/n' LEASE RETURN HISTORIES OF WESTSDOPE CUTTHROAT AND BULL TROUT IN THE UPPER FLATHEAD RIVER BASIN, MONTANA STATE DOCUMENTS COLLECTION JUL -8 |986 MONTANA STATE LIBRARY 1515 E. 6th AVE. HELENA, MONTANA 59620 Prepared By: Bradley B, Shepard - Project Biologist Karen L. Pratt - Project Biologist Patrick J, Graham — Project Leader ^'ONITANA STATE UBRARY uei AVE. ntlENA, MONTANA 59620 Sponsored By; Environmental Protection Agency Region VIII, Water Division ‘ Denver, Colorado Contract No. R008224-01-5 Steering Committee for the lathead River Basin Environmental Impact Sti- ,y T June, 1984 iJiY 0 1 1996 JAN 28 1998 " -5 'iS29 FE8 3 2900 OEC 1 8 2002 OEC 3 1 2003 TABLE OF OOOTENIS INTRODUCTION WESTSLOPE CtHTHRDAT TROUT STOCK ASSESSMENT EMBRYONIC DEVELOPMENT Egg Deposition through Hatching Hatching through Pry Emergence STREAM RESIDENCE Distribution in Streams Habitat Used Small (<100 mm) Cutthroat Large (100-200 mm) Cutthroat Trout. . Pood Habits EMIGRATION OF JUVENILES Age Composition Timing PLA3HEAD RIVER - FLATHEAD LAKE RESIDENCE Seasonal Movement Pood Habits Lake Distribution adult spawning migration SPAWNING Timing and Distribution Characteristics of Adults Physical Characteristics of Spawning sites GROWTH PAGE 1 2 2 2 3 3 4 4 7 7 7 9 9 10 10 1 4 16 16 1 7 1 7 19 19 22 22 24 ■ ' ii TABLE OP COOTENnS (Cont.) PAGE BULL TROUT 2 9 STOCK ASSESSMENT. 2 9 EMBRYONIC DEVELOPMENT 2 9 Egg Deposition through Hatching 29 Hatching to Fry Emergence 3o STREAM RESIDENCE 3 0 Distribution in Streams 3 1 Habitat Used 3 4 Small (<100 mm) Bull Trout 3 4 Large (100-200 ram) Bull Trout 3 4 Food Habits 3 8 EMIGRATION OF JUVENILES 3 8 Age exposition 3 8 Timing 3 8 FLATHEAD RIVER - FLATHEAD LAKE RESIDENCE 40 Seasonal Movement 4o Food Elabits 4o Lake Distribution 4i ADULT SPAWNING MIGRATION 41 SPAWNING 4 2 Timing and Distribution 42 Characteristics of Adults 47 Physical Characteristics of Spawning Sites 4 7 GROWTH 49 CONTRASTING SURVIVAL STRATEGIES 5 4 iii TABLE OF CONTENIS (Cont.) PAGE EMBRYONIC DEVELOPMENT 5 4 STREAM RESIDENCE 5 4 Distribution in Streams 54 Social Order 5 5 Fish Size and Spatial Segregation 55 EMIGRATION OF JUVENILES 5 6 FLATHEAD RIVER - FLATHEAD LAKE RESIDENCE 5 6 ADULT SPAWNING MIGRATION 5 7 SPAWNING 5 7 Timing and Distribution 5 7 Characteristics of Adults 57 MANAGEMENT IMPLICATIONS 5 8 RECREATIONAL FISHERY 5 8 COAL DEVELOPMENT IN CANADA 5 8 OIL AND GAS 5 9 FOREST MANAGEMENT ACTIVITIES 5 9 Streamflow and Water Tenperature 5 9 Sedimentation 6 o Effects on Spawning and Incubation 6o Effects on Juvenile Rearing 6i Instream and Streambank Cover 6 1 Primary Productivity 6 2 OTHER SPECIES 6 3 SCULPIN5 6 3 Stock Assessment 6 3 iv TABLE OF CONTENTS (Cont.) PAGE Spawning and E^rly Development 6 3 Habitat 6 8 Age and Growth 6 8 Food Habits 6 8 Parasites 6 8 WHITEFISH 7 0 Stock Assessment 7 o Spawning and Early Development. 7 0 Stream Residence. 70 LITERATURE CITED 7 4 APPENDIX A A1 APPENDIX B . B1 APPENDIX C Cl LIST OF TABLES TABLE 1 Time of year, water temperature during incubation and fry size at emergence for westslope cutthroat trout in the Flathead River St. Joe River, Wolf Lodge Creek and Priest Lake drainages. ... 5 2 Densities of age I and older cutthroat (fish/100 m^) observed in pools of tributaries to river drainages in Montana and Idaho. 5 3 Mean densities (fish/100 m^) and standard deviations (S.D.) of cutthroat and bull trout by stream order 6 4 Mean densities (fish/100 m^) and standard deviations (S.D.) of cutthroat and bull trout by stream reach 6 5 Densities (fish/100 m^) of cutthroat trout age 0, age I, age II, age III, all cutthroat and age I and older cutthroat observed in pools, runs, riffles, and pocketwaters of the upper Flathead River Basin 8 6 Average depth and velocity of the focal point selected by juvenile westslope cutthroat trout of various sizes (>100, <100 mm) or ages living in tributary streams (N = number of tributar- ies surveyed) 8 7 PercQit (number of cutthroat trout in each migration class trapped leaving tributaries to the Flathead River and confuted from scale samples collected from the North Fork, Middle Fork, lower Flat- head River and Flathead Lake for the time period 1976 to 1981. . ii 8 Percent conposition of migration classes in westslope cutthroat trout populations sampled from lakes, rivers and tributaries in Montana and Idaho 12 9 Number of days trapping occurred, number of juvenile cutthroat passed downstream through traps, and number of trapped juvenile cutthroat per trap-day by month from North Fork tributaries during 1976 to 1980 and from Middle Fork tributaries during 1981 13 10 Characteristics of westslope cutthroat spawning including time of year, size of spawner, sex ratio and fecundity of migratory or resident stocks observed in river drainages of Montana and Idaho 2 0 11 Characteristics of resident and migratory westslope cutthroat trout redds including redd size (disturbed area) , water depth, velocity and streambed conposition 23 vi LIST OP TABLES (Cont.) TABLE PAGE 12 Characteristics of scales and length at scale formation for westslope cutthroat trout in river drainages of Montana and Idaho during their first year 2 5 13 Back-calculated lengths at annulus formation of westslope cut- throat trout in the upper Flathead basin and other rivers and tributary streams in Montana and Idaho (adapted from Lukens 1978) 2 6 14 Mean calculated total length growth increments (millimeters) for westslope cutthroat trout that entered Flathead River and Flat- head Lake after spending one to four years in tributary streams. Fish were collected during the years 1962 through 1982 2 8 15 Tenperature units, days required, and approximate dates for eye up, hatch, and emergence of bull trout embryos and alevins in field and laboratory conditions (adopted from Weaver and White 1984) 2 9 16 Number and percentage survival of bull trout embryos in various substrate mixtures in laboratory channels. A total of 800 fertilized eggs were planted per mixture (unpublished data, Montana State Cooperative Fisheries Research Unit, Bozeman, Montana) 3 o 17 Mean density of bull trout observed by snorkel ing in tributaries to the Flathead and Idaho river drainages. Includes only those tributaries where bull trout were observed (N = number of tributaries) 32 18 Mean densities of bull trout estimated from electrofishing in the Flathead and the Toboggan, MacKenzie and Wigwam drainages of British Columbia 3 2 19 Mean densities of age 0, age I, age II, age III, all bull trout and age I and older bull trout in pools, runs, riffles and pocketwater of the upper Flathead River basin (1979-1981) .... 33 20 Flow pattern or habitat units used by juvenile bull trout and Dolly Varden in streams of Mai tana, British Columbia and Alaska. 3 3 21 Cover used by juvenile bull trout and Dolly Varden in streams of Alaska, Montana, and British Columbia 3 5 22 Depth and velocity used by juvenile bull trout in the Flathead and general depth and velocity measures of juvaiile bull trout in streams of British Columbia, adopted from Griffith 1979 . . . vi i 36 LIST OF TABLES (Cont.) TABLE P^E 23 Substrate asscx:iated with juvenile bull trout in British Columbia and the Flathead 3 7 24 Percent of age I, II, III, and IV bull trout emigrating from tributary streams 3 9 25 Number of days trapping occurred, number of juvenile bull trout passed downstream through traps, and number of trapped juvenile bull trout per trap day by month from North Fork tributaries during 1976 to 1980 and Middle Fork tributaries during 1981. . . 39 26 Characteristics of bull trout spawning, including time of year, size of spawner, sex ratio and fecundity observed in river drain- ages of Montana, Idaho and British Coluik^ia 4 6 27 Characteristics of bull trout redds including redd size (disturb- ed area) , depth of egg deposition, water depth, velocity and streambed conposition observed in river drainages of Montana, Idaho and British Columbia 48 28 Back-calculated lengths at annulus of bull trout during their first four years from lake and riverine collections frcxn drain- ages in Montana, Idaho and British Columbia 5 0 29 Chemical parameters of the lower reaches of major tributaries of the North and Middle Forks of the Flathead River in October, 1980, Total alkalinity and conductivity were measured in the field. BDL indicates the value for the parameter is below the detection limit 51 30 Monthly minimum and maximum water temperatures of six North Fork and four Middle Fork tributaries 52 31 Bull trout growth (millimeters) in various waters 5 3 32 Distribution of sculpins, mountain whitefish and brook trout in tributaries of the North and Middle Forks of the Flathead. + = present, - = absent 6 4 33 Ihe lei^th at maturity, fecundity and relationship between fecundity and fish length for slimy and shorthead sculpins ... 67 34 Average length of shorthead and slimy sculpins from the Flathead and ranges of lengths observed for all sculpins aged during this study, compared to collections of Glasser et al. 1981, Peden 1982, and Craig and Wells 1976 69 vi i i LIST OF TABLES (Cont.) TABLE PAGE 35 Distribution of v^itefish by size class (less than 152 mm and 152 irm or larger) , expressed as number (percent) of total reaches of tributary streams sanpled in the upper Flathead Basin 36 Mean density and range of densities of vrfiitefish observed in stream reaches 1-5 and stream orders 2-5 in surveyed sites within tributaries to the North and Middle Forks of the Flathead timbers in parentheses indicate number of sites where whitefish were observed 7 3 LIST OF FIGURES FIGURE PAGE 1 Movement of juvenile cutthroat (less than 225 mm) in the upper Flathead River Basin, returns within one year 1962-1981 1 5 2 Movement of cutthroat greater than 225 mm in the upper Flathead River Basin, returns within one year 1962-1981 18 3 Movement of adult bull trout from U.S. tributaries of the North Fork Flathead River, returns within one year 1962-1981 43 4 Adult bull trout movement from Canadian tributaries of the North Fork Flathead River, returns within one year 1962-1981 44 5 Bull trout movement in the Middle Fork Flathead River, returns within one year 1962-1981 4 5 X LIST OF APPENDICES APPENDIX PAGE A Summary of results for downstream trapping of juvenile westslope cutthroat and bull trout in upper Flathead River tributaries from 1976 to 1981 ai B Sumnary of tag return information illustrating movement of west- slope cutthroat and bull trout in the upper Flathead River Basin b l C Age-growth information for westslope cutthroat and bull trout in the upper Flathead River drainage ci xi INTRODUCTION This report presents life history and habitat requirement information for westslope cutthroat and bull trout populations in the upper Flathead River Basin, which includes Flathead Lake, the mainstem Flathead River above Flathead Lake, North Fork of the Flathead River, Middle Fork of the Flathead River and tributaries to these waters. 'Hie South Fork of the Flathead River, Stillwater River, Whitefish River and Swan River drainages were not included in this study. The information presented in this report is a synthesis of data collected primarily during a five-year baseline fisheries study (1978 to 1982) of the upper Flathead Basin funded by the Environmental Protection Agency and conducted by the Montana Department of Fish, Wildlife and Parks (MDFWP). We also incorporated information collected during other MDFWP studies funded by the Bureau of Reclamation, Bonneville Power Administration and USDA Forest Service. The following reports were used as primary refer- ence sources and are not cited individually in the text: Montana Department of Fish Wildlife and Parks (1979), Graham et al. (1980), Fraley et al. (1981), Leathe and Graham (1981), McMullin and Graham (1981), Fraley and Graham (1982), Leathe and Graham (1982), Shepard et al. (1982), MDFWP (1983a), MDFWP (1983b), MDFWP (1983c), Shepard and Graham (1982), Shepard and Graham (1983a), and Pratt (1984). These reports should be consulted if more detailed information on a particular aspect of these investigations is needed. Other fisheries studies presently being conducted by MDFWP include a basin-wide micro-hydro cumulative impact study in the Swan River drainage funded by the Bonneville Power Administration and a study evaluating the inlets of timber harvest in Coal Creek, a tributary to the North Fork of the Flathead River, funded by the USDA Forest Service, Flathead National Forest. Life history and habitat information were organized by life-stage, beginning with embryonic development and continuing through tributary resi- dence, juvenile emigration, Flathead River-Flathead Lake residence, and concluding with migration of adult spawners back to the spawning grounds. Growth information is presented by species. We also included information regarding our present knowledge of sculpin and mountain whitefish life his- tories. This report does not address kokanee, the dominant sport fish in the basin in terms of harvest and angler use, because this information is presently being collected in two separate studies being conducted by MDFWP under contract to the Bonneville Power Administration. Life history information for kokanee will be presented at the conclusion of these two studies . 1 WESTSLOPE CUTTHROAT TROUT STOCK ASSESSMENT Behnke (1979) recognized three commonly occurring life history patterns of westslppe cutthroat throughout their native range. Resident fish spend their entire life within a tributary stream. Fluvial cutthroat trout rear up to three years in tributary streams emigrate to a river to grow to maturity, and return to their natal tributary to spawn. Adfluvial cutthroat trout spawn and rear in tributary streams but move into lakes to mature. Growth of fish is generally more rapid in rivers and lakes than in tributary streams; consequently, adults from fluvial populations are usually larger than resi- dent adults and adfluvial adults often grow larger than fluvial adults within the same system. Presently, the downstream emigration of juveniles is the only way to distinguish between resident and migratory (either fluvial or adfluvial) forms of juvenile cutthroat trout, Averette and MacPhee (1971) also con- cluded that behavioral rather than morphologic differences were the only way to separate resident and adfluvial cutthroat trout in the St. Joe River drainage, Idaho. They stated that to be able to group these different life history forms into discrete stocks required proof of genetic isolation via temporal or spatial isolation during spawning. Since they found both life history forms spawning in the same sections of many lower St. Joe tribu- taries, they concluded no evidence existed that showed discrete spawning. We presently have no evidence from either electrophoretic analyses or spawning ground surveys to conclude genetic isolation has occurred for the jtiiree life history forra^(other than a^ve physical migration barriers) in the ufper Flathead Basin. Genetic mixing may occur frequently enough to prevent stock differentiation and migratory behavior is based on social and environmental cues in conjunction with genetic codes. For example, during years of lower than average streamflows, juvenile progeny from resident parental stock may migrate downstream seeking more favorable growing environments in response to increased competition for food and space (Chapman and Bjornn 1969), General- ly, mature adults (age IV and older) of each life history form can be differ- Qitiated based on size with the largest adults (>350 mm) being adfluvial, medium sized adults (approximately 250 to 350 mm) being fluvial and small adults «250 mm) indicating resident fish. EMBRYONIC DEVELOPMENT Terminology used in this report is defined as follows: Alevin - a small fish which has just hatched, still has a yolk sac and does not actively feed. Embryo - fertilized egg. Emergoice - fry leave the gravel. Fry - a small fish which has recently absorbed the yolk sac and begun actively feeding. 2 Hatch - process between egg and alevin stage. Hatch Duration - time period from the hatching of the first egg until the last egg hatches. Incubation - period of egg development. Swim up - fry swim up from the streambed after emergence by gulping air to fill their swim bladder. Temperature Units - (°C) number of degrees above freezing multiplied by the nunber of days above freezing. Embryonic development of both cutthroat and bull trout is affected by water temperature, concentrations of dissolved oxygen and streambed composi- tion. Water temperature affects timing of incubation, duration of hatch and embryo survival. Increased fine sediments within the streambed can prevent oxygenated water from reaching embryos, trap metabolic wastes within inter- stitial spaces surrounding the embryos, and form a physical barrier prevent- ing fry emergoice. The information presented below originated from both fish culture research, laboratory experiments and field observations. Em BsBQsitifln through Hatghing After eggs have been deposited in the gravels and fertilized, the embryos required 310 temperature units to hatch (Smith et al. 1983). Ihe incubation period for cutthroat embryos in the upper Flathead River basin extends from iidd-May_throi^ A^ depending on time of spawning and water temperature. Egg survival has been related to the age of spawning adults, temperature of water where adults reside before spawning, genetic variation within the stock and amount of fine sediment present in the substrate. Mature two and three year old cutthroat trout have less viable gametes than mature four and five year old fish (Smith et al. 1983, Daryle Hodges, Murray Springs Hatch- ery, Eureka, Montana, personal communication). Adult cutthroat trout held in cool (2-4^) water temperatures produced more viable eggs than those held in a constant water temperature of 10°C (Smith et al. 1983). Genetic variab- ility is necessary for the production of viable eggs (Allendorf and Phelps 1980). In laboratory studies, embryo survival to hatching was generally less than 50 percent when the percentage of fine sediment (material less than 6.35 mm) within the redd exceeded 20 percent (Idaho Cooperative Fisheries Research Unit, University of Idaho, Moscow, unpublished data). .thi-ough Friy Smerganoe After hatching, alevins remained within the interstitial areas of the streambed gravels until they accumulated an additional 110 to 150 temperature units before absorbing the yolk sac and emerging as fry (Daryle Hodges, Murray Springs Hatchery, Eureka, Montana, personal communication). Heimer (1969, 1970) estimated that survival of westslope cutthroat trout eggs to fry emergence ranged from 30 to 34 percent in tributaries to Priest Lake, Idaho. 