Effective population size and the genetic consequences of commercial whaling on the humpback whales (Megaptera novaeangliae) from Southwestern Atlantic Ocean

Abstract Genotypes of 10 microsatellite loci of 420 humpback whales from the Southwestern Atlantic Ocean population were used to estimate for the first time its contemporary effective (Ne) and census (Nc) population sizes and to test the genetic effect of commercial whaling. The results are in agreement with our previous studies that found high genetic diversity for this breeding population. Using an approximate Bayesian computation approach, the scenario of constant Ne was significantly supported over scenarios with moderate to strong size changes during the commercial whaling period. The previous generation Nc (Ne multiplied by 3.6), which should corresponds to the years between around 1980 and 1990, was estimated between ~2,600 and 6,800 whales (point estimate ~4,000), and is broadly compatible with the recent abundance surveys extrapolated to the past using a growth rate of 7.4% per annum. The long-term Nc in the constant scenario (point estimate ~15,000) was broadly compatible (considering the confidence interval) with pre-whaling catch records estimates (point estimate ~25,000). Overall, our results shown that the Southwestern Atlantic Ocean humpback whale population is genetically very diverse and resisted well to the strong population reduction during commercial whaling.

Analysis of humpback whale sounds in shallow waters of the Southeastern Arabian Sea: An indication of breeding habitat.

The primary objective of this work was to present the acoustical identification of humpback whales, detected by using an autonomous ambient noise measurement system, deployed in the shallow waters of the Southeastern Arabian Sea (SEAS) during the period January to May 2011. Seven types of sounds were detected. These were characteristically upsweeps and downsweeps along with harmonics. Sounds produced repeatedly in a specific pattern were referred to as phrases (PQRS and ABC). Repeated phrases in a particular pattern were referred to as themes, and from the spectrographic analysis, two themes (I and II) were identified. The variation in the acoustic characteristics such as fundamental frequency, range, duration of the sound unit, and the structure of the phrases and themes are discussed. Sound units were recorded from mid-January to mid-March, with a peak in February, when the mean SST is ~28°C, and no presence was recorded after mid-March. The temporal and thematic structures strongly determine the functions of the humpback whale song form. Given the use of song in the SEAS, this area is possibly used as an active breeding habitat by humpback whales during the winter season.

Migração de baleias-jubarte: o que falta conhecer? / Humpback Whale Migration: what else needs to be known?

As baleias ocorrem em todos os oceanos do planeta e realizam migrações entre áreas de alimentação e reprodução. Determinar rotas e destinos migratórios é essencial para estabelecer planos de conservação e estratégias de gestão. A telemetria por satélite é um método muito eficiente para estudar o comportamento e os movimentos de animais. A baleia-jubarte se reproduz no litoral central e nordeste do Brasil, desde o Rio de Janeiro até o Rio Grande do Norte. Investigando as hipóteses existentes sobre as possíveis rotas migratórias das baleias-jubarte, verificou-se que animais do Banco dos Abrolhos (16-18oS) adotam uma rota migratória relativamente retilínea e se alimentam ao sul da Convergência Antártica, em águas afastadas da costa a nordeste e leste da Georgia do Sul e das Ilhas Sandwich do Sul. Mesmo com os resultados já obtidos, ainda faz-se necessário realizar estudos adicionais para avaliar o uso do habitat nas áreas de reprodução e para verificar se os animais distribuídos em outras áreas do litoral do Brasil fazem uso das mesmas rotas migratórias e áreas de alimentação.

Whales inhabit all oceans and typically perform migrations between feeding and breeding areas. To determine migration routes and destinations is essential for the implementation of proper conservation and management plans. Satellite telemetry is an efficient method to investigate the behavior and movements of migratory animals. Humpback whales winter along the central and northeast coast of Brazil, from Rio de Janeiro to Rio Grande do Norte. This study tested hypotheses about the migratory routes and feeding destinations and discovered that whales wintering in the Abrolhos Bank (~16-18oS) adopt a relatively linear migration route and feed south of the Antarctic Convergence in offshore waters to the northeast and east of South Georgia and the South Sandwich Islands. Despite these results, additional studies are necessary to assess habitat use in the breeding grounds and to investigate whether whales from other areas off Brazil use the same migratory routes and feeding grounds.