Patrick J. Braaten

Potential Influence of Harvest on Shovelnose Sturgeon Populations in the Missouri River System

Abstract The collapse of the European and Asian caviar industry has raised concern about the overexploitation of shovelnose sturgeon Scaphirhynchus platorynchus in the Missouri River. Unfortunately, little is known about the potential effects of harvest on the population dynamics of this species. Therefore, this study was conducted to describe the population characteristics (e.g., growth, longevity, and mortality) and to determine the influence of exploitation and harvest regulations (minimum length limits) on the yield, size structure, and egg production of shovelnose sturgeon from three sites in the Missouri River using a Beverton–Holt equilibrium model. Despite differences in the population characteristics (e.g., growth and longevity) of shovelnose sturgeon among sites, all populations responded similarly to harvest at the conditional natural mortality rates (death rate in the absence of harvest) used in our simulations (i.e., 5% and 20%). Our simulations of yield indicated that growth overfishing (i.e...

Spatiotemporal Variation in Density of Larval Bighead Carp in the Lower Missouri River

Abstract Bighead carp Hypophthalmichthys nobilis, an exotic planktivore, was introduced into Arkansas in 1973 and subsequently dispersed upstream through the Mississippi River and its tributaries. Early life history characteristics of bighead carp in North American rivers have not been documented. The objectives of this study were to examine the temporal and spatial variation in the density of larvae and to estimate the spawning date of bighead carp in the lower Missouri River. We sampled larval fish once per week at four sites between White Cloud, Kansas, and Lexington, Missouri, from May through July 1997 and 1998. Density of larval bighead carp varied spatially and temporally. Larval bighead carp were collected at all four sites (Lexington, Kansas City, and St. Joseph, Missouri, and White Cloud, Kansas) only on June 25, 1997; on July 2 and 9, 1998, they were collected only at Kansas City and Lexington, Missouri. Density was greatest (24.4 larvae/m3) at the most downstream site (Lexington, Missouri) and...

Standard Weight (Ws ) Equation and Length Categories for Shovelnose Sturgeon

Abstract Weight–length data were compiled from 32 populations of shovelnose sturgeon Scaphirhynchus platorynchus (N = 11,820) from nine states within the geographic distribution of the species. We used the regression-line-percentile technique, which provides a 75th-percentile standard, to develop the standard weight (Ws ) equation. The proposed equation in metric units is log10 Ws = −6.287 + 3.330 log10FL; Ws is weight in grams and FL is fork length in millimeters. The equivalent equation in English units is log10 Ws = −4.266 + 3.330 log10FL; Ws is weight in pounds and FL is fork length in inches. These equations are proposed for use with shovelnose sturgeon between 120 mm (5 in) and 1,050 mm (41 in). Values for relative weight (Wr ) calculated with the Ws equation did not consistently increase or decrease with increasing fish length, indicating absence of length bias. We propose the following length categories for calculation of proportional stock density (PSD) and relative stock densities (RSDs): stock,...

Development and evaluation of bioenergetic-based habitat suitability criteria for trout

We constructed energetic models of habitat use for 82–322 g rainbow trout (Oncorhynchus mykiss) in a large regulated river, and 8–28 g Colorado River cutthroat trout (O. clarki pleuriticus) in a small headwater stream, to determine if observed summer habitat use by these species could be attributed to net energy acquisition, and to develop habitat suitability criteria based on net energy gain. Metabolic models of energy expenditure were derived from literature sources, but measurements of energy availability were site-specific. From the energy models, we assigned a suitability value of 1.0 to the entire range of velocities where positive net energy gains were predicted, and a suitability value of zero to velocities where negative net energy gains were predicted. Predicted net energy gain velocities were compared with observed velocities used by each species. For rainbow trout, the energetic model predicted energetically profitable velocities ranging from 5 to 45 cm s−1. Predicted velocities were similar to velocities used by rainbow trout. This indicated that rainbow trout, as a group, were using energetically profitable stream locations, but some rainbow trout used non-profitable velocities. For Colorado River cutthroat trout, the energetic model predicted energetically profitable velocities ranging from 5 to 45 cm s−1; however, Colorado River cutthroat trout used significantly lower velocities than predicted. The dissimilarity between velocities predicted and used by Colorado River cutthroat trout may be attributed to their inability to utilize energetically profitable velocities available in the stream because of depth restrictions The results suggest that the predictive abilities of energetic models vary between streams because of differences in depth and velocity availability.

