Publicação
Estimation of the nesting abundance of the green sea turtles (Chelonia mydas) on Poilão Island
| Resumo: | This study centres on the Bijagos Archipelago in Guinea-Bissau, a vital nesting ground for four ´ sea turtle species. Among these, Poilao Island is particularly notable for its substantial green turtle ˜ population. Monitoring strategies commonly involve counting turtle tracks to estimate the number of emergences. The primary objectives of this study are to estimate the abundance of emerging female turtles and to assess the reliability of emergence counts, emergence counts corrected with a correction factor, track counts and stranded counts in estimating total emergences. To achieve these goals, these metrics were compared using a point-based system. Generalized Additive Models (GAMs) and Generalized Additive Models for Location, Scale, and Shape (GAMLSS) were utilized due to their flexibility in modelling complex data and their strong predictive capabilities. The study’s findings suggest that counting emerging turtles at high tide and multiplying by a correction factor is the most effective way to estimate the total number of total emergences on Poilao Island. The reliability of track counts and ˜ emergence counts (not corrected with the correction factor) seems to depend on nesting density. On the other hand, models showed that track counts are a better metric than stranded counts for estimating turtle emergences regardless of nesting density. Our results show that both GAM and GAMLSS models showed equal predicting performance. Over the past three years, the estimated number of unique turtles emerging in Poilao is expectedly 29,529 turtles. Additionally, the estimated number of clutches during ˜ the same period is expectedly 46,006, aligning with previous literature estimates. The insights derived from this study contribute to refining methodologies for monitoring the green turtle population of Poilao˜ Island, which is critical for the effective conservation and management of this species’ nesting habitats in the Bijagos Archipelago. |
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| Autores principais: | Louro, João Luís Miranda |
| Assunto: | Tartaruga-verde Poilão Tartaruga Marinha Modelos Aditivos Generalizados Modelos Aditivos Generalizados para Localização Escala e Forma Tese de mestrado 2024 |
| Ano: | 2024 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | This study centres on the Bijagos Archipelago in Guinea-Bissau, a vital nesting ground for four ´ sea turtle species. Among these, Poilao Island is particularly notable for its substantial green turtle ˜ population. Monitoring strategies commonly involve counting turtle tracks to estimate the number of emergences. The primary objectives of this study are to estimate the abundance of emerging female turtles and to assess the reliability of emergence counts, emergence counts corrected with a correction factor, track counts and stranded counts in estimating total emergences. To achieve these goals, these metrics were compared using a point-based system. Generalized Additive Models (GAMs) and Generalized Additive Models for Location, Scale, and Shape (GAMLSS) were utilized due to their flexibility in modelling complex data and their strong predictive capabilities. The study’s findings suggest that counting emerging turtles at high tide and multiplying by a correction factor is the most effective way to estimate the total number of total emergences on Poilao Island. The reliability of track counts and ˜ emergence counts (not corrected with the correction factor) seems to depend on nesting density. On the other hand, models showed that track counts are a better metric than stranded counts for estimating turtle emergences regardless of nesting density. Our results show that both GAM and GAMLSS models showed equal predicting performance. Over the past three years, the estimated number of unique turtles emerging in Poilao is expectedly 29,529 turtles. Additionally, the estimated number of clutches during ˜ the same period is expectedly 46,006, aligning with previous literature estimates. The insights derived from this study contribute to refining methodologies for monitoring the green turtle population of Poilao˜ Island, which is critical for the effective conservation and management of this species’ nesting habitats in the Bijagos Archipelago. |
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