Migração de jubartes: uma história escrita nas barbatanas
Data
2022-07-28
Autores
Salloum, Kalil Cardoso 
Orientadores
Torrente-Vilara, Gislene
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Como quase a totalidade de estoques reprodutivos de baleias jubarte, Megaptera
novaeangliae, no mundo, a população A, que vista a costa brasileira, realiza uma
migração anual entre zonas de altas latitudes, onde se alimentam no verão, e zonas
de médias e baixas latitudes, onde ocorre a reprodução e parto. Abrolhos é
tradicionalmente o principal destino da espécie no Brasil, e se assumia que esta
permanecia em jejum ao sair de sua região de alimentação antártica. Entretanto,
observações recentes de indivíduos se alimentando na costa brasileira, somadas com
recordes em números de encalhes e avistamentos crescentes na região sudeste do
país, levam a necessidade de reavaliar parte do conhecimento atual sobre a migração
da espécie. A análise da razão entre isótopos estáveis de carbono e nitrogênio ao
longo da placa de barbatanas de baleias é uma técnica que vem ganhando destaque
para analisar padrões migratórios, e apresentamos neste documento sua primeira
aplicação em indivíduos encalhados em território brasileiro. Com ela, a alimentação
em águas próximas ao Brasil foi confirmada em dois indivíduos juvenis, com valores
de δ
13C características de zonas tropicais e subtropicais. Valores de δ
15N nas placas
também indicam um nível trófico maior das fontes de alimento nesta área em
comparação com o krill antártico. Tais indícios podem ajudar a explicar a alta de
encalhes, com mais animais se aproximando da costa para buscar alimento e
interagindo com aparatos de pesca, e podem ser indicativos de mudanças climáticas
que impactam na disponibilidade de alimento em regiões antárticas. A expansão da
técnica para mais indivíduos de jubarte pode auxiliar a clarificar tais mudanças em
nível de população.
Humpback whales, Megaptera novaeangliae, from the breeding stock A undergo an annual migration between high latitude zones near Antarctica, where they feed during summer, and medium and low latitudes where breeding occurs in winter, just like most humpback populations. The Abrolhos Bank is the main breeding destination for those whales in the Brazilian coast, and it was assumed that the whales would remain in a state of fasting when away from the Antarctic feeding grounds. However, recent sightings of individuals feeding in the Brazilian coast, atypical stranding events and the rise in observations of whales in the southeast of the country lead to the need of revaluating the current knowledge on its migration. Carbon and Nitrogen stable isotope ratio analysis throughout the length of a whale’s baleen is a technique that has been gaining momentum in determining migratory patterns. We here present its first application in whales that stranded in the coast of Brazil. Applying it, we could confirm that feeding near Brazilian waters has occurred in two tested individuals, which presented δ 13C values similar to tropical and subtropical regions in the most recently formed part of their baleen plates. A rise in δ 15N values in the same region indicate the higher trophic level of the food sources in the Atlantic when compared to Antarctic krill. This information can help explain some stranding events, with the animals getting closer to the coast to look for prey and therefore interacting more often with fishing nets and other threats, and might also indicate the effect of climate change in the food availability in the Antarctic feeding ground. We recommend expanding the sample size to help assess those feeding and migratory changes in a population level.
Humpback whales, Megaptera novaeangliae, from the breeding stock A undergo an annual migration between high latitude zones near Antarctica, where they feed during summer, and medium and low latitudes where breeding occurs in winter, just like most humpback populations. The Abrolhos Bank is the main breeding destination for those whales in the Brazilian coast, and it was assumed that the whales would remain in a state of fasting when away from the Antarctic feeding grounds. However, recent sightings of individuals feeding in the Brazilian coast, atypical stranding events and the rise in observations of whales in the southeast of the country lead to the need of revaluating the current knowledge on its migration. Carbon and Nitrogen stable isotope ratio analysis throughout the length of a whale’s baleen is a technique that has been gaining momentum in determining migratory patterns. We here present its first application in whales that stranded in the coast of Brazil. Applying it, we could confirm that feeding near Brazilian waters has occurred in two tested individuals, which presented δ 13C values similar to tropical and subtropical regions in the most recently formed part of their baleen plates. A rise in δ 15N values in the same region indicate the higher trophic level of the food sources in the Atlantic when compared to Antarctic krill. This information can help explain some stranding events, with the animals getting closer to the coast to look for prey and therefore interacting more often with fishing nets and other threats, and might also indicate the effect of climate change in the food availability in the Antarctic feeding ground. We recommend expanding the sample size to help assess those feeding and migratory changes in a population level.
Descrição
Citação
SALLOUM, Kalil Cardoso. Migração de jubartes: uma história escrita nas barbatanas. 2022. 27 f. Trabalho de conclusão de curso (Graduação em Bacharelado Interdisciplinar em Ciência e Tecnologia do Mar) - Instituto do Mar, Universidade Federal de São Paulo, Santos, 2022.