Trends and seasonality of the occurrence of hatched egg capsules of Rioraja agassizi (Müller & Henle 1841) (Chondrichthyes: Rajiformes) in a South Brazilian beach, Southwestern Atlantic Ocean.

The Rio skate Rioraja agassizi is endemic to coastal waters of the Western South Atlantic. The species is common in the coasts of Argentina, Uruguay and Brazil. Previous studies performed in South Brazil, demonstrated that its hatched egg capsules are the most abundant among the co-occurring species. The aim of this study was to assess seasonality in the monthly frequency of egg capsules of R. agassizi at Praia do Cassino (33°07′34″S 52°38′22″W/ 33.126080°S 52.639327°W), southernmost coast of Brazil, over a two-year sampling. The egg capsules were manually collected from the edge of the beach in a belt transect of 1 km long and ca. 0.1 km width, on a weekly basis. After the collections, the capsules were taken to the laboratory for identification at the species level and morphometric measurements. To study the seasonality in the oviposition in R agassizi, data were analyzed monthly, seasonally and annually; accordingly, the data were expressed as non-parametric and heterogeneous, thus, statistical tests were applied to verify trends, significant differences, and descriptive parameters within each scale. In the annual and interannual data, there were statistically significant differences and trends between the sampling periods. Thus, these series of data collected are in fact random and the values demonstrated a randomness in the study site. As for the seasonal data, at least one of the seasons has a significantly different distribution. [ABSTRACT FROM AUTHOR]