Distribuição batimétrica e avaliação populacional de Callinectes ornatus Ordway, 1863 no litoral sudeste brasileiro em um período de 10 anos.
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Data
2021-02-26
Autores
Rodrigues, Larissa Rosa
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Universidade Estadual Paulista (Unesp)
Resumo
Características como temperatura, salinidade, substrato e exposição à luz são importantes fatores que regulam a abundância, distribuição ecológica, processos fisiológicos como locomoção, alimentação e acasalamento dos crustáceos decápodes. Callinectes ornatus Ordway, 1863, conhecido popularmente como siri-azul, é constantemente capturado como fauna acompanhante nos arrastos camaroeiros na região de Ubatuba, o que pode levá-lo a desenvolver estratégias que visam manter sua população. O presente trabalho teve como objetivo realizar análise batimétrica e avalição populacional da espécie, avaliando a variação diuturna na abundância e comparando coletas com 10 anos de diferença de C. ornatus na região de Ubatuba – SP. As coletas foram realizadas mensalmente, de janeiro a dezembro de 2000 e 2010, utilizando um barco camaroeiro equipado com redes de arrasto do tipo “double-rig”, nas profundidades de 2, 5, 10, 15, 20, 25, 30, 35 e 40 metros. Em 2000 também foram realizadas coletas noturnas nos 2, 5 e 15m de profundidades. Foram coletadas amostras de água e sedimento para analisar temperatura de fundo e de superfície, salinidade, sedimento e matéria orgânica. Foi observado um predomínio dos indivíduos de C. ornatus em menores profundidades, reduzindo essa quantidade ao aumentar as profundidades de coleta. Essa preferência provavelmente está relacionada com a menor competição dessa região, apontando a preferência de C. ornatus por áreas menos povoadas. Nessa região obtivemos dados de menor salinidade e alta concentração de matéria orgânica. Verificou-se que as fêmeas possuem uma ocupação diferente de acordo com os tamanhos de indivíduos. Já os espécimes machos foram mais abundantes nas profundidades mais rasas, possivelmente em busca de fêmeas primíparas, para acasalamento. Em comparativo nictemeral da população de C. ornatus, observou-se maior atividade no período diurno, diferente do congênere C. danae Smith, 1869 com quem pode compartilhar nicho. Tal fato pode ser estratégia para evitar competição com a outra espécie e permitir a coexistência com sucesso de ambas. Além disso, alguns dos camarões capturados pela pesca de arrasto, possuem o hábito noturno, entre eles destaca-se o camarão sete-barbas e camarão branco, o que faz a pesca mais efetiva nesse período. Os machos em fase de intermuda (MSC) estão distribuídos nas mesmas profundidades em que as fêmeas em fase de calcificação do exoesqueleto (MSB), sendo predominantes entre 2 e 5m de profundidade. Essas regiões mais rasas possuem menor quantidade de espécie, fazendo com que os espécimes de C. ornatus não fiquem tão suscetíveis aos predadores, agindo como uma possível estratégia de proteção da população. Comparando as coletas de 10 anos, apesar da redução sutil e pouco significativa no número total, ocorreu uma modificação nos picos de reprodução de C. ornatus, o que pode estar demonstrando uma estratégia para manter a população no local. Em 2000 as fêmeas embrionadas foram mais abundantes no verão, sendo registrado um segundo pico durante o outono. Esse fato, pode ser um indicativo de plasticidade reprodutiva, como tentativa de manter uma reprodução eficiente e conservar a abundância da espécie. Com base neste estudo, foi possível inferir estratégias de uma população de C. ornatus para se manter mesmo com os impactos antrópicos no litoral de São Paulo.
