The western South Atlantic (WSA) humpback whale population inhabits the coast of Brazil during the breeding and calving season in winter and spring. This population was depleted to near extinction by whaling in the mid-twentieth century. Despite recent signs of recovery, increasing coastal and offshore development pose potential threats to these animals. Therefore, continuous monitoring is needed to assess population status and support conservation strategies. The aim of this work was to present ship-based line-transect estimates of abundance for humpback whales in their WSA breeding ground and to investigate potential changes in population size. Two cruises surveyed the coast of Brazil during August-September in 2008 and 2012. The area surveyed in 2008 corresponded to the currently recognized population breeding area; effort in 2012 was limited due to unfavorable weather conditions. WSA humpback whale population size in 2008 was estimated at 16,410 (CV = 0.228, 95% CI = 10,563–25,495) animals. In order to compare abundance between 2008 and 2012, estimates for the area between Salvador and Cabo Frio, which were consistently covered in the two years, were computed at 15,332 (CV = 0.243, 95% CI = 9,595–24,500) and 19,429 (CV = 0.101, 95% CI = 15,958–23,654) whales, respectively. The difference in the two estimates represents an increase of 26.7% in whale numbers in a 4-year period. The estimated abundance for 2008 is considered the most robust for the WSA humpback whale population because the ship survey conducted in that year minimized bias from various sources. Results presented here indicate that in 2008, the WSA humpback whale population was at least around 60% of its estimated pre-modern whaling abundance and that it may recover to its pre-exploitation size sooner than previously estimated.
Pós-graduação em Zoologia, Universidade Estadual de Santa Cruz, Ilhéus, BA, 45662–900, Brasil;Instituto Aqualie, Av. Dr. Paulo Japiassu Coelho, 714, Sala 202, Juiz de Fora, MG, 36033–310, Brasil;Sea Mammal Research Unit–SMRU, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife, KY16 8LB, United Kingdom;Pós-graduação em Zoologia, Universidade Estadual de Santa Cruz, Ilhéus, BA, 45662–900, Brasil;Instituto Aqualie, Av. Dr. Paulo Japiassu Coelho, 714, Sala 202, Juiz de Fora, MG, 36033–310, Brasil;Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul–GEMARS, Av. Tramandaí, 976, Imbé, RS, 95625–000, Brasil;Instituto Aqualie, Av. Dr. Paulo Japiassu Coelho, 714, Sala 202, Juiz de Fora, MG, 36033–310, Brasil;Laboratório de Ecologia Comportamental e Bioacústica–LABEC, Departamento de Zoologia, Instituto de Ciências Biológicas, Universidade Federal de Juiz de Fora, R. José Lourenço Kelmer, Juiz de Fora, MG, 36036–900, Brasil;Laboratório de Ecologia e Conservação da Megafauna Marinha–EcoMega, Instituto de Oceanografia, Universidade Federal do Rio Grande, Av. Itália, km 8, Rio Grande, RS, 96203–900, Brasil;Instituto Aqualie, Av. Dr. Paulo Japiassu Coelho, 714, Sala 202, Juiz de Fora, MG, 36033–310, Brasil;Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA Fisheries, 7600 Sand Point Way NE, Seattle, WA, 98115–6349, United States of America;Cascadia Research Collective, 218 ½ 4th Ave W, Olympia, WA, 98501, United States of America
Recommended Citation:
Guilherme A. Bortolotto,Daniel Danilewicz,Artur Andriolo,et al. Whale, Whale, Everywhere: Increasing Abundance of Western South Atlantic Humpback Whales (Megaptera novaeangliae) in Their Wintering Grounds[J]. PLOS ONE,2016-01-01,11(10)