Diet of the freshwater stingray Potamotrygon motoro (Chondrichthyes: Potamotrygonidae) on Marajó Island (Pará, Brazil)

Abstract

The stomach contents of 137 examples of Potamotrygon motoro caught in 3 locations (Muaná, Afuá and Lake Arari) on Marajó Island were analysed. The values of the Index of Relative Importance (IRI) and its respective percentage (%IRI) were calculated. The level of repletion 1 (¼ full) was the most representative for both sexes, as well as for immature and mature specimens. Most of the food items found were well-digested. The food items identification indicated the presence of 15 orders, including insects, mollusks, crustaceans, annelids and fish. Differences in diet were observed among the locations studied when comparing %IRI, crustaceans being the most preferred in Afuá, fish in Lake Arari and mollusks in Muaná.Keywords: fish feeding, Estuarine habitats, Chondrichthyes. Dieta da raia de água doce Potamotrygon motoro (Chondrichthyes: Potamotrygonidae) na Ilha de Marajó (Pará, Brasil) Resumo O conteúdo estomacal de 137 exemplares de Potamotrygon motoro provenientes de 3 localidades (Muaná, Afuá e Lago Arari) na ilha de Marajó foi analisado. Os valores do Índice Relativo de Importância (IRI) e respectiva porcentagem (%IRI) foram calculados. O nível de repleção 1 (¼ cheio) foi o mais representativo para ambos os sexos, assim como para exemplares imaturos e maduros. A maioria dos itens alimentares analisados encontrava-se bastante digerido. A identificação dos itens alimentares indicou a presença de 15 ordens, incluindo insetos, moluscos, crustáceos, anelídeos e peixes. Diferenças na dieta entre os locais amostrados foram observadas ao se comparar as %IRI, sendo crustáceos o item preferencial em Afuá, peixes no Lago Arari e moluscos em Muaná.Palavras-chave: alimentação de peixes, ambientes estuarinos, Chondrichthyes.

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

“…Wetherbee et al, (1990) mentioned that high percentages of empty stomachs or low levels of repletion are common in marine elasmobranchs. The results of other studies confirm that this also seems to be a common feature for freshwater stingrays (CharvetAlmeida, 2006;Rincon, 2006;Almeida et al 2010). …”

“…However, Almeida et al (2010) did not observe sexual differences in the diet of P. motoro on the Marajo Island in Brazil. Similar findings, reporting either the presence or absence of sexual differences among congeneric species of marine batoids, were cited by PoloSilva and Grijalba-Bendeck (2008) and Payán et al (2011) for Rhinobatos and Belleggia et al (2008) for Bathyraja.…”

“…Specimens were collected using seine nets, gillnets, spears and casting nets in accordance with Charvet-Almeida (2006) and Almeida et al (2010). The gillnet was the most widely used technique, and the nets were checked every 3 hours throughout the day (12 hours).…”

“…Empty stomachs were not considered in the calculation of how often food items were found, as was plant matter which was more likely to have been ingested, as in other potamotrygonids (Charvet- Almeida, 2006;Garrone-Neto, 2009;Almeida et al, 2010).…”

Catfishes as prey items of Potamotrygonid stingrays in the Solimões and Negro rivers, Brazilian Amazon

“…"cururu", P. motoro, and Paratrygon aiereba) were found to have different groups of catfishes (Callichthyidae, Cetopsidae, Doradidae and Loricariidae) in their stomachs. Almeida et al (2010) and Vasconcelos & Oliveira (2011) also found catfishes in the stomach of P. motoro, in the Marajó Island (which has connections with Amazonas and Tocantins Rivers) and in the Cariaú River (Amapá State), respectively.…”