Composition and abundance of invertebrate benthic fauna in Farfantepenaeus paulensis culture pens (Patos Lagoon estuary, Southern Brazil)

Abstract Annual Farfantepenaeus paulensis landings in Patos Lagoon are highly variable, and pen culture in shallow estuarine areas has been developed as an alternative for artisanal fishermen. However, there is a concern about the impact of this system in the natural environment. This study was conducted to evaluate macrobenthos occurrence and variation in relation to rearing cycle and production characteristics of pen culture in Patos Lagoon estuary. Macrobenthic invertebrates, organic matter and mud content were sampled inside and outside pens (control). Six major groups (Polychaeta, Tanaidacea, Isopoda, Gastropoda, Amphipoda and Bivalvia) were observed and 11 species were identified. After 21 days of culture, benthos abundance inside pens dropped by around 86%, but no differences between the stocking densities were detected. Benthic species showed different responses to the shrimp culture, and the impact (predation and/or disturbance) on abundance of the macrobenthic invertebrate community was noted. Mud and organic matter content did not differ across sampled areas during culture period. Shrimp attained higher average weight in lowest stocking density. Although the impact of the pen culture is apparently limited to the fenced area and restricted to a short period (3–4 months), the expansion of this method of culture in the shallow waters areas of the Patos Lagoon must be monitored to ensure that greater than expected impacts do not occur.