Theses and Dissertations at Montana State University (MSU)
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Item Status of northern pearl dace and chrosomid dace in prairie streams of Montana(Montana State University - Bozeman, College of Letters & Science, 2018) Stringer, Allison Louise; Chairperson, Graduate Committee: Alexander V. ZaleNon-native Northern Pike Esox lucius are predators that negatively affect native fish assemblages, possibly including those in Montana prairie streams, where their effects had not been investigated heretofore. I compared fish assemblages of prairie streams with and without Northern Pike and other non-native predators, with a focus on three species of concern that are probably particularly susceptible to predation (Northern Pearl Dace Margariscus nachtriebi (hereafter pearl dace), Northern Redbelly Dace Chrosomus eos, and Northern Redbelly Dace x Finescale Dace hybrids C. eos x C. neogaeus [hereafter hybrid dace]). I documented fish assemblages at 140 sites across the historical distribution of Northern Redbelly Dace and hybrid dace (hereafter collectively referred to as chrosomid dace), including 88 sites in the historical distribution of pearl dace. I estimated percent declines in distribution by comparing the number of currently occupied historical streams with the total number of historical streams and then determined if cooccurrence of pearl dace or chrosomid dace with non-native predators was different than predicted by chance. I augmented my dataset with fish collections from 5 additional sources and evaluated whether sites with and without Northern Pike differed in native species richness (with a Poisson regression) or assemblage composition (with a discriminant function analysis). Pearl dace distribution declined 63.3 to 83.3%, and chrosomid dace distribution declined 32.0% to 67.2%, depending on how declines were calculated. Pearl dace almost never co-occurred with Northern Pike or non-native trout and chrosomid dace rarely co-occurred with them. Native minnow species richness was 52% lower at sites with Northern Pike than at sites without Northern Pike. Predation probably caused the observed changes. Pearl dace are at extreme risk and chrosomid dace are at moderate risk of extirpation from Montana, and non-native predators appear to be the biggest threat to their continued persistence. Exclusion of Northern Pike from drainages where they have not yet invaded will afford fisheries managers the best chance of conserving native minnows in Montana prairie streams.Item Relations among arctic grayling, nonnative salmonids, and abiotic conditions in the Big Hole River, Montana(Montana State University - Bozeman, College of Letters & Science, 2017) McCullough, Austin Robert; Chairperson, Graduate Committee: Christopher S. GuyArctic Grayling Thymallus arcticus in Montana have experienced declines in abundance and distribution over the last century, which contributed to the species being designated as a Species of Concern and petitioned for protection under the Endangered Species Act. Conservation of Arctic Grayling in the Big Hole River watershed was based on presumed environmental influences. Interactions with nonnative species, increasing stream water temperatures, drought, and habitat alterations are suggested to influence Arctic Grayling abundances, although sparse quantitative information exists to support these hypotheses. My objective was to evaluate the influence of these biotic and abiotic factors on Arctic Grayling abundances using data collected in the Big Hole River drainage from 1983 through 2015. Arctic Grayling and nonnative salmonids were sampled at 32 sites, stream temperature data were collected at 33 sites, stream discharge data were collected at 21 sites, and habitat data were collected at 441 sites. Ordinary least squares and quantile (Tau = 0.90) regression analyses were used to evaluate the relationships among Arctic Grayling catch per unit effort (CPUE), nonnative salmonids CPUE, stream temperature, stream discharge, and habitat condition. The strongest univariate relationship was a positive correlation between the CPUE of Arctic Grayling > or = age 1 and Brook Trout Salvelinus fontinalis CPUE (r = 0.55, N = 77), which was contrary to the a priori predicted relationship. Multivariate analyses suggested that high water temperatures and low discharges during drought conditions have the greatest limiting influences on the CPUE of Arctic Grayling > or = age 1; Brown Trout CPUE, low water temperatures, and high maximum discharges were suggested as having the greatest limiting influences on age-0 Arctic Grayling CPUE. My findings support current management to increase discharge during drought conditions and further explore relationships between Arctic Grayling CPUE, habitat conditions, and Brown Trout CPUE.Item Evaluation of suppression methods targeting non-native lake trout embryos in Yellowstone Lake, Yellowstone National Park, Wyoming, USA(Montana State University - Bozeman, College of Letters & Science, 2017) Thomas, Nathan Andrew; Chairperson, Graduate Committee: Christopher S. GuyNon-native Lake Trout Salvelinus namaycush threaten to extirpate native Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri in Yellowstone Lake, Yellowstone National Park. Suppression of Lake Trout in Yellowstone Lake has been ongoing since 1995, primarily by gillnetting. Unfortunately, bycatch of Yellowstone Cutthroat Trout is associated with this removal method, which targets adult and subadult Lake Trout. Alternative methods effective