = 0.24, 95% CI: 827-2,249). While the aerial survey is considered a snapshot of the local spring aggregation in Disko Bay, the genetic approach estimates the abundance of the source of this aggregation. As the whales in Disko Bay primarily are adult females that do not visit the bay annually, the genetic method would presumably yield higher estimates. The studies indicate that an increase in abundance observed between 1998 and 2006 has leveled off.

Identification of Potential Foraging Areas for Bowhead Whales in Baffin Bay and Adjacent Waters

“…However, binned data allowed for long-term data collection from areas where it would otherwise be impossible to gather information on diving behaviour of bowhead whales. Genetic analysis of skin biopsies from bowhead whales in Disko Bay revealed a large proportion of females (81%) similar to those found in previous studies (Heide-Jørgensen et al, 2010;Wiig et al, 2011;Rekdal et al, 2015). The explanation for the sex segregation remains unresolved although it has been suggested that Disko Bay is used by post-lactating, pregnant, or resting females to regain fat deposits that are otherwise more energetically demanding to acquire in other areas (Heide-Jørgensen et al, 2010).…”

“…Bowhead whales arrive in Disko Bay, their most important feeding ground in West Greenland, around January and February (Laidre et al, 2008;Laidre and HeideJørgensen, 2012;Heide-Jørgensen et al, 2013;Rekdal et al, 2015). Satellite tracking studies of bowheads in West Greenland have shown that they depart Disko Bay in mid to late May and move almost diagonally northwest, crossing Baffin Bay and reaching Bylot Island between late May and July (Heide-Jørgensen et al, 2003a, 2012bLaidre and Heide-Jørgensen, 2012).…”

A hidden getaway for bowhead whales in the Greenland Sea

“…Perpendicular angles were measured with inclinometers when abeam to a sighting and converted to distances from the track line (e.g. Rekdal et al 2014). Based on the distance distribution of the detections, strip census sampling with a transect width of 600 m was applied (Buckland et al 2001).…”

Rebuilding beluga stocks in West Greenland

“…() and Rekdal et al . () was used to estimate the detection probability, density and abundance of belugas. This involved first estimating the parameters of a hidden Markov model for whale availability and then integrating these with the line transect data, using both perpendicular and forward distances, to detected whales to estimate detection probability (see Borchers et al ., for details).…”