3 Fry emerged from the streambed from early July to late August in upper Flathead River Basin tributaries. Cutthroat trout in the St. Joe River, Wolf Lodge Creek and Coeur d'Alene Lake drainages, Idaho emerged earlier (Table 1). Fry were approximately 20 mm long at emergence in tributaries to the Flathead River and Lake Coeur d'Alene (Table 1), STREAM RESIDE:^«:E Resident and migratory stocks of cutthroat trout were indistinguishable as juvQiiles and were combined in the following discussion. Resident adult cutthroat trout were often observed alcxigside migratory juveniles in streams in the basin. Aggressive behavior was frequently displayed by resident adult cutthroat trout toward smaller juvenile cutthroat and bull trout. Species distributions, habitat use, and food habits are described by size group. Habitat used by juvenile fish was analyzed for fish smaller than 100 mm and fish larger or equal to 100 mm. Food habits were analyzed for fish smaller than 110 and larger or equal to 110 mm. Comparative data was often available only by age of fish rather than size of fish and is reported as such. An age 0 fish was in its first summer of life, and age I fish had completed one full year and was in its second summer of life. Distribution la Cutthroat trout were observed in 89 (97%) of the 92 tributaries surveyed in the ujper Flathead basin, and were the only trout species present in 28 (30%) of the surveyed tributary streams. Only eight (9%) of the streams were inaccessible to other trout due to permanent or seasonal barriers to fish movement. Densities of cutthroat trout in Flathead River tributaries were generally higher than those reported for other drainages, exc^t Wolf Lodge Creek, Coeur d'Alene, Idaho (Table 2). Cutthroat trout densities were highest in small streams (low stream order), and backwaters or side channels of larger streams (Tables 3 and 4). High densities of juvenile cutthroat trout were observed in several small streams characterized low gradient and associated with small high mountain lakes. Hartman and Gill (1968) also reported cutthroat in "small level streams" some of which were associated with lakes. However, when other species were present, cutthroat trout were observed in areas of moderate to high gradients. Griffith (1970) believed interspecific interactions between cutthroat and brook trout resulted in a longitudinal distribution for these two species within streams with cutthroat trout inhabiting the high gradient headwater areas and brook trout inhabiting the low gradient regions. High densities of cutthroat trout were found in upper reaches of tribu- tary drainages (Table 4). Many of these cutthroat aj^ared to be residents. Averett and McPhee (1971) reported resident cutthroat trout predominated upper basin tributary populations and migratory cutthroat trout were more dominant in lower tributary and mainstem populations in the St. Joe River drainage, Idaho. 4 Table 1. Time of year, water temperature during incubation and fry size at emergence for westslope cutthroat trout in the Flathead River, St. Joe River, Wolf Lodge Creek and Priest Lake drainages. Emergence period Incubation temperature Size at emergence Drainage Source July-August 2-10°C 23 mm Flathead River Johnson 1963 This study June -July 2-13°C St. Joe River Averett and McPhee 1971 Mauser 1972 June 9-17°C 20 mm Wolf Lodge Creek Lukens 1978 A August— 13-21°C — Priest Lake Bjornn 1957 Fry emergence completed. Table 2. Densities of age I and older cutthroat (fish/lOOm^) observed in pools of tributaries to river drainages in Montana and Idaho. Drainage Cutthroat/ 100 m2 Tributaries used in average Source Citation Flathead River 17.7 89 This Study S.F. Clearwater River 1A.3 3 Shepard 1983 Lemhi River 3.0 1 Homer 1978 St. Joe River 1.4 9 Thurow and Bjornn 1977 Lochsa River 0.8 6 Graham 1977 Selway River 1.1 8 Graham 1977 Coeur d'Alene Lake 26.1 6 Lukens 1978 5 Table 3. Mean densities (fish/100 m^) and standard deviations (S.D.) of cutthroat and bull trout by stream order. Stream^'^ order Number of surveyed reaches Cutthroat Bull trout Mean S.D. Mean S.D. 2 45 8.3 15.6 0.9 2.2 3 98 5.0 6.0 0.6 1.3 4 36 1.4 2.2 0.4 0.8 5 5 0.7 0.8 1.0 1.2 jL/ Stream order refers to the location of the stream in the drainage and its relative size. First order streams have no tributaries, second order streams begin vtere two first order streams join, and so on. Table 4. Mean c^sities (fish/100 m^) and standard deviations (S.D.) of cutthroat and bull trout by stream reach. Stream — reach Number of surveyed reaches Cutthroat Bull trout ^fean S.D. Mean S.D, 1 88 4.3 7.0 0.5 1.2 2 56 5.1 10.8 0.7 1.9 3 27 7.2 12.3 1.0 1.8 4 11 5.3 8.1 6.5 1.0 5 2 0.5 0.4 0.1 0.1 )J Stream reaches were homogenous portions of a stream with respect to channel gradient, relative size, and adjacent land form. Stream reaches Vvere numbered frcm the mouth upstream. 6 Cutthroat trout were most frpjuently fc^d in habitat units (e.g. pool, riffle or run) smaller than 200 m^ and 100 m^. Densities of cutthroat trout were higher in pool habitats than in any other habitat type (Table 5). Shepard (1983) found densities of cutthroat trout larger than 50 mm were significantly higher (p<0,l) in pool than riffle, run or pocketwater habitats in tributaries to the South Fork of the Clearwater River, Idaho. Cutthroat trout densities were higher in pools because fish used the entire water column (depth) by "stacking up" where suitable water velocities and cover existed. Habitat Hssd Sipall «1Q.Q mml Cutthroat Cutthroat trout fry and fingerlings were found along stream margins in both main stream channels and small side channels. Small groups of fry were observed in low velocity areas within pools, while solitary individuals were seen along the fringes of fast water (runs and riffles). In tributaries to the Flathead River, fry and fingerlings were more abundant in pools and runs than riffles or pocketwaters (Table 5). Glova and Mason (1974) reported larger numbers of young coastal cutthroat (Salmo clarki clarki) in riffles and glides than in pools when coho (Qncorhynchus kisutch) were present. When coastal cutthroat were alcaie they were evenly distributed between pools, glides, and riffles. Within habitat units, cutthroat trout selected areas of homogeneous depths and velocities. Young cutthroat trout used shallow areas, approxi- mately 0.3 m deep, where water velocities were less than 0.15 mps. In other drainages, cutthroat trout were found in areas with water depths between 0.05 and 0.50 m where water velocities were 0.11-0.36 mps (Table 6). Juvenile cutthroat trout usually maintained a fixed position in the water column, 0.1- 0.4 m above the streambed where water velocities were between 0.02 and 0.46 mps (Table 6). Small juvenile cutthroat trout were generally within 0.2 m of overhead cover. This cover could be provided by overhanging brush, undercut banks, water depth, large substrate or a broken water surface. When other fish species or older cutthroat trout were present, juvenile cutthroat trout were consistently closer to cover. Hansen (1977) also found cutthroat trout used the same types of habitat. Cutthroat trout fry held near the water surface in shallow water areas using partially submerged twigs, overhanging branches and shade as cover Fingerlings were distributed throughout the water column and were associated with submerged cover. lAige. ■(,J.QQr2Q0 mm) Cutthroat Trout Larger juvenile cutthroat trout were most numerous in main channel pools. Run and pocketwater habitats were used more than shallow riffle areas (Table 5). Ihe preference exhibited by cutthroat trout for pools has been reported by other researchers (Horner 1978, Shepard 1983). Shepard (1983) found significantly higher densities of cutthroat trout larger than 50 mm in pools than in run, pocketwater or riffle habitats. He also found that cutthroat trout densities were higher in runs than in pocketwaters or riffles. 7 Table 5. Densities (f ish/lOOm^) of cutthroat trout age 0, age I, age II, age all cutthroat and age I and older cutthroat observed in pools, runs, riffles and pocketwaters of the upper Flathead River Basin. Habitat Units Age Pools (394) Runs (637) Riffles (574) Pocketwater (188) 0 1.4 1.3 0.6 0.5 I 1.7 1.4 0.4 0.7 II 4.7 2.2 0.4 2. 1 III 11.3 3.5 1.2 2.3 All cutthroat 19.1 8.4 2.6 5.6 Age I and older 17.7 7.1 2.0 5.1 Table 6. Average depth and velocity of the focal point selected by juvenile westslope cutthroat trout of various sizes (>100, <100 ram) or ages living in tributary strearas (N = number of tributaries surveyed) . (N) Depth selection (m) Velocity selection (ra) Fish size/age Citation 37 0.31 0.10 <100 mm This Study 27 0.29 0.10 Fry Griffith 1970 26 0.46 0.11 1+ Griffith 1970 56 0.43 0.10 1+ Hansen 1977 55 0.62 0.22 100-200 Iran This Study 37 0.49 0.14 11+ Hansen 1977 7 0.50 0.21 II 1+ Hansen 1977 44 0.50 0.11 11+ Griffith 1970 16 0.46 0.12 II 1+ Griffith 1970 8 Cutthroat trout moved into faster and deeper water as they grew. Everest (1969) and Hansen (1977) reported the same type of response. Individuals maintained a constant position in water 0.4-1.2 m deep where water velocities were 0.09 to 0.24 mps. Westslope cutthroat trout in North Idaho streams used similar types of areas (Table 6). Debris (both over the water’s surface and partially submerged) was used extensively as cover by cutthroat trout 100 mm and longer. Larger debris (logs, rootwads or branches at least 10 cm in diameter) were preferred by larger cutthroat trout. Often this large debris created pools by catching streambed material above it and forming a plunge pool. Complex cover in the form of debris jams, rootwads, substrate and undercut banks has also been reported to be important for cutthroat trout in other areas and may be a particularly important component of winter habitat (Griffith 1979, Hansen 1977, Bustard and Narver 1975). Cutthroat trout developed social hierarchies in pools. Social hier- archies were maintained beneath overhead cover in deep water areas where cutthroat trout were "stacked" vertically in the water column. Territorial behavior was usually exhibited in the presence of visually isolating cover types. food Cutthroat trout were oj^rtunistic feeders. The most common insects in the benthos were usuaHy the most common items in the diet. Dipterans (true flies) and Ephemeroptera (mayflies) were the most common items in the diet of fish 110 mm and smaller. Trichoptera (caddisflies) and Plecoptera (stone- flies) were also consumed. Winged insects were rare in the stomachs of small cutthroat trout. Cutthroat trout used a wider diversity of food items as they increased in size. Individuals larger than 110 mm frequently used caddisflies in addition to trueflies and mayflies. Mayflies most commonly ingested were E^hemerellidae, Baetidae and Heptageniidae. The free living caddisflies Rhyacophilidae and retreat building Hydropsychidae were common in the diet. Limnephilidae, a small case building caddis was also present in cutthroat trout stomachs. Stoneflies, beetles (Coleoptera) , ants (Hymenoptera) and spiders (Arachnida) were also eaten. Winged insects became an important component in the diet as cutthroat trout increased in size. EMIGRATION OP JUVENILES Juvenile westslope cutthroat and bull trout initiated a migratory life history pattern by leaving tributaries and moving downstream into the North and Middle Forks of the Flathead River. The majority of juvenile westslope cutthroat trout leaving tributary streams continued moving downstream to the lower Flathead River and Flathead Lake. Some cutthroat trout remained in the rivers year round. It appeared the upper Middle Fork of the Flathead River (above Bear Creek) supported a larger riverine population of westslope cutthrc^t trout than either the lower Middle Fork or the North Fork. The following summarizes age composition of emigrating juveniles and timing and duration of their migration. 9 hgs. Compositi-QQ Most juveniles emigrated from tributary streams primarily at age II and III {'teble 7). The age composition of juveniles passing through downstream traps located near the mouths of tributaries corresponded closely to migra- tion classes assigned using scales from cutthroat trout captured in the lower Flathead River and Flathead Lake (Table 7). Migration classes determined from scale analyses for cutthroat trout captured in the North and Middle Forks of the Flathead River showed a higher percentage of migration class I fish (21 and 22 percent, respectively) than those (±)served leaving tributar- ies (4 percent). The age composition of Challoige Creek emigrants corre- sponded closely to migration classes assigned using scale analyses taken from fish captured in the Middle Fork of the Flathead River, suggesting that Challenge Creek suj^wrts a fluvial spawning population. These data were compared to research on cutthroat trout in other lake- river systems (Table 8). Fish which migrated at ages II and III predominated t populations, although a larger percentage of fish migrating at age I were collected in the rivers (Table 8). Age I fish may contribute a higher percQitage to riverine populations as a result of displacement from tributaries. Timing Juvenile cutthroat trout emigrated from Middle Fork Flathead River tributaries primarily during June and from NOrth Fork tributaries during June and July (Table 9 and i^^)endix A), Juvenile cutthroat may have moved out of tributary streams in May and June but our traps were inefficient or inoperable during high water. The timing of juvenile emigraticai from upper Flathead River tributaries was similar to that reported for other migratory populations of westslope cutthroat. Lukens (1978) reported that juvenile westslope cutthroat emigrated from Wolf Lodge Creek into Lake Coeur d'Alene, Idaho from early May through mid-July, Juvenile westslope cutthroat emigrated from Young Creek into I^ke Koocanusa, Montana as early as March, with the majority leaving during June and July and another peak was observed in September and October (May 1972, May and Huston 1974, May and Huston 1975). The juvenile westslope cutthroat trout emigration from Hungry Horse Creek to Hungry Horse Reservoir, Montana extended from June to August, peaking between July 1 and July 20 (Huston 1969, 1972, 1974), Ihurow and Bjornn (1978) reported juvenile cutthroat emigrated primarily during the spring from tributaries to the St. Joe River, Idaho. Several researchers have reported cutthroat trout moving downstream during the fall (Bjornn and Mallet 1964, Chapman and Bjornn 1969, Thurow 1976, May and Huston 1974, 1975, May 1972). Many of these researchers believed cutthroat trout emigrated from tributaries during the fall in search 10 Table 7. Percent (number) of cutthroat trout in each migration class trapped leaving tributaries to the Flathead River and computed from scale samples collected from the North Fork, Middle Fork, lower Flathead River and Flathead Lake for the time period 1976 to 1981. Location Years of migration Type of Data Percent (number) of cutthroat by age class at migration I II III IV Coal Creek 1977 Trap 1 36 38 25 ( 2) ( 83) ( 86) ( 57) Akokala Creek 1976- Trap T 20 56 24 1977 ( 1) ( 47) (132) ( 56) Red Meadow Cr. 1977, Trap 1 28 60 11 1979 ( 3) ( 62) (135) ( 24) Whale Creek 1977 , Trap 5 33 56 6 1978 ( 4) ( 28) ( 48) ( 5) Trail Creek 1977 , Trap 2 58 33 7 1979 ( 4) (129) ( 74) ( 15) Mainstem North 1977 , Trap 5 50 37 8 Fork 1979 ( 2) ( 20) ( 15) ( 3) Challenge Creek— 1980 Trap 21 38 41 0 (33) ( 60) ( 65) ( 0) Geifer Creek 1981 Trap 0 50 49 1 ( 0) ( 45) ( 44) ( 1) Tributary Average 4 37 47 12 (49) (474) (599) (161) North Fork of 1980 Scales 21 33 39 6 Flathead River (27) ( 44) ( 50) ( 8) Middle Fork of 1980 Scales 22 33 42 3 Flathead River (41) ( 58) ( 78) ( 6) Lower Flathead 1980 Scales 6 57 34 3 River (14) (142) ( 86) ( 8) Flathead Lake Scales 4 43 49 4 (15) (148) (170) ( 15) l_l A small tributary to Granite Creek, a large Middle Fork Flathead River tributary. 11 Table 8, Percent composition of migration classes in westslope cutthroat trout populations sampled from lakes, rivers and tributaries in Montana and Idaho. Acre at miqration Location 1 2 3 4 Source Tributaries to Flathead River—' 4 37 47 12 This study 2/ North Fork Flathead— River 21 33 39 6 This study Middle Fork Flat--'^ head River 22 33 42 3 This study 2/ Lower Flathead— River 6 57 34 3 This study 2/ Flathead Lake— 4 42 49 5 This study 2/ Priest Lake, Idaho— — 38 57 5 Bjornn 1957 2/ Upper Priest Lake— Idaho 6 35 58 — Bjornn 1957 2/ Hungry Horse Res — ervoir, Montana 6 74 19 1 Huston 1972 2/ Lake Koocanusa,— Montana 7 60 33 — May et al. 1983 2/ Lower St. Joe- River , Idaho 26 67 7 — Averette & MacPhee 1971 2/ Upper St. Joe- River , Idaho — 17 68 5 Rankel 1971 2/ St. Joe River,— Idaho — 40 59 1 Johnson 1977 Kelly Creek, 30 70 — Johnson 1977 Idaho _!/ Migration classes based on the age of emigrating juveniles passed through downstream traps. 2J Migration classes based on interpreting growth patterns from scale analysis . 