at causing mortality in Lake Trout early life stage(s) could be used simultaneously with gillnetting to improve suppression effectiveness. The vulnerability of salmonid embryos suggest increasing Lake Trout embryo mortality is feasible and because population growth rates are sensitive to age-0 survival an effective embryo suppression method could have population-level effects. Thus, the primary objective of this study was to evaluate the efficacy of methods to increase mortality of Lake Trout embryos. In situ experiments tested the effect of suction dredging, electroshocking, tarping, and Lake Trout carcass deposition on embryo mortality. The secondary objective of this study was to evaluate interstitial water flow using NaCl dry injection to better understand the feasibility of using chemicals for embryo suppression. Concurrent laboratory studies have shown that Lake Trout embryos experience high mortality after chemical exposure. Tarping and suction dredging were not effective at increasing embryo mortality. Electroshocking caused 0.92 mortality of embryos at the substrate surface but only 0.38 at 20 cm depth in the substrate. Lake Trout carcass deposition caused 0.99 mortality of embryos, both at the surface and at 20 cm in the substrate. The direction and rate of interstitial water flow was not consistent and future work on a larger scale is needed to inform the feasibility of chemical suppression. Hypoxic conditions within the carcass sites may have caused embryo mortality. In addition, carbon dioxide CO 2 and hydrogen sulfide H 2S are byproducts of organic matter decomposition that harm developing salmonid embryos. Embryo suppression methods are unlikely to replace traditional Lake Trout suppression methods. However, the success of Lake Trout carcass deposition shows potential for the development of an effective additional suppression method that could be implemented on a large scale.Item Dynamics of Yellowstone cutthroat trout and lake trout in the Yellowstone Lake ecosystem : a case study for the ecology and management of non-native fishes(Montana State University - Bozeman, College of Letters & Science, 2015) Syslo, John Michael; Chairperson, Graduate Committee: Christopher S. Guy; Christopher S. Guy and Todd M. Koel were co-authors of the article, 'Trophic overlap and temporal diet shifts for a nonnative and a native salmonid in Yellowstone Lake, Yellowstone National Park' submitted to the journal 'Transactions of the American Fisheries Society' which is contained within this thesis.; Christopher S. Guy, Todd M. Koel, Patricia E. Bigelow, Philip D. Doepke, Brian D. Ertel and Jeffrey L. Arnold were co-authors of the article, 'Response of Yellowstone cutthroat trout to suppression of non-native lake trout in the Yellowstone Lake ecosystem' submitted to the journal 'Canadian journal of fisheries and aquatic sciences' which is contained within this thesis.The introduction of lake trout Salvelinus namaycush into Yellowstone Lake preceded the collapse of the native Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri population. As a system with a simple fish assemblage and several long-term data sets, Yellowstone Lake provided a unique opportunity to evaluate the ecology of a native salmonid in the presence of a non-native salmonid population undergoing suppression in a large natural lake. Diet data for Yellowstone cutthroat trout and lake trout were evaluated at varying densities to determine the effects of density on diet composition. Temporal diet shifts from 1996-1999 to 2011-2013 were likely caused by limitation of prey fish for lake trout. Diets, stable isotopes, and depth-related patterns in CPUE indicated lake trout > 300 mm consumed primarily amphipods, making them trophically similar to Yellowstone cutthroat trout from during 2011-2013. A lake trout removal program was initiated during 1995 to reduce predation on Yellowstone cutthroat trout. Abundance and fishing mortality were estimated for lake trout from 1998 through 2013 and Yellowstone cutthroat trout from 1986 through 2013. Density-dependence was evaluated by examining individual growth, weight, maturity, and pre-recruit survival as a function of abundance. In addition, a simulation model was developed for the lake trout- Yellowstone cutthroat trout system to determine the probability of Yellowstone cutthroat trout abundance persisting at performance metrics given potential reductions in lake trout abundance. Estimates of Yellowstone cutthroat trout abundance varied 5-fold and lake trout abundance varied 6-fold. Yellowstone cutthroat trout weight and pre-recruit survival decreased with increasing Yellowstone cutthroat trout abundance; however, individual growth and maturity were not related to abundance. Lake trout population metrics did not vary with lake trout abundance. Simulation model results were variable because of uncertainty in lake trout pre-recruit survival. Conservative estimates for required lake trout reductions were > 97% of 2013 abundance for a > 70% probability of Yellowstone cutthroat trout persistence at the performance metrics outlined in the Native Fish Conservation Plan. Lake trout removal will likely reduce lake trout abundance and result in Yellowstone cutthroat trout recovery if the amount of fishing effort exerted in 2013 is maintained for at least 15 years.Item Efficacy of suppressing non-native lake trout in an isolated backcountry lake in Glacier National Park(Montana State University - Bozeman, College of Letters & Science, 2014) Fredenberg, Carter Roger; Chairperson, Graduate