Abundance and spatio-temporal distribution of two Southwest Atlantic endemic shrimps: changes after 20 years

Abstract

This study compares the abundance and the spatio-temporal distribution of the shrimps Artemesia longinaris and Pleoticus muelleri, and their relationship with environmental factors (bottom temperature and salinity; sediment texture) at Fortaleza Bay, in Ubatuba, São Paulo State. We performed the samplings from November 1988 until October 1989, and repeated it 20 years later, from November 2008 until October 2009. In both periods, individuals and environmental factors were obtained monthly in seven sampling stations. The relationship between environmental factors and abundance was accessed with a Redundancy Analysis (RDA). In the first period, 3088 specimens of A. longinaris and 151 of P. muelleri were collected, whereas in the second period only 1252 A. longinaris and 72 P. muelleri were found. In both periods, both species were more abundant in stations near the bay’s mouth and in the coldest months. The RDA indicated a positive correlation between species abundance and salinity, and a negative correlation with sediment silt and clay content. The increase in this grain size in the second period may have contributed to the decrease of both species’ abundance. The decrease in salinity during the second period’s winter may also have limited their abundance. This study shows that sedimentation in Fortaleza Bay in these 20 years had positive and negative impacts depending on each species’ habitat. Changes in sediment and salinity could be driving the abundance of these species.