Characteristics such as temperature, salinity, substrate type and exposure to light are important factors that regulate abundance, ecological distribution, physiological processes such as locomotion, feeding and mating of decapod crustaceans. Callinectes ornatus Ordway, 1863, popularly known as blue crab, is constantly captured as bycatch in shrimp trawlers in the Ubatuba region, which can take to develop strategies to maintain its population. This study aimed to carry out bathymetric analysis and population evaluation of the species, evaluating the diurnal variation in the abundance and comparing collections with 10 years of C. ornatus difference in Ubatuba - SP. Collections were carried out monthly, from January to December 2000 and 2010, using a shrimp boat equipped with double-rig trawls, at depths of 2, 5, 10, 15, 20, 25, 30, 35 and 40 meters. In 2000, night collections were also performed at 2, 5 and 15m depths. Water and sediment samples were collected to analyze bottom and surface temperature, salinity, Phi sediment and organic matter. A prevalence of C. ornatus individuals was observed at shallower depths, reducing this amount when increasing the depths of collection. This preference is probably related to the lesser competition in this region, indicating the preference of C. ornatus for less populated areas. In this region, we obtained data with lower salinity and a high concentration of organic matter. It was found that females have a different occupation according to the sizes of individuals. Already the male specimens were more abundant at shallower depths, possibly in search of primiparous females, for mating. In comparative diurnal population of C. ornatus, greater activity was observed in the daytime, differently from the congener C. danae Smith, 1869 who can share niche. Such fact can be a strategy to avoid competition with other species and allow the successful coexistence of both. In addition, some species of shrimp caught by trawling, have a nocturnal habit, among them the seabob shrimp and white shrimp, which makes the most effective fishing in that period. The males in the intermuda phase (MSC) are distributed at the same depths as the females with exoskeleton calcification phase (MSB), being predominant between 2 and 5m deep. These shallower regions have fewer species, causing C. ornatus specimens are not so susceptible to predators, acting as a possible population protection strategy. Comparing the 10-year collections, despite the subtle and insignificant reduction in the total number, there was a change in the peak of reproduction of C. ornatus, which may be demonstrating a strategy to mantains the local population. In 2000 the embryonic females were more abundant in summer, and recorded a second peak during autumn. This fact may be indicative of reproductive plasticity, as an attempt to maintain an efficient reproduction and to conserve the abundance of the species. Based on this study, it was possible to infer strategies of a population of C. ornatus to maintain itself despite the anthropic impacts on the coast of São Paulo.
Characteristics such as temperature, salinity, substrate type and exposure to light are important factors that regulate abundance, ecological distribution, physiological processes such as locomotion, feeding and mating of decapod crustaceans. Callinectes ornatus Ordway, 1863, popularly known as blue crab, is constantly captured as bycatch in shrimp trawlers in the Ubatuba region, which can take to develop strategies to maintain its population. This study aimed to carry out bathymetric analysis and population evaluation of the species, evaluating the diurnal variation in the abundance and comparing collections with 10 years of C. ornatus difference in Ubatuba - SP. Collections were carried out monthly, from January to December 2000 and 2010, using a shrimp boat equipped with double-rig trawls, at depths of 2, 5, 10, 15, 20, 25, 30, 35 and 40 meters. In 2000, night collections were also performed at 2, 5 and 15m depths. Water and sediment samples were collected to analyze bottom and surface temperature, salinity, Phi sediment and organic matter. A prevalence of C. ornatus individuals was observed at shallower depths, reducing this amount when increasing the depths of collection. This preference is probably related to the lesser competition in this region, indicating the preference of C. ornatus for less populated areas. In this region, we obtained data with lower salinity and a high concentration of organic matter. It was found that females have a different occupation according to the sizes of individuals. Already the male specimens were more abundant at shallower depths, possibly in search of primiparous females, for mating. In comparative diurnal population of C. ornatus, greater activity was observed in the daytime, differently from the congener C. danae Smith, 1869 who can share niche. Such fact can be a strategy to avoid competition with other species and allow the successful coexistence of both. In addition, some species of shrimp caught by trawling, have a nocturnal habit, among them the seabob shrimp and white shrimp, which makes the most effective fishing in that period. The males in the intermuda phase (MSC) are distributed at the same depths as the females with exoskeleton calcification phase (MSB), being predominant between 2 and 5m deep. These shallower regions have fewer species, causing C. ornatus specimens are not so susceptible to predators, acting as a possible population protection strategy. Comparing the 10-year collections, despite the subtle and insignificant reduction in the total number, there was a change in the peak of reproduction of C. ornatus, which may be demonstrating a strategy to mantains the local population. In 2000 the embryonic females were more abundant in summer, and recorded a second peak during autumn. This fact may be indicative of reproductive plasticity, as an attempt to maintain an efficient reproduction and to conserve the abundance of the species. Based on this study, it was possible to infer strategies of a population of C. ornatus to maintain itself despite the anthropic impacts on the coast of São Paulo.
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Palavras-chave
Ecologia, Ubatuba, Community structure, Reproductive plasticity, Nictemeral