Ecology of the pink-shrimp Penaeus paulensis in Patos Lagoon estuary

Study Extent

Pink-shrimp abundance, size structure and water parameters are registered in the Patos Lagoon Estuary and the oceanic adjacent beach, Cassino Beach, located in the coastal plain of southern Brazil. A total of eight sites are sampled each month, with five replicates each.

Sampling

A total of eight sites are sampled each month, with five replicates each. The gear used to obtain biological samples is a picaré net, an active net designed to operate in shallow regions. The net is 9 m long, with mesh size (opposing knots) of 5 mm in the central pane and 13 mm in the wings. The water temperature (mercury thermometer), salinity (refractometer) and transparency (Secchi disk) data are collected at each station. The organisms are preserved with formaldehyde (4% solution).

Quality Control

Researchers and the classical methods are the same employed since the beginning of the time series. Thus, methodology influence is minimal. Sampling is always performed under supervision of experienced researchers.

Method steps

1. The biological samples were performed with a beach seine (9 m in length, 13 mm opposing knots and 5 mm in the center) in the shallow areas (average depths lower than 1.5 m). Samples were monthly performed in eight sites with five replicates. The temperature (mercury thermometer), salinity (refractometer) and transparency data (Secchi disk) are obtained in conjunction with the biological samples for each sampling site.

The sampled decapod crustaceans are composed by juveniles of pink-shrimp Penaeus paulensis (Pérez-Farfante, 1967).

1. Penaeus paulensis
   common name: pink-shrimp rank: species
2. Animalia
   rank: kingdom
3. Arthropoda
   rank: phylum
4. Malacostraca
   rank: class
5. Decapoda
   rank: order
6. Penaeidae
   rank: family
7. Penaeus
   rank: genus

The Patos Lagoon at the southern Brazilian coastal plain (Rio Grande do Sul state) is the largest (10,360 km2) choked lagoon in the world. With a NE SW direction the lagoon extends from the city of Porto Alegre (30º30’ S) to Rio Grande (32º12’ S). In the southern estuarine region, approx. 10% of total area, a single and narrow inlet connects this lagoon to the Atlantic Ocean. The major tributary rivers at the northern and central areas of Patos Lagoon, and the São Gonçalo channel at the southern area, are significant freshwater sources from an extensive drainage basin. The hydrodynamics of Patos Lagoon estuary is strongly controlled by the discharge of tributary rivers and the action of predominant meteorological factors like winds, rainfall and evaporation.