Population structure, fecundity and ecological aspects of freshwater shrimp species (Decapoda, Palaemonidae) of an urban forest fragment in central Amazonia, Brazil

Abstract

Information about population structure, ecological aspects and reproductive biology of Amazonian freshwater shrimps is scarce in the scientific literature and concentrated in studies conducted in rivers. In this study we present data about species composition, population structure, abundance, fecundity and effects of abiotic factors on the distribution of freshwater shrimps in small streams at an urban forest fragment in Manaus, Central Amazonia. We collected the shrimps using minnow-traps in 12 first- and second-order streams in dry and rainy seasons. We found four species: Macrobrachium ferreirai Kensley & Walker, 1982, Macrobrachium inpa Kensley & Walker, 1982, Macrobrachium nattereri (Heller, 1862) and Pseudopalaemon amazonensis Ramos-Porto, 1979. First order streams had a higher number of species. Adults and juveniles of all species and ovigerous females were found in the majority of the sampling events. Males were more abundant and larger than females in all species of Macrobrachium. All species had a few, large eggs. The abundance of M. nattereri was affected by stream size and temperature. The population structure of the studied species was different from those in other studies on shrimp populations in Central Amazonia and other regions of Brazil, indicating effects of sampling methods and the structure and size of water bodies on the population structure in different regions. The presence of ovigerous females in all sampling periods indicates continuous reproduction.