Conservation status of the loggerhead sea turtle in Brazil: an encouraging outlook

Marcovaldi, Maria Ângela; Chaloupka, Milani

doi:10.3354/esr003133

Cited by 120 publications

(91 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For R max , we used maximum population growth rates observed at nesting sites: 0.064 yr −1 for loggerheads (Brazil; Marcovaldi & Chaloupka 2007) and 0.139 yr −1 for green turtles (Florida, USA; Chaloupka et al 2008). These maximum population growth rates were chosen because the observed populations were at low density and are thought to have similar life history traits to the Mediterranean populations of each species.…”

Section: Pbrmentioning

confidence: 99%

How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean

Casale¹,

Heppell²

2016

Endang. Species. Res.

View full text Add to dashboard Cite

Mediterranean populations of loggerhead Caretta caretta and green sea turtles Chelonia mydas are subject to several anthropogenic threats, with documented mortality from incidental capture in fishing gear. However, how such mortalities actually affect the populations is uncertain without an estimate of population size. We derived a theoretical demographic structure for each species in the Mediterranean, assuming a stationary age distribution in a stable population with constant proportions of turtles in each life stage, using distributions of age-specific vital rates. We incorporated uncertainty into the main vital rate parameters to identify a likely order of magnitude of turtle abundance in different life stages. Through this approach, we aim to (1) provide a rough estimate of all population stage classes, particularly the juvenile classes that are most subject to fisheries interactions, (2) provide an estimate of reproductive life span, (3) identify and review the key demographic parameters, and (4) identify the priority gaps in our information in need of further investigation. The range of population abundance estimates from the models constructed with uncertainty (95% CI) was 0.81−3.38 million loggerheads and 0.26−2.21 million green turtles, Mediterranean-wide. When we calculated the potential biological removal for the segment of the population at risk of fisheries capture, our estimates were comparable to or lower than the estimated bycatch levels in fisheries. Although the model assumes a stable population and provides only a rough estimate of abundance, these results suggest that the current bycatch level should be regarded as unsustainable for Mediterranean turtle populations.

show abstract

Section: Pbrmentioning

confidence: 99%

How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean

Casale¹,

Heppell²

2016

Endang. Species. Res.

View full text Add to dashboard Cite

show abstract

“…As tartarugas marinhas constituem uma exceção, pois o monitoramento realizado pelo Projeto TAMAR/ICMBio permite observações sobre a efetividade do programa de preservação apontando para um ligeiro, porém constante aumento das populações de C. caretta (Marcovaldi & Chaloupka, 2007) e D. coriacea (Thomé et al, 2007). Para as tartarugas de água doce, em especial P. expansa e P. unifilis, que são as mais estudadas, ainda não existem estimativas consistentes sobre o tamanho das populações.…”

Section: Conclusõesunclassified

Efeitos de Fatores Ambientais na Reprodução de Tartarugas

Júnior

2009

Acta Amaz.

View full text Add to dashboard Cite

ResumoPara as espécies de tartaruga que apresentam a determinação sexual dependente da temperatura da incubação o local e o momento da desova, exercem influências que vão além da definição do sexo dos embriões. A influência do local da desova se estende a todo o desenvolvimento embrionário afetando o comportamento e o tamanho dos filhotes. O momento em que ocorre a desova trará conseqüências ao ambiente térmico dos ninhos à medida que a temperatura e a umidade variam ao longo do ano. A umidade será decisiva nas trocas hídricas e gasosas entre os ovos e o meio afetando a absorção do vitelo e o crescimento dos embriões. As cheias e os alagamentos são importantes fatores de perda de ninhos nas espécies de tartaruga de água doce. A desova no momento adequado possibilita uma incubação segura, sem a interferência de alagamentos dos ninhos e conseqüente morte dos embriões. A predação dos ninhos varia de acordo com o local da desova, o tipo e a abundância de predadores e a profundidade da câmara de ovos. A escolha de pontos de desova no interior da vegetação, onde a taxa de predação é geralmente menor, nem sempre é a estratégia mais frequentemente adotada pelas tartarugas, uma vez que esse procedimento pode levar a uma maior exposição das fêmeas aos predadores, à diminuição do sucesso da eclosão ou a alterações na razão sexual provocadas por diferenças na temperatura da incubação.PalavRas-chave: quelônios, nidificação, embriogênese, predação, eclosão. Environmental factors effects in turtles reproduction AbstrActTurtle species in which the sex determination is dependent of incubation temperature, the nest site and the laying moment will affect more than embryo sex determination. The influence of the laying site extends all over the embryonic development, affecting hatching weight and size. The time of the egg-laying will bring consequences to the nest thermal environment, as the temperature and humidity change throughout the year. The humidity will be decisive in gaseous and hydric exchanges between eggs and the environment, affecting yolk absorption and embryo growth. Floods and inundation are important factors related to nest loss in freshwater turtle species. Egg laying at the appropriated time makes a safe incubation possible, without the interference of nest inundation and subsequent embryo death. The nest predation varies according to the egg-laying site, type and abundance of predator and nest depth. The choice of areas in the middle of vegetation, where the predation rate is generally smaller, is not always the most used strategy by turtles, since this procedure can decrease the hatching success or provoke changes in sex ratio.

show abstract

“…Along the Brazilian coast, most studies of loggerhead sea turtles focus on adult females on nesting beaches, and the majority of nesting occurs in the states of Bahia and Espírito Santo (Marcovaldi & Chaloupka 2007). Although information for immature individuals during their oceanic and neritic stages is fragmentary, it is known that the southern coast of Rio Grande do Sul state, southern Brazil, is an important foraging area for both stages of Caretta caretta (Martinez-Souza 2009, Barros 2010.…”

Section: Introductionmentioning

confidence: 99%

Age and growth of loggerhead sea turtles in southern Brazil

Petitet¹,

Secchi²,

Avens³

et al. 2012

Mar. Ecol. Prog. Ser.

View full text Add to dashboard Cite

The juvenile and subadult 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 from both neritic and oceanic stage individuals. The age estimation was based on the number of growth marks in the humerus; however, for larger turtles early growth marks were resorbed and therefore it was necessary to use a correction factor to account for the lost growth marks. The estimated ages indicate that the oceanic stage lasts 8 to 19 yr (average: 11.5 yr). Schnute's growth model was fit to age-at-length data, as its shape is versatile and it does not require data from all life stages (i.e. hatchlings through adults near asymptotic size). However, because the shape of Schnute's curve was almost linear for the age window comprising our data, a linear regression ultimately provided a better fit to the data, yielding an age at maturation estimate of 32 yr. Somatic growth rates were calculated through incorporation of the Body Proportional Hypothesis into conversion of growth mark measurements to estimates of carapace length. Growth rates from neritic stage South Atlantic loggerheads were similar to those reported for neritic loggerhead sea turtles from the North Atlantic Ocean, but were lower than those of oceanic loggerheads from the South Atlantic Ocean. This finding suggests that local environmental conditions influence loggerhead sea turtles' growth rates as well as the energy expenditure during migrations, energy allocation and genetic origin.

show abstract

Conservation status of the loggerhead sea turtle in Brazil: an encouraging outlook

Cited by 120 publications

References 26 publications

How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean

How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean

Efeitos de Fatores Ambientais na Reprodução de Tartarugas

Age and growth of loggerhead sea turtles in southern Brazil

Contact Info

Product

Resources

About