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Document Type

Thesis - University Access Only

Award Date

2015

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Steven R. Chipps

Abstract

Endemic to the Missouri and Mississippi rivers, the Pallid Sturgeon (Scaphirhynchus albus) has been listed as an endangered species since 1990. Construction of six main-stem dams along the Missouri River has altered spawning and nursery habitats, while obstructing upstream migrations of adults and downstream drift of larvae. Because of their scarcity in the wild, the biotic and abiotic requirements of age-0 Pallid Sturgeon larvae are not fully understood. This knowledge gap has been deemed significant because it is this life stage that is believed to act as a bottleneck to the recovery of the species. The objectives of my study were to 1) parameterize and evaluate a foraging model for age-0 Pallid Sturgeon, 2) evaluate the critical and lethal temperature maxima for Pallid and Shovelnose Sturgeon (Scaphirhynchus platorynchus) of different sizes and acclimated to different temperatures, 3) evaluate the performance of a combined foraging-bioenergetics model using a series of long-term feeding and growth trials, and 4) apply the foraging-bioenergetics model using empirical data from the Missouri River. The foraging model encompassed a Type II functional feeding response along with gut evacuation and satiation parameters to allow us to reliably estimate daily prey consumption of age-0 Pallid Sturgeon. Factors such as water temperature, prey type (Daphnia spp., Chironomidae and Ephemeroptera larvae) and prey density were all shown to significantly affect consumption rates of larval fish. Additionally, simulations of daily energy return of larval fish (19-50 mm) showed that a diet comprised entirely of zooplankton would be insufficient for fish to gain weight, as opposed to fish feeding on Chironomidae or Ephemeroptera larvae. The second objective aimed to understand the physiological limits of age-0 Scaphirhynchus spp. to acute increases in temperature (Critical and Lethal Thermal Maxima). While neither Pallid nor Shovelnose differed in their response to increasing temperatures, they were both strongly affected by body size and acclimation temperatures. As such, smaller fish acclimated at colder temperatures were less tolerant of higher temperatures when compared to larger fish acclimated at warmer temperatures. CTM (29.49-34.39°C) and LTM (29.95-35.71°C) values generated for both species, regardless of size or acclimation temperature, were also found to be higher than the maximum water temperatures observed in 5 shallow water habitats during the growing season of 2011. For the third objective, three different size classes of fish were grown for 7 to 14 days under differing temperature and prey density regimes. Observed final weight, final length, and total number of prey consumed were compared to values generated from the foraging-bioenergetics model. The model provided reliable estimates (within 13% of observations) of fish weight, length, and prey consumed after the bioenergetics portion of the model had been calibrated to account for temperature and prey density effects. Lastly, I used an individual-based modeling approach to estimate the influence of temperature, velocity, and prey abundance on age-0 Pallid Sturgeon growth. To do so, empirical data from three sites of the Missouri River were used to generate growth outputs (weight and length) for a 100-day growing season. Higher growth was shown to occur at sites where high densities of Ephemeroptera and Chironomidae larvae occurred throughout the growing season. Shallow water habitats with temperatures ranging from 17 to 25 °C and moderate water velocities (0.3 m/s) were also found to positively affect growth rates.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

169

Publisher

South Dakota State University

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Rights Statement

In Copyright