Comparison of Three Larval Fish Gears to Sample Shallow Water Sites on a Navigable River

Fish sampling within rivers can be challenging, particularly for early life stages. We sought to evaluate the ability of three larval sampling devices (light traps, benthic sleds, and activity traps) to sample a shallow, structurally diverse area in a navigable river. Larval fish were sampled for 8 weeks from June 17 through August 3, 2002. The results indicated that larval abundances peaked during late June. The light trap collected more larvae (9,221 individuals) than the benthic sled (396 individuals) and activity trap (65 individuals). The light trap also collected more taxonomic groups than the benthic sled and activity trap (I I groups versus 7 and 5 groups, respectively). Light-trap catch per unit effort was significantly higher than that for both benthic sleds and activity traps for the most common taxonomic groups (Cyprinidae [Notropis and Piniephales spp.], Athermidae, and Lepomis spp.). The coefficient of variation was lower for the light trap (214%) than for the benthic sled (966%) and activity trap (279%). While light traps may be limited in determining associated larval fish densities, they can be an effective means of determining species presence or absence and their relative abundance. Of the gears evaluated, we found that light traps were the most effective in sampling larval fish in shallow, structurally diverse areas of a large navigable river.