Abundance and Assemblage Structure of Fish Larvae in the Lower Missouri River and Its Tributaries

Abstract

Most of the backwater habitat in the floodplain of the lower Missouri River has been eliminated, but the lower reaches of tributaries have flow and depth characteristics similar to backwaters. We sampled the assemblages of fish larvae and age‐0 juveniles in the lower 8 km of four tributaries and in the Missouri River main channel to determine the extent to which riverine species use these backwaters for early life history stages. We also sought to determine which tributary characteristics were associated with use by riverine species. Densities of 8 of the 10 fish taxa analyzed were greater in tributaries than in the Missouri River in 1987 and 1988. The composition of the larval fish fauna varied: carpsuckers Carpiodes spp., goldeye Hiodon alosoides, freshwater drum Aplodinotus grunniens, and common carp Cyprinus carpio occurred in large rivers; whereas mostly gizzard shad Dorsosoma cepedianum, nearctic cyprinids (mostly emerald shiner Notropis atherinoides and red shiner Cyprinella lutrensis), and sunfishes Lepomis spp. occurred in small tributaries. Assemblages in large tributaries included large‐river and small‐tributary taxa. The gradient in assemblage composition, from small‐tributary fauna to large‐river fauna, corresponded to a gradient in channel morphometry, from shallow waters and coarse substrate to greater channel depths and fine sediments. The complex pattern of flow between the Missouri River and its tributaries and the diversity of tributary morphometry were associated with, and may be critical to, productivity and the maintenance of a diverse fish fauna.

Otolith trace element and stable isotopic compositions differentiate fishes from the Middle Mississippi River, its tributaries, and floodplain lakes

“…Larval fishes are common in many floodplain lakes, with rheophilic taxa comprising an increasing proportion of fish assemblages in lakes as river-floodplain connectivity increases (Scheimer, 2000); larval fishes are also known to frequently drift into and out of connected floodplain lakes (Grift et al, 2003;Csoboth & Garvey, 2008). Tributary streams may also contribute to fish assemblages in large rivers, at least near their confluences (Brown & Coon, 1994;Robinson et al, 1998;Kiffney et al, 2006). Larval fishes are sometimes abundant in the main channel of large rivers, suggesting that main channels may be more hospitable as larval nursery areas than previously thought; species composition of larval fishes in the main channel is often distinct from that of off-channel habitats (Holland, 1986;Dettmers et al, 2001).…”

Exploring riverine zooplankton in three habitats of the Illinois River ecosystem: Where do they come from?

“…Such exchanges likely enhance biological activity and increase food-web complexity in large river ecosystems (Junk et al 1989;Brown and Coon 1994;Dewey and Jennings 1992). Increased zooplankton biomass and species diversity in main channels occurs as floodwaters recede, further suggesting washout from off-channel sources (Saunders and Lewis 1988a;Pace et al 1992).…”

Composition and Abundance of Drifting Fish Larvae in the Canadian River, Texas

“…For all months other than June, density was less than 2 fish100 m" for all species in both years of the study. Drift densities of larval fish reported from other streams have been substantially greater (e.g., Scott andNielsen 1989, Harvey 199 1, Brown andCoon 1994). Low densities of larval fish observed in our study may indicate that this portion of the Canadian River is relatively unproductive compared to other systems that have been studied.…”