Date of Award:

5-13-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Advisor/Chair:

Phaedra Budy

Abstract

Triploid (sterile) trout potentially offer a more risk-averse option for stocking popular non-native sport fish; however the relative performance (e.g., survival and growth) of triploid versus diploid fish in natural settings is not well understood. I evaluated the relative performance of triploid versus diploid brook trout (Salvelinus fontinalis) stocked in high mountain Uinta lakes in response to food availability and lake morphology. I chose a set of 9 lakes that included a range of elevation and lake morphology. I observed no difference in CPUE or relative weight (Wr) of both types of trout in all lakes. Food availability (e.g., zooplankton and macroinvertebrates) varied substantially among lakes; however I observed no discernible difference between diploid and triploid diets, diet preference, or isotopic trophic signatures. Physical lake characteristics (e.g., dissolved oxygen [DO, mg/L] and temperature [°C]) were within or near optimal brook trout conditions (metabolically beneficial range) during the summer, but over-winter DO reached near lethal levels under the ice. In sum, between the two strains, I did not observe any significant differences in relative performance measured across a number of indices; however the size distribution of diploid fish was marginally (20 mm) skewed towards larger fish (a difference likely not great enough to be detectable by the average angler). In contrast to the similarity in performance between strains, I did observe considerable variability in performance of brook trout across lakes as a function of lake productivity, food availability, and most importantly fish density. Fish performance was greater in lakes with a lower density of stocked fish. Overall, the results from this study indicate triploid brook trout offer a viable and risk-averse alternative to stocking diploid fish in Uinta mountain lakes. Stocking triploid fish should decrease the threat of uncontrolled expansion into adjacent water bodies, while still allowing managers to maintain a popular non-native sport fishery.