Publicação
Environmental constraints on population structure and condition of coastal and estuarine crabs : (Crustacea: Brachyura)
| Resumo: | Crabs are amongst the most conspicuous and ecologically important organisms inhabiting nearshore environments. Their complex life cycle and bioindicator capacity makes them good models for the study of distribution and abundance patterns of marine fish and benthic invertebrate populations. Such knowledge is essential for explaining species occurrence and demographic patterns, predicting the success of biological indicators and controls, as well as for conservation and management purposes of exploited populations and ecosystems. In this study, the impacts of specific environmental constraints at different life phases of estuarine and coastal crabs on population structure and physiological condition were evaluated and related to habitat quality. During settlement and recruitment events, the patchiness of artificial substrates significantly influenced settlement estimation, and strong water currents might have resulted in a decoupling pattern between supply and settlement. Estuarine sandy habitats presented higher quality for early recruits than seagrass ones. In fact, vegetated habitats were not of higher quality for crab populations than non-vegetated and rocky-shore ones. Adult-juvenile cannibalism showed potential to structure intertidal crab assemblages, especially under shortage of food and refuge. Interestingly, mangrove crabs were more affected by climatic season than by pollution, and coped well with several combinations of vegetation and sewage load. Specific constraints of different life stages, individually and in combination, must be considered for full understanding distribution and abundance patterns of crab populations. Furthermore, the relative importance of a specific constraint is likely to change throughout ontogenesis, and the mechanisms by which it interacts with other environmental variables and processes, sometimes synergistically, have also to be considered. This study constitutes an extension to the knowledge on population structure and physiological condition of coastal and estuarine crabs and other marine invertebrate and fish species, and on their use as indicators of ecological status of habitats and ecosystems. |
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| Autores principais: | Amaral, Valter Luís Morgado, 1978- |
| Assunto: | Biologia marinha Aquacultura Teses de doutoramento |
| Ano: | 2008 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Crabs are amongst the most conspicuous and ecologically important organisms inhabiting nearshore environments. Their complex life cycle and bioindicator capacity makes them good models for the study of distribution and abundance patterns of marine fish and benthic invertebrate populations. Such knowledge is essential for explaining species occurrence and demographic patterns, predicting the success of biological indicators and controls, as well as for conservation and management purposes of exploited populations and ecosystems. In this study, the impacts of specific environmental constraints at different life phases of estuarine and coastal crabs on population structure and physiological condition were evaluated and related to habitat quality. During settlement and recruitment events, the patchiness of artificial substrates significantly influenced settlement estimation, and strong water currents might have resulted in a decoupling pattern between supply and settlement. Estuarine sandy habitats presented higher quality for early recruits than seagrass ones. In fact, vegetated habitats were not of higher quality for crab populations than non-vegetated and rocky-shore ones. Adult-juvenile cannibalism showed potential to structure intertidal crab assemblages, especially under shortage of food and refuge. Interestingly, mangrove crabs were more affected by climatic season than by pollution, and coped well with several combinations of vegetation and sewage load. Specific constraints of different life stages, individually and in combination, must be considered for full understanding distribution and abundance patterns of crab populations. Furthermore, the relative importance of a specific constraint is likely to change throughout ontogenesis, and the mechanisms by which it interacts with other environmental variables and processes, sometimes synergistically, have also to be considered. This study constitutes an extension to the knowledge on population structure and physiological condition of coastal and estuarine crabs and other marine invertebrate and fish species, and on their use as indicators of ecological status of habitats and ecosystems. |
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