12 Table 9. Niunber of days trapping occurred, number of juvenile cutthroat passed downstream through traps, and number of trapped juvenile cutthroat per trap-day by month from North Fork tributaries during 1976 to 1980 and from Middle Fork tributaries during 1981. May June July August September October North Fork Tributaries (1976-1980) Trap Days 29 42 443 424 264 131 Number of Fish 67 271 2233 541 126 5 Fish/Trap Day 2.31 6.45 5.04 1.28 0.48 0.04 Middle Fork Tributaries (1981) Trap Days — 33 78 62 14 — Number of Fish — 82 31 16 3 — Fish/Trap Day 2.48 0.40 0.23 0.21 “ 13 of suitable overwinter cover. Trail Creek, a North Fork Flathead River tributary, was the only tributary tra5^)ed during this study where relatively high numbers of juvenile cutthroat trout emigrated during the fall (Appendix A). Bjornn (1971) believed fall-winter outmigratiois from Big Springs Creek, Idaho may have been related to winter carrying capacity of upstream areas. Bustard and Narver (1975) found that cutthroat trout preferred to overwinter in sidepools containing rubble substrates and bank cover. Some salmonids altered interstitial spaces within tlie streambed as water temperatures fell below 7°C (Everest 1969, Mauser 1972, Morrill 1972). Trail Creek's lower reach (which is isolated from upper Trail Creek by a segment of dry channel located approximately 13 km above its mouth) may not provide adequate over- winter habitat and fish numbers may exceed the capacity of winter habitat. Hiere was also evidence that juvenile cutthroat trout migrated upstream into Trail Creek from the North Fork Flathead River during the spring. Johnson and Bjornn (1978) described movement patterns of westslope cutthroat trout in the North Fork Clearwater River and St. Joe River drainages, Idaho to consist of movement into upper areas of the drainage and into tributaries during the spring and early summer, little movement over the course of the summer, and then downstream movement in the fall in tributaries and the mainstem rivers. This movement pattern was also reported for juvenile steelhead in the Clearwater River drainage, Idaho (Reingold 1964). Once juvenile cutthroat moved into the North and Middle Forks of the Flathead River their movements were not as well documented. From 1979 to 1982, we tagged 2,781 juvenile cutthroat trout. Twenty-one of these tagged fish were recaptured, a return rate of only 0.8 percent. A summary of tag return data indicated that juvenile cutthroat trout generally moved in a downstream direction (Figure 1 and /^jpendix B). Uie time juvenile cutthroat trout spent migrating downriver through the North and Middle Forks to the mainstem Flathead River and Flathead Lake was variable. It appeared that some juvenile fish entered the Middle and North Forks from tributaries during the spring and early summer and moved rapidly down river to the junction of the North and Middle Forks. They then spent one to two months moving downriver to the Flathead Lake-River estuary. Other juveniles moved downriver slowly, spoiding from one to two months in the mainstem North and Middle Forks. FLATHEAD RIVER - FLATHEAD LAKE RESIDENCE When addressing juvenile to subadult and subadult to adult life stages of westslc^ cutthroat and bull trout in the upper Flathead River basin, we combined Flathead River and Flathead Lake residence because fish apparently used these two areas seasonally during their growth from juveniles to adults. The character of the 36 km portion of the Flathead River immediately above Flathead Lake changes during the year due to the fluctuating pool level (vertical fluctuations of approximately 3 m) caused by the impoundment of Flathead Lake by Kerr Dam. This 36 km portion of the river is functionally similar to an estuary and we refer to it as such. The Flathead River below the confluence of the South Fork (74 km above Flathead Lake) is considered partially regulated due to the contribution of the regulated South Fork. blVaA dO HINON 15 Figure 1. Movement of juvenile cutthroat (less than 225 mm) in the upper Flathead River Basin returns within one year 1962-1981. Daily water levels in the South Fork and Flathead River below the South Fork are controlled by Hungry Horse Dam and can fluctuate vertically as much as 2.5 meters. These releases help keep the lower Flathead River from freezing over. Juvenile, subadult and adult cutthroat trout used both the lower Flathead river and Flathead Lake because they provided a more stable environment and available food resources which allowed fish to grow at faster rates than in tributaries. Seasonal Movement The majority of the downstream migrating juvenile cutthroat trout probably arrived at the confluence of the North and Middle Forks from late August through September. Some juvenile cutthroat trout were present in the lower Flathead River (near Kalispell) throughout the year. Our data indicated that some juvenile cutthroat trout remained in the river during the first winter they arrived, and possibly loiger, before entering Flathead Lake. Juvenile, subadult and adult cutthroat trout appeared to inhabit the lower portion of the Flathead River during the winter months, probably in response to availability of macroinvertebrates. Catch per effort information provided from electrofishing showed that juvenile cutthroat trout abundance in the lower river increased during the fall and winter in both 1979 and 1980, before declining again in the early spring. We also have tag return data indicating some adult cutthroat trout moved up into the lower river from Flathead Lake during January through April, prior to the spawning season. Food Habits Westslope cutthroat trout in Flathead Lake depended on terrestrial insects during the spring, summer and fall months. Sixty-four percent of the cutthroat trout stomachs sampled during the winter were empty (six times the number of empty stomachs found during the other three seasons). A small sample of cutthroat trout (eight fish) captured in the lower Flathead River during January, 1981 were found to have full stomachs containing primarily riverine aquatic insects. Results from other studies of cutthroat trout food habits in lakes revealed that cutthroat trout consumed many different types of prey. Food habits of cutthroat trout generally related to prey type, abundance and availability as well as the species composition of the fish community. Westslope cutthroat trout fed mostly on Daphnia. terrestrial insects and aquatic Diptera in Lake Koocanusa, Montana, with Daphnia eaten exclusively throughout the winter (McMullin 1979). McMullin (1979) also reported that westslope cutthroat trout ingested very few DafAmia in Hungry Horse Reser- voir, Montana, but depended primarily on terrestrial insects and aquatic Diptera. In lakes of northern Idaho, cutthroat trout fed almost entirely on terrestrial and aquatic insects (Bjornn 1957, Jeppson and Platts 1959). Zooplankton was found to be an important food item for cutthroat trout in many western lakes (Benson 1961, Antipa 1974, and numerous studies summarized by Carlander 1969). 16 LaJS£ Distribution Cutthroat trout were found to be distributed throughout Flathead Lake. Concentrations of cutthroat trout were occasionally encountered during the spring months in the northeast portion of the lake, where the Flathead and Swan rivers enter the lake. The spring concentrations were believed to be related to increased food availability in the form of dense Dipteran hatches. Small concentrations of cutthroat trout were occasionally observed near kokanee spawning areas. Cutthroat trout may have been feeding on kokanee eggs at that time. Cutthroat trout were captured most frequently in floating gill nets set during the spring, fall and winter. The lower numbers of cutthroat trout captured in summer floating gill net sets was probably related to avoidance of high surface water temperatures (>20^C). McMullin (1979) observed that westslcpe cutthroat trout preferred temperatures less than 18°C, while Bell (1973) reported the preferred temperature range of cutthroat trout to be 9.5 to 12.9^. Floating gill net catches of cutthroat trout were associated with the presence or absence of emerging Dipterans in the spring. In areas where Diptera were hatching, large numbers of cutthroat were captured in floating gill net sets, indicating the ability of cutthroat trout to key on this available food source. ADULT SPAWNING MIGBATION Adult cutthroat trout abundance was found to increase in the lower mainstem as early as OctdDer. Adult cutthroat trout abundance was noticeably higher in the Kalispell area of the mainstem by December in both 1979 and 1980. Adults appeared to hold in the area of the Flathead River near the mouth of the Stillwater River prior to migrating upstream to spawn. During the early spring (March and April) adults moved slowly upriver traveling the 7 km between the mouth of the Stillwater River to the Steel Bridge in 40-49 days. NO similar adult cutthroat trout holding areas were found in the Flathead River above Kalispell. Early movement into the lower river and the long holding period exhibited by adult cutthroat trout may be related to food availability dis- cussed previously. Adult fish may build up energy reserves by moving into the food rich river during the winter to feed in preparation for the sub- sequent spawning migraticn. Although we have no evidence to indicate that there was any difference between sizes or ages of early versus late migrating spawners, adult cutthroat trout which moved into the lower river early tended to migrate further upstream than later arrivals. Of all adult cutthroat trout (fish larger than 350 mm) tagged in the mainstem Flathead River from 1961 through 1981, 173 were recaptured. Ninety- six of the recaptured fish were recaptured in the mainstem. Of the 77 adult cutthroat trout which left the mainstem, 41 (53%) were recaptured in the North Fork drainage, four (5%) were recaptur^ in the Middle Fork drainage, three (4%) were recaptured in the Stillwater River drainage, 27 (35%) were recaptured in Flathead Lake, and one each were recaptured in the Whitefish river and Swan River drainages (Figure 2, and 2^:pendix B). The distribution of recaptures may not accurately reflect the true distribution of movement because of differential probabilities of recapture due to both variable angling effort and tag return compliance between drainages. Adult-sized fish UV'BA dO HlNOn 18 Figure 2. Movement of cutthroat greater than 225 mm in the upper Flathead River Basin, returns within one year 1962-1981. tagged in the upper porticai of the basin were generally recaptured down river from their tagged locatican (Figure 2). It can be inferred that adult cutthroat trout moved upstream from Flathead Lake and the mainstem Flathead River to waters throughout the upper basin for spawning. The North Fork drainage obviously provided important cutthroat trout spawning habitat (Appendix B, Table B-5), Adult cutthroat trout moved slowly into the lower mainstem during the fall and winter, began moving rapidly upriver sometime in the spring, and after spawning was completed, moved rapidly back downstream to the mainstem of the Flathead River by mid-summer JVdult cutthroat trout tagged in the mainstem and recaptured in the North Fork drainage were caught in May, June and July, with the latest recapture occurring on 19 July. We believe the majority of fish recaptured were spent adults returning to the mainstem and Flathead Lake because most of these fish were recaptured after 15 June when river flows and turbidities were more conducive for angling. The fastest and furthest upstream movement recorded for an adult westslope cutthroat was 212 km in 87 days, an average of 2.44 km per day. This fish moved upstream to McLatchie Creek in the Canadian porticxi of the North Fork. SPAWNIN3 Timing aM Piste ibution Migratory adult cutthroat trout (those that grow to maturity in waters other than their natal tributaries) moved into tributaries to the upper Flathead River during the spring when streamflows were high. Spawning occur- red during May and June (Table 10), Adults left the tributaries soon after spawning, usually by the beginning of July. Previous fishery investigators studying the North Fork drainage of the Flathead River reached similar con- clusions (Block 1955, Johnson 1963). Huston et al. (1984) believed water temperature and streamflow were important cues triggering westslope cutthroat trout spawning movement and redd construction in tributaries to Lake Kooca- nusa, Montana. Residoit westslope cutthroat trout were also found to spawn in May and June. Most resident adults probably spawned within a short distance of their summer residence and in most cases probably within their "home” pool (Miller 1957) . The distribution of westslope cutthroat trout spawning within the ujper Flathead Basin is not well known; however, spawning activity has been docu- mented in several small and intermediate sized tributaries within the upper basin. Johnson (1963) also reported higher numbers of juveniles in small versus large Flathead Basin tributaries and speculated that adult cutthroat selected these small tributaries for spawning to reduce the mortality associated with a shifting streambed which can occur in large tributaries, Scott and Crossman (1973) stated that cutthroat spawned only in "small, gravelly streams". Lukens (1978) believed that a large number of spawning adult westslc^ cutthroat moved upstream from Lake Coeur d'Alene into small first order (in some cases intermittent) streams to spawn. Table 10. Characteristics of westslope cutthroat spawning including time of year, size of spawner, sex ratio and fecundity of migratory or resident stocks observed in river drainages of Montana and Idaho. CO CM CO 1^ >> ON ON iH 3 (U (U 4-) 3 n 4-1 (U o U o C c CO 4J OJ A! u o o C (U X 3 (0 cj m c CO 4-1 (U (» P4 Ph -4 o •H o m .c ^ Po « U> (U O w X rH o\ O ON eg 3 3 3 ON > CCJ ON H pp •-< *3 ^ S W W C S -H cs o vO vO 00 0 . 1 1 • • t . . X ‘H pH cs 1 1 cs O CO cs 1 0) -P • • • • 1 1 .. • • • • .. • • 1 CO CO M 5 o o • O • o . o • 1 i-H ^-4 /~s /-N o CS VO o cs lO vO (U m CO m c^ CO vO vD 00 'O’ 'O’ cs 'O’ 1 -Cf 'cr CO CO 3 1 1 1 1 1 1 1 1 1 B 3 ON vO o m 1 cs vO -cr 00 C4-4 i l-i vf m vO o <3N cs m cs 0 CO CO CO CS cs cs cs v--' .C tii p M 00 (U 0 5 3 (U 3 00 cs ■ hJ CO 3 1 1 1 1—1 CO rH rH m ch a P 1 1 1 t'' CJN m r'' CO o (0 3 1 1 1 CO CS CO CO CO CO o p 3 fo Po •3 >N Po 3 fo Po Po u P P p P P P P p P P P •H 3 O 0 3 0 O 0 3 0 0 0 o .3 P P P 3 C4-I P P PI p p p p 1 P 3 3 TO 00 3 3 3 3 3 3 3 3 P P •rl 3 P P T) P P P P »4-4 3 00 00 3 3 00 00 3 00 00 00 00 •rl •H •H 3 1-4 •rl •rl s •rl •H •rl •rl 1-4 Pi v-.' X v. / X X s ^-1 1 3 O 00 p^ 3 3 3 3 JO 3 3 3 - i=i 3 3 3 3 is 3 3 3 00 •H •rl 3 3 3 3 X 3 3 •S S5 •o 1 •-3 1 •o 1 •o 1 3 3 Hj X 1 B 3 P Jo JO Jo Jo P P Jo Po •H O. 3 3 3 3 3 3 3 H W 3 X X S X r4 r-H X X 3 •> 3 1 41 3 0i 0i .1 P 3 iH P P P 3 3 A 3 < 3 3 3 CO cnl 1— 1 3 P - P > P>; > 3 (b pH 00 CJ X 3 •H •rl •rl 41 3 3 3 > Pi pej Pi 3 3 p 3 3 P •rl 3 3 2 3 O 3 o P •H 3 00 3 Pi 3 •a c -3 3 XI 3 P O 3 X •rl 3 3 X 3 OC 3 3 3 3 3 3 CJ O 3 O P 3 O O 0 3 0 3 3 P 0) P (U P PI P Jo > TJ P r4 CJ 44 O 44 3 44 3 44 3 44 3 00 3 P P 3 3 X 3 •H P O P O P O 3 3 O 00 3 XJ O M-4 3 X X 3 3 X 3 X 3 X 3 41 X 3 3 3 X rH 41 H . M P rH rH fH O eg 3 3 3 O 3 P Q JP pH PC Pi 44 :s 1-4 CO 20 Table 10. (Continued). a ><3 c. c 3 0 P- 3 O C in 1-1 1-1 l-l 00 c O to 3 O o« c/1 •r-1 OV rC ’t-JOV PQ '—4 H Pq r-H > 4J •r ■o 0 1 1 3 1 1 O 1 1 0) F*4 to vO o • • X •H CO pH (U 4J • • «« CO (0 o o • • pH /“N o (U CO GO 1 •sT /~v C 1 1 s CO 1 VO iw g Vj m O W v-^ CN V— ^ CO GO cu c e 01 OJ 3 GO ►J CO CO 1 a 1 -O' CO (U 1 CO > o tH 'U p l-l 1-4 CO u o O •H 01 •M 4-1 rC 4J CO cO 1 4J U 1-4 (U CO GO GO 14-1 a •H •H •H s X 4-3 01 Po tw c cO O GO ?o o a 4J ►o GO "H •rH 1 01 in Q 6 > rH H CM •H 3 *H •H o 4J 14-4 •R ct, O a 01 H CO cO < pq #1 M 01 01 .i«5 4»5 -H CO 01 a OJ 4-3 01 GO 0 1-4 01 O CO ■U 43 U O 43 s CO cO cO H 01 T3 •a 'T3 cd •rH H P * H M O 4-4 3 a pq CO to c i- cn c: »r“ C 2 (O Q. t/) cr> ■a c ca o cr> i-H "O c n3 O • CO VO rC to •-I AJ Oi GO 1— ^ oj c C QJ O O r— i -4-3 S ^ CO O to M o cn flH rH <|cvj|ro| 21 Characteristics Qt AdultS. Hhe minimum size at maturity of westslope cutthroat trout captured in Flathead Lake during this study was 349 mm. We assumed that adult cutthroat trout which follow an adfluvial life-history pattern were generally larger than 350 mm. Block (1955) and Johnson (1963) reported similar minimum sizes for migratory adult cutthroat trout in the Flathead Basin (Table 10). Huston (1973, 1972, 1969) and Huston et al. (1984) reported similar sizes for migra- tory adults in Hungry Horse Reservoir, and Lake Koocanusa (Table 10). Migra- tory adults in the Lake Coeur d'Alene, Idaho system were slightly smaller (Lukens 1978). Tbe sex ratio of mature cutthroat in Flathead Lake averaged 1:2.2 (males; females) which was similar to average sex ratios reported in other areas of Montana and Idaho (Table 10). No fecundity estimates were conducted for cutthroat trout during this study; however, we assumed fecundities were similar to those reported by Johnson (1963) and Huston (1972). i^roximately 1,000 eggs per westslope cutthroat female were collected at the Murray Springs Hatchery from 1980 to 1982 (files, Murray Springs Hatchery, Eureka, Montana). These fish were Hungry Horse Reservoir (which impounded the South Fork Flathead River) stock. During this study, no conclusive data were collected to identify homing ability, repeat spawnings or spawning mortality associated with adfluvial spawning adults, Huston et al. (1984) found that approximately 70 percent of the 1977 spawning run into Young Creek from Lake Koocanusa homed accurately. Huston (1972, 1973) identified 24 percent of the 1970 spawning run into Hungry Horse Creek from Hungry Horse Reservoir as being repeat spawners and believed alternate year spawning was occurring. Huston et al. (1984) docu- mented 0.7 to 2.9 percent of the 1974 to 1977 westslope cutthroat trout spawning runs into Young Creek were repeat spawners. An estimated ten to twenty percent of the spawning adults ascending Young Creek were believed to be repeat spawners (personal communication, Bruce May, MDFWP, Kalispell, Montana). Data on gonad condition of mature sized (>350 mm) westslope cutthroat trout captured in gill nets set in Flathead Lake suggested alter- nate-year spawning was prevalent. The potential for spawning mortality is high. Huston et al. (1984) found that post-spawning mortality ranged from 27 to 60 percent between 1970 and 1977 in Young Creek, a Lake Koocanusa tribu- tary. Pl^y-Sical Charag-teriatics oL Spawning sites Cutthroat trout spawned over streambed areas composed predominantly of gravels ranging in size from 2 to 50 mm (Table 11). Size of redds averaged 0.9 to 1.0 m long by 0.4 to 0.45 m wide for migratory cutthroat and 0.6 m long by 0.32 m wide for resident cutthroat. Average water depths over redds ranged from 17 to 20 cm and average water velocities ranged from 0.30 to 0.37 mps. Adult cutthroat trout which moved from Lake Koocanusa into Young Creek generally spawned at the lower end of pools in water averaging 25.6 cm deep, over a streambed consisting primarily of gravel (25 to 76 mm in size) (files, Montana Department of Fish, Wildlife and Parks, Kalispell, Montana). Scott and Crossman (1973) report^ that cutthroat trout redds were approximately 0.30 m in diameter and eggs were covered by 150-200 mm of gravel. 