Food resource utilization of the skates Rioraja agassizii (Müller & Henle, 1841) and Psammobatis extenta (Garman, 1913) on the continental shelf off Ubatuba, South-eastern Brazil

Abstract

The feeding habits of Rioraja agassizii (syn. Raja agassizii) and Psammobatis extenta (syn. Psammobatis glansdissimilis) of the South-eastern Brazilian coast were studied by means of stomach content analysis. The samples were obtained on eight seasonal oceanographic cruises, carried out between October 1985 and July 1987. The importance of each food item was evaluated on the basis of the Index of Relative Importance and the feeding similarity by Percentage of Similarity. The results indicated that both species are benthic feeders, preying mainly on Crustacea, especially Amphipoda, Caridea and Brachyura. Teleostei were also important for R. agassizii. Seasonal variation of the diet seems to be associated with the availability of the prey, whose distribution and abundance are related to the dynamics of the water masses of the region. Juveniles and adults of P. extenta exploited the same resources while juveniles and adults of R. agassizii presented low diet similarity during most of the year. Caridea were an important food for all length classes of R. agassizii, while Amphipoda were for smaller specimens, and Teleostei for larger ones. The feeding overlap between the two species was higher during autumn 1986, winter 1986 and winter 1987.

Analysis of food habits of skate Rioraja agassizii (Elasmobranchii, Rajidae) from southern Brazil

“…In both samples, all specimens were adults, which is confirmed in the literature (Oddone et al, 2007). According to Muto et al (2001), R. agassizii feeds on benthic items, mainly crustaceans such as shrimp and crabs, corroborated by the results obtained in the sample collected between [2005][2006]. Food chronology of this skate was also studied by Soares et al (1999), which concluded that its diets was also based on crustaceans and small teleostei fish.…”

“…Food chronology of this skate was also studied by Soares et al (1999), which concluded that its diets was also based on crustaceans and small teleostei fish. Soares et al (1999) and Muto et al (2001) performed his works on the coast of Ubatuba (Sao Paulo-SP State, Brazil) from scientific cruises, in a different sampling scenario from that conducted by commercial fishing boats.…”

“…cyclophora, A. castelnaui, and A. platana, from catches of the fishing fleet landed in Itajaí (Santa Catarina State, Brazil), are classified as abundant in pair trawling. Muto et al (2001) also consider R. agassizii and Psammobatis extenta (Garman, 1913) important in terms of abundance and biomass on the coast of Ubatuba (SP State, Brazil).…”

Insectivory in Potamotrygon signata (Chondrichthyes: Potamotrygonidae), an endemic freshwater stingray from the Parnaíba River basin, northeastern Brazil

“…Ontogenetic differences in dietary habits and between immature and mature individuals have been reported for freshwater stingrays by Charvet- Almeida (2006) and Silva and Uieda (2007), as well as for marine batoids (Muto et al, 2001;Moura et al, 2008).…”

Diet composition and feeding habits of the eyespot skate, Atlantoraja cyclophora (Elasmobranchii: Arhynchobatidae), off Uruguay and northern Argentina

“…Thus, seasonal changes in the diet are often related with differences in prey abundance between seasons (Muto et al, 2001). In the study area, shrimps are more abundant in the warm season than in the cold season (Iorio et al, 1996;Scelzo et al, 2002), indicating that A. cyclophora may be adapting its feeding habits to seasonal changes in prey abundance.…”