Drift of characin larvae,Bryconamericus deuterodonoides,during the dry season from Andean piedmont streams

Synopsis The downstream transport of fish larvae is well known from temperate running waters, but there exists remarkably little information for tropical streams. We sampled drift in two Andean piedmont streams during the dry seasons of 1986–1988. Bryconamericus deuterodonoides (Characidae) larvae were found to be extremely abundant in some drift collections, with peak drift densities exceeding those of temperate streams by as much as an order of magnitude. Drift of fish larvae displayed pronounced diel periodicity, with more than one-quarter of a million larvae collected during the night compared to two individuals during the day. Fish larvae were more abundant during the latter compared to early part of the dry season, even in years when streams were reduced to small isolated pools by the end of the season. These observations indicate that the dry season represents an important period of reproduction for the characid, Bryconamericus deuterodonoides, and possibly other neotropical fish species.