22 0) o CN O 'a' r' o CO n '3' 00 ro CO m in 'tj* CO •4-> (C W ^ •* 5-< ^T3 § S in CN C" (N l§ a « to rH g “H +j CO T3 rH QJ (d I 23 GROWTH Scale samples were used as the primary method to estimate growth. CXitthroat trout emerged as fry at a length of approximately 20 mm and grew 20 to 40 mm during their first year. Scales first formed on cutthroat trout at lengths of 38 to 44 mm. Scales were not found to cover the entire body surface until fish were 63-68 mm (Brown and Bailey 1952). Cutthroat trout that had not formed scales or had only one or two growth rings (circuli) by the beginning of their first winter did not form annuli (yearly growth marks) . An estimated 61 percent of the cutthroat trout sampled for age-growth analysis from the upper Flathead basin had not formed a first year annulus, similar to results from the North fork Clearwater and Upper St. Joe rivers, Idaho (Table 12). A smaller percentage (30-40%) of scales examined from cutthroat trout collected in the mainstem Flathead River and Flathead Lake were missing a first year annulus, comparable to percentages of missing annuli observed in the lower St. Joe and Salmon River basins. The differ- ence between the percentages of cutthroat trout missing a first annulus in Flathead River and Lake versus the upper portion of the basin may be caused by one or more of the following reasons; 1) the presence of slower growing resident cutthroat trout contributing to the sample from the upper basin; 2) colder water temperatures in upper basin tributaries slowing growth; and 3) the contributicxi of cutthroat trout reared in the Whitefish and Stillwater river systems to the sampled population from the main river and lake. Growth of cutthroat trout in ujper Flathead tributaries was generally similar between tritutaries and differences were likely caused by differences in thermal regimes (Appendix C). Juvenile cutthroat trout grew to average lengths of 45-63 mm, 90-110 mm, 130-150 mm by the end of their first, second and third years of stream residence, respectively (Table 13 and Appendix C). Growth appearred to be slower in the present stucty for North Fork tributaries than growth described by Johnson in the early 1960's, especially between ages II and III (Table 13). This difference may have been due to consistent bias in scale reading, the difference between scale length-body length relation- ships used during the two studies, or a change in growth rates. After emigrating from natal rearing tributaries cutthroat trout grew an average of 89 to 119 mm compared to an average of 40 to 60 mm for similar years in tributaries (Table 14). After the initial burst of growth the first year after emigration from tributaries, yearly growth slowed slightly to average between 44 to 90 mm. Growth appeared to slow as fish reached sexual maturity (age V and older). Tsblc 12» ChsiTflc tGiris t ICS of scfllcs 3nd Icngtli 3t scslc fonnstion forWGstslopc cuttliTost trout in river drainages of Montana and Idaho during their first year. (U 00 cfl .s CO O 00 CO CO •H S 5^ 4-1 CO CO >-l p •H I— I C4-C P c cu o iH •H CO U O CO CO g 4J O •< i*-( Xl 3 u cn H X) 3 4J CO CO •rl rC H rN. er> cu cu ti4 a CO X 4J 4-) CU CU > < CO 43 AC /-s •U C cu 1-1 O •H AS O |ii CO CO 2; B .H (U ■H TO T3 X3 X> C cO "3 CO CO -3 4-1 4-1 CU CO X) CO > . rH C I— I ’H 1^4 CO Pd 1^ 44 CO 0\ '■D I VO 00 'O' I OV CN r>. A A VI VI 'O' m 'O' vD OV VO CO 'T I 00 CO VO 'O' I CNJ 'O' p'' 0\ (U 4«S Pi CN CO CN 00 r' ov CO •I-) CO vO vO CJV CTV C3V CO f'' r-4 <-a pH CTi O ct •ro 3 < X S hJ M (U 44 CO £ g CO *-3 CU 03 cu rH • 0 0 CJ 44 3 44 X X CO 0 CO • E 03 • • pH X i-H •H 44 44 • 3 3 CO C/1 Z 3 CO Ph CO o m • • • o o '0' o sr VO CO vO vO I CN ov 1 CN 1 CN 1 1 rH I CO 1 1 1 VO 1 CO O VO m 00 % CO >4 3 CU o CJ V CO r' cu 44 CO E cn 03 C CO 3 O X 03 U3 CO p; 25 Table 13. Back-calculated lengths at annulus formation of westslope cutthroat trout in the upper Flathead basin and other rivers and tributary streams in Montana and Idaho (adapted from Lukens 1978) . Age Drainage (N)^^ 1 2 3 4 5 6 7 Rivers Mainstem Flathead 250 55 103 157 242 305 336 381 River (1981) Main rivers of 559 56 119 196 287 333 378 Flathead drain- age (1963) North Fork Flathead 197 54 97 138 166 214 River (1977-80) Middle Fork Flat- 183 60 110 164 223 275 head River (1979-80) South Fork Flathead 113 59 108 155 206 273 323 River (1981) Salmon River (1963) 474 60 100 174 254 322 371 — St. Joe River 347 66 101 153 212 251 306 (1971) Tributaries North Fork Flat- 106 58 114 178 216 244 302 ... head tributaries (1963) North Fork Flat- 1,820 54 100 145 189 247 head tributaries (1977-81) Middle Fork Flat- 880 54 100 149 205 254 293 head tributaries (1980-81) Hungry Horse Cr. 1,239 73 121 162 — — — — (1969-72, 74) Young Creek 92 49 109 160 (1974) St. Joe tribu- 161 72 142 216 taries (1963) 26 Table 13. (Continued). Drainage (N) 1 2 3 4 5 6 7 Wolf Lodge Cr. (1978) 324 73 111 136 185 — — — Kelly Creek (1977) 208 66 101 153 212 251 306 Priest and Upper Priest Lake tributaries (1957) Lakes 232 85 129 171 201 254 Flathead Lake (1962-81) 573 64 120 189 261 311 350 382 N equals sample size for age 1. Age 2 through 7 sample sizes were likely lower . 27 Table 14. Mean calculated total length growth increments (millimeters) for westslope cutthroat trout that entered Flathead River and Flathead Lake after spending one to four years in tribu- tary streams. Fish were collected during the years 1962 through 1982. Length increments (mm) between annuli tributary (n) I II III VI V VI VII Flathead River 1 { 14) 56 89 90 • - 2 (142) 57 53 119 58 35 28 -- 3 ( 86) 50 41 53 99 56 33 49 4 ( 8) 56 40 46 54 100 45 41 Flathead Lake 1 ( 15) 56 98 76 55 61 39 — . 2 (148) 65 56 99 63 46 33 -- 3 (170) 61 49 50 95 55 39 39 4 ( 15) 64 53 47 49 91 44 -- 28 BULL TROUT STOCK ASSESSMENT Most bull trout in the Flathead Basin are adfluvial. Possible excepticais were found in Hay Creek and several streams draining large lakes in Glacier Park, Hay Creek flows through a boggy meadow near its mouth and may be difficult for adfluvial adult bull trout to ascend during most years. Kintla, Loggingr Harrison, Cyclone, and McDonald creeks may provide spawning and rearing habitat for bull trout which mature in lakes within each of those drainages. EMBRYONIC DEVELOPMENT Terminology used in this portiai of the report is defined in the WESTSDOPE CUTTHROAT TROUT section. jggg Deposition through Hatching Bull trout required approximately 350 temperature units (®C) after fertilization to hatch (Weaver and White 1984). This was similar to the incubation period for Dolly Varden (380 temperature units) documented by Armstrong and Blackett (1980). Hatching is completed after 100-145 days, usually at the end of January (Weaver and White 1984, Allan 1980, Blackett 1968, Heimer 1965) (Table 15). Laboratory investigations reported incubation periods of 126 days at 2^ and 95 days at 4°C (McPhail and Murray 1979). •feble 15. Temperature units, days required, and approximate dates for eye up, hatch, and emergence of bull trout embryos and alevins in field and laboratory conditions (adopted from Weaver and White 1984) . Stage of development Temperature units (°C) from fertilization Number of days from fertilization Approximate date Field Eye up 200 35 October 17 Hatch 350 113 January 3 Emergence 634 223 April 22 Laboratory Eye up 366 42 November 1 Hatch 504 62 November 21 Elnergence 825 103 January 1 29 Approximately 40-50 percent of deposited bull trout eggs survived through hatching in excavated redds (Blackett 1968, Allan 1980). McPhail and Murray (1979) reported egg to fry survival varied in different water temper- atures. They found 0-20, 60-90 and 80-95 percent of the eggs survived to hatching in water temperatures of 8-10, 6, and 2-4°C, respectively. Sediment affects bull trout egg survival as it does other salmonids. The preliminary work of Weaver and White (1984) demonstrated that approxi- mately 15 percent of the fertilized bull trout eggs survived to hatch in laboratory channels with a spawning substrate containing 30 percent material less than or equal to 6.35 mm in diameter (Table 16). Table 16. Number and percentage survival of bull trout embryos in various substrate mixtures in laboratory channels (unpublished data, Montana State Cooperative Fisheries Research Unit, Bozeman, Montana) . Gravel mixture Percentage of <6.35 irm : >2.0 mm s.ur.viving-eiiib.ry.05^ 50 • • 29 0 40 • 23 1 30 • « 18 21 20 • • 12 38 10 • • 6 48, 0 • • 0^ 38* ^ Based on number of eyed eggs placed in channel estimated from percent of eyed eggs alive in Heath trays. ^ One control channel had 17.5 percent of planted embryos, which could not be accounted for. Hatching Eiy Emergence The period of hatching to fry emergence may be divided into two periods for bull trout; 1) alevin growth and 2) fry growth prior to emergence from the gravels. Anadromous Dolly Varden and bull trout alevins required at least 65-90 days to absorb their yolk sacs. Unlike cutthroat trout, bull trout remained within the interstices of the streambed as fry for up to three weeks before filling their air bladders (McPhail and Murray 1979). Parr marks developed and feeding began while fry were still in the gravel. Bull trout reached lengths of 25-28 mm before emerging from the streambed and filling their air bladders. STREAM RESIDENCE Habitat used by juvenile fish was analyzed for fish smaller than 100 mm and fish larger or equal to 100 mm. Food habits were analyzed for fish smaller than 110 and larger or equal to 110 mm. Comparative data was often available only by age of fish rather than size of fish and is reported as 30 such. An age 0 fish was in its first summer of life, and age I fish had completed one full year and was in its second summer of life. Distribution in Stceams Bull trout were present in 63 (71%) of the 89 surveyed tributaries, but their distribution within these streams was often limited. Bull trout were present in only 50 percent of the stream reaches where fish were observed. Most streams containing bull trout also su^Jorted cutthroat trout. Two exceptional areas supporting only bull trout were Paola Creek and a section of Kintla Creek above a barrier falls. Accessibility of stream reaches to spawning adults influenced, but was not the only factor limiting the distribution of bull trout. Juvenile bull trout were found in areas inaccessible to spawning adults in Yakinikak, Challenge, Dodge, Skyland, Basin and Bowl creeks. Apparently juveniles moved upstream for rearing in these streams. Water temperature also aj^ared to influence juvenile bull trout distri- bution in the Flathead River Basin. Streams such as Akokala and Camas creeks supported populations of cutthroat trout but were not used by bull trout even though they were accessible and contained apparently suitable habitat. Max- imum mcaithly water temperatures in July and August approached 19°C in Akokala Creek and 25°C in Camas Creek compared to 15 to IS'^C in other streams where bull trout were present. Reaches containing high densities of juvenile bull trout were frequently influenced by cold perennial springs. Higher bull trout densities were observed in areas where water temperatures were 12°C or less. Bull trout distribution in other drainages were also believed to be influenced by cold perennial springs (Oliver 1979, Allan 1980). Bull trout densities were usually lower than cutthroat trout densities in Flathead tributaries. Ihis was attributed in part to underwater census techniques often being less efficient for bull trout (Shepard and Graham 1983). However, higher densities of bull trout were observed in Flathead tributaries than other drainages where underwater census ing was used (Table 17), but were lower when compared to electrofishing estimates (Table 18). Bull trout were observed more frequently in third and fourth order tributaries to the upper Flathead River, although densities of juvenile bull trout were highest in second and fifth order streams (Table 3). Platts (1979) reported bull trout abundance increased as stream order decreased in tributaries to the South Fork Salmon River, Idaho and bull trout were not seen in any fifth order streams. Juvenile bull trout used all sizes of pools, riffles, runs, and pocket- waters in streams in the upper Flathead drainage. Bull trout numbers increased, but densities did not, as the size of habitat units increased. Most age classes were found in similar densities in pools, runs, riffles and pocketwater (Table 19). Juvenile bull trout in Flathead tributaries appeared to be more ubiquitous in their use of habitat features than juvenile bull trout and Dolly Varden in other drainages (Table 20). 31 Table 17. Mean density of bull trout observed by snorkeling in tributaries to the Flathead and Idaho river drainages. Includes only those tributaries where bull trout were observed (N = number of tributaries) . N Mean density Age 1+ f ish/lOOm^ Range of densities f Ish/lOOm^ Drainage Source 63 1.3 0. 1-7.1 Flathead This study 3 0.22 0.05-0.65 Salmon Sekulich 1978 2 0.003 <0.01 Saint Joe Thurow and Bjornn 1977 5 0.49 0,10-2.17 Lochsa Graham and Bjornn 1976 3 0.34 0.19-0.63 Selway Graham and Bjornn 1976 1 0.89 Bear Valley Cr. Petrosky, un- pub. data 2 0.03 0.16-0.01 Salmon Konopackey , un- pub. data Table 18. Mean densities of bull trout estimated from electrofishing in the Flathead and the Toboggan, MacKenzie and Wigwam drainages of British Columbia. N Mean estimated density fish/100 Range of estimated density fish/lOOra^ Drainage Source 7 5.4 0.1-15.5 Flathead This study 3 11 1-31 Toboggan Tredger 1979 3 14 1-39 MacKenzie & Hill Ptolemy 1979 32 Table 19. Mean densities of age 0, age I, age II, age III, all bull trout and age I and older bull trout in pools, runs, riffles and pocketwater of the upper Flathead River basin (1979-1981). Habitat unit Age Pools (394) Runs (637) Riffles (574) Pocketwater (188) 0 0.3 0.3 0.1 0.1 1 0.6 0.5 0.5 0.1 2 1.6 0.4 0.3 0.4 3 0.4 0.2 0.1 0.2 All bull trout 5.2 2.2 1.8 1.2 Age 1 and 4.6 1.7 1.3 1.1 older Table 20. Flow pattern or habitat units used by juvenile bull trout and Dolly Varden in streams of Montana, British Columbia and Alaska. Flow pattern Drainage Citation All habitat units Flathead, MT This study Rolling or broken flow Wigwam, B.C. Oliver 1979 Pools MacKenzie, B.C. McPhail St Murray 1979 Runs Toboggan, B.C. Tredger 1979 Shallow riffle (age I) Price of Wales Island Alaska Cardinal 1980 Pools (age II, III) Prince of Wales Island Alaska Cardinal 1980 Side pools, eddies Hood Bay Cr., Alaska Blackett 1968 Riffles, pools Hood Bay Cr., Alaska Armstrong and Elliott 1972 Riffles Sukunka, B.C. Stuart and Chrlslott 1979 Riffle-glide MacKenzie, Hill Creeks B.C. Ptolemy 1979 33 HaMtat Used Entail KlOO mm) Bull Trout Small juvenile bull trout «100 mm) were most often observed closely ^sociated with instream cover in the form of streambed material (cobble and boulders) and submerged fine debris. These cover types provided small pockete of slow water (average velocity of 0.09 mps) allowing fish to hold positions with little energy expenditure (often immediately above the stream- bed) near high velocity, food bearing water. Juvenile bull trout and Dolly Varden were reported to use similar cover types and water velocities by researchers working in other drainages (Tables 21 and 22). Small juvenile bull trout were able to use any site above the wetted stream bottom where suit^le cover was available. Their use of streambed material for cover permitted them to use a much wider range of sites than cutthroat trout utilized. Small bull trout were located immediately above, on, or within the streambed (mean distance above the streambed = 0,03 m). Turning over stream- bed material was often the only way to locate small bull trout. Oliver (1979) and Griffith (1979) also reported finding bull trout within the streambed. When bull trout densities were compared to streambed composition for all reaches surveyed in the Flathead drainage, the highest densities were ob- served in streams with a streambed predominated by gravel and cobble. How- ever, at the microhabitat level, small bull trout were generally observed over small sized substrate (silt and sand) which had accumulated behind water vel^ity obstructions used as cover. A comparison of streambed compositions used by juvenile bull trout in the Flathead with that used by juvenile bull trout in other drainages was difficult due to the different methods used to (^scribe substrate composition? however, since substrate appeared to be an important habitat component, we presented a comparison usinq broad size classes (Table 23). Large ,(100-200 mml Bull Trout Juvenile bull trout 100 mm and longer were associated with the stream ^ttom, using dispersed instream cover and small pockets of slow water. As • grew they used faster water (0-0.12 mps) and were located higher :m toe water column (0.08 m above the streambed) in deeper water (0.45 m mean depth). Little comparative data was available for bull trout 100 mm and larger (Table 22). Griffith (1979) observed age II bull trout in water SliSSia^^ ^ ^ Silverhope Creek, British Larger juvenile bull trout were associated with large submerged debris, which may be dispersed or in complex pooling structures (debris jams) similar to areas where cutthroat were observed. Bull trout 100 mm and larger were either directly under cover or in open areas (often not associated with the 34 Table 21. Cover used by juvenile bull trout and Dolly Varden in streams of Alaska, Montana and British Columbia. Species Cover type Drainage Source Dolly Varden Debris (coarse, under- cut banks, fine ob- structive) Tye-one-ohn, AK Little Toad Three Mile Cardinal 1980 Substrate Silverhope, B.C. Griffith 1979 Debris Toboggan, B.C. Tredger 1979 Bull trout Undercut banks Mackenzie, B.C. Ptolemy 1979 Fine debris, sub- strate Flathead, MT This Study Substrate Wigwam, B.C. Oliver 1979 35 4-1 •rl • O O iH 0% (U > na +j C -H (Q ^ <4-1 ,G -H 4J ).( a O (U TJ a iH to V4 00 a o -o tJ C CO CO •tJ CO CO "H (U ^ g 4-> P CO iH iH O fi-i CJ (U rC XI CO 4J •rl 4-1 iq •rl •H pq 4-4 3 V1-* O o M 4J CO 0 rH to rH cu 3 1-1 X 4J CO 3 3 o •i-j P4 4J So X iH rH TO 3 (U rO CO 3 CU iH >N •rl 4J c •H 0) O > O 3 iH •I-) (U > CH O TU c CO CO cu }-( X 3 u CO a, cO cu cu Q 0 CN CM (U r-| ,Q to H (U CJ )-4 3 O CO o> 0^ 0\ ON o^ 1^ ON ON ON ON 1— ( ON ! w I 0) oo CO c •H to a • • • u u CJ . . • pq pq pq CJ pq’ • (1) d) C 'H -H CO N N bO CD 0) O « « ua CJ o O to CO H s ^ cu cx o rC V4 (U > CO c CO 00 00 o H 'O to (U X 4-1 to 1^ T) to (U ,c 4J CO I— I (U oc fo >N + + H M o o 1^ l-l M MH IW M o t-H o + 1— 1 V A 1 o m cn i-H (D CD ociic 0 ua • o 1 m o o o o ON 1/N CM CM O >3- r-4 o o I O II o cd'^ • • o o I O II o • IX o -C 4-t /-N a 0 'cr n 1^ u*i CM • • • • • 0 O O O — I 1 I I I I CM >-i m CM »cf • • • • • o o o o o O CO 00 CO o o I 00 II o • IX o 'O- m On >3- o o I O II IX (0 (U u 3 CO to cu 0 CO 1-1 cu a cu CJ 4-t to 4J •rl jq to o 36 Table 23. Substrate associated with juvenile bull trout in British Columbia and the Flathead. 0) 00 CO G •H CO Q 00 1^ CTi 01 C/3*.H I ON ON •H ON <3N Vn 43 r>. f'. O ON ON ■o ON ON ON ON ON ON 3 (0 (0 •H 43 H 43 43 P •H >N M p S (U p O 00

