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Métodos de monitorização e tendências numéricas de tartarugas verdes em Poilão, o local de reprodução mais importante da África
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Abstract(s)
A ilha de Poilão, nos Bijagós, é a mais importante praia de nidificação das tartarugas-verdes no
Atlântico Oriental. Os objetivos deste estudo, realizados na ilha de Poilão, são: 1) estimar os
erros associados aos métodos de contagem de parâmetros populacionais (número de fêmeas a
desovar e número de rastos deixados pelas fêmeas na praia), 2) estimar as taxas de sucesso
desova na ilha de Poilão, 3) estimar a abundância de ninhos e 4) compreender qual a tendência
populacional. Durante a temporada de 2019 contaram-se as tartarugas-verdes encontradas na
praia a desovar durante o pico da maré cheia e os rastos deixados pelas mesmas (censos
'normais'), e em noites de censos intensivos contaram-se todas as fêmeas que subiram às praias
entre as 19h00 e as 7h00, para estimar as tartarugas 'perdidas' pelos censos normais. Seguiramse ainda 279 tartarugas-verdes até à desova ou regresso ao mar. O sucesso de desova médio foi
77.9%. Este estudo permitiu corrigir os valores das contagens obtidas pelos ‘censos normais’,
estimando-se que o número real de fêmeas para o ano de 2019 foi 12719. Considerando o
sucesso de desova e o número real de tartarugas por praia, o total estimado de ninhos no ano de
2019 foi 18567. Na ilha de Poilão, a tendência populacional tem sido marcadamente positiva,
mas há muita variação interanual no número de desovas, tendo sido o ano de 2019 um fraco
ano. Este estudo vai permitir melhorar a monitorização e as estimativas populacionais desta
importante população.
The island of Poilão, in Bijagós, is the most important nesting beach for green turtles in the Eastern Atlantic. The objectives of this study, carried out on the island of Poilão, are: 1) to estimate the errors associated with methods of counting population parameters (number of females to spawn and number of tracks left by females on the beach), 2) to estimate success rates spawn on the island of Poilão, 3) estimate the abundance of nests and 4) understand the population trend. During the 2019 season, green turtles found on the beach spawning during the peak of the high tide and the trails left by them ('normal' censuses) were counted, and on intensive census nights all females that climbed were counted. to the beaches between 7:00 pm and 7:00 am, to estimate the 'lost' turtles by normal censuses. This was followed by 279 green turtles until they spawned or returned to the sea. The average spawning success was 77.9%. This study allowed correcting the values of the counts obtained by the 'normal censuses', estimating that the real number of females for the year 2019 was 12719. Considering the spawning success and the real number of turtles per beach, the estimated total of nests in the year 2019 was 18567. On the island of Poilão, the population trend has been markedly positive, but there is a lot of interannual variation in the number of spawns, with 2019 being a poor year. This study will improve monitoring and population estimates for this important population.
The island of Poilão, in Bijagós, is the most important nesting beach for green turtles in the Eastern Atlantic. The objectives of this study, carried out on the island of Poilão, are: 1) to estimate the errors associated with methods of counting population parameters (number of females to spawn and number of tracks left by females on the beach), 2) to estimate success rates spawn on the island of Poilão, 3) estimate the abundance of nests and 4) understand the population trend. During the 2019 season, green turtles found on the beach spawning during the peak of the high tide and the trails left by them ('normal' censuses) were counted, and on intensive census nights all females that climbed were counted. to the beaches between 7:00 pm and 7:00 am, to estimate the 'lost' turtles by normal censuses. This was followed by 279 green turtles until they spawned or returned to the sea. The average spawning success was 77.9%. This study allowed correcting the values of the counts obtained by the 'normal censuses', estimating that the real number of females for the year 2019 was 12719. Considering the spawning success and the real number of turtles per beach, the estimated total of nests in the year 2019 was 18567. On the island of Poilão, the population trend has been markedly positive, but there is a lot of interannual variation in the number of spawns, with 2019 being a poor year. This study will improve monitoring and population estimates for this important population.
Description
Dissertação de Mestrado apresentada no
ISPA – Instituto Universitário para obtenção de grau
de Mestre em Biologia Marinha e Conservação.
Keywords
Tartaruga-verde Sucesso de desova Fatores de correção das contagens de rastos Tendência populacional Green turtle Nesting success Track count correction factors Population trend