Diet composition of larval and young-of-year shovelnose sturgeon in the Upper Missouri River

Abstract

Obtaining food following the transition from endogenous to exogenous feeding and during the first year of life is a critical event that strongly influences growth and survival of youngof-year fishes. For shovelnose sturgeon Scaphirhynchus platorynchus, limited information is available on food habits during the first year of life. The objective of this study was to quantify diet components of shovelnose sturgeon during the transition from endogenous to exogenous feeding and during the youngof-year life stage in the North Dakota and Montana portions of the Missouri River. Young-of-year shovelnose sturgeon were sampled between early August and early September 2003. Shovelnose sturgeon initiated exogenous feeding by 16 mm, and individuals 16-140 mm fed exclusively on two macroinvertebrate orders (Diptera and Ephemeroptera). Youngof-year shovelnose sturgeon exhibited an apparently high feeding success as 99 of 100 individuals contained food in the gut. The number of organisms in the gut increased exponentially with fish length for larval Diptera (r 2 ¼ 0.73, P < 0.0001) and linearly (r 2 ¼ 0.12, P ¼ 0.0006) for larval Ephemeroptera, but the number of Diptera pupae in the gut was not significantly related (P ¼ 0.55) to length of young-ofyear shovelnose sturgeon. The length of ingested prey was linearly related to fish length for Diptera larvae (r 2 ¼ 0.20, P ¼ 0.002), whereas the relationship between lengths of ingested Ephemeroptera larvae and lengths of young-of-year shovelnose sturgeon was best described by a power function (r 2 ¼ 0.50, P < 0.0001). These results provide the first quantification of feeding dynamics for young-of-year shovelnose sturgeon in a natural river environment.

Seasonal Diet Composition of Adult Shovelnose Sturgeon in the Middle Mississippi River

“…In support of this, we found that a variety of larval benthic aquatic insects comprised shovelnose sturgeon diets in the freeflowing stretch of the MMR, although this depended on season. This dominance of aquatic insects in the diet of the shovelnose sturgeon has been previously reported for the Platte River (Shuman, 2003), upper Mississippi River (Hoopes, 1960;Helms, 1974;Carlson et al, (2) 1985), and the Missouri River (Held, 1969;Modde and Schmulbach, 1977;Carlson et al, 1985;Megargle, 1997;Berry, 2002;Braaten et al, 2006;Wanner et al, 2007). Variability among seasons in diet composition likely depended on seasonal environmental conditions and patterns of invertebrate recruitment.…”

“…Diet composition and quantity can dramatically influence condition and thus influence reproduction. Shovelnose sturgeon diets have been quantified in several large rivers: Platte River (Shuman, 2003), upper Mississippi River (Hoopes, 1960;Helms, 1974;Carlson et al, 1985), and Missouri River (Held, 1969;Modde and Schmulbach, 1977;Carlson et al, 1985;Megargle, 1997;Berry, 2002;Braaten et al, 2006;Wanner et al, 2007). Although many shovelnose sturgeon diet studies have been completed, we are unaware of any studies that have been conducted in the MMR, which is free-flowing and geologically unique to the remainder of the Mississippi River drainage.…”

The influence of depth and velocity on age‐0 Scaphirhynchus sturgeon prey consumption: Implications for aquatic habitat restoration

“…Following capture, individuals were measured to fork length (when a well‐defined fork was present) or total length (excluding the caudal filament; Braaten et al, ) to the nearest mm. Each individual was then preserved in 100% ethanol and stored at approximately 0°C.…”

“…Recent studies have also evaluated diet composition of age‐0 Scaphirhynchus sturgeon (Braaten, Fuller, & McClenning, ; Civiello et al, ; Gosch et al, ; Harrison, Slack, & Killgore, ; Sechler et al, ; Sechler, Phelps, Tripp, & Garvey, ), and Gosch, Civiello, Gemeinhardt, Bonneau, and Long () found that age‐0 pallid and shovelnose sturgeon ( Scaphirhynchus platyrhynchus ) consumed similar prey items; however, relationships between prey consumption and habitat, such as depth and velocity, were not investigated. Furthermore, past research has focused on the depths and velocities at, or very near, the point of capture rather than quantifying habitats available to age‐0 Scaphirhynchus sturgeon at a variety of spatial scales.…”

Age‐0 Sturgeon Accessibility to Constructed and Modified Chutes in the Lower Missouri River

“…Water velocity was measured near the bottom with a Marsh-McBirney flowmeter at the middle of the each sample run. Age-0 sturgeon were measured for fork length when a well-defined fork in the caudal fin was present; however, total length (excluding the caudal filament) was also measured for small individuals lacking a well-defined fork (Braaten et al 2007). Individuals 109 mm were considered age 0 (Ridenour et al 2011) and individuals 23 mm were excluded from the depth and velocity analyses described below to minimize the potential for drifting larvae to be included in these analyses (i.e., individuals > 23 mm were considered exogenously feeding larvae).…”