Relations between physicochemical factors and abundance of fishes in tributary confluences of the lower channelized Missouri River

Abstract We sampled fish from seven tributary confluences in the lower channelized Missouri River from June 1996 through July 1998 to examine the influence of physicochemical factors in the Missouri River and tributary confluences on the abundance of fishes in tributary confluences. Twenty-six species and one hybrid were collected during the course of the study, but 10 species (river carpsucker Carpiodes carpio, goldeye Hiodon alosoides, sauger Stizostedion canadense, common carp Cyprinus carpio, shortnose gar Lepisosteus platostomus, freshwater drum Aplodinotus grunniens, channel catfish Ictalurus punctatus, gizzard shad Dorosoma cepedianum, white crappie Pomoxis annularis, and smallmouth buffalo Ictiobus bubalus) composed 90% of the fish collected. Catch per effort (log10[(number of fish/100 m2) + 1]) of fishes was significantly greater in early spring (March 1997) and summer (June 1996) than in winter (December 1996 and January 1997) samples. Multivariate ordination partitioned physicochemical factors ...

An experimental test and models of drift and dispersal processes of pallid sturgeon ( Scaphirhynchus albus ) free embryos in the Missouri River

Free embryos of wild pallid sturgeon Scaphirhynchus albus were released in the Missouri River and captured at downstream sites through a 180-km reach of the river to examine ontogenetic drift and dispersal processes. Free embryos drifted primarily in the fastest portion of the river channel, and initial drift velocities for all age groups (meanu2009=u20090.66–0.70xa0mu2009s−1) were only slightly slower than mean water column velocity (0.72xa0mu2009s−1). During the multi-day long-distance drift period, drift velocities of all age groups declined an average of 9.7% day−1. Younger free embryos remained in the drift upon termination of the study; whereas, older age groups transitioned from drifting to settling during the study. Models based on growth of free embryos, drift behavior, size-related variations in drift rates, and channel hydraulic characteristics were developed to estimate cumulative distance drifted during ontogenetic development through a range of simulated water temperatures and velocity conditions. Those models indicated that the average free embryo would be expected to drift several hundred km during ontogenetic development. Empirical data and model results highlight the long-duration, long-distance drift and dispersal processes for pallid sturgeon early life stages. In addition, results provide a likely mechanism for lack of pallid sturgeon recruitment in fragmented river reaches where dams and reservoirs reduce the length of free-flowing river available for pallid sturgeon free embryos during ontogenetic development.

Comparison of Age and Growth Estimates for River Carpsuckers Using Scales and Dorsal Fin Ray Sections

Abstract Several studies have indicated that use of scales to age river carpsuckers Carpiodes carpio is difficult. Thus, an alternative body structure may reduce variability in aging this species and provide more accurate estimates of the growth history and age structure of river carpsucker populations. We compared the precision of age determinations and means of back-calculated lengths at age of river carpsuckers between two readers and between the use of scales and dorsal fin ray sections from 172 individual fish collected in the Missouri River. Age agreement between the two readers was 71% for both scales and fin rays. Similarly, age agreement between scales and fin rays within readers was 68% and 72%. Precision of age determination by both readers declined after age-5 for both structures. Generally, more annuli were detected on fin rays than scales as fish age exceeded 5 years. Means of back-calculated lengths for ages 1–4 were significantly greater (P < 0.05) for fin rays than scales. Excluding ages ...

First-Year Growth, Condition, and Size-Selective Winter Mortality of Freshwater Drum in the Lower Missouri River

Abstract We compared first-year growth and relative condition (Kn ) of the 1997 and 1998 year-classes of freshwater drum Aplodinotus grunniens among three sites in a 235-km reach of the channelized Missouri River and tested for the occurrence of size-selective overwinter mortality during the first winter. Prewinter mean length was 15 mm greater, mean weight was 8 g greater, and mean Kn was 5% greater at the upstream site than at the downstream site. The prewinter mean length of age-0 freshwater drum was significantly greater in 1997 (115 mm) than in 1998 (109 mm), but Kn was significantly greater in 1998 (107) than in 1997 (102). There was no evidence that density-dependent interactions influenced prewinter growth and Kn. Size-selective overwinter mortality of the smallest size-classes of freshwater drum occurred at two of three sites during the 1997–1998 winter, and Kn decreased 9–15%. Size-selective overwinter mortality of the 1998 cohort of freshwater drum did not occur during the 1998–1999 winter, and...

Stranding of Pentagenia vittigera Following Flow Reductions in the Lower Missouri River

ABSTRACT During a nine-day period in December 1995, water levels in the lower Missouri River declined 1.65 m as a direct result of upstream flow regulation for navigation. We observed numerous aquatic invertebrates, predominately Pentagenia vittigera, on a mud flat downstream from a wing dike in the lower Missouri River. The estimated number of P. vittigera stranded on this single mud flat was 6,400 individuals. Based on an analysis of December discharge and water levels from 1980–1994, it appears that the rate of water level declines and subsequent stranding of P. vittigera were rare events; nonetheless, rapid decreases in discharge associated with the transition between the navigation and non-navigation seasons can negatively impact P. vittigera.