Dinâmica populacional de Macrobrachium olfersii (Caridea: Palaemonidae) ao longo do Rio Ribeira de Iguape, litoral sul do estado de São Paulo
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Data
2018-07-18
Autores
Ribeiro, Crislene Cristo
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo deste estudo foi verificar a dinâmica populacional do camarão M. olfersii ao longo do Rio Ribeira de Iguape, enfocando a distribuição espaço temporal, período reprodutivo, recrutamento, razão sexual, maturidade sexual, crescimento e longevidade. Os camarões foram coletados mensalmente de janeiro a dezembro de 2007, em quatro regiões ao longo do Rio Ribeira de Iguape (Eldorado, Sete Barros, Registro e Iguape) por meio de armadilhas e peneira. Todos animais coletados foram identificados e quantificados, e após a subamostragem, mensurados na região do comprimento da carapaça (CC) e sexados. Obteve-se 23.818 indivíduos, sendo 9.691 analisados (6.655 jovens, 1.746 machos, 892 fêmeas e 398 fêmeas ovígeras) com tamanho variando de 2,2 a 25,4 mm CC. A região de Iguape foi representada por 4.913 inds, seguida de Registro (1.714), Sete Barras (1.666) e Eldorado (1.398). As comparações entre as técnicas de coleta evidenciaram que mais de 95% da abundância total foi obtida pela peneira junto a vegetação marginal, sendo a maior parte dessa abundância constituída pelos jovens, resultando na menor média de tamanho dos indivíduos obtidos nesta técnica de coleta. A população foi estatisticamente menor em Iguape tendo alta frequência de jovens, indicando que os indivíduos estão realizando o comportamento de migração a montante do rio, após completar o desenvolvimento larval no estuário. O período reprodutivo foi descontínuo em Eldorado, Sete Barras e Registro e contínuo em Iguape, todos com pico no verão. Tal fato pode ser devido à proximidade de Iguape com a região estuarina, onde as larvas são capazes de alcançar o estuário mesmo quando a vazão do rio é menor (inverno). A razão sexual total da população foi a favor dos machos (1M:0,73F), assim como para as regiões de Eldorado, Registro e Iguape, possivelmente por esses indivíduos apresentarem maior longevidade em relação as fêmeas. Além disso, os desvios da proporção de 1:1 foram registrados principalmente no período reprodutivo, quando os machos estão mais móveis, sendo capturados mais facilmente. A maturidade individual das fêmeas foi de 7,0 mm CC, enquanto a maturidade populacional foi de 10,9 mm CC. O crescimento diferiu estatisticamente entre machos (CC=31,85[1-exp-1,75(t-0,0032)]) e fêmeas (CC=23,67[1-exp-1,75(t-0,0965)]), indicando que esta espécie apresenta dimorfismo sexual, sendo os machos maiores que as fêmeas. Em relações as regiões, em geral, tanto machos quanto fêmeas apresentaram menor tamanho e longevidade, e maior taxa de crescimento em Iguape, provavelmente devido a maior ocorrência de jovens nesta região. Os resultados desta pesquisa foram importantes para compreender a dinâmica populacional do camarão M. olfersii no Rio Ribeira de Iguape, bem como, poderá funcionar como ferramenta para a gestão dos recursos pesqueiros, visando à sustentabilidade da pesca e valorização das comunidades do Rio Ribeira.
