Functional trophic composition of the ichthyofauna of forest streams in eastern Brazilian Amazon

Abstract

This study aimed to describe the functional organization of the ichthyofauna of forest streams from northeastern Pará State, Brazil, based on behavioral observation of species' feeding tactics. Seven streams were sampled between June and November, 2010, during snorkeling sessions, totaling 91h 51min of visual censuses at day, dusk, and night periods. Seventy three species distributed in six orders, 26 families and 63 genera were observed, with dominance of Characiformes, followed by Siluriformes. From information gathered by ad libitum observations, each species was included in one of 18 functional trophic groups (FTGs), according to two main characteristics: (1) its most frequently observed feeding tactic; and (2) its spatial distribution in the stream environment, considering their horizontal (margins or main channel) and vertical (water column) dimensions. The most frequent FTGs observed were Nocturnal invertebrate pickers (9 species), Diurnal channel drift feeders (8 spp.), Diurnal surface pickers (7 spp.), and Ambush and stalking predators (6 spp.). The FTGs herein defined enable a comparative analysis of the structure and composition of ichthyofauna in different basins and environmental conditions, which presents an alternative approach to the use of taxonomic structure in ecological studies. The ichthyofauna classification based in FTGs proposed in this study is compared to three other classifications, proposed by Sazima (1986), Sabino & Zuanon (1998) and Casatti et al. (2001).

Land cover, riparian zones and instream habitat influence stream fish assemblages in the eastern Amazon

“…Many energy sources supporting tropical stream food webs (e.g., terrestrial arthropods, leaves, seeds, fruits) originate from riparian vegetation (Brejão, Gerhard, & Zuanon, 2013). Land cover varied along a gradient ranging from 100% primary vegetation to deforested agricultural areas.…”

“…Gymnotiformes are nocturnal fishes that often take refuge in undercut banks during daytime (Brejão et al, 2013;Maxime & Albert, 2009). etheostoma, Erythrinus erythrinus, Gymnotus gr.…”

Habitat use by Astyanax taeniatus (Jenyns, 1842) (Characiformes: Characidae) in a coastal stream from Southeast Brazil

“…Avoiding shallow waters has been reported as a strategy related to reduce predation risk and to avoid refuge-poor areas (Liefferinge et al, 2005). In fact, the shallow areas of these coastal streams tend to be avoided by small fish species due the presence of ambush predators, such as H. malabaricus (Mazzoni & Iglesias-Rios, 2002;Brejão et al, 2013), and aquatic birds that are very abundant in the study area.…”

Diet of the electric knife-fishes, Gymnotus omarorum, is described in Laguna Blanca Río Pilcomayo National Park, Formosa province, Argentine

“…Al igual que Gymnotus cf. coropinae, este gimnótido, captura sus presas por emboscada y/o acecho (Brejão et al, 2013). Insectos, invertebrados acuáticos y peces se encuentran comúnmente asociados a las raíces y hojas de plantas acuáticas, y potencialmente sirven de alimento a buena parte de los peces asociados a las macrófitas (Neiff & Carignan, 1997), esta observación se encuentra respaldada con lo observado en este trabajo, el total del alimento consumido en este período de tiempo es de origen autóctono.…”