Blue whale population structure along the eastern South Pacific Ocean: evidence of more than one population

Abstract

Blue whales (Balaenoptera musculus) were among the most intensively exploited species of whales in the world. As a consequence of this intense exploitation, blue whale sightings off the coast of Chile were uncommon by the end of the 20th century. In 2004, a feeding and nursing ground was reported in southern Chile (SCh). With the aim to investigate the genetic identity and relationship of these Chilean blue whales to those in other Southern Hemisphere areas, 60 biopsy samples were collected from blue whales in SCh between 2003 and 2009. These samples were genotyped at seven microsatellite loci and the mitochondrial control region was sequenced, allowing us to identify 52 individuals. To investigate the genetic identity of this suspected remnant population, we compared these 52 individuals to blue whales from Antarctica (ANT, n = 96), Northern Chile (NCh, n = 19) and the eastern tropical Pacific (ETP, n = 31). No significant differentiation in haplotype frequencies (mtDNA) or among genotypes (nDNA) was found between SCh, NCh and ETP, while significant differences were found between those three areas and Antarctica for both the mitochondrial and microsatellite analyses. Our results suggest at least two breeding population units or subspecies exist, which is also supported by other lines of evidence such as morphometrics and acoustics. The lack of differences detected between SCh/NCh/ETP areas supports the hypothesis that eastern South Pacific blue whales are using the ETP area as a possible breeding area. Considering the small population sizes previously reported for the SCh area, additional conservation measures and monitoring of this population should be developed and prioritized.

Genetic differentiation between humpback whales (Megaptera novaeangliae) from Atlantic and Pacific breeding grounds of South America

“…Our results are also similar to a recent study that detected some possible migrants between two blue whale ( Balaenoptera musculus ) populations at the southeastern Pacific Ocean but also found significant differences for both mitochondrial and microsatellite markers between these populations (Torres‐Florez et al . ).…”

Estimates of Abundance and Trend of Chilean Blue Whales off Isla de Chiloé, Chile

“…However the apparent lack of genetic substructure observed along the Chilean coast [5] suggests seasonal segregation is limited. Other whale species with common wintering grounds but long-term fidelity to different feeding areas in the North Pacific exhibit female-mediated population structure (e.g.…”

Photogrammetry of blue whales with an unmanned hexacopter

“…These measurements were consistent with lengths of blue whales previously measured using photogrammetry from manned aircraft (Gilpatrick and Perryman ), particularly for those whales photographed in the Eastern Tropical Pacific (females with calves averaged 22.4 m in length), which have been genetically linked to the whales feeding off southern Chile (Torres‐Florez et al . ). Body width measurements were also taken at the point on the whales' body that equaled 40% of the body length from the rostrum, where widths were variable in whales of adult size (Fig.…”