Preferência de micro-habitat pelo camarão Macrobrachium jelskii (Miers, 1877) em um açude artificial no município de Cruz das Almas, Bahia

Abstract

Macrobrachium jelskii belonging is a palemonid shrimp occurring in almost all South America. This study aimed to analyze the habitat preference of M. jelskii from an urban weir in Cruz das Almas, Bahia. Samples were taken monthly from March 2015 to February 2016. Micro-habitats were selected according to the local vegetation (micro-habitat 1 - Eleocharis sp.; micro-habitat 2 - Cabomba sp.; micro-habitat 3 - Nymphaea sp.). Specimens were collected and immediately stored in plastic flasks properly labeled containing 70% ethanol. In the laboratory, all specimens were identified, sexed and their carapace length (CC) were measured. A total of 6,428 individuals were collected, of which 114 were juveniles, 3,035 were adult males and 3,279 adult females (220 ovigerous). There were no significant differences in the number of individuals by micro-habitat. The overall sex ratio was skewed towards females (X2 = 9.35, p <0.001). There were significant differences in the number of individuals between genders in each microhabitat and females showed preference for microhabitat 1, while males preferred the other two microhabitats. Females showed larger carapace length than males (F = 433.8, p = 0.00). Micro-habitat 1 statistically differed from the other two showing larger individuals. Differences in CC were also observed between males and females in each micro-habitat. Micro-habitat 1 showed more females of larger sizes, while in micro-habitat 2 there were smaller sized males. There were no micro-habitat preference by the ovigerous females, although most of ovigerous females were sampled in the micro-habitat 1. The overall reproductive pattern seasonal-continuous, with a reproductive peak in August 2015. There was no correlation between the reproductive pattern and rainfall regime. Considering each microhabitat separately, a seasonal reproductive pattern was detected and still not correlated with rainfall regime. Our data demonstrated that the microhabitat 1, characterized by the macrophyte Eleocharis sp., is a more suitable microhabitat for the survival of M. jelskii, especially females that carry eggs and need greater amount of nutrients and protection.