P Ip 3 O (U Tl 'H p p p p p W Ph H O O O O m o CM I I u-i m m l/N O CM NO m o CM cn I I m CO m lo fH CnJ fH •H SB •.9 0) a ‘H CO N oo c 00 01 o ui 43 a O CO H s C - CO 43 OO P OO 0) O > 43 tH O -H 0) 0) Q. O. O O 0 CO 0ii -o G CO 'H CO CO to rs 'O 73 QJ 0) •H O O 0) 0) o. o. M (0 >N CM !>n CO fH iH no iH iH 43 0) iH 0) 43 (U .a > 3 > 43 p 0 CO 0 CO 0 p CO f— 1 u M 43 P U (U P (U 00 00 ns p > Nd o lO o o nO nO iH (0 CO NO NO 1^ m NO nC 3 43 p rp 0) rH O 3 O 0) ns iH 73 (U 43 CO > C 43 3 > CO CO 43 CO CO P CO 3 CO P o SB o TO CO (U 43 P CO fp fp >Ncn ON ON 43 p •H •H P CJ 0 O P TO 0) p a CO tJ < 37 streambed) of pools. Individuals directly under cover held their positions even during disturbances. Bull trout in open areas of pools reacted quickly to disturbances by moving under cover. .good Habits Bull trout less than 110 mm were opportunistic feeders. Ephemeroptera (mayflies) and Diptera (true flies) were the most abundant aquatic insects in benthic sanples and the most common food item in bull trout stomachs. Qiironomids, a type of true fly, were the most abundant and frequently used food item. Heptagenid and Baetid mayflies were also commonly used foods. Juvenile bull trout greater than 110 mm were more piscivorous. Sculpins and other bull trout have been identified in juvenile bull trout stomachs. Fish were increasing consumed during the fall months. Horner (1978) also found bull trout to be highly piscivorous. EMIGRATION OF JUVEMILES Juvenile bull trout initiated a migratory life history pattern by leaving tributaries and moving downstream into the North and Middle Forks of the Flathead River. Virtually all juvenile bull trout moved downstream through the Flathead River to Flathead Lake, The following will summarize the age compositicsi of emigrating juveniles and the timing and duratiai of their migration. ComBOSiti-QD Juvenile bull trout emigrated from upper Flathead River tributaries primarily at age II (49%) with smaller percentages outmigrating at age I or III (18 and 32%, respectively) (Table 24). Juvenile bull trout were also found to emigrate from rearing areas in tributaries from ages I to III in systems draining into large lakes in Idaho and British Columbia (Bjornn 1957, Oliver 1979, McPhail and Murray 1979). Oliver (1979) found that juveniles in Ram Creek, a small tributary to Wigwam River, in the Kootenay River drainage, British Columbia, emigrated at age I and II (primarily age II), while juveniles emigrated from the Wigwam River primarily at age II and III, Bjornn (1957) was able to recognize migration classes using scales from bull trout in the Priest Lake drainage of Idaho. Migration classes for bull trout captured in Flathead Lake were difficult to assign by idaitifying changes in growth from scale samples. This difficulty may be related to the wide variety of growth environments and food utilized by juvenile bull trout during their migration to Flathead Lake. Timing Juvenile bull trout emigrated from tributaries to the North and Middle Forks of the Flathead River primarily during June and July (Table 25 and Appendix A). Timing of emigration was similar to cutthroat juveniles. Since we were unable to effectively trap during high spring flows, we could not document the numbers of juvenile bull trout emigrating during May and early June. Oliver (1979) reported that juvenile bull trout emigrated continuously 38 Table 24. Percent of age I, II, III and IV bull trout emigrating from tributary streams. Years Type Percent (number) of bull trout of of by age class of migration Location migration data I II III IV Red Meadow Cr. 1973, 79 Trap 6 76 18 0 ( 3) ( 42) (10) (0) Trail Creek 1977, 79 Trap 34 43 19 3 (41) ( 52) (23) (4) Geifer Creek 1981 Trap 0 37 63 0 ( 0) ( 26) (45) (0) Average 18 49 32 2 (44) (120) (78) (4) Table 25. Number of days trapping occurred, number of juvenile bull trout passed downstream through traps, and number of trapped juvenile bull trout per trap day by month from North Fork tributaries during 1976 to 1980 and Middle Fork tributaries during 1981. June July August Sep tember October North Fork tributaries (1976-1980) Trap days 42 443 424 264 131 Number of Fish 42 709 340 116 6 Fish/trap day 1.00 1.60 0.80 0.44 0.04 Middle Fork tributaries (1981) Trap Days 43 74 62 14 ... Number of Fish 60 28 19 8 — Fish/Trap Day 1.40 0.38 0.26 0.57 — 39 throughout the summer-fall season in the Wigwam drainage, British Columbia. Using circumstantial evidence, McPhail and Murray (1979) suggested two down- stream migrations of juvenile bull trout; 1) a spring migration of newly emerged fry, and 2) a fall migration of "larger 1+ and 2+ individuals". Juvenile bull trout movement through the Flathead River system to Flat- head Lake is not well understood. We tagged 618 juvenile bull trout during the study and only two (0.3%) were recaptured. Very few juvenile bull trout were observed during underwater counts (or captured by anglers) in the North and Middle Forks. We speculated that the majority of the outmigrating juvenile bull trout moved quickly downstream through the river system during the summer. When juvenile bull trout were observed in the two forks they were often found alaig the river margins, FLATHEAD RIVER - FLATHEAD LAKE RESIDENCE tipyeipeat. Limited data suggested juvenile bull trout probably moved downriver into the mainstem Flathead River during the same time period as juvenile cut- throat, from August through September. Juvenile bull trout appeared to inhabit the partially regulated portion of the river throughout the year before moving into Flathead Lake. It is possible that some bull trout reside to maturity in the lower river. Fourteen bull trout 200 to 400 mm tagged in the main river were recaptured. Ten of these fish were recaptured in the main river (9 moved less than 4 km), three were recaptured in the lake and one moved up into the North Fork of Flathead River (^pendix B), Food Habits Bull trout were found to be highly piscivorous and opportunistic pre- dators, eating whatever species of fish available. Bull trout in Flathead Lake fed primarily on fish (fish were found in approximately 91 percent of the bull trout stomachs which contained food). The three whitefish species were the most important year-round food item. Food habits varied seasonally with the meet important food items being kokanee during the spring, yellow perch in the winter and lake and mountain whitefish during the summer and fall. Scavenging fish viscera discarded by anglers may be an important summer food source for bull trout in Flathead Lake. Approximately 40 percent of the bull trout stomachs examined were empty. Bjornn (1957) observed a similar percentage of empty stomachs from bull trout captured in Priest and tpper Priest Lakes, Idaho. Small bull trout (<300 mm) in Flathead Lake fed extensively on slimy sculpins, while larger bull trout (>550 mm) used kokanee and whitefish almost exclusively for food. On the average, bull trout were able to consume prey that were approximately 43 percent of their own length. Bull trout in other inland Northwest lakes were found to feed primarily on fish. Bjornn (1957) found that bull trout fed heavily on kokanee salmon in Priest Lake, while v/hitefish were more heavily utilized in Upper Priest Lake, probably because kokanee were less abundant in Upper Priest Lake. More recently, mysids were found to be the most important bull trout prey item in Priest Lake, probably 40 due to the decline of kokanee and whitefish populations (Rieman and Lukens 1979). In Lake Pend Oreille, Idaho bull trout fed mostly on kokanee salmon (Jeppson and Platts 1959). Subadult bull trout captured by electrofishing in the Flathead River were frequently found in areas of high yearling whitefish density, suggesting whitefish may be an important food item of bull trout in the Flathead River. Horner (1978) found that bull trout were highly predacious in Big Springs Creek, Idaho with nearly 100 percent of their stomachs containing fry. OistributiQn Catches of bull trout in gill nets were generally largest in the north end of Flathead Lake during 1980 and 1981 agreeing with earlier findings of Hanzel (1970). Bull trout catches during August were highest in sinking nets set in water deeper than 14 m corresponding to the lower end of the thermo- cline with temperatures of 15®C or less. Summer distribution of bull trout in Flathead Lake appeared to be dependent upon availability of prey in the form of whitefish and water temperatures, but this relationship did not hold through the fall. Bull trout continued eating whitefish even though peamouth were the most abundant prey species at the depth (and temperature) zone inhabited by bull trout. ADULT SPAWNIN3 MIGRATION Migration of adult bull trout into the mainstem Flathead River from Flathead Lake began in April and peaked during May and June when river flows were high. Adult bull trout spawners apparently moved slowly upriver through the spring and early summer, arriving at the North and Middle Forks sometime in late June through July. We believe adult bull trout held in the mainstem North and Middle Forks, probably near the mouths of their spawning tributary destinations, for up to a month. During this time, feeding was believed to be limited, although anglers reported capturing a few adult bull trout whose stomachs contained fish (personal communication, Lee Secrest, Polebridge, Montana) . Adults entered the tributary streams from late July through September with the majority moving into tributaries during August. These adults held in areas of the creeks with abundant cover (deep pools, log jams, undercut banks, etc.). Dunn (1981) found that large pools with abundant cover were important holding areas for adult steelhead trout in Wooley Creek, Califor- nia. Adult bull trout aj^ared to migrate primarily during the night in Flathead River tributaries similar to adult bull trout in tributaries to the L^^r Arrow Lakes (McPhail and Murray 1979). After spawning was completed, adults remained on the spawning grounds for a very short time, then moved rapidly out of the tributaries. Upon reaching the river, adults moved rapidly back down to the lower river and lake. There was some evidence from anglers to indicate adult bull trout may initiate feeding on spawning concentrations of mountain whitefish during their migration back down to the lake (personal communication, John Fraley, Montana Department of Fish, Wildlife and Parks, Kalispell, Montana). 41 Three of six adult bull trout (>450 mm) tagged in the lower mainstem of the Flathead River were recaptured in the North Fork, but all were recaptured more than eight months after the tagging date. Seventeen adult bull trout tagged in the North Fork drainage and one tagged in the Middle Fork drainage were recaptured in the mainstem Flathead River, while 28 adults tagged in the North Fork drainage and two tagged in the Middle Fork drainage were recap- tured in Flathead Lake (Figures 3 through 5 and Appendix B). The longest documented movement was 223.6 km by an adult bull trout which was tagged 31 August, 1976 moving out of Howell Creek, a North Fork tributary in Canada, and recaptured 22 January, 1978 in Flathead Lake at Blue Bay. llie longest movement documented in the Middle Fork drainage was 207.6 km by an adult bull trout which was tagged 4 Septeniber, 1980 in Granite Creek (a Middle Fork Flathead River tritwtary) and recaptured on 19 July, 1981 in Flathead Lake near Big Arm, SPAWNIN3 Timioa snd Bistribution Adult bull trout in the uf^jer Flathead River spawned during a relatively short time period in the fall, primarily in September and October. Other populations of inland bull trout in the Northv^est have been reported to spawn at a similar time of year (Table 26). Timing of spawning activity in the upper Flathead River basin was believed to be initiated in response to several environmental cues including water temperature, photoperiod and streamflow. We found that bull trout spawning activity began when maximum daily water temperatures dropped below 9°C, Spawning was generally completed by mid-October. Spawning activity of anadromous Dolly Varden and other non- anadromous bull trout populaticns occurred at water temperatures between 5 and 9°C (Blackett 1968, Leggett 1969, Needham and Vaughan 1952, McPhail and Murray 1979). Adult bull trout consistently used specific spawning grounds within the upper Flathead River basin. Of 185 stream reaches covering 750 km of Flat- head trifcwtaries surveyed, bull trout redds were located in only 48 reaches covering 215 km (28%). Areas selected for spavming were large streams characterized by high stream order (higher stream order indicates larger tributaries closer to the mainstem rivers), low D-90 measurements (D-90 is defined as the diameter of a stone in the streambed which is larger than 90 percent of all streambed material), low channel gradient, and a larger per- centage of gravel and ccbble in the streambed. Adult bull trout also appeared to select areas: 1) directly influenced by groundwater recharge? 2) in low gradient areas at interfaces between high gradient and low gradient portions of a stream channel? and 3) where the stream split into multiple channels. High gradient-low gradient channel interfaces and multiple channel areas were characteristics of an aggrading stream channel. Aggrading areas were also characterized by recently deposited, loosely compacted gravels resulting from annual peak streamflow events. These conditions provided ideal spawning habitat. 43 Figure 3. Movement of adult bull trout from U.S. tributaries of the North Fork Flathead River returns within one year 1962-1981. ’ O) cc UJ H UJ S o _J 44 Figure 4. Adult bull trout movement from Canadian tributaries of the North Fork Flathead River returns within one year 1962-1981. 45 Table 26. Characteristics of bull trout spawning, including time of year, size of spawner, sex ratio and fecundity observed in river drainages of Montana, Idaho and British Columbia. (U o >.1 D O CO 'O D 4-1 w w •rl H )-i 01 > 03 •H iH O t •H 4J 03 CU (U ,13 j-4 cr\ DO o^ pH V4 1^ 00^ cj 3 cn 0) cr> S IS .-I 1-5 cu S •H vC 0) !>mH •U CO ^ S TJ 0) 3 ^ U CO 0) DC P*4 DC 01 cs 00 I I m 00 O’ -vT I I I CM 00 00 >-i 0) > < 00 3 5 -H •H CO 4-1 B 0. o •H CO CO H 01 OC 3 •S 3 )-i Q 1 3 uo 00 C3^ rO M r— 4 o S 3 as o >-i 3 .3 l-l OvJ u rH CN 3 4J O 3 3 3 rQ 3 O- 4J .3 M XI V4 X3 u s 3 3 o a S O 3 a o 3 s o 0) 03 CO 4J O 3 4-> .3 3 4J XI 3 4J 4-1 O 1 1 4J O 4J O 4J o 3. 4-1 35 33 0- 4J a. 4J 0. u 3 O •H •rl 3 O 3 3 3 o CO o B a CO O CO O CO o 3 *> 3 A •H W -rl •H 3 rQ •* o X Ai •V S Xi Xi ^ 3 3 u 3 3 3 3 3 > XI 0) iH 3 XJ rH «S #5 3 i-H •H > i-i O 5-1 O xi 54 Xi O Pi 3 •H 3 CJ CJ & CJ 3 3 3 u rH p^: > o 3 > XI Xi r-H 3 •H x: 3 u x: 5h •rl X •rl TJ C Pi 3 w •rl 5-4 3 O Pi >4 CO O 3 CO 3 3 •H N < -H 3 •H pC4 X 0 (U 4-1 B )-i 4J C 4-1 > C C o C 3 CJ •H 3 5h -H O 3 3 •H Xi cd •U fcX 3 1-4 •o 3 4-J Pi X 35 TD CO oO s 3 (X PQ 3 C O PQ 3 C M rH •H 3 3 (X 3 3 o 1—4 3 pH ^2 Pi S 33 s O Ui CJ Ph 46 Fork length 2^1 Timing of spent adults migrating downstream. 3/ Standard deviation. McPhail and Murray (1979) listed low channel gradient and a streambed composed of walnut sized gravel as requirements for bull trout spawning in MacKenzie Creek, British Columbia. Allan (1980) and Heimer (1965) reported spawning bull trout used areas influenced by groundwater and concluded groundwater provided a stable environment for incubating embryos during .pa winter months when harsh environmental conditions normally exist. Brook trout, another inland charr, also spawn directly over areas of upwelling groundwater or in spring-f^ tributaries (Webster and Eiriksdottir 1976, Carline 1980). Characteristics qf Adults. Adult bull trout in the upper Flathead River basin were larger than adult bull trout from other drainages (Table 26). Due to their larger size, fecundity rates were also higher than any reported. The sex ratio of adult bull trout entering Flathead River tributaries was estimated to be 1.0:1.1 (males: females), similar to sex ratios reported for populations in British Columbia and Idaho (Table 26). Mature adults were from five to nine years of age. We recorded the presence of "precocious" male bull trout (215 mm in length and three years of age) in Coal Creek, a tributary to the North Fork of the Flathead River. Allan (1980) recorded the presence of juvenile bull trout that matured in their natal tributaries in the Clearwater River drain- age, Alberta. Spawning behavior of adult bull trout has been described in detail by several researchers (Needham and Vaughan 1952, Block 1955, Leggett 1969, Blackett 1968, McPhail and Murray 1979, Allan 1980). Spawning bull trout in Flathead tributaries exhibited similar behavior patterns. Generally, the female selected the spawning site and the male defended it. It was possible that spawning pairs formed during the migration upstream. We hypothesized that pairing may have occurred at the mouths of tributary streams as numerous bull trout moved into our upstream traps as pairs. McPhail and Murray (1979) also reported bull trout moving upstream in pairs in MacKenzie Creek, British Columbia. We believed repeat spawning occurred for some bull trout in the Flat- head; however, we also found a number of mature-sized bull trout in Flathead Lake during summer and fall sampling indicating that at least some adults did not spawn every year. Allan (1980) reported that 27 percent of the adult bull trout tagged in Timber Creek, Alberta returned to spawn the following year. He also documented the return of one female three years in succession. Physigal Chaiac-texiatibs. oL spawning Sites Bull trout generally spawned in runs or tails of pools. Measurements of bull trout redds in ufper Flathead River tributaries revealed that the average area of disturbed streambed was larger than redds measured in Alberta and British Columbia (Table 27). This size differential was probably related to the larger size of adult bull trout in the upper Flathead River basin. The average water depth over redds recorded during this study was 0.28 m (range: 0.15 to 0.35 m), illustrating bull trout in the Flathead system spawned in relatively shallow water when compared to other studies (Table 26). Table 27 Characteristics of bull trout redds Including redd size (disturbed area), depth of egg deposition, water depth, velocity and streambed composition observed in river drainages of Montana, Idaho and British Columbia. o *8 ' ^ 3 > O *0 o u u w > 0 fO O a u -o (Q a a> •U 01 ^ » *0 CO p o . 0^0 06 ^ (Hi ^ CO (« c a SCO (Q n) w o> u J2 q £ a U O o n X n X t*4 w ni W *J iH M .251 p 0) .C bo a > o •H 0) ^ O :x 06 PC a o ^ « O O. X m3 0) > ^ M ‘H M >, O pS -H o> o « u *j 'T3 O rt o od c O 01 3 X Q 48 Water velocities (measured at 0.6 depth at the front edge of the redd depression) ranged between 0.24 to 0.61 mps. Eggs were covered with 0.10 to 0.20 m of gravel. These findings were consistent with water velocities and egg deposition depths reported for bull trout redds investigated in other drainages (Thble 27). The composition of the streambed in Flathead tributary spawning areas was also similar to that measured in spawning grounds used by bull trout in other drainages (Table 27). GEOmi Juvenile bull trout grew to average lengths of 71 mm, 117 mm, and 171 mm at age I, II and III, respectively, in the North Fork drainage, and 51 mm, 96 mm and 152 mm in the Middle Fork drainage {Table 28). Early growth of juvenile bull trout is slower in the Middle Fork drainage, probably due to Qivironmental factors. Middle Fork tributaries appeared to be more productive than North Fork tributaries (Table 29). The thermal regimes for Middle Fork tributaries were similar to North Fork tributaries for mean monthly maximum temperatures, but mean monthly minimums were lower in the summer months for several North Fork tributaries (Table 30). Perhaps bull trout growth was enhanced in cooler North Fork tributaries. McPhail and Murray (1979) found that bull trout fry grew to larger sizes at lower temperatures and grew largest at 4*^. Annual growth increments calculated using scale samples from bull trout collected from Flathead Lake averaged 68 mm the first year and 62 mm the second year (Appendix C, Table C-6). After the second year, incremental growth increased to an average of 74 mm between the second and third years, indicating that a portion of the fish emigrated from tributaries to a more favorable growth environment. After the third year, average incremental growth increased again to 88 mm a year and remained reasonably consistent up to age eight (range 88 to 95 mm per year) reflecting increased growth follow- ing the movement of fish from the tributaries into Flathead Lake and the shift in diet from invertebrates to fish (Table 31). 