University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1990 Floodplain distribution of fishes of the Bitterroot River, with emphasis on introduced populations of northern pike Thomas Stiles Jones The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Jones, Thomas Stiles, "Floodplain distribution of fishes of the Bitterroot River, with emphasis on introduced populations of northern pike" (1990). Graduate Student Theses, Dissertations, & Professional Papers. 2376. https://scholarworks.umt.edu/etd/2376 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. Maureen and Mike MANSFIELD LIBRARY Copying allowed as provided under provisions of the Fair Use Section of the U.S. COPYRIGHT LAW, 1976. '? Any copying for commercial purposes or financial gain may be undertaken only with the author's written consent. MontanaUniversity of FLOODPLAIN DISTRIBUTION OF FISHES OF THE BITTERROOT RIVER, WITH EMPHASIS ON INTRODUCED POPULATIONS OF NORTHERN PIKE By Thomas Stiles Jones B.S., University of Montana, 1986 B.S., University of California, 1984 Presented in partial fulfillment of the requirements for the degree of Master of Science University of Montana 1990 Approved by Chairman, Board of Examiners (9aZ:. $o; Date UMI Number: EP36247 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation MbMMng UMI EP36247 Published by ProQuest LLC (2012). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest' ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 Jones, Thomas S., M.S., October 1990 Wildlife Biology Floodplain Distribution of Fishes of the Bitterroot River, with Emphasis on Introduced Populations of Northern Pike (69 pp.) Director: Andrew L. Sheldon Introduction of exotic species into aquatic systems is common and potentially risky. Ten years ago northern pike (Esox lucius) were introduced into the Bitterroot River in western Montana. Because the vast majority of northern pike in the Bitterroot live in floodplain backwaters (sloughs), I examined the relationship between characteristics of the off-channel habitats and their fishes. In each of 41 backwaters examined, presence/absence data were obtained for 18 fish categories, and 23 variables were measured to characterize slough size, cover, water chemistry, and plant species presence or absence. Sloughs were clustered by fish species using detrended correspondence analysis. Discriminant function analysis was then applied to find habitat variables that could be used to distinguish the clusters. The habitat variables discriminated sloughs containing "large" fish, those holding "small" fish, and pike sloughs. Sloughs containing salmonids were not entirely separable from sloughs containing other large fishes. Important variables in discriminating between slough types are maximum depth, area of vegetation, range of dissolved oxygen between the surface and the bottom, average temperature, area of woody cover, and the presence of several plant species. The significance of this discrimination is that the four sloughs in which northern pike exist are of different character from those in which they are absent. In at least one slough containing pike, the fish were relatively fast growing and short lived compared to other pike populations. Recruitment was low with two weak or absent year classes. Northern pike numbers probably will not increase substantially because of poor recruitment and lack of habitat. At current levels, pike do not pose a serious threat to other species in the river system. Acknowlwedgements I would like to thank Dr. Andrew Sheldon and the rest of my committee, Dr. Richard Hutto, Dr. Dan Pletscher, and Don Peters for their efforts in aiding me with the design of this thesis and comments on the manuscript. I would also like to thank Dennis Workman and the Montana Department of Fish Wildlife and Parks for encouragement of this project through equipment loans, funding, and time. Joseph DosSantos of the Confederated Salish-Kootenai Tribes also donated equipment and suggestions. For help with field work, photos, and shuttling, I acknowledge the help of Milo Burcham, Donna Leeper, Joel Tohtz, Don Eaton, and Bob Petty. In addition I am grateful to Dick Martin for letting me conduct research on his land, which includes the slough at which most of the pike biology data was taken. i i i TABLE OF CONTENTS Page Abstract ii Acknowledgements iii Table of Contents iv List of Tables v List of Figures vi Introduction 1 Study Site 7 Methods Sloughs 9 Pike 13 Results Slough Habitats 17 Fishes of the Floodplain 1 8 Association of Fish Species: Detrended Correspondence Analysis 19 Habitat Relationships: Discriminant Function Analysis 23 Pike of the Bitterroot River 29 Discussion Habitat Analysis 35 Colonization of Pike 42 Biology of Pike 45 The Future of Pike in the Bitterroot River 49 Appendix 53 References 64 i v LIST OF TABLES Page Table 1: Values of variables used in the discriminant analysis with three slough types. 