Gerald E. Mestl

An Alternative Hydrograph for the Missouri River Based on the Precontrol Condition

Abstract The Missouri River and its tributaries have been impounded and channelized, and their hydrographs, sediment and organic matter dynamics, and floodplain connectivity have been altered, adversely impacting native fish and wildlife and leaving many species with an uncertain future. Using stage and discharge data collected prior to dam construction, we defined the precontrol hydrograph and compared it with the present hydrograph and with hydrographs proposed by the U.S. Army Corps of Engineers. We offer an alternative to present operations based on the precontrol percentage of total annual discharge for each day of the year, averaged monthly. Our model may be used to restore the seasonality of flow and to minimize discharge peaks until floodplain planning and management can provide a public corridor contiguous to the river to allow reestablishment of high discharge.

Swimways: Protecting Paddlefish through Movement-centered Management

ABSTRACT Attempts to mitigate lack of formal interjurisdictional paddlefish management have been made in the United States through the Mississippi River Interstate Cooperative Resource Association (MICRA). We used 1988–2009 data from the MICRA paddlefish (Polyodon spathula) stock assessment database—a database containing mark-recapture and biometric information on more than 30,000 individually marked wild paddlefish and more than 2 million hatchery origin paddlefish—to estimate survival and movement across large and potentially biologically relevant spatial scales. Paddlefish frequently moved between political jurisdictions with differing conservation strategies and harvest regulations and showed differences in survival parameter estimates throughout their range. We argue that the degree of interjursidictional movements, spatially variant survival rates, and conservation concerns associated with paddlefish necessitate more cohesive interjurisdictional management. Based on criteria used to establish flyway...

Population Genetic Structure of Nebraska Paddlefish Based on Mitochondrial DNA Variation

Abstract Eighty-three paddlefish Polyodon spathula that were collected from 1995 to 1999 from the Missouri River Galvins Point Dam tailwater were analyzed for genetic variation in the mitochondrial DNA d-loop region. Additional samples from Montana, South Dakota, and Louisiana were used for comparative purposes. To facilitate the efficient analysis of numerous paddlefish samples, we applied a method that employs polyacrylamide gel electrophoresis (PAGE) to resolve restriction fragment length polymorphisms (RFLPs) amplified by polymerase chain reaction (PCR). DNA sequencing of 10 paddlefish revealed 22 polymorphic sites. Polymerase chain reaction–RFLP analysis of 93 paddlefish using three restriction enzymes detected six of the polymorphic sites and revealed six distinct haplotypes. All of the observed haplotypes were found in the Missouri River Galvins Point Dam tailwater. No temporal differentiation was observed among the 1995, 1998, and 1999 samples from the Missouri River Galvins Point Dam tailwater. P...

Assessment of pallid sturgeon relative condition in the upper channelized Missouri River

ABSTRACT During the spring 2015 sampling efforts on the Missouri River, several adult pallid sturgeon (Scaphirhynchus albus) were captured in a visually emaciated condition. As pallid sturgeon recovery efforts continue throughout the Missouri River, this may negatively impact the local population and hamper recovery. Therefore, the objectives were to (1) assess the annual variation in pallid sturgeon condition, (2) determine how condition varies amongst gender and reproductive status and if condition affects fecundity, (3) determine the annual proportion of reproductive female pallid sturgeon, and (4) test several hypothesized factors which may contribute to variations in pallid sturgeon condition. Overall, the relative condition of pallid sturgeon has significantly declined over the past 12 years, except for the large adult-sized fish (> 840 mm fork length). Pallid sturgeon condition began to decline in 2013 then rapidly declined in 2014 and even more in 2015. The mean annual pallid sturgeon condition reached record lows in 2015. Females had a higher overall Kn compared to males and sexually reproductive fish had a significantly higher Kn for both genders. Overall, 28% of the females captured have been in reproductive condition; however, that frequency appears to be declining with condition. Also, relative condition was not correlated with the number of eggs released by reproductively ready females. Correlation between pallid sturgeon condition and hypothesized variables did not result in any statistically significant relationships that would explain the variations in pallid sturgeon condition. As pallid sturgeon recovery continues throughout the lower Missouri River, concern arises over whether or not the current habitat available and river management can support a viable pallid sturgeon population.

Metazoan Parasites of Young-of-the-Year Paddlefish from Lewis and Clark Lake, Nebraska, U.S.A.

Abstract Young-of-the-year paddlefish, Polyodon spathula (Polyodontidae), from Lewis and Clark Lake, an impoundment of the Missouri River in Nebraska, U.S.A., were surveyed for parasites. In 2001 and 2002, 28 and 48 fish were examined for parasites, respectively. Only the nematode Rhabdochona decaturensis infected fish collected in 2001, but 8 parasite taxa (R. decaturensis, Spinitectus sp., Camallanus sp., Contracaecum sp., Marsipometra sp., Diclybothrium hamulatum, Ergasilus elongatus, and 1 unidentified leech) infected fish collected in 2002. Rhabdochona decaturensis was the most common parasite, occurring in 21.4% of fish in 2001 and 79.2% of fish in 2002. Prevalence of other parasite species infecting fish from 2002 was 33% or less. The helminth community of young-of-the-year paddlefish in both years was dominated by nematodes. This study is the first report on parasites of young-of-the-year paddlefish and documents a new host record for R. decaturensis.

Temporal Trends of Channel Catfish Population Characteristics in the Missouri River, Nebraska

Abstract Channel catfish (Ictalurus punctatus) are a popular target for Nebraska anglers, and the proportion of Nebraska anglers targeting catfish is consistently 50% or greater on an annual basis. Commercial fishing for channel catfish was legal on the Missouri River, in Nebraska, from the 1800s until 1992. Several studies have been published regarding channel catfish population characteristics in this reach prior to the closure of commercial fishing; however, there have been no long-term assessments done post-closure. There is concern among anglers and managers about numbers and size of channel catfish in the Missouri River and a desire to better understand population dynamics in order to better manage channel catfish stocks. The goal of this study was to assess spatial and temporal changes in population characteristics of channel catfish in the Missouri River, Nebraska from 1998 – 2013. Specifically, we asked: (1) did channel catfish population characteristics differ among four reaches of the river from 1998 to 2013 and (2) did channel catfish population characteristics exhibit any temporal trends within reaches from 1998 to 2013? We found channel catfish in Nebraska portions of the Missouri River are characterized by slow growth and high mortality. The majority of fish sampled were age-3 or younger and fish age-6 or older were rare. Mean lengths have decreased since the early 1990s and are similar to mean lengths before closure of commercial fishing. Relative abundance decreased in two reaches and was below the 15 y mean in all reaches from 2008-2013. We recommend management goals and objectives be updated and individual goals and objectives intended to decrease mortality and improve size structure be developed for the four study reaches.