49 Table 28. Back-calculated lengths at annulus of bull trout during their first four years from lake and riverine collections from drainages in Montana, Idaho and British Columbia. Drainage Year I II III IV Lakes Flathead 1963-81 68 (929) 130 (929) 204 (926) 292 (851) Flathead 1963 71 (289) 140 (289) 208 (289) 323 (245) Hungry Horse Reservoir 72 (212) 144 (212) 225 (185) 324 (130) Priest Lake 1957 71 ( 61) 114 183 310 Upper Priest Lake 1957 66 ( 41) 102 155 239 Lake Koocanusa 67 (162) 123 (162) 212 (157) 309 ( 96) Rivers & Streams North Fork Flathead 1955 76 ( 80) 150 ( 51) 234 ( 44) 335 ( 43) North Fork Flathead 1977-1982 71 (820) 117 (478) 171 (109) 317 ( 30) Middle Fork Flathead 1981-1982 51 (456) 96 (407) 152 (234) 284 ( 5'2) Upper Basin combined 1977-1982 65 (870) 108 (594) 160 (220) 288 ( 61) Toboggan Creek 1979 48 ( 44) 99 ( 37) 165 ( 20) 229 ( 5) 50 01 Oi O •i-i > •f- ja lO +J O CO 3 •o C t_ O (U U 4J (U 1> TJ = c (O > a» 3 ^ -H /I d) C JZ - *1- 4-> E ro (O CL •o i. o f— Vi- to (U *— 3 to r— to h- ^ 0) x; o 00 CO (U CD I— •r- QJ q: -f- to (U 1 (u x: . x: » 4J +J » <0 c • t r— •1— -(-> : IX ■0 E . : 0 (U (U ) Lu s “O >> 4^ •r* > u 3 •o c o (-> >> 4J ■r* r— C to *1™ +J r- O to >— ^ to + to z + + to o + + CD ro o z z I 'O' o CO o o CO O) (U orocnc\jLr)Lr)Oc\jtr>CMcOc\jcDLi-inr~> 'a-rocvjc'ocooo.-Hr-toO'O-fr^gg^g u2CTvrocOp^Lr)rooc\jrooo^co.-<£T>Lr> ro.-.c\jco.O'OOoor^.t^i'>.Lntnroooooco r-t^a-oorocn ••••••••... CM'-Hr-iuorocnvDrv.r'^vocTi coco'^c^^cD ro CM CO 00 QQQOQQCOOOOQ cQcocQ .com . . . •coSgmmg o V V r^r^roror-sfo cn COOOcOOOCD'3'rOi-''?rt-HOOO o<^cocm r~~i LO ro ro dj C31 fO c •r* to i~ T3 JvC S- o $- o •“tf'^oO'O'O'M'roiocoi^'d'Ln •-•OOOf-Hr-iOOOOOO 000000000000 to TO o to CCCr— to O 'r- fO to too OE-i'i'O OJt— EvocTtiSOi-fOcocnvo >>'o tocoo-i^o-M-i—iaoroot o«a:_icQ«a:u.co:»<:cooicct: c o c •f sz +-> QJ <0 c > OJ OOLOLOOlOOOO vj"!— tr^CTiO^CMCDt— I CMCMCMr— co*-4C3>orocnLD Ln'O'Loro^a-cMLnroi— 4CM oro'O-'O-r-tLorooorof^ loloctii— tor^*— 'Ocor^ ro 00 — J — J CM — J — J — J 1—4 1—4 LO QOOQQQQOOrO 00 OQ • 00 00 CO CO • V o ror^M'CTtcriroLDro r0^r-4r0r-4ur)0>— Ir— 4 CM .—4 O o 1 CM ro ,-4 0 1 0 CD LO 00 QJ cn to '3' Lf) ^ r-4 £0 0 0 0 r-4 0 0 0 0 0 to 0 S- X) jtc: L. >1 0 i- L4_ i. (U QJ J- 1— QJ X3 QJ -0 •— C r— 2 ( to 1 — z <_> =: <_) z 00 1 000000 000000 (Z 0 QJ c to CO +-> 0 5 • r- +J QJ r— u L. c c 5 ro X L. 40 OJ 40 (O 0 f— 0 0 S- 4-> CD m C_) c_> z CD 0 LO 51 103 295 Table 30. Monthly minimum and maximum water temperatures of six North Fork and four Middle Fork tributaries. North Fork Middle Fork Month tributaries tributaries July Mean minimum 5.6 6.8 Mean maximum 12.7 13.5 August Mean minimum 7.9 10.1 Mean maximum 15.8 15.8 September Mean minimum 4.9 8.0 Mean maximum 12.5 11.8 Table 31. Bull trout growth (millimeters) in various waters. 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' E E E E.^ E — E ^ E ^ E c E c E c E c E c E c E c ' — ' — ' ' ' ■' — ' "rol C •r- 0 1 > CO S_ Oj CO (U d) CD LO a> ID CD (u C" 3 oj (0 T3 CD r-H C/I CD C d) U) -J 3 f-H ' — &- I 03 JxC cu 0 U 03 •r— T3 (/) .-H S_ zn. oo 0 1 t- 03 00 ax: (LI 0 0. d) «/) 0^ (J i_ >>co 3.^ +J x: •1- .-H 0 s: S- LD «/) s- 4J X: r- fO cncD CU CU cu 03 1— CD q; C r-C •1— Q. r““ 3 03 L- CX. U- ac _J Q. =3 cr> CTi ^ (>o • cn r~^ t-H i-H n3 C 4-> C O O) C 4-> S~ W >» O 13 03 • 1-5 □c s: oQ 03 ua o 53 CONTRASTING SURVIVAL STRATEJGIES EMBRYONIC DEVELOPMENT Because spawning occurs at different times of the year cutthroat and bull trout are exposed to different environmental conditions during their early life stages. Fall egg deposition and overwinter incubation subjects bull trout eggs to a harsh environment of cold temperatures and low flows. Bull trout afpeared to select areas of groundwater recharge in ujper Flathead River tributaries which may minimize the effects of harsh winter temperatures and the formation of anchor ice. Heimer (1965) reported high survival and relatively rapid development of bull trout eggs in areas influenced by groundwater in the Clark Fork River. In contrast, cutthroat embryos in tributaries to the Flathead River system incubated for a short period of time during the spring during variable streamflows and water temperatures. Johnson (1963) suggested cutthroat may spawn in small tributaries to avoid streambed movement which can occur in large tributaries during peak flow events. Early survival may be enhanced by: 1) large size at emergence, 2) rapid growth to reach a size to avoid predation, 3) protective coloration, and 4) species distribution. Bull trout seem to maximize fry size at emergence. Mann and Mills (1979) state, "nevertheless in most species it is likely that the larvae from the largest eggs are best equipped to survive under difficult conditions". Large eggs and alevin size is typical of fishes with long cold incubation periods (Mann and Mills 1979) like bull trout. Fry which hatch in early spring may be subjected to an initial period of limited food avail- ability and starvation (Mann and Mills 1979). Bull trout size at emergence is maximized by the unusual habit of remaining in the gravel and feeding after yolk sac absorption. They also develop parr marks unusually early which provides them with criptic coloration to avoid predation (Balon 1980). Cutthroat trout were 10 mm smaller or two-thirds the size of bull trout when they emerged from the gravels. Cutthroat trout used low gradient areas of small streams for spawning and rearing. Hiese areas may compensate for the selective disadvantage of small fry size by providing shallow nursery areas less accessible to predators. STREAM RESIDENCE Bi&tr.iJ?.utlQn In streams Juvenile cutthroat and bull trout used the space available in streams differently. Bull trout were found closely associated with the streambed near submerged cover forming pockets of low velocity water. Cutthroat trout were found throughout the water column beneath overhead types of cover. Tlierefore, bull trout used the streambed as habitat, while cutthroat trout used the water column. 54 Social Order The habitat used by juvenile cutthroat and bull trout provides a basis for describing, in general terms, the social structure each species adopts. Bull trout are territorial, defending a fixed site with a focus consisting of a small pocket of low velocity water near the streambed. Cutthroat trout formed dominance hierarchies throughout the water column of pools. Social structure may influence potential fish production by minimizing aggressive behavior (Chapman 1966, Noakes 1978). Visual isolation, a charac- teristic of fixed site territoriality, reduces this aggression (Noakes 1978, Chapman 1966). When visual isolation is not available, fish densities can be maintained at higher levels by the formation of dominance hierarchies (Noakes 1978). Cutthroat trout densities may be maintained at higher levels than bull trout because cutthroat form dominance hierarchies, while bull trout did not. Increasing juvenile bull trout production in streams would require increasing visual isolation since usable space, in the form of streambed surface area, is fixed. Bull trout would be very susceptible to any loss of wetted streambed area. Social order has also been related to feeding strategies (Gerking 1959, Noakes 1978). Cutthroat trout fed on drifting insects on the water's surface or in the water column. Optimum feeding areas for cutthroat trout were toward the head of pools near complex currents in the middle of the water column where drifting insects were readily available. Juvenile bull trout foraged along the stream bottom; therefore, optimum feeding sites were near the streambed surface close to the food source. fish Spatial Segregation Intraspecific interactions were also minimized by spatial segregation of different size fish. Smaller cutthroat and bull trout usually used shallow- er, slower water than older fish. C^jects providing cover for small fish did not provide adequate cover for larger individuals. Spatial segregation and social order minimized intra- and interspecific interactions between juvenile trout. Small cutthroat trout were separated from small bull trout by their use of the water column and from other cut- throat trout by their use of shallower areas. Larger juvenile trout of both species were separated by vertical spacing in the water column and their use of cover. Positions used by bull trout in the water column tended to maxi- mize their concealment and minimize their use of energy. Cutthroat trout held positions in the water column and probably used more energy to maintain their feeding positions and were less concealed than bull trout. As bull trout grew in size, they moved up into the water column and used pools more often increasing the potential for interaction with cutthroat trout. Where resident adult cutthroat trout were present alongside juvenile bull trout, aggressive encounters were frequently observed. If juvenile bull trout were conspicuous in pools, they were chased by resident adult cutthroat trout until they retreated under cover. EMIGRATION OF JUVENILES Juvenile cutthroat and bull trout appeared to emigrate from tributary streams at similar ages and during the same times of year. Information on movement of juveniles in the Flathead River was sketchy, making it difficult to assess any possible interaction which may have occurred during migration. We believe juvenile bull trout moved quickly downstream (through the upper river system) while a portion of juvenile cutthroat trout remained in the two forks of the river for longer time periods (up to a year). The only juvenile bull trout located in either the North or Middle forks of the Flathead River were found along the river margins (near shore) in the Middle Fork. Segments of the cutthroat trout population a^ieared to be fluvial. Bull trout did not seem to exhibit this type of fluvial life history pattern in the Flathead, but do did so in other river systems (Armstrong and Morrow 1980). Where large lakes are present, bull trout usually follow an adfluvial life history pattern. For the highly piscivorous bull trout, the advantage gained by migrating into a large lake with abundant prey must outweigh the disadvantages of moving long distances to and from spawning and rearing habitat. Ccnversely, the insectivorous cutthroat trout exhibited all three life history patterns, possibly indicating no overriding advantage was gained by following one of the three potential life-history patterns. FLATHEAD RIVER - FLATHEAD LAKE RESIDENCE Cutthroat trout depended on terrestrial and aquatic insects for food. Limited winter sampling of cutthroat trout in Flathead Lake indicated that when insects and types of zooplankton usually preferred as food were unavail- able, the fish starved. Some cutthroat trout may move up into the lower river from Flathead Lake to take advantage of the constant supply of aquatic macroinvertebrates that were available throughout the winter. Cutthroat trout food preferences also dictated their distribution in Flathead Lake vertically as well as horizontally. Water surface and shoreline areas throughout the lake were used by cutthroat during the entire year except in the summer months when warm surface water temperatures forced cutthroat to seek cooler deeper waters. Bull trout in Flathead Lake had a consistent food source in the form of fish and were not compelled to seek food in the Flathead River during the winter months. During the fall, when pygmy whitefish concentrated in the lower Flathead River, bull trout in the lower river used them for prey. Bull trout in Flathead Lake were found vertically throughout the water column during the spring, winter and fall when the lake was homothermous. During the summer bull trout were found in moderately deep water and fed on mountain and lake whitefish. Cutthroat and bull trout juveniles appeared to use the river as a staging area before entering the lake, while adults used the river seasonally because of the increased food available and as a staging area prior to their upstream spawning migrations. 56 ADULT SPAWNING MIGRATION Adult cutthroat trout completed their spawning migration in a relatively short time period (two to three months) , while adult bull trout spent as long as seven months traveling to and from spawning areas. Cutthroat trout spawn- ing migrations coincided with peak spring streamflows allowing cutthroat trout to use smaller streams for spawning and perhaps enhancing their ability to pass partial barriers and move higher upstream into tributaries than adult bull trout. Cutthroat trout spawners were less available to anglers during most of their spawning migration due to high turbid spring flow conditions. SPAWNING Timing ^ Distribution Spawning westslope cutthroat and bull trout were found to be temporally and possibly spatially segregated. Bull trout spawned during the fall and cutthroat spawned during the spring. Spatial segregation of spawning has not been well documented, but it appears the majority of bull trout spawning occurred in large tributaries or in the lower reaches (nearest the rivers) of small tributaries. Limited data suggested cutthroat spawned in small tribu- taries and headwater areas which may have been related to the fact that spawning gravels in small streams were less likely to be disturbed by high spring flows (Johnson 1963). This spatial segregation could also be a result of the differential accessibility into streams during high spring versus low fall discharges. Chaiag-tLaclstics oL Adults Adult bull trout were much larger than migratory adult cutthroat trout; however, they were not in natal tributaries at the same time so no inter- action occurred at the spawning grounds between migratory adults of the two species. MANAGEMENT IMPLICATIONS RECREATIONAL FISHERY Several studies were conducted to evaluate the recreational fishery in Flathead Lake, mainstem Flathead River, and the North Fork Flathead River during 1981 (Graham and Fredenberg 1983, Fredenberg and Graham 1982, Fredenberg and Graham 1983, Sutherland 1982). Kokanee made up ninety-two percent of the angler harvest in Flathead Lake. Cutthroat trout made up two percent and bull trout one percent of the Flathead Lake angler harvest. The average length of bull trout caught in Flathead Lake was 574 mm and anglers released approximately half of the bull trout caught because of an 18 inch (457 mm) minimum size limit. The average length of westslope cutthroat trout caught by anglers in Flathead Lake was 320 mm. The estimated harvests of cutthroat trout, bull trout, and kokanee in the mainstem Flathead River were 8,557, 1,827, and 76,830 fish, respectively. The kokanee harvest included the popular snag fishery which harvested the bulk of kokanee. The average lengths of westslope cutthroat and bull trout caught in the mainstem were 280 and 581 mm, respectively. An estimated 16,381 cutthroat trout and 404 bull trout were harvested from the NOrth Fork Flathead River. During 1981, Sutherland (1982) estimated that approximately 740,000 recreational visitor days were spent on Flathead River and Lake associated with water based recreation with an estimated total net value of five million dollars. These estimates are considered conservative because of the assump- tions and techniques used to generate them. Approximately 342,600 of these days and 1.74 million dollars were attributed to fishing. This included the kokanee fishery which accounted for approximately 90 percent of the total. More importantly, the study estimated the preservatioi values of water based recreation as reflected in preservation of water quality at 96 million dollars. Management of the fishery in the Flathead basin depends upon maintaining high quality water, preserving habitat used for spawning, rearing and maturation, and controlling the harvest to ensure adequate recruitment for maintaining fish populations. GOAL DEVELOPMENT IN CANADA Development of coal reserves in the Canadian portion of the Flathead River could have significant impacts on fish resources in the basin. Howell Creek has consistently supported 10 percent of the known bull trout spawning for the entire basin. Montana Department of Fish, Wildlife and Parks biolo- gists prepared comments on the probable impacts of coal development on fish resources in the basin. These comments focused on problems foreseen with increased sedimentation, nutrient enrichment, heavy metals pollution and increased human activity. Sage Creek Coal received approval in principle for its Stage II application in early 1984 from the provincial government of British Columbia. 