25 Table 2: Discriminant function coefficients for three slough types 26 Table 3: Classification results for discriminant analysis with four slough types. 28 Table 4: Values of variables used in the discriminant analysis with four slough types. 30 Table 5: Discriminant function coefficients for four slough types 31 Table 6: Population estimates for northern pike from two sloughs. 32 Table 7: Size-at-age for northern pike from North America and Europe. 47 Table A1: Habitat variables from Bitterroot sloughs 54 Table A2: Plant species distribution 57 Table A3: Fish species distribution 58 Table A4: Capture records, large pike, slough 19, 1897 59 Table A5: Capture records, large pike, slough 19, 1988 60 Table A6: Capture records, small pike, slough 19, 1987 61 Table A7: Capture records, small pike, slough 19, 1988 62 Table A8: Capture records, all pike, slough 41, 1987 63 v LIST OF FIGURES Page Figure 1: Map of the study area showing slough locations 8 Figure 2: Ordination of taxa on first two detrended correspondence axes 20 Figure 3: Ordination of sloughs in DCA space with three slough types 21 Figure 4: Ordination of sloughs in DCA space with four slough types 22 Figure 5: Discrimination by habitat variables of three slough types 24 Figure 6: Discrimination by habitat variables of four slough types 27 Figure 7: Length-frequency diagram for pike, 1987 33 Figure 8: Length-frequency diagram for pike, 1988. 34 Figure 9: Length-weight relationship for pike 36 Figure 10: Von Bertalanffy growth curve for male pike 37 Figure 11: Von Bertalanffy growth curve for female pike 38 v i Introduction Efforts to improve fisheries through the introduction of exotic species is common but potentially risky. For years fish managers, collectors, and anglers have introduced game fish, bait fish, and invertebrates into waters. In western Montana, populations of rainbow trout (Oncorhynchus mykiss), Yellowstone cutthroat trout (O. clarki bouvieri), brown trout (Salmo trutta), brook trout (Salvelinus fontinalis) and lake trout (S. namaycush) have been introduced into waters already containing native populations of westslope cutthroat trout (O. clarki lewisi) and bull trout (Salvelinus confluentus). Increasing angler interest in species such as northern pike (Esox lucius), walleye (Stizostedion vitreum vitreum), and smallmouth bass (Micropterus dolomieui) is resulting in pressure on managing agencies to increase the range of these species, and in some areas these fishes have already been introduced by anglers. Nilsson (1986) and Moyle et al. (1986) summarize the potential hazards of introducing new species. Perhaps the most obvious hazard is the introduction of predators which can threaten native fishes. Nile perch (Lates niloticus) virtually wiped out native fishes in the Nyanza Gulf of Lake Victoria, East Africa (Hughes 1986). Wheeler and Maitland (1973) discuss several cases in which introduced pike eliminated brown trout populations. They suggested 1 2 planning methods of controlling a new species before allowing introductions. Pike have also been known to destroy populations of trout and of other species that are "sensitive to predation" in Ireland (Nilsson 1986). Predation is not always a negative effect, however. Predators are sometimes introduced to control stunted populations (Powell 1973). Sauger-walleye hybrids have been considered for the control of stunted yellow perch in western Montana. This idea was rejected, however, because the hybrid is not sterile (Don Peters, Department of Fish, Wildlife, and Parks, personal communication). Another risk associated with exotics is elimination by competition. Whitefish (Coregonus spp=) were introduced into lakes in