Idade e crescimento da tartaruga-cabeçuda (Caretta caretta) no litoral sul do Rio Grande do Sul / Age and growth of loggerhead sea turtle (Caretta caretta) in Southern Brazil

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

16/12/2010

RESUMO

The juvenile and sub-adult stages of loggerhead sea turtles (Caretta caretta) are poorly studied in Brazil. We present age estimates and a growth model for loggerhead sea turtles in the South Atlantic Ocean obtained through skeletochronological analysis of humeri obtained from both neritic and oceanic stage individuals. Since it was validated that each increment growth corresponds to one year for loggerhead sea turtle, the number of lines of arrested growth (LAGs) was taken as the age estimated. For larger turtles a correction factor was applied to solve for lost LAGs. This correction factor was based on two models, the first denoted naïve makes no distinction between inter- and intra-individual variability and the second denoted hierarchical, takes this distinction into account. The hierarchical model had the best fit to the data set, probably because these reptiles experience stochastic conditions through their life cycle, so that some individuals may grow more than others. The estimated ages indicate that the duration of the pelagic stage is 8 to19 years (average 11.5 years) and the age at maturation ranges from 25.7 to 39.2 years (average 31.2 years). Schnute‟s growth model was fit to age-at-length data, due to its versatility in shape and no requirement of size data for hatchlings up to individuals at old ages with near asymptotic size. However, since the shape of Schnute`s curve was almost linear for the age-window comprising our data, a linear regression ultimately yielded a slightly better fit. The Body Proportional Hypothesis was incorporated in the calculation of growth rates. Growth rates from neritic stage South Atlantic loggerheads were similar to those reported for neritic loggerhead sea turtles from the North Atlantic, but lower than for oceanic loggerheads from South Atlantic. This finding suggests that local environmental conditions influence turtle‟s growth rates, as well as, the energy expenditure during migrations, energy allocation and genetic origin.

ASSUNTO(S)

modelo de schnute schnute‟ s growth model age growth skeletochronology sea turtles rio grande do sul south coast brazil rio grande do sul litoral sul oceanografia biologica tartaruga marinha idade esqueletocronologia crescimento caretta caretta brasil caretta caretta

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