Committee: Christopher S. GuyPrior to the recent invasion of non-native lake trout Salvelinus namaycush, Glacier National Park (GNP) supported approximately one-third of the remaining natural lake habitat supporting threatened bull trout Salvelinus confluentus. However, bull trout populations have recently declined and are at high risk of extirpation in several lakes in western GNP due to the establishment of lake trout. In 2009, the U.S. Geological Survey and the National Park Service began suppressing lake trout in Quartz Lake (352 ha) to reduce impacts to native bull trout. The objectives of this study were to: (1) describe the demography of the lake trout population during the suppression program (2009-2013); (2) identify the timing and location of lake trout spawning; (3) determine the most efficient combination of gill net mesh color and twine diameter to capture juvenile lake trout (age 2 to age 4); (4) assess the effects of suppression on the growth rate of the lake trout population and use this information to model harvest scenarios; and (5) determine whether suppression negatively impacted bull trout. Lake trout exhibited slower growth, lower condition, and lower fecundity relative to other populations. Spawning locations were identified on cobble and boulder substrates (depths 2-20 m) near the base of two avalanche chutes where adults began aggregating between 1 and 9 October prior to thermal destratification (11-12 C°). Catch rates of spawning (ripe) adults were highest 12-25 October when temperatures declined to below 10 C°. Gill nets with 0.1 mm twine thickness and green color increased catchability of juvenile lake trout. Although density dependent parameters were not included, population simulation models indicated the population was growing exponentially and would likely reach carrying capacity within ten years without suppression. Suppression resulted in declining population growth rates (lambda) from 1.23 prior to suppression to 0.61-0.79 during suppression. Bull trout redd abundances remained stable throughout the suppression period. My results indicate targeted suppression successfully reduced lake trout abundance and that continued suppression at or above observed exploitation levels is needed to ensure continued population declines and to avoid impacts to the bull trout population.Item Predator-prey interactions between introduced trout and long-toed salamanders and ways to mitigate nonconsumptive effects(Montana State University - Bozeman, College of Letters & Science, 2014) Kenison, Erin Kennedy; Chairperson, Graduate Committee: Andrea Litt; Andrea R. Litt, David S. Pilliod and Thomas E. McMahon were co-authors of the article, 'Nonconsumptive effects of introduced trout predators on long-toed salamanders: changes in morphology and life history' submitted to the journal 'Journal of herpetology' which is contained within this thesis.; Andrea R. Litt, David S. Pilliod and Thomas E. McMahon were co-authors of the article, 'Adding vegetation structure to reduce nonconsumptive effects of introduced trout: a novel method for amphibian conservation?' submitted to the journal 'Journal of herpetology' which is contained within this thesis.Predators can increase prey through mortality, but also have the capacity to alter behavior, morphology, and life history through nonconsumptive effects. In many historically fishless lakes in western North America, trout have been introduced for recreational fishing and are associated with reducing and extirpating populations of amphibians, including long-toed salamanders (Ambystoma macrodactylum). Salamanders and trout may coexist in some lakes, as larvae are able to alter foraging behavior by avoiding open water, foraging at night in shallow water, and hiding in cover to avoid predation. However, salamanders may experience nonconsumptive effects due to these behavioral changes. We sought to estimate the nonconsumptive effects of trout on morphology and life history of larval salamanders. We caught salamander larvae using minnow traps in northwestern Montana during the summers of 2012 and 2013 and compared body morphology measurements and size at and timing of metamorphosis between lakes with and without trout. Salamanders in lakes with trout were smaller: they weighed less, had shorter body lengths, and had shorter and narrower tails. Salamanders in lakes with trout were also less likely to metamorphose, did so later in the summer, and had smaller total and tail lengths at metamorphosis. These changes in morphology and life history likely were a result of reduced foraging to avoid predator attacks. We conducted a field experiment in 2013 to investigate whether adding vegetation structure could reduce nonconsumptive effects of trout on salamander larvae by providing refugia and reducing perceived risk of predation. We constructed field enclosures in lakes with and without trout and quantified changes in salamander growth and differences in size at metamorphosis with and without added structure. Salamanders appeared to detect trout cues because they grew more slowly in lakes with trout, even though trout had no ability to consume salamanders. Added vegetation structure did not influence growth rates, but did increase the probability of salamanders that reached metamorphosis. Future research efforts should investigate whether adding vegetation structure to whole lakes can mitigate the nonconsumptive effects of trout, provide a feasible alternative to fish removal, and facilitate coexistence between salamanders and trout.