Use of main channel and shallow-water habitat by larval fishes in the lower Missouri River

Abstract

I developed a series of research objectives organized in a spatial hierarchy to characterize larval fish nursery habitat within the lower Missouri River. Native carpsucker spp./buffalo spp. (Carpiodes spp./Ictiobus spp.) and chub spp. (Macrhybopsis spp.) catch-per-unit-effort (CPUE) was higher within sandbar aquatic terrestrial transition zone (ATTZ) than main channel. Local-environmental factors accounted for the greatest proportion of variance in larval fish CPUE within sandbar ATTZ, followed by hydrologic and finally geomorphic factors at macro- and meso-habitat scales. At the microhabitat scale, the larval fish assemblage and carpsucker spp./buffalo spp. selected areas [lesser than or equal to] 10 cm deep with current velocities [lesser than or equal to] 5 cm/s. Silver/bighead carp (Hypophthalmichthys molitrix/nobilus) exhibited no selection based on water depth or current velocity. Chub spp. selected depths between 20-50 cm and areas 2-3 m from the waters edge. The larval fish assemblage and several taxa exhibited a significant nocturnal increase in CPUE within the primary channel and sandbar ATTZ at the macrohabitat scale in contrast to previous research indicating turbid rivers lacked a diel cycle in larval fish drift.