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

Abstract

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 (11 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 Pimephales spp.], Atherinidae, 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.

Comparison of four types of sampling gears for estimating age-0 yellow perch density

“…The benthic sled and push trawl are both designed to actively ride along the substrate and capture benthic and demersal fishes (Herke 1969;Rogers 1985;Niles and Hartman 2007). Both gears provided low but more precise estimates of mean age-0 yellow perch density and similar length-frequency distributions.…”

Use of main channel and two backwater habitats by larval fishes in the Detroit River

“…Light traps were illuminated with a 12-hour chemical light stick. Light traps are efficient at sampling larvae in structurally complex areas (Niles and Hartman, 2007) and are preferable over plankton nets when vegetation is dense (Holland, 1986). The embayment at FI was usually b 1 m deep, which further restricted the use of large plankton nets.…”

Temporal distribution and taxonomic composition differences of larval fish in a large navigable river: A comparison of artificial dike structures and natural habitat

“…Dike structures were somewhat different (number of dikes, angle from riverbank, distance between individual dikes and length of dikes); however, each increased habitat heterogeneity. Artificial dike structures were not only dominated by the rocks used for construction, but also had some low hanging vegetation and woody debris (Niles and Hartman, 2007). Each of the artificial dike structure sites consisted of a series of dike structures.…”

“…The reference sites were determined to be of high or low quality based upon velocity characteristics (Niles and Hartman, 2007) and the amount of potential cover available to larval fish. High quality natural reference areas had a large bench width (similar to the artificial structure sites) and typically had snags, woody debris, low hanging vegetation and lower water velocity in comparison to low quality reference sites.…”