Estrutura populacional e biologia reprodutiva do camarão-da-amazônia <i>Macrobrachium amazonicum</i> (Heller,1862) (Decapoda: Palaemonidae) em um estuário da região nordeste do Pará, Brasil

Abstract

This study aimed to investigate the abundance, population structure and reproductive characteristics (size at first maturity and spawning time) of the Amazon river prawn, Macrobrachium amazonicum, captured in northeast Pará, Brazil. This fishing resource is economically important in the area. M. amazonicum was abundant in the region during the study period (August/08 to July/09), especially in the Curral Velho community. During the rainy season however, there was an accentuated decrease in abundance of this resource. Morphometric relationships that presented allometric negative growth showed a larger increment in growth in cephalotorax and carapace length compared to other body structures. The angular coefficient (b), observed in biometric regressions indicated a negative allometry growth in both sexes, showing that individuals grow considerably faster relative to their biomass increment. According to the size at first maturity found in this study, a minimum capture size of 12mm for females and 12.5mm for males, is recommended.

Reproductive biology of Macrobrachium amazonicum (Heller, 1862) (Decapoda: Palaemonidae) in a reservoir situated in Minas Gerais State, southeastern Brazil

“…Studies conducted with the same species also demonstrated the occurrence of ovigerous females during all sampling months, but with peaks in some of them. Freire et al (2012) found a greater abundance of females with eggs in January and February. They reported that the peaks refer to better physiological conditions, i.e., higher accumulation of energy during reproductive periods; while Silva (2011) observed a higher frequency of ovigerous females from September to November and in January, pointing out that this occurred in raining periods.…”

Does the oscillation of the water volume of the reservoir influence in the same way in fish diet?

“…M. amazonicum represents the main freshwater shrimp, presenting a fast development and wide adaptive plasticity to the several environments (Vergamini et al, 2011). In terms of the seasonal changes observed in the diet of the carcinophagous guild, these may be the result of the water level increase in the reservoir providing new shelters for the shrimps, hampering their capture (Freire et al, 2012), besides the carried sediment influencing the water transparency, slowing the phytoplankton growth, making food more restricted to the individuals, factors which may also decrease the shrimp availability. However, the reduction of the water volume promotes the decrease in the colonization area, sediment precipitation occurs, increasing the water transparency and the insolation allowing the proliferation of microalgae, food for the shrimp, and consequently, a greater availability of these individuals may occur.…”

Population structure and relative growth of the Amazon shrimp Macrobrachium amazonicum (Heller, 1862) (Decapoda: Palaemonidae) on two islands in the fluvial-estuarine plain of the Brazilian Amazon

“…This great environmental plasticity of the species has been related to intraspecific differences ranging from morphological characteristics (Porto, 2004) to genetic variations (Peixoto, 2002;Pileggi and Mantelatto, 2010;Vergamini et al, 2011) which might reflect specific conditions of survival, development, reproduction, focused on artificial environments (Coelho et al, 1982;Lobão et al, 1996;Moraes-Riodades and Valenti, 2002;Moraes-Valenti and Valenti, 2007;Marques et al, 2012). Relative growth in natural populations are poorly known (Flexa et al, 2005;Silva et al, 2007;Bentes et al, 2011;Freire et al, 2012) and the available data are not yet sufficient for a satisfactory comprehension of the plasticity of the species in relation to environmental changes in the many Amazon ecosystems (Maciel and Valenti, 2009).…”