Feeding ecology of immature Lithodoras dorsalis (Valenciennes, 1840) (Siluriformes: Doradidae) in a tidal environment, estuary of the rio Amazonas

Abstract

Studies of feeding ecology are important for the evaluation of interactive processes in fish communities. This study evaluated the feeding ecology of Lithodoras dorsalis (Doradidae) from streams within the Amazon estuary delta (Brazil), a macro-tidal area, on different pluviometric periods. A total of 371 young specimens was collected during 12 months of sampling (July 2010 to June 2011). The species diet was composed of 28 food items analyzed by Repletion Index, Alimentary Index and Niche Breadth. Young L. dorsalis was classified as herbivore with a frugivory tendency due to the high importance of fruit and seeds in its diet. Food intake varied among sampled months, with the lowest intake being recorded during the rainy-dry season transition period, and the highest at the beginning of the dry season. The importance of food items and the composition of the diet were different throughout the year, probably due to the daily tides that allow fish to access new environments and the pluviometric periods. These results provide important data on the feeding ecology of Amazonian doradids. The study also emphasized the importance of allochthonous resources, derived from the riparian forest, which reinforces the importance of this habitat for the conservation of Neotropical freshwater fishes.

The role of Lithodoras dorsalis (Siluriformes: Doradidae) as seed disperser in Eastern Amazon

“…In our study, there was a dominance of young specimens (8 to 33cm) because the Amazon River mouth is known as a nursery or growth area for L. dorsalis, a migatory fish that reproduce in upstream areas of Amazonas River (Goulding, 1980). Despite the presence of only young specimens, the results obtained from the study of L. dorsalis' feeding corroborated the cited above: the bigger the individuals, the bigger the possibility of obtaining fruits and seeds (Barbosa et al, 2015).…”

“…Lithodoras dorsalis, as well as other species of the Doradidae family, is essentially frugivorous (Ringuelet et al, 1967;Stevaux et al, 1994;Santos et al, 2004;Santos et al, 2006;Barbosa et al, 2015). In the Amazon mouth, E. oleracea, M. linifera and M. flexuosa were the most consumed fruit species and contributed the highest proportional weight to L. dorsalis diet.…”

“…With an increased body size, catfishes started to consume other fruits such as açaí E. oleracea and aninga M. linifera, and also increased the abundance and diversity of items consumed per individual, e.g. crustaceans (see Barbosa et al, 2015 to access the complete diet of L. dorsalis). This higher fruits and seeds intake is evidence that L. dorsalis can be a disperser species, since one of the factors that influence the efficiency of a disperser is the number of seeds consumed per visit to the plant (Schupp, 1993;Schupp et al, 2010).…”

“…As shown for Barbosa et al (2015), we expect L. dorsalis' diet to consist mainly of fruits; (ii) What is the relationship between the size of individuals and fruit consumption? We expect that with increasing length there is an increase in the amount of consumed fruits, positively affecting the potential seed dispersal activity; (iii) Are the seeds consumed by rock-bacu destroyed during digestion?…”

“…This species is exploited by commercial and local fisheries in the Amazon mouth and occurs in northern South America in the Amazon estuary and neighboring coastal areas of French Guiana (Sabaj, Ferraris, 2003). Lithodoras dorsalis eat fruits and seeds and possible play a role as seed disperser (Goulding, 1980;Kubitzki, Ziburski, 1994;Barbosa et al, 2015). There are few studies focusing on seed dispersal by catfishes when compared to other frugivorous fish groups such as characids (Brycon spp.)…”