Distribution and abundance of fin whales (Balaenoptera physalus) in the Northeast and Central Atlantic as inferred from the North Atlantic Sightings Surveys 1987-2001

NAMMCO Scientific Publications 7:49-72 01/2009; 7:49-72. DOI: 10.7557/3.2705


North Atlantic Sightings Surveys (NASS) is a series of large scale international cetacean line transect surveys, conducted in 1987, 1989, 1995 and 2001, that covered a large part of the central and eastern North Atlantic. Target species were fin (Balaenoptera physalus), common minke (B. acutorostrata), pilot (Globicephala melas) and sei (B. borealis) whales. Here we present new estimates of abundance
for fin whales from the 2 most recent surveys and analysis of trends throughout the survey period. Fin whales were found in highest densities in the Irminger Sea between Iceland and Greenland. Abundance of fin whales in the survey area of the Icelandic and Faroese vessels (Central North
Atlantic) was estimated as 19,672 (95% C.I. 12,083-28,986) animals in 1995 and 24,887 (95% C.I.
18,186-30,214) in 2001. The estimates are negatively biased because of whales diving during the passage of vessels, and whales being missed by observers, but these and other potential biases are
likely small for this species. The abundance of fin whales increased significantly over the survey period. For all areas combined the estimated annual growth rate was 4%. An estimated annual increase of 10% in the area between Iceland and Greenland was responsible for most of this overall increase in numbers of fin whales in the area. Although high, the estimated rates of increase are not out of bounds of biological plausibility and can thus be viewed as recovery of a depleted population. However, the apparent pattern of population growth and the whaling history in the area indicate that
fin whales made a significant recovery during the first half of the 20th century and that the recent observed high growth rates cannot be explained solely by recovery after overexploitation.

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    • "Assuming that the MDH-1 and MPI genes indeed are post-translational modified and alternatively spliced, respectively, in fin whales, are there any characteristics of their cellular function and the biology of fin whales that may provide a clue as to why? North Atlantic fin whales are believed to undertake seasonal movements between feeding and breeding areas (Rørvik and Jonsgård 1981; Donovan 1991; Víkingsson et al. 2009). Fin whales are filter feeders, preying primarily on zooplankton (e.g., euphasiids) to build up adequate fat storages for periods with limited nutritional intake (Hinga 1979; Lockyer 1986, 2007; Víkingsson 1990, 1997). "
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    ABSTRACT: The appeal of genetic inference methods to assess population genetic structure and guide management efforts is grounded in the correlation between the genetic similarity and gene flow among populations. Effects of such gene flow are typically genomewide; however, some loci may appear as outliers, displaying above or below average genetic divergence relative to the genomewide level. Above average population, genetic divergence may be due to divergent selection as a result of local adaptation. Consequently, substantial efforts have been directed toward such outlying loci in order to identify traits subject to local adaptation. Here, we report the results of an investigation into the molecular basis of the substantial degree of genetic divergence previously reported at allozyme loci among North Atlantic fin whale (Balaenoptera physalus) populations. We sequenced the exons encoding for the two most divergent allozyme loci (MDH-1 and MPI) and failed to detect any nonsynonymous substitutions. Following extensive error checking and analysis of additional bioinformatic and morphological data, we hypothesize that the observed allozyme polymorphisms may reflect phenotypic plasticity at the cellular level, perhaps as a response to nutritional stress. While such plasticity is intriguing in itself, and of fundamental evolutionary interest, our key finding is that the observed allozyme variation does not appear to be a result of genetic drift, migration, or selection on the MDH-1 and MPI exons themselves, stressing the importance of interpreting allozyme data with caution. As for North Atlantic fin whale population structure, our findings support the low levels of differentiation found in previous analyses of DNA nucleotide loci.
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    Deep Sea Research Part II Topical Studies in Oceanography 01/2008; 55(1-2):254-268. DOI:10.1016/j.dsr2.2007.09.020 · 2.19 Impact Factor
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    ABSTRACT: An aerial line transect survey of fin whales (Balaenoptera physalus) conducted off West Greenland in 2007 was used to estimate the current abundance of fin whales on this summer feeding ground. The line transect abundance was 4,656 animals (cv=0.46) with no corrections for whales missed by the observers and whales that were submerged during the passage of the survey plane. The abundance estimate is furthermore only representing the coastal areas of West Greenland and sightings at the westernmost areas of the strata suggest that the entire Baffin Bay-Davis Strait summer abundance of fin whales could be considerably larger.
    Journal of Cetacean Research and Management 09/2010; 11(2).
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