Date of Award
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Biology
First Advisor
J. E. Marsden
Abstract
Fish stocking is commonly used globally to reintroduce and conserve native species. However, stocked fish can have adverse effects on naturally produced (i.e., wild) fish and often fail to re-establish self-sustaining populations due to maladaptations to hatchery environments and unintentional domestication selection. Behaviors adapted to hatchery environments are often suboptimal for natural environments compared to those of wild fish; however, the retention of hatchery-related behaviors throughout the lifetime of stocked fish is understudied. My dissertation addressed this knowledge gap by testing the hypothesis that stocked fish maintain behaviors across life stages that may hinder their performance and differ from those of wild conspecifics. To address this hypothesis, I compared foraging and movement behaviors between stocked and wild lake trout (Salvelinus namaycush) in Lake Champlain using diet analyses and acoustic telemetry.I assessed lake trout foraging behaviors based on stomach fullness, diet composition, and fish condition using stomach content, lipid, and fatty acid analyses. Overall, wild lake trout had empty stomachs less frequently and consumed more prey fish compared to stocked fish across all sizes and collection seasons. Fish condition represented by lipid content was also greater for wild lake trout compared to stocked fish across all sizes. However, stocked and wild lake trout had similar prey species selection and primarily consumed alewife (Alosa pseudoharengus), which had the greatest lipid content among abundant offshore prey fishes in the lake. Together, these results demonstrate that stocked lake trout have lower foraging success and consume less energy than wild fish in the same system from juveniles to mature adults. These differences also indicate that wild fish have a disproportional effect on the forage base with greater predatory pressure compared to stocked lake trout. I compared movement behaviors between stocked and wild lake trout across life stages based on regional distribution, distance traveled, and vertical distribution (i.e., depth use) using acoustic telemetry. Differences in spawning distributions of adult stocked and wild lake trout were further investigated based on lake-wide spawning site use and receiver residency duration. I estimated regional distribution of stocked and wild lake trout using a new movement model (combined linear and non-linear interpolated paths) that was selected based on a framework I developed to compare performance among multiple movement models according to five criteria. My results demonstrated that wild lake trout had greater three-dimensional distributions compared to stocked fish across life stages including up to 34% increased average number of regions used, further distance traveled by up to 50%, and up to 44% increased standard deviation of daily depth compared to stocked individuals. These behavioral differences between stocked and wild fish were typically greatest during fall when reproduction occurs. Site-specific comparisons of stocked and wild adult lake trout distributions during fall demonstrated significant differences in lake-wide spawning site selection and longer durations spent at individual sites for stocked adults compared to wild fish. These space-use differences during the spawning season were largely driven by substantial use of an artificial structure located near a fish hatchery by stocked adults, while presence of wild fish was minimal. My results, combined with previous research, suggest spawning by stocked lake trout at this artificial site has little to no contribution towards natural recruitment and therefore may represent a substantial loss of reproductive effort by stocked fish.
Language
en
Number of Pages
239 p.
Recommended Citation
Futia, Matthew, "Born To Be Wild: Hatchery Rearing Has Life-Time Effects On Foraging And Movement Behaviors Of Lake Trout Salvelinus Namaycush" (2024). Graduate College Dissertations and Theses. 1948.
https://scholarworks.uvm.edu/graddis/1948