The aim of this study was to verify the population dynamics of prawn M. olfersii along the Ribeira de Iguape river, focusing on the distribution, reproductive period, recruitment, sex ratio, sexual maturity, growth and longevity. The prawns were collected monthly from January to December 2007, in four regions along the Ribeira de Iguape river (Eldorado, Sete Barros, Registro and Iguape) by traps and sieve. All animals were identified and quantified, and after the subsampling, measured in the region of carapace length (CC) and sexed. A total of 23,818 individuals were obtained, of which 9,691 were analyzed (6,655 juveniles, 1,746 males, 892 females and 398 ovigerous females), ranging from 2.2 to 25.4 mm CC. The Iguape region was represented by 4,913 individuals, followed by Registro (1,714), Sete Barras (1,666) and Eldorado (1,398). The comparisons between the collection methods showed that more than 95% of the total abundance was obtained by the sieve in the marginal vegetation. Most of this abundance was represented by the juveniles, resulting in the smaller average size of the individuals obtained in this collection method. The size of the population was statistically lower in Iguape with a high frequency of juveniles, indicating that the individuals are performing the migratory behavior upstream of the river after the larval period in the estuary. The reproductive period was discontinuous in Eldorado, Sete Barras and Registro and continuous in Iguape, but all with peak in the summer. This fact may be due to the proximity of Iguape to the estuarine region, where larvae are able to reach the estuary even when the river flow is low (winter). The sex ratio of the population was in favor to males (1M: 0.73F), as well as for the regions of Eldorado, Registro and Iguape, possibly because these individuals present greater longevity in relation to females. In addition, deviations of the 1:1 ratio were recorded mainly in the reproductive period, when males are more mobile and can be captured easily. The individual sexual maturity of the females was 7.0 mm CC, while the population maturity was 10.9 mm CC. Growth differed statistically between males (CC=31,85[1-exp-1,75(t-0,0032)]) and females (CC=23,67[1-exp-1,75(t-0,0965)]), indicating that this species shows sexual dimorphism, with males being larger than females. In relation to the regions, in general, both males and females presented smaller size and longevity, and higher growth rate in Iguape, probably due to the higher occurrence of juveniles in this region. The results of the present research were important to understand the population dynamics of the prawn M. olfersii in the Ribeira de Iguape river, as well as, it can function as a tool for the management of the fishing resources, aiming at the sustainability of the fishing and valorization of the communities of the Ribeira River.
The aim of this study was to verify the population dynamics of prawn M. olfersii along the Ribeira de Iguape river, focusing on the distribution, reproductive period, recruitment, sex ratio, sexual maturity, growth and longevity. The prawns were collected monthly from January to December 2007, in four regions along the Ribeira de Iguape river (Eldorado, Sete Barros, Registro and Iguape) by traps and sieve. All animals were identified and quantified, and after the subsampling, measured in the region of carapace length (CC) and sexed. A total of 23,818 individuals were obtained, of which 9,691 were analyzed (6,655 juveniles, 1,746 males, 892 females and 398 ovigerous females), ranging from 2.2 to 25.4 mm CC. The Iguape region was represented by 4,913 individuals, followed by Registro (1,714), Sete Barras (1,666) and Eldorado (1,398). The comparisons between the collection methods showed that more than 95% of the total abundance was obtained by the sieve in the marginal vegetation. Most of this abundance was represented by the juveniles, resulting in the smaller average size of the individuals obtained in this collection method. The size of the population was statistically lower in Iguape with a high frequency of juveniles, indicating that the individuals are performing the migratory behavior upstream of the river after the larval period in the estuary. The reproductive period was discontinuous in Eldorado, Sete Barras and Registro and continuous in Iguape, but all with peak in the summer. This fact may be due to the proximity of Iguape to the estuarine region, where larvae are able to reach the estuary even when the river flow is low (winter). The sex ratio of the population was in favor to males (1M: 0.73F), as well as for the regions of Eldorado, Registro and Iguape, possibly because these individuals present greater longevity in relation to females. In addition, deviations of the 1:1 ratio were recorded mainly in the reproductive period, when males are more mobile and can be captured easily. The individual sexual maturity of the females was 7.0 mm CC, while the population maturity was 10.9 mm CC. Growth differed statistically between males (CC=31,85[1-exp-1,75(t-0,0032)]) and females (CC=23,67[1-exp-1,75(t-0,0965)]), indicating that this species shows sexual dimorphism, with males being larger than females. In relation to the regions, in general, both males and females presented smaller size and longevity, and higher growth rate in Iguape, probably due to the higher occurrence of juveniles in this region. The results of the present research were important to understand the population dynamics of the prawn M. olfersii in the Ribeira de Iguape river, as well as, it can function as a tool for the management of the fishing resources, aiming at the sustainability of the fishing and valorization of the communities of the Ribeira River.
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Palavras-chave
período reprodutivo, maturidade sexual, razão sexual, crescimento, longevidade, reproductive period, sexual maturity, sex ratio, growth, longevity