58 OIL AND GAS Oil and gas exploration in the Flathead drainage has been steadily increasing, especially in the North Fork area. Presently, no sites have been developed commercially, although drilling of exploratory wells has begun. Shell Canada is planning to develop carbon dioxide wells in the upper north Pork Flathead River to provide for enhanced oil recovery from existing oilfields in Northern Alberta. Their proposal calls for about 25 wells, 30 kilometers of new road, 50 kilometers of upgraded roads, 80 kilometers of infield gathering pipelines, and a processing facility. Construction is anticipated to begin in 1986 and be coirpleted by 1989. Potential impacts from these developments include increased sedimentation from roads, increased access and human population resulting in increased fishing pressure, pipline construction causing increased sedimentation and the possibility of pipeline failure, and potential dissruption of groundwater aquifers during drilling. FOREST MANAGEMENT ACTIVITIES Forest management activities (including logging, roading, oil and gas exploration and any other activity which disturbs the land surface) in the upper Flathead basin could potentially affect the capability of tributary streams to produce fish which recruit to the Flathead Lake and River fishery. Our studies have documented the importance of these tributaries in providing spawning and rearing habitat for westslope cutthroat and bull trout in the basin. Forest management activities can impact this habitat by altering flow and temperature regimes, increasing sedimentation rates, changing rates of organic debris recruitment, and altering primary productivity rates and sources. Shepard and Grah^ (1983b) found that the streambed of Coal Creek (a North Fork tributary) contained a significantly higher percentage of fine sediment than three neighboring drainages. The Flathead National Forest allows a 50 percent increase in sediment over natural levels produced off Forest Service lands during forest development in all sensitive fishery tributaries, and allows a 100 percent increase in non-sensitive tributaries even though many of these non-sensitive tributaries support fish (Forest Service, USDA 1983). Water yields in streams draining Forest Service lands are allowed to be increased from 5 to 10 percent, depending on the stability of the stream channel and the use of the stream. Several streams, most noteably Big Creek (a North Fork tributary), would have water yield increases above the "acc^table” 5 to 10 percent level according to the Forest Service Plan (Forest Service, USDA 1983). StreamflQw and Water Temperature Canopy modification within a drainage can significantly alter the timing and quantity of water flowing from that drainage (Gibbons and Salo 1973, Chamberlin 1982). Opening up areas on north-facing slopes will trap snow and ^use it to melt over a longer time period, dampening peak flows and augment- ing late summer flows. Conversely, removing timber from a south-facing slope can increase peak flows and reduce water available for late summer flows. Water yields generally increase with increasing canopy removal and these increases are as permanent as the changes in the forest hydrologic system 59 that cause them (Harr et al. 1979). Augmenting late summer streamflows may benefit trout populations by increasing the available usable space within the stream. Managing the forest to augment late summer flows can increase peak flows and dramatically change stream channels. Reducing late summer flows would reduce the amount of living space available for juvenile trout and impede access to spawning areas by fall spawning bull trout. Ihe cumulative impact of reducing late summer streamflows in several tributaries to the North Fork Flathead River could decrease summer river flows. This river segment has been designated as a scenic and recreational river under the National Wild and Scenic Rivers Act. Floating is a popular use of the river, and recreational use of the river has been increasing. Lower summer river flows could have a significant impact on the floatability of the river. Removal of streamside vegetation increases maximum water temperatures in direct proportion to the surface area of the stream exposed (Gibbons and Salo 1973). We have data suggesting that juvenile bull trout may prefer cooler maximum summer water temperatures than cutthroat trout. Removing large areas of forest canopy within a tributary drainage may increase water temperatures which could shift the species composition from one favoring bull trout to one favoring cutthroat. Streamside vegetation also helps insulate the stream during winter months, moderating low water temperatures and reducing the formation of anchor ice (Gibbons and Salo 1973). Sedimentation Inorganic sediment normally originates from non-point sources (Murphy et al. 1981). Gibbons and Salo (1973) reviewed 25 articles on the production of sediment as it related to logging and roading and found that logging roads were the major source of man-caused stream sediments. Sffeots on Spawning and incubation The fact that excessive amounts of fine sediment has a detrimental effect on salmon id embryo survival has been well documented and summarized by Cordone and Kelly (1961), Gibbons and Salo (1973), Iwamoto et al. (1978) and Reiser and Bjornn (1979). Fine sediment levels in Coal Creek were signifi- cantly higher than levels in Big, Whale and Trail creeks, suggesting that land management activities in Coal Creek may be degrading bull trout spawning habitat. More detailed information is needed for determining the origin and transport rate of sediment to Coal Creek, so measures can be implemented to reduce sediment input to the stream. The relationship between streambed composition and bull trout embryo survival needs to be developed to better predict the impacts of sedimentation on bull trout recruitment. Ongoing research which addresses this question is presently under way at the Montana State University Cooperative Fisheries Research Uhit. 60 Effects m Juvenile Rearina Deposition of sediment onto the streambed can affect salmonid rearing habitat by: 1) modifying the complexity of habitat and decreasing the interstitial spaces used by aquatic macroinvertebrates which supply the bulk of the food resource for juvenile salmonids (Reiser and Bjornn 1979, Bjornn et al. 1977, Gibbons and Salo 1973); 2) reducing pool volume which may reduce summer and overwinter rearing habitat for juvenile salmonids (Bjornn et al. 1977, Reiser and Bjornn 1979); and 3) blanketing cobble and boulder substrate preventing the use of inter- stitial spaces within the streambed by overwintering juvenile salmonids (Everest 1969, Bustard and Narver 1975, Bjornn et al. 1977) . Leathe and Graham (1983) found a significant non-linear negative relationship (r=-0.75; p<.10) existed between the density of juvenile bull trout and the percentage of fine sediment in several tributaries to the Swan River, Montana. A reduction in pool volume caused by the deposition of sediment may also reduce the number of adult bull trout which spawn in a particular tributary. Adult bull trout were frequently observed holding in deep water provided by pools after they entered spawning tributaries to the Flathead River. Ihese large fish (up to 8 kg) may remain in tributaries for as long as two months. The majority of that time is probably spent hiding either in deep pools or under log jams, Dunn (1981) found that pool volume was the most important holding pool characteristic influencing summer steelhead numbers in holding pools of the 13 variables he tested. We believe pool volume may be as important for holding adult bull trout. Instream ^ Stxeambank Cover Vegetation manipulation along streambanks can change the amounts of large debris recruited to the stream channel over time. Generally, large quantities of debris enter the stream channel immediately following harvest activities. Organic debris are an important component in headwater streams. They influence channel morphology by creating plunge pools, trapping gravels, adding nutrients, and providing cover (Brown 1974, Meehan et al. 1977, Bryant 1980, Boussu 1954). If too much large size debris (trees and stumps) enter the stream channel, debris jams capable of diverting the stream channel may result (Meehan et al. 1969, Bryant 1980). In severe cases, large debris jams accompanied by extremely high streamflows may move the entire debris jam down the stream course in a phenomenon termed "flush-out" (Brown 1974). Flush- outs can be particularly damaging to fish habitat. 61 Primary Productivity Murphy et al. (1981) and Hunt (1979) recently suggested that removal of streambank vegetaticxi may improve the ability of a stream to support fish by increasing primary productivity. We are concerned that long-term sources of allochthonous (derived outside the stream channel) nutrient sources would be sacrificed by cutting riparian vegetation. This vegetation contributes the coarse particulate matter (CPOM) used by macro-invertebrate shedders which provides the bulk of the nutrients available in headwater tributary streams (Cummins 1973, Meehan et al. 1977). 62 OTHER SPECIES SCULPINS Two species of sculpins, slimy (Cottus cognatus) and shorthead (Cottus confusus) . were present in the two forks of the Flathead River and their tributaries {Table 32). The slimy sculpin is the most widely distributed sculpin in North America (Lindsey 1956). In ccaitrast, the distribution of the shorthead sculpin is limited. It is considered a rare and endangered species in Canada (Maughan 1976) and a species of special concern in Montana (Holton 1980). Both species were prevalent in the North Pork, but were infrequently observed in the Middle Fork. T^ie lack of sculpins in the Middle Fork may have been an artifact of sampling bias. Sculpins were difficult to observe snorkeling; and snorkeling was the primary method used to collect fish infor- mation in the Middle Fork drainage, while both snorkeling and electrofishing were used in the North Pork drainage. Si^wning and Sculpins spawned in the spring, probably late in April or May. Many gravid, but few ripe females, were found in mid and late April. Glasser et al. (1981) reported shorthead sculpins spawned in mid-i^ril. Craig and Wells (1976) reported slimy sculpins spawned in May. Individuals of both species were mature at three years of age. A few two year olds were collected but none were mature. Glasser et al. (1981) and Petrosky and Waters (1975) found mature slimy sculpins that were two to three years old. Slimy sculpins in Alaska did not mature until they were four years old (Craig and Wells 1976). The smallest mature sculpins observed were 50 mm males and 75 mm females. Other researchers have noted similar minimum sizes for mature sculpins (Table 33). Shorthead sculpins up to 116 mm and seven years of age have been c±>served in reproductive condition in the Flathead. Craig and Wells (1976) report slimy sculpins up to seven years of age. Fecundity is related to fish size in sculpins, as it is with other fishes. Although no egg counts were conducted during this study, fecundity information was available from the literature (Table 33). Adhesive eggs were laid in clusters on the underside of rubble to boulder size substrate. The areas selected were free of silt. Siltation has been known to reduce slimy sculpin production (Petrosky and Waters 1975). Egg incubation has not been studied for either slimy or shorthead sculpins. Information was available for Cottus bairdi (mottled sculpin) . Eggs hatch within 30-40 days if incubated at 48-50OF (Bailey 1952), or within 20 days if incubation temperatures are between 55-59°F (Hann 1927). 63 Table 32. Distribution of sculpins, mountain whitefish and brook trout in tributaries of the North and Middle Forks of the Flathead. + = present, - = absent. Mountain Drainage Sculp in Whitefish Brook trout North Fork Canyon McGinnis Kimmerly + Big + Langford + Hallowatt + Werner Kletomus Skookoleel Nicola Camas + Dutch + Anaconda + Logging + Coal + Cyclone + Dead Horse South Fork Coal ? Mathias ? Quartz + Cummings + Hay + Moran + Bowman + Akokala + Parke + Longbow Red Meadow + Moose + Whale + Shorty Ford Kintla Starvation + Trail + Ketchikan Yakinikak Tuchuck Kishenehn + Spruce + Sage + + + + + + + + + + + + + + + + + + + + 64 Table 32. (Continued) Drainage Sculpin Mountain Whitef ish Brook trout Cauldrey + + Burnham + 9 - Howell + + - Cab in + + - Commerce + - - Middlepass + - - Packhorse + + - Forsey + + - McEvoy + + - Middle Fork McDonald + Lincoln - + + Walton - + Deerlick - + + Harrison - + + Nyack - + - Coal + Pine hot - + + Stanton - + + Timnel - - — Muir - — — Paola — Park >■ + Dickey + - + Ole - + + Essex - — Bear + + + Geifer + + + Sky land - - — Charlie — Long - + Bergsicker - - — Twenty-five Mile - Granite - Challenge — + Dodge - Lake - Miner Morrison + Puzzel - Lodgepole + + — Whistler - - Schafer - + •• Dolly Varden + Argosy - - _ West Fork Schafer — — _ Table 32. (Continued) Mountain Sculp in Whitef ish Brook trout Calblck Cox Clack Bowl + Basin + Strawberry + Trail South Fork Trail Gateway East Fork Strawberry + + + + Table 33. The length at maturity, fecundity and relationship between fecundity and fish length for slimy and shorthead sculpins. Species Citation Length at maturity (mm) Fecundity (no. of eggs) Fecundity equation Slimy Petrosky and Waters 1975 43-111 59-645 Eggs = 10 . lx (length) Slimy Craig & Wells 1976 68-99 59-339 — Slimy Vanvilet 1964^^ — 82-1291 Shorthead 2/ Glasser et al— ' 1981 — — F = 14.15 (S.L. - 531) Shorthead Peden 1982 (Flathead) — 128-690 — Shorthead (Flathead) 20-116 J^/ Adapted from Craig and Wells 1976 Adapted from Peden 1982. other species of sculpins hatch at sizes as small as 3.0 mm, and are 9- 15 mm before they resemble adult fish (Richardson and Washington 1980, Bailey 1952) . Habitat Sculpins were observed in the middle and lower reaches of North and Middle Pork tributaries. They were rarely present in headwater streams. Peden (1982) reports shorthead sculpins were rarely found above an ele^^tion of 1,372 m (4,500 feet). In contrast, Maughan (1976) found shorthead sculpins in headwaters in areas over 976 m (3,200 feet) elevation. Maughan (1976) found shorthead sculpins in areas not used by other species of Cottus. however, in Coal Creek (a tributary to the North Fork of the Flathead River) slimy and shorthead sculpins have been deserved in the same portion of the stream. Peden (1982) did not notice any zonaticai of the two species. In several areas we noted exclusive use of a stream by a single species of sculpin. In areas where the species coexisted, like Coal Creek, hit>ridiza~ tion (caifirmed with electrophoretic analysis) did occur (unpublished data, MDFWP, Kalispell, Montana). Sculpins were characteristically found in mcst habitat units of any size stream in regions with large clean substrate. Although a few were found along the fringes of pools, most individuals were in the fast water areas of riffles, runs and pocketwater. Bailey and Bond (1963) reported sculpins in riffle areas. Peden (1982) noted sculpins used riffles and areas of complex flow patterns which were not necessarily associated with the broken water of riffles. Slimy sculpins preferred cool waters, selecting water 11-13°C and did not survive in water 20°C (Symons et al. 1976). ^ GJLQMth Sculpins collected during this study grew at similar rates as those collected by Peden (1982) and Glasser et al. (1981) (Table 34). By the end of their first year, sculpins were between 30 and 39 mm. Between the first two years, the sizes of fish could distinctly place individual fish in the I and 11+ age classes. The size of sculpins in all other age classes over- lajped (Table 34). Average sizes of age II, III and IV shorthead sculpins in Trail Creek were 55, 68 and 84 mm, respectively. Although few were collect- ed, slimy sculpins seemed to grow at a similar rate. Slimy sculpins in Alaska grew at rates similar to Flathead sculpins, although both grew slower than growth reported for other populations of slimy sculpins (Craig and Wells 1976) . Food Habits Sculpins fed primarily on benthic insects. Limited stomach analyses demonstrated sculpins used mayflies (primarily Baetidae and Heptageniidae) and stoneflies. In other areas, dipterans, particularly chironomids, were the predominant food item in the diet of slimy sculpins, particularly young fish (Petrosky and Waters 1975, Craig and Wells 1976). Older sculpins utilized mayflies (Petrosky and Waters 1975). 68 Table 34. Average length of shorthead and slimy sculp ins from the Flathead and ranges of lengths observed for all sculpins aged during this study., compared to collections of Glasser et al. 1981, Peden 1982, and Craig and Wells 1976. I II III IV V VI VII Flathead Shorthead 34 55 68 84 101 no 111 Slimy — 46 61 78 — — — Combined 31-39 46-64 53-84 73-110 94-105 no 106-116 Flathead (in Canada) Combined (Peden 35-39 45-51 60-70 1982) Clearwater Shorthead 30-35 41-47 54-56 66 77 (Classer et al. 1981) Chandalar Slimy (Craig & 28-44 45-59 54-79 55-87 74-95 83-107 99-104 Wells 1976) 69 Fish have been observed occasionally in sculpin stomachs. Both cut- throat fry and other sculpins were observed in stomachs. Sculpins have been reported as predators on eggs and fry of many salmonid species, however, in the 15 studies reviewed by Moyle (1977), only 0.6 percent of the sculpins had ingested salmonid eggs or fry. Sculpins will feed on fry or eggs, but do not seem to limit trout production (Moyle 1977). The role of sculpins as forage for trout has been demonstrated in both lake and stream habitats (Moyle 1977) . Parasites Sculpins collected in the North Fork and Coal Creek frequently contained large parasitic worms within their body cavity (Ligula). Ihe worms were so large the abdomens of parasitized fish were noticeably distended. WHITEFISH Stock Assessment Three species of whitefish were present in the upper Flathead basin; mountain (Pros opium williamsoni) , lake (Coregonus clup^formis) and pygmy (Prosopium coulteri). Uie mountain whitefish was widely distributed in lake and riverine habitats of the u£per basin (Table 35), Lake and pygmy white- fish were found only in Flathead Lake and their life history will not be reviewed here. Sgawning aod Early Pevelc>p.ment Mountain whitefish spawn in the fall from October through December (Scott and Crossman 1973, May and Huston 1975, Daily 1971). Spawning distri- bution of mountain whitefish has not been documented in the upper Flathead River basin. Fish movements and fry distribution provide a general view of the probable spawning distribution. Whitefish were observed primarily in the main forks of the Flathead River during October and probably spawned in the river and in large tributaries. Whitefish fry were c±>served in side channels of the North Fork and several tributaries in the basin. Fry were observed in Dolly Varden, Akokala and portions of Hay creeks. In the Kootenai River drainage, mountain whitefish deposited their eggs in the main river and several tributaries during October, when water temperatures dropped to 5°C (May et al. 1983). Davies and Thompson (1976) associated declining water temperatures with pre-spawning movements. Whitefish congregate in large pools of the river before spawning (Davies and Thomfson 1976). In the Kootenai River, three year and older whitefish broadcasted their eggs over gravels 25 to 200 mm in diameter, generally in riffle areas with depths of 0.15 to 0.61 m and velocities of 0.27-0.78 mps (May and Huston 1975). ResidsQce Whitefish distribution in streams was limited. Whitefish were observed in 39 percait of the streams and 28 percent of the reaches surveyed (Table 35). Whitefish 152 mm and larger were found in 37 percent of the surveyed 70 Table 35. Distribution of whitefish by size class (less than 152mm and lb2mm or larger), expressed as number (percent) of total reaches or tributary streams sampled in the upper Flathead Basin. Total Whitefish <152 mm Whitefish >152 mm Any size Whitefish Reaches sampled 185 19(10%) 48(19%) 52(28%) Streams sampled 92 24(26%) 34(37%) 36(39%) streams. Small whitefish (<152 mm) were located in only 26 percent of the streams and 10 percent of the reaches surveyed. Fry were rarely observed in streams. Whitefish were most often observed in the lower portions of larger tributaries characterized by highest stream order and lowest stream reach (Thble 36). Whitefish were more frequently seen in Middle Fork tributaries than in North Fork tributaries. In both the North and Middle Fork drainages, whitefish were more common in the streams draining Glacier National Park. This distribution may be explained by the warmer temperatures of Glacier National Park streams, many which flow from large lakes. It appears that streams were used seasonally by whitefish. April elec- trofishing surveys in tributary streams of the North Fork did not locate any whitefish. We believe whitefish moved into the lower portion of tributary streams to feed during peak river discharges, Whitefish moved out of tribu- taries during August. Over one hundred whitefish per day have been trapped moving downstream out of tributaries during the month of August, Similar whitefish movements were documented in the Sheep River drainage in Canada (Davies and Thompson 1976) which were also attributed to a food seeking response. 