Macrozoobentos em viveiros de engorda de camarão marinho Litopenaeus vannamei (boone, 1931) (crustacea, decapoda, penaidae) no estuário dorio Jaguaribe, Ceará, Brasil

Abstract

The aim of this study was to characterize the benthic macrofauna of the cultivation farm of shrimps from the species Litopenaeus vannamei before the settlement and fishing, as well as to observe the effect of the shrimp predation on the macrofauna through an exclusion experiment. In order to characterize the macrofauna, samples from the supplying, middle and draining areas had been collected from the shrimp farms with five different duplicates for each area in the two moments of the cultivation. To evaluate the predation effect, gathering from the inside and outside of twenty-seven cages in a shrimp farm during the cultivation cycle had been carried through. The gathering of the organisms from the bottom of the shrimp farms as well as from the interior of the cages had been carried through with a PVC 15cm of diameter. The cages had an area of 25cm ² and 12cm of height and mesh of 3mm of opening, being covered with a screen of 0,1mm during the first days of experiment in order to block the insertion of any predator. The polychaeta presented the highest medium density, being the species Capitella sp. the most abundant. The organisms had had greater densities in the gathering that occured before the settlement, moment when it did not have shrimps in the interior of the farms. The area with the highest medium density in the shrimp farms was the supplying. In the exclusion experiment, it was observed that the medium densities in the interior of the cages had been higher than in the areas outside the cages that were subjected to the predation of shrimp. This fact proves the importance of the Benthic macrofauna in the diet of these crustaceans, since the shrimp uses it as a natural food source. It was also possible to realize that the Benthic macrofauna suffered some alterations in its community in the presence and absence of the shrimps, because some species had started to dominate the environment whereas others were extinguished. Beyond the predatory pressure of the shrimps, this fact can have been also caused for the existence of biological interactions between the species of the macrofauna that can have occurred inside and outside of the cages, prevailing the Capitella sp., that seems to have been the most successful under the conditions of the experiment.