| Remarks |
Occurs in the main channels of major rivers or side branches; not known to occur in seasonally inundated floodplain forests or in forest steams of the Amazon's terra firme; known from both high-conductivity (50-250 µS/cm), sediment-laden whitewater rivers such as the Amazon river and low conductivity (5-25 µS/cm), sediment poor blackwater rivers such as the Rio Negro. Dissolved oxygen levels in these rivers are always relatively high (3-6 mg/L) and temperature typically similar from the surface to the bottom (29-32°C). In the Tefé region, this species is caught with beach seines and trawl nets at depth up to 10 meters in areas with weak currents, such as in large eddies, sheltered bays or "paranás" (side-branches of the main river channels that wind their way through the whitewater "várzea" floodplain); occurs syntopically with Sternopygus macrurus in whitewater habitats, but never with Sternopygus atrabes. This species does not occur where currents near the substrate exceeded 0.1 m/sec. At daytime it is usually encountered near submerged structures such as fallen trees and driftwood, and at night it moves into shallower water and away from structures. Specimens are collected on both sand and mud bottoms. It does not live in groups as indicated by electrode surveys and its sporadic occurrence in nets. Sexually mature males were never encountered, but gravid females were found along the edge of whitewater floodplain areas and in paraná channels during the rising water months of January and February. Feeds mainly on autochthonous insect larvae which it encounters on the substrate; the presence of small pieces of wood in many of the stomachs indicate that it forages among organic detritus on the river bed rather than within rafts of floating meadows or marginal macrophytes (Ref. 55493). |