72 Table 36. Mean density and range of densities of whitefish observed in stream reaches 1-5 and stream orders 2-5 in surveyed sites within tributaries to the North and Middle Forks of the Flathead. Numbers in parentheses indicate number of sites where whitefish were observed. Reach Order Reach number Mean density Densities range Order Mean density Densities range 1 1.7(33) 0.1-16.9 5 5.6( 4) 1.3-16.9 2 0.9(16) 0.1- 2.6 4 1.1(21) 0.1- 4.3 3 0.9( 4) I o 3 0.9(29) 0.1- 1.6 4 — ( 1) 1.2 2 — ( 1) 0.1 5 ... 73 LITERAamE CITED Allan, J.H. 1980. Life history notes on the Dolly Varden char (Salvelinus malma) in the upper Cldarwater River, Alberta, Alberta Energy and Natural Resources, Fish and Wildlife Division, Red Deer, Alberta, Canada, Allendorf, F.W. and S.R. Phelps. 1980. Loss of genetic variation in a hatchery stock of cutthroat trout. Transactions American Fisheries Society 109:537-543. Antipa. R. 1974. 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Thesis, University of Victoria, Victoria, British Columbia, Canada. Lestelle, L.C. 1978. The effects of forest debris removal on a population of resident cutthroat trout in a small headwater stream. M.S. Thesis, University of Washinton, Seattle, Washington, USA. Lindsey, C.C. 1956. Distribution and taxonomy of fishes in the Mackenzie drianage of British Columbia. Journal Fisheries Research Board Canada 13(6) ;759-789. Lukens, J.R. 1978. Abundance movements and age structure of adfluvial westslope cutthroat trout in the Wolf Lodge Creek drainage, Idaho. M.S. Thesis, University of Idaho, Moscow, Idaho, USA. Mann, R.H.K. and C.A. Mills. 1979. Demographic aspects of fish fecundity syirposium. Zoological Society of London, 44:161:177. Mallet, J.L. 1963. The life history and seasonal movements of cutthroat trout in the Salmon River, Idaho. M.S. Thesis, University of Idaho, Moscow, Idaho, USA. Maughan, E.L. 1976. A survey of fishes of the Clearwater River. 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An appraisal of the cutthroat trout fishery of the St. Joe River. M.S. Thesis, University of Idaho, Moscow, Idaho, USA. Reiser, D.W. and T. Bjornn. 1979. Habitat requirements of anadromous salmonids. General Technical Report PNW-96. U.S. Forest Service. 54pp. Reingold, M. 1964. Movement of juvenile steelhead between tributary and mainstem streams. Idaho Department of Fish and Game, Project No. 1-000-07 Segment 2, Boise, Idaho, USA. Richardson, S.L, and B.B. Washington. 1980. Guide to identification of some sculpin (Cottidae) larvae from marine and brachish waters of Oregon and adjacent areas in the Northeast Pacific. U.S. Department of Commerce, National Oceanic and AtiiKDSpheric Administration, National Marine Fisheries Service. Circular 430, District of Columbia, Washington, USA. Rieman, B.E., J.R. Lukens. 1979. Priest Lake Creel Census, Idaho Pish and Game, Lake and reservoir investigations. Job Conpletion Report F-73-R-1, Boise, Idaho, USA, Scott, W.B. and E.J. Crossman. 1973. 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In conjunction with Montana Department of Fish, Wildlife and Parks, Kalispell, Montana, USA. Symons, P.E.K. 1974. Territorial behavior of juvenile Atlantic salmon reduced predation by brook trout. Canadian Journal of Zoology. 52:677-679. Symons, P.E.K. , J.L. Metcalfe and G.D. Harding. 1976. Upper lethal and pre- ferred temperatures of the slimy sculpin Cottus coonatus. Journal Fisheries Research Board Canada. 33(1) : 180-183. Tappel, P.D. 1981. A new method of relating spawning gravel size ccxrposition to salmonid embryo survival. M.S. Thesis, University of Idaho, Moscow, Idaho, USA. Thurow, R.P. 1976. The effects of closure to angling on cutthroat trout populations in two tributaries of the St. Joe River, Idaho. M.S. Thesis, University of Idaho, Moscow, Idaho, USA. Thurow, R.P. and T.C. Bjornn. 1975. St. Joe River - Cutthroat trout and northern squawfish studies. Job number 1. Life history of St. Joe River cutthroat trout. Jcb performance report F-60-R-6. 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Upwelling water as a factor influencing choice of spawning sites by brook trout (Salvelinus fontinalis) . Transactions of the Anerican Fisheries Society 105: 416-421. APPENDIX A Summary of results for downstream trapping of juvenile westslope cutthroat and bull trout in upper Flathead River tributaries from 1976 to 1981. Cutthroat - Akokala Creek June 1976- July -1977 Auqust September October Trap Days 13 39 37 24 Number of Fish 130 258 12 1 — Fish/Trap Day 10.00 6.61 0.32 0.04 — Cutthroat - Coal Creek 1977 June July August September October Trap Days — 31 31 30 20 Number of Fish — 381 79 12 0 Pish/Trap Day — 12.29 2.55 0.40 0.00 June Cutthroat - Trail Creek 1977-1979-1980 jIuIv August September October Trap Days 7 76 62 47 20 Juvenile Fish 27 422 97 73 48 Juvenile Fish/ Trap Day 3.86 5.55 1.56 1.55 2.40 Cutthroat - Red Meadow Creek 1976-1977-1979-1980 June Julv August September October Trap Days 17 16 72 60 39 Juvenile Fish 114 663 45 1 0 Juvenile Fish/ 6.70 10.87 .62 .02 — Trap Day A1 Cutthroat - River Trap 1977-1979-1980 June July Aucoist Sept^iibej: Ogipbei. Trap Days — 27 58 36 12 Juvenile Pish — 107 174 23 3 Juvenile Fish/ Trap Day 3.96 3.00 .64 .25 Dolly Varden - Red Meadow Creek June 1976, 1977 July , 1979 Auqust September October Trap days 15 83 72 60 39 Number of Fish 19 143 42 2 0 Fish/Trap Day 1.27 1.72 0.58 0.03 0.00 Dolly Varden - Trail Creek 1977, 1979 June July Auqust September October Trap Days 5 62 62 46 20 Number of fish 22 273 106 47 0 Fish/Trap Day 4.40 4.40 1.71 1.02 0.00 Dolly Varden - Whale Creek 1977 June July August Sebtsnbei^ October Trap Days 1 31 31 30 20 Number of Fish 1 22 59 11 0 FishArap Day 1.00 0.71 1.90 0.37 0.00 Dolly Varden - Big Creek 1977 June July August Sect ember October Trap Days — 31 31 . 30 20 l^amber of Pish — 25 49 2 2 PishArap Day — 0.81 1.58 0.07 0.10 A2 Dolly Varden - Coal Creek 1977 June July August Septeniber October Trap Days 31 31 30 20 Number of Fish — 33 7 7 2 FishAtap Day — 1.06 0.23 0.23 0.10 Dolly Varden - Giefer Creek 1981 June July Auqust September October Trap Days Number of Fish Fish/Trap Day 27 55 2.04 21 11 0.52 Dolly Varden “ 1981 Jime July Bear Creek August September October Trap Days 30 31 31 7 Number of Fish 3 9 11 3 — Fish/Trap Day 0.10 0.29 0.35 0.43 — — A3 APPENDIX B Summary of tag return information illustrating movement of westslope cutthroat and bull trout in the upper Flathead River Basin. Appendix Bl. Cutthroat moving into or out of tributaries of the North and Middle CO AS O I 5 g rC •P CJ •H 0) IS CO p (U 0X1 ^ CO H C 00 o CO H 0 o (U 00 p. CO H P a: p o4 G cu tP o o b 0 o 0 •TO t3 73 13 73 no CO <-H 1^ vD r>» I I I I CO CM r>. ■sT CO MT MT VO Mj- CS) CN f-c (N F-i cs r» cx) m O O vO c» r>. CM vO uo m CM o o 1^ CM vO vC vO vO vO CO rH f-H t-H Mj" CM I I I I I I I I I o o o 73 73 TO 0.0,0 0 0 p 73 73 P. P P P P P P P r-l CO CM 'O CM ^ vO CO CO Mr CO cjv (30 00 Mf CO cv CO CM 07 MT VO mT MT f—( 07 07 07 (37 07 07 CO CO CO CO CO CO CO O vO C37 mT f-t O UO CO CM (37 CM r«. 00 I I I I MT •-< CO V — I r— I »— I 1— ( CM CM vO vD vO .-t t-H CO CO Mr >-H rH CM CM CM CM VO vO VO vO o o o o o o 73 *0 73 'O 73 *0 (N uo m m I VO vn mt CO I I I I I I I I I I I I CM m IT) (O vo iTi Mt CO OD 07 o Oi CO lO CM 'T ■— I CM vO vn 1 0 0 0 vO m 1 m 0 sr 00 <• 0 :§ pH 1 rH 1 rH 1 (37 1 MT 1 rH 1 1 rH »H CM vO CM CM 1 CM 1— ( CM CO rH rH fH CM CM 1 (37 1 1 C37 1 m 1 10 1 LTl 1 m 1 1 1 mT 1 mT 1 m 1 tn 1 1 1 vO 1 1 1 1 1 1 vO 1 , vO AS p B ■7 0 73 l-l 0 0 0 CO AS (U 0 0 s W < Pi Bl Movement (km) Tag Tag Tag Within Out of Total (km) Mark Recapture Length type color number sector sector movement Direction o •o S* & 9 o cv. o o 3 TJ 73 O O 73 -O 3 O •3 0,0 0 3 ■3 TS O O -3 73 O CM ON CM CO CM m r>. CM CM r-l CM ON CM 00 00 m ON 1—1 m CM CO r-4 ^ CM V ro I I I I I I I I I I 11^ 00 I CO I MJ- 00 -iT I CM I I I I I I CM i-H CJN CM CM lO CM CM O 00 Os 00 CM MT CO CM CM 00 O pH o CM O V CO MT m NO CM NO m CO CM o m CM pH 00 CO sr ON CO CO CM CO 1^ CO o NO O o CM CO CJN -a- NO m m m m in m o O o CO CO CO 0k 0k «% 0k 0k 0k •1 0k CM CM CM CM CM r— i m m in MT NO CM CO NO CO CO CO m rH CO CO CO o o NO X •H -3 C 3 00 W 3 C O, •H O, 3 < V-i n MT MT vO f-* in CM cy\ CM 00 CM CM CM CM CM CM m Mr CM 00 NO 00 00 i-H CM CM CM CM CM MT ON CO CM CO m CO CM CM CM CO O i-H m vo CM CO CO MT I I I I I I o ON ON NO NO NO NO NO 00 o CM C3N o P^ p^» CjN ON p> p* p- p^ 1 1 00 NO 00 1 1 P'- 1 1 1 1 1 m m O NO 1 1 1 1 CO NO 1 1 00 CM CJN 'a' 1 1 CM •— 1 vO •sT CM CM m NO CM rH rH rH CM CM rH 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 O 00 ON ON 00 00 P^ 00 ON NO 00 ON p» CO 00 o o ON O ON ON ON P- NO NO NO p* o 00 00 CM P^ 00 CJN P' P^ p» NO P^ r>. m NO 1 1 NO 1 1 P^ 1 1 1 1 1 1^ 1 1 1 m 1 CM in 1 CO 1— 1 1 pH CO -a" 00 1 CO CO CJN 1 o 1 CM CM CM 1 1 CM 1 CO 1 1 rH CM 1 rH 1 ■— 1 p^ 1-H CM 1 CM rH 1 1 rH 1 NO 1 1 00 1 PN. 1 00 1 P^ pt 1 1 Mf 1 •a- CJN 1 P^ 1 I p. 00 1 ON /“S • rH IP u M pH I u • N-X Nd M 3 i-i 3 rX 3 3 3 3 3 o 3 M 3 3 U 3 O O 3 M U W •rl fo CJ pH 3 M O CJ O 4J 3 r-N M 3 3 3 /••n U O rH 00 3 O ,o rH 3 '3- r-l On 1— 1 o > CM T3 O rH O rH 5 •rl 3 NO •u rs •rl 00 M 00 t— 1 rH 3 rH •3 U 3 3 O 3 3 >«✓ 3 3 •3 3 M Pi O •rl >-l U 3 O •rl 3 4-1 H X u: H CO O w X PQ CO B2 Appendix B2. Bull trout moving into or out of tributary streams from (to) another river sector. c o o o o o -o TS Ta o o o o o TS 'O 'O T3 TD OOOOOOOOOO 'U'U'O'U'O'U'OTa'uta i§ T3 T3 O g g § g o o o o •u 'O X) Xl 4J B c Si iH 0 CO C3N cr> vO m m vD m o CM o 00 vO m CO I-H 00 vO CJN CM 00 vO 00 vD LO vO m vD 00 00 CM o O C H o ^H I-H ^H I-H r*H ^H f-H I-H I-H I-H f-H f-H f-H f-H r-H f-H r— H QJ B B (U > o CM M S O O <3- CO vO m o 00 vO d* ^H CO cn f-H vD • 1 • 1 1 1 u CJ '— ivocor- (CN m'-.r^mm^or^r^ ro lO lO lO lO o o o o o o lO lO lO lO lO LT) bO O nj fH H O O O sf --HVO oooooooooooooooo .4 0 a CO a (U Pi AS Mf MT -a- 1^ 00 p^ ON 00 pH PH pH uo f-M 1 1 PH 1 1 1 1 1 1 o uo 1 pH Mf CM o I-H 1 00 1 I-H 1 I-H . 1 ON CM 1 t I-H 1 1 CM 1 1 1 1 CM 1 VO 1 1 00 pH 1 vO 1 PH 1 CM pH pH MT 1^ pH O pH UO uo l><. PH 1 00 pH 1 P-- 1 1 PM PH pH 1 CJN 1 CO O 1 1 CM CO 1 CM O CM 1— H pH pH 1 CM CJN 1 CM 1 1 1 1 O 1 1 o 1 00 Cm ON ON I-H pH f-H 00 I (Ti 0> CO I 00 . vx) UO (T> CO O CO cr> CN vO vO vO CO CM O cr> o vO 00 csl SD 1^ X5 CN . — t O 00 . — * vO vO UO ^ m vo m ro m m m mill I cs m cs 00 I I I I ro vO c vO 'O’ m m uo m m m I m I I CO I m CM cr\ •-I CM I 1-1 I I CM I \o • m m cn m uo m m m I I I m m m I CM .-I CM CM I I I I f-H CO C t m vo vo m uo m m I I I I C3^ vT -✓ AS (U 0) 01 o 01 0) 0) 0) 03 iH Vh 60 >H CO U CJ CO u ^ 01 \ /~H q CJN X 01 vO H O •H iH CO uo iH VO •H 00 CO CO 03 H^ CO CO >H 0 ^ 0 »4-l 1-4 o O CO CJN CO f-H fH CO so CO so 00 CO CO m CM CJS 1^ 00 CO 3- . n. •H 3- CJN CJN O o o o o O O m o so o CO rH rH rH rH rH rH rH rH o o o o o o 'O "O 'O 73 T3 'O CO m CM m o o o o o o •TO T3 'O T3 'O 73 COOComOOCMvOOOO o o o o o o o •XJ 10 TD 73 73 13 T3 vO'd’iAO'— lOr^OOLTii-H CO m vo 00 00 00 CO m 00 00 cocrvcomoNcocMvooicM ooooo--ioaNCN'^o •-H CM i-H CM CM iH 1—1 CM f— < CM m m \o «g- 00 O O O O CM -< uo m uo m » vO sQ ViO vQ f'-C'* I r-i^p^t^r^sor^ I I m I I I 1 I r- 1 CMOOi-cCOmTsOCOCO I CM CMCM |i-4i-4i-4i— 4CMCO— 4 I I O I I I I I I I ONONi-hONONONOOOOONOO so 00 00 C3N 1^ r^r^t^i^r^cJN ir^r^t^ r" I I I r>. CO r-- n- I I CM o I CM I I I 0O0OCMCOi-4t^ I COCMCO I I I I I I CM I II cMsoi-iincMi^i-Ht^i-cr^ sO vO ViO vO vO vO vO vO r^r^r^soi^r-'f^r^c^ I I I I C" I I I 1 I m cMcoi-4 1 coinincofOi-4 CM CM CO 00 -H --4 1-4 I I I I I I I I I I o o o sOOOOOONOnONONi— 4 1-41—4 B IH • 1^ iS illi CJ W4 CU s_ CU CJ CU (U g >H a iH /— \ iH fo C.J c> CJ . CU CU /— s /-N cc 4J c M O rH 00 c fH C CU m 13 O rH o •r •H O iC CO rH rH (U rH CC CO O CA 3 >- »H •H CO o f= H u rc B4 10-23-76 5-31-78 673 2 3 4055 Appendix B3. Distance cutthroat and bull trout moved after being tagged in the main river, North Fork, Middle Fork or Lake, Flathead River Basin, Montana. Distance moved (miles) None 2-47 48-95 96-144 145-192 193-240 Cutthroat Main River 62 134 69 21 3 3 North Fork 29 68 25 12 2 1 Middle Fork 26 30 10 10 1 1 Lake 1 2 -- -- -- -- TOTAL 118 234 104 43 6 5 Percent 23 46 20 8 1 1 Bull trout Main River 6 12 4 1 North Fork 21 9 6 7 22 16 Middle Fork 14 29 7 -- 3 1 TOTAL 42 54 19 8 31 19 Percent 24 31 11 5 18 11 B5 Appendix B4. Percentage (number of fish) of the tag returns in which fish had moved 2-47 km. 48-95 km. 96-144 km. 145-192 km 193- 240 km, or had not moved. N None 1 2-47 Distance moved in river (km) 1 /I C 1 no Cutthroat (510) 23% (118) 46% (234) 20% (104) 8% (43) 1% (6) 193-240 1% (5) Bull trout (173) 24% (42) 31% (54) 11% (19) 5% (8) 18% (31) 11% (19) B6 Appendix B5. Cutthroat trout (225-614 mm) marked in Flathead River between November and May 1952-1982 which were returned, listed by section of the basin and month of return. Percent of each month's return is presented for each basin section. x: (o 4-> +J c o o 4-> 5^ C\J (T> O CM tn CM CT> ^ CM CX3 in cx) CM tn CM CM 00 cxj m n CM — I— t ro C3^ C30 o CM ooomo^a- O ^ t— ( cn 00 1^ ^ CM oo CM o ID C7> 00 ^ r-H CM 00 ^ (7» LO — 'CM CM LD CO CM CO in 00 CM 00 00 lO CM T— I ro 3 c ro r5 >» s~ fO 3 S» O) x: o •r“ (U >, U) 3 i- S~ >> c CD la a. CO 3 3 13 ze: c z: •3 '3 OJ $- $- XI $_ OJ (L) E 0) XI Xi (U XI E E +-> o CLI (U CL +-> > u O) o o CU oo o z Q B7 s- o -(-> o OJ I/) 1/1 fO XI o ro CD 4- O c o 3 XI •r~ i- 4J c o o o CM CM CO 1X1 oi o CO LO ro CO CO CD 1/1 CL) *4- 5- O 3 4-> t- a. ai CO Xi u E CU 3 S- recaptures (26) APPENDIX C Age-growth information for westslope cutthroat and bull trout in the Upper Flathead River drainage. North Fork 1977- 55 Drainage 1931 (2,107) 1977 58 (743) 1980 51 (795) 100 .917) 144 (1.192) 186 (287) 242 (18) 106 (729) 152 (466) 195 (135) 248 (5) 94 (749) 133 (470) 171 (115) 227 (9) Middle Fork 1980- 55 Drainage 1981 (880) 1980 58 (428) South Fork 1981 58 Drainage (199) TOTAL 55 (3,096) North Fork 1977& 54 River 1980 . ( 197) 1977 58 (70) 1980 52 (127) North Fork 1977- 54 tributaries 1981 (1.820) 1977 58 (673) 1979 54 (288) 1980 51 (668) 1981 55 (191) Middle Fork 1980 60 River (183) 101 (792) 153 (499) 213 (136) 264 (19) 293 (3) 103 (386) 153 (276) 221 (92) 275 (17) 106 (199) 152 (180) 202 (97) 256 (19) 323 (1) 100 (2,908) 146 (1,871) 194 (520) 251 (56) 301 (4) 97 ( 191) 138 ( 129) 166 ( 35) 214 ( 3) 112 (64) 147 (22) 90 (127) 135 (107) 166 (35) 214 (3) 100 (1.726) 145 (1,063) 189 (252) 247 (15) 105 (665) 152 (444) 195 (135) 248 (5) 101 (249) 153 (169) 203 (34) 265 (4) 94 (622) 132 (363) 173 (80) 234 (6) 97 (190) 143 (87) ^13 (3) 110 (183) 164 (167) 223 (85) 275 (17) Cl Appendix Cl. (Continued) Year I II III IV V VI Middle Fork 1980- 54 100 149 205 254 293 tributaries 1981 (880) (792) (499) (136) (19) (3) 1980 57 98 138 195 (245) (203) (109) (7) 1981 53 101 153 207 253 (632) (586) (387) (126) (16) South Fork 1981 59 108 155 206 273 323 River (113) (113) (107) (69) (11) (1) C2 Appendix C2. Back-calculated length at annulus for cutthroat trout, listed by tributary, in the North Fork portion of the Flathead River basin. Age Creek name Year I II III IV V Langford Creek 1980 56 (148) 103 (148) 147 (84) 197 (26) 250 (4) Coal Creek 1977 60 (250) 108 (245) 151 (151) 189 (61) 173 (1) 1979 57 (25) 102 (14) 136 (4) 174 (3) 1981 56 (78) 101 (78) 145 (59) 213 (3) Cyclone Creek 1981 55 (113) 94 (112) 142 (28) Logging Creek 1980 46 (33) 88 (30) 136 (9) Moran Creek 1980 51 (78) 88 (76) 116 (32) Hay Creek 1980 49 (113) 91 (108) 134 (82) 166 (29) 225 (1) Akokala Creek 1977 56 (214) 103 (213) 149 (166) 188 (49) 189 (2) Red Meadow Creek 1977 52 (68) 100 (68) 146 (43) 197 (12) 1979 52 (223) 101 (195) 153 (134) 194 (19) 184 (2) 1980 50 (127) 100 (123) 138 (76) 172 (12) Moose Creek 1980 50 (159) 86 (136) 117 (79) 144 (13) 178 (1) Whale Creek 1977 64 (82) 118 (80) 175 (52) 238 (6) 329 (1) Trail Creek 1977 54 (59) 98 (59) 147 (32) 254 (7) 362 (1) 1979 58 (40) 101 (40) 161 (31) 223 (12) 347 (2) 1980 45 (81) 90 (80) 126 (17) 173 (2) C3 Appendix C3. Back-calculated lengths of cutthroat trout, listed by tributary, from the Middle Fork portion of the upper river basin. Creek name Year I II III IV V Essex Creek 1981 53 96 146 201 (90) (82) (46) (7) Park Creek 1981 60 no 156 208 (54) (52) (44) (13) Ole Creek 1981 49 100 154 207 287 (94) (94) (90) (33) (4) Muir Creek 1981 51 100 145 206 (83) (59) (42) (8) Bear Creek 1981 63 118 172 222 273 (90) (89) (82) (37) (4) Geifer Creek 1981 55 105 149 199 (119) (108) (45) (4) Challenge Creek 1980 56 99 138 (158) (125) (65) Dodge Creek 1981 46 82 130 182 228 (102) (102) (38) (24) (8) Basin Creek 1980 57 94 130 177 (78) (69) (35) (4) C4 Table C4. Incremental growth of cutthroat (growth per year for each age class) determined from back-calculated lengths at annulus for fish collected from different portions of the basin during different years between 1962-1981. Portion of Growth Increment period Flathead drainage N 0-1 1-2 2-3 3-4 Lake (62-81) 573 64 56 69 72 Mainstem (81) 250 55 48 51 90 Main portions (63) 559 56 63 77 91 North Fork (77-80) 197 54 43 41 28 Middle Fork (79-80) 183 60 50 54 59 North Fork tribu- 106 58 56 64 38 taries (63) North Fork tribu- 1820 54 46 45 44 taries (77-81) Middle Fork tribu- 880 54 46 49 56 taries (79-81) C5 Table C-5. Back calculated lengths at annulus formation of bull trout in the upper Flathead Basin (1968-1981). rH 1 1 1 1 1 1 X n ^3* CO <3* 1 1 1 1 1 1 — Cx X-. 1 1 1 1 1 1 1— 1 CM 00 00 1 in •St 1 1 1 1 1 HH CO CO in CM 1 in 1 1 1 1 1 > VO x-' 1 VO — ' 1 1 1 1 1 VO cr> VO CM •St CO tx. sd- 1 1 1 1 1 VO CM VO o rx VO CM 1 1 1 1 1 HH lO in r-t m x-' in — ' 1 1 1 1 1 > (/) 3 VO OD VO 00 o 'd' cn in 1 1 1 1 1 E CO VO CO VO S3- — CO — ' 1 1 1 1 1 E x^ cn .—X .—X .—X X c > CM rx. .-1 CO rH CM rx r-4 oo«d-co«d-orxo0'd- (U cr> CM CT> in O r-i cn VO CM CM 1—4 VO CM 1 1— CM cr* C4 00 CO CM C\Jx_^CO 1 x—^ x.—-* x»-^ 1 la o .^“x ^■x X X X X S h- VO »— • sr 00 in o in CM incMCMcooocncovocnvD CT» VO O CM VO VO VO rx LnLnocMvocMin«a-co HH 1-H rH CM cr> T— 4 t— 4 1—4 1—4 CM 1—4 i-H r— 4 HH rt x_. X_— X*-. x_^ x_^ 1— < 00 r— < fx. VO o o rxCO«:tCMCOCOCn ■a i- ip p >> ro O 3 ro dl l4_ (U O O) S. ^ J:d •3 cu o > > c ■o -is: s Ol CU .c (0 •r- .--“x -r-^-x o 0) O d) (U ■o ■M _J ct: •— I s- q; •— 4 -ir'CU’OPS- C iQ $- 00 O 00 in P P ro C_> C_> dJ fO n- T3 o TO m Li_ -a cn OJ O CJ (U O Lt- •P -P Px to -P 00 Ol ■p o CU J- x: 3 Q. <0 S- 40 xj 40 cn > t- c_) QC t— 3: s- •o CL O r— 1—4 3 o c: < ZD Ll. 2: Lu^ s: u-x— •O z C6 Table C6. Incremental growth (growth between years) of bull trout during their first four years determined from back-calculated lengths at annulus, collected from various parts of the Flathead Basin. Area Year 0-1 Incremental 1-2 growth 2-3 3-4 Lake 1963 (Rahrer) 69 68 115 129 Lake 1963 68 62 72 86 Lake 1968 68 57 67 73 Lake 1980 59 60 67 75 North Fork 1955 (Block) 76 74 84 101 North Fork 1977-1981 72 45 53 148 Middle Fork 1981 49 44 51 127 C7 ^ ' ' ' ' ^uEK .11 ,.>fit*i ■ , ■ ' ■''"* '.l^ ll.'. Ij^d ^<'W ((ti!' : I Njf&'’..' r-ir,>'-;^ SuRil?'' I