who compared fishes collected by trawling the Napo River main channel in Ecuador, with fishes collected by seining its margins. Main channel trawl efforts produced 41 of the 132 total species recorded. Twenty of the 41 trawled species were restricted to the main channel, while beach samples were more similar to other beach samples up to 325 km away than they were to immediately adjacent main channel samples. The boundary between shallow and deep water faunas observed by Stewart et al. (2002) occurred at approximately two meters depth, approximately the same depth at which fish vision in turbid rivers of the Amazon is no longer possible (Muntz, 1982), and just beyond the depth at which seining or wade sampling becomes inef