Theses and Dissertations at Montana State University (MSU)
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Item Relating the reproductive performance of westslope cutthroat trout to trait specialization to screen for artificial selection vulnerability in a conservation hatchery(Montana State University - Bozeman, College of Letters & Science, 2022) Preul-Stimetz, Taylor Nicole; Chairperson, Graduate Committee: Christine VerhilleTo mitigate westslope cutthroat trout (WCT; Oncorhynchus clarkii lewisi) declines, Montana Fish, Wildlife, & Parks carries out large scale restorations, including wild-origin stocking efforts from conservation hatcheries. Although hatcheries have made progress in limiting the effects of artificial selection on stocked populations, concerns remain that rearing practices inadvertently reduce the diversity propagated into the wild. The objective of this research was to identify traits of WCT driving poor survival or reproduction in a hatchery, allowing managers to reduce artificial selection by screening for fish requiring alternative rearing. In Chapter 1, I repeatedly measured 18 behavior, morphology, and health traits from hatchery intake (July 2019) to spawn (June 2021). I identified traits with low within- relative to between-individual variation as traits likely to be indicative of specialization. As specialists tend to maximize performance under a narrow range of conditions, they may be vulnerable to artificial selection within hatcheries. In Chapter 2, I tested whether the specialized traits identified in Chapter 1, growth rate, or age at hatchery intake of individual WCT could predict survival or reproduction. In Chapter 1, I identified nine specialized (relative condition, weighted health index, health index, body shape, energetic reserves, latency, and upper jaw, lower jaw, and anal fin residual length) traits. I hypothesized these traits would predict later survival or reproductive performance. In Chapter 2, I identified October 2019 daily growth rate in weight and every replicate length measurement after October 2019 to strongly predict total ovulated eggs and total number of hatch embryos produced by females. However, among individual variation in the median percent hatch embryos was not explained by maternal size. Male gamete quality and fertilization success was consistently high, and I found no biologically significant predictors of reproductive performance for males. I also found no predictors of survival for males or females. Despite high total ovulated eggs and total hatch embryo success for females, variable female median percent hatch embryos suggests that quality of ovulated eggs is driving current limitations to WCT hatchery reproduction. I recommend further investigation into impacts of rearing stressors and post-ovulatory aging on female WCT and their reproductive performance.Item Reproductive ecology of hatchery-origin pallid sturgeon upstream of Fort Peck Reservoir, Montana(Montana State University - Bozeman, College of Letters & Science, 2020) Cox, Tanner Lewis; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'First maturity, spawning periodicity, and follicular atresia of hatchery-origin pallid sturgeon in the Missouri River above Fort Peck Reservoir, Montana' submitted to the journal 'Journal of applied ichthyology' which is contained within this thesis.; Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Reproductive ecology and behavior of hatchery-origin pallid sturgeon in the Missouri River above Fort Peck Reservoir, Montana' submitted to the journal 'Journal of applied ichthyology' which is contained within this thesis.Conservation propagation of pallid sturgeon above Fort Peck Reservoir has successfully recruited a new generation of spawning-capable pallid sturgeon to a location that would otherwise have fewer than 30 remaining. Successful recovery of pallid sturgeon will now rely on spawning in locations that provide adequate drift distance for larvae to recruit. Prior to this study, all reproductively-active female pallid sturgeon underwent ovarian follicular atresia. The reasons for and prevalence of ovarian follicular atresia were unclear, spawning periodicity of females remained undescribed, and remaining prepubescent fish indicated that age- and size-at-first maturity would vary more than currently described. Furthermore, spawning location, spawning-related interactions among conspecifics, and substrate composition at spawning locations remained undescribed. We used data on reproductive status and location to describe age- and size-at-first maturity, the prevalence of ovarian follicular atresia during first gametogenic cycles, spawning periodicity for female and male pallid sturgeon, where spawning occurs, if spawning locations are related to discharge, if substrate characteristics at the spawning locations were similar to other river reaches, and if female, male, and atretic female pallid sturgeon use the river similarly. Pallid sturgeon matured at older ages and larger sizes than described for other populations with females maturing at 18 years old and males at 15; however, prepubescent pallid sturgeon as old as 20 were documented. During the presumed-first gametogenic cycle, 62.5% of female pallid sturgeon underwent follicular atresia. Females had biennial reproductive cycles, and males had annual and biennial reproductive cycles. Reproductively-active male and female pallid sturgeon were found in similar locations, while locations of atretic female pallid sturgeon varied. The furthest upstream locations of pallid sturgeon including locations in the Marias River occurred during 2018 when discharge was at an unprecedented high. Spawning occurred in locations less than 131 km from the river-reservoir transition zone, which does not provide adequate drift-distance for larvae. Altering discharge and water temperature at Tiber Dam to mimic observed values in 2018 may increase use of the Marias River by pallid sturgeon during spawning, which would provide adequate drift distance to larvae.Item Description of the reproductive structure, size, growth, and condition of hatchery-origin white sturgeon in the lower Columbia River, British Columbia, Canada(Montana State University - Bozeman, College of Letters & Science, 2020) Maskill, Paige Anne Camas; Chairperson, Graduate Committee: Christopher S. Guy; James A. Crossman, Christopher S. Guy and Molly A. H. Webb were co-authors of the article, 'Describing the reproductive structure of the hatchery-origin population of white sturgeon in the lower Columbia River, British Columbia, Canada' which is contained within this thesis.Conservation aquaculture has been successful in preventing extirpation of endangered white sturgeon Acipenser transmontanus in the lower Columbia River (LCR), Canada. The goals of this project were to 1) determine if the hatchery-origin (HO) population has reached puberty as many fish are of an age and body size to begin contributing to spawning and 2) assess the size, absolute growth rate (AGR), and relative condition factor (Kn) of the population. The reproductive structure (sex and stage of maturity) of the HO population was assessed using multiple tools (gonadal biopsy analyzed histologically, ultrasound, endoscopy, and plasma sex steroids). The accuracy of each tool was determined by comparing the assigned sex to the true sex determined by histological analysis of a gonadal biopsy. A subobjective was to determine whether gonadal development was homogenous (assessed in fish captured in LCR and Lake Roosevelt, WA, USA). All fish assessed were pre-meiotic males (n=158) or pre-vitellogenic females (n=174) and had yet to reach puberty. Endoscopy and gonadal biopsy analyzed histologically were the most accurate tools with accuracies > 97%. Gonadal development was homogenous in females but 38% of the males exhibited non-homogenous testicular development, with a few precocious cysts that contained germ cells in an advanced stage of development compared to the predominant phase seen throughout the biopsy. The size, AGR, and Kn were compared among sex, age, and river zone. While the mean Kn indicated that the HO white sturgeon were in average condition relative to all HO fish within the LCR, they were lower in condition compared to the full transboundary population (Canada and USA). This reflects a difference in the environmental or physiological conditions of the fish in the LCR and those captured throughout the transboundary reach. Results of this work will be important to determine the reproductive dynamics of the hatchery-origin population over time (e.g., age and size at puberty, sex ratio), and specifically when these fish will begin spawning in the wild. Additionally, this information will help to develop other standardized monitoring programs which can track the reproductive structure of a population over time using tools with known accuracy rates.