Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. % S‘ V .F48 Resident Trout and Movement: Consequences of a New Paradigm Michael K. Young Rocky Mountain Forest and Range Experiment Station 222 S. 22nd Street, Laramie, Wyoming 82070 Restricted Movement: Abstract The Prevailing Paradigm Trout living in streams have been thought to move Unlike their anadromous relatives, stream-resident very little throughout their entire lives. Recent trout are often considered to be relatively immo- research has demonstrated that adult brown trout, bile. For example, Northcote (1992) stated that Colorado River cutthroat trout, brook trout, and the “home ranges for [such] yearling and older rainbow trout werefar more mobile than previously salmonids are ... usually a few tens ofmeters.” The believed. The mobility oftrout has probably affected notion of restricted movement ofstream-dwelling estimates offish abundance, perceptions ofhabitat trout has persisted for over 50 years (Hoover and quality, and the delineation ofpopulations, and Johnson 1937; Gerking 1959), and has been could nullify the desired outcome ofrestrictive applied to trout species as different as cutthroat angling regulations. Also, byfragmenting streams trout (Oncorhynchus clarki) (Miller 1957; we may be reducing the probability ofpersistence of Heggenes et al. 1991) and brown trout (Salmo native trout populations by restricting movement F:fmttd)fStefkmcKT952; Bachman 1984). and thus restricting population yize. sDjy IVIHiS INkdync d 0*1 =ti 81 d3S %bl Advaaii oibiDv i.iVH USDA vQsn Forest Service Forest Service Fish Habitat Relationships Program Leaders or Representatives FHR Currents Purpose National FHR Program Region 8 The USDA Forest Service Fish JWeafsfhreiyngL.toKnerOsffhinceer - WCiilndldiyfeA,.FWiislhli&amBso,taSnoyutShteafrfn Region & Habitat Relationships Program Fish Wildlife Department 1720 Peachtree Rd. was established to further the ULotgaahn,StaUtTe U8ni4v3e2r2s-i5t2y10 N.W Atlanta, CA 30367 development offisheries Region 9 technology and transfer this Region 1 technology to field biologists. Bob Hollingsworth, Northeast Region With ever increasing demands KathyMoynan, Northern Region USDA Forest Service for natural resources, protection (Anadromous Fish Program) 310W. Wisconsin Ave. and management of aquatic Nez Perce National Forest Milwaukee, WI 53203 Route 2, Box 475 communities requires biologists Grangeville, ID 83530 to be knowledgable of current Region 10 - research findings and state-of- " Brian Sanborn, Northern Region Ron Dunlap, Alaska Region the-art techniques. The purpose (Resident Fish Program) Wildlife, Fish & BotanyStaff ofFHR Currents is to provide a _ DFeedeerrlaoldgBeuiNladtinigo,naBloFxor4e0s0t JFuendeearaul,OAfKfic9e9B8u0i2l-di1n6g2,8Box 21628 vehicle to quickly disseminate Butte, MT 59703 information important to field- Intermountain/Northern Region USDA level biologists in the Region 2 Forest Service. Kerry Overton, Fish ResearchWorkUnit R. Nick Schmal, Rocky Mountain Region Intermountain ResearchStation & Wildlife, Fish BotanyStaff 316 E. Myrtle St. Univ. ofWyoming, College ofAgriculture Boise, ID 83702 RO. Box 3354 WY Laramie, 82071-3354 Associates Submissions: Regions Glenn Chen Bryce Rickel, Southwest Region Fisheries Biologist/MonitoringSpecialist, Ifyou wish to submit a paper for <- Wildlife, Fish & Botany Staff USDA Forest Service publication in FHR Currents, Federal Building Fish 61Wildlife Department please contact the following A5l1b7uqGuoelrdqAuvee,l,NSM.W87102 ULotgaahn,StaUtTe U8ni4v3e2r2s-i5t2y10 > people for information and guidelines: , w, Region 4 Fred Mangum Aquatic EcosystemAnalysis Lab 105 Page School JT(ee7rc0rh7yn)iBc4oah4le1r-Eg3d/6iKt6ao9rresn Kenfield " : W3SOi2geld4odenl2ina5f,etL,.hUFTBSitr.so8hw4n&4,0B1IonttaenrymoSutanftfain Region BPrroivgoh,aUmTYou84n6g0U2niversity \ Ken Roby _ - Six Rivers National Forest Hydrologist, USDA Porest Service Region 5 Pacific Southwest ExperimentStation Fisheries Department PO. Box 245 1330 Bayshore Way Jerry Boberg, Pacific Southwest Region Berkeley, CA 94701-0245 Eureka, CA 95501 ^ - (Anadromous Fish Program) Six Rivers National Forest Larry Schmidt 1330 BayshoreWay Stream Systems Technology Center Artwork by: Eureka, CA 95501 USDA Porest Service Jerry Boberg, Rocky Mountain ExperimentStation SixRivers National Forest 240 W. Prospect Jeffery Reiner, Pacific Southwest Region Port Collins, CO 80526-2098 (Resident Fish Program) Lake Tahoe Basin ManagementUnit MarkVinson 870 Emerald Bay Rd., Suite 1 South Lake Tahoe, CA 96150 Hydrologist/Monitoring Specialist, USDI Bureau ofLandManagement & Pish Wildlife Department Region 6 Utah State University, Logan, UT 84322-5210 Deborah Konnoff, Pacific Northwest Region & Wildlife, Pish Botany Staff 333 S.W. 1stAve., RO. Box 3623 Portland, OR 97208 FHR Currents Unfortunately, the methods used in movement New Views of Movement studies favor relocating immobile fish (Gowan et ah, in press). The procedure for most studies was Recent research in the Midwest and the Rocky to mark fish in relatively short reaches ofstreams, Mountains has disputed the paradigm ofimmobil- return to these same reaches weeks to a year later ity ofstream-dwelling trout. Clapp et al. (1990) to resample them, then discuss only the recapture and Meyers et al. (1992) used radiotelemetry to of marked fish. Usually few ifany areas outside monitor the positions oflarge brown trout in the selected reaches were sampled. Because most Michigan and Wisconsin, and observed seasonal marked fish that were recaptured came from the movements of over 30 km. Similarly, Young (in reaches where they were originally marked, the press) implanted transmitters in over 50 adult authors considered this evidence for a lack of brown trout in tributaries of the North Platte River movement. But they typically failed to address the fate of the 15 to 90% ofmarked fish that were iknmWyanodmihnygpo.th1eosbiszeerdvetdhaftisfhismhobveignagnasspafawrnaisng96 never recaptured, or attributed their absence to migrations from the river to the tributaries in late mortality or lost marks. Studies employing other techniques, such as direct observation, were - July, wintered in the tributaries (often in deep pools), and returned to the river during spring handicapped because fish were not followed high flows (Figure 1). Young (in review) used the during all seasons or at night (e.g., Bachman same technique to monitor much smaller Colo- 1984). Until the last five years, potential move- ment had been inadequately evaluated. rado River cutthroat trout (O. c. pleutiticus) and Figure 1. Brown trout movements in the North Platte River drainage. The dotted line represents hypothesized summer-fall movements into the tributaries, and the dashed line represents hypoth- esized spring-summer movements into the river. Small letters represent observed movements of three brown trout: fish "a" moved 23 km, fish "b" moved 66 km, and fish "c" moved 96 km. FHR Currents — m detected movements averaging over 300 (and Up- and downstream effects. Another beliefis the up to 2.4 km) in mid-summer. Twenty-four-hour overriding importance oflocal habitat on fish observations ofboth species revealed numerous populations. For example, structural rehabilitation movements of over 100 m and up to 1.1 km has been thought to increase the abundance of (Young, unpublished data). Using two-way fish trout in a treated reach by increasing survival, but traps to monitor movement, Riley et al. (1992) this assumption has never been verified. In con- observed extensive, continuous movements of trast, Riley and Fausch (in press) attributed the brook trout (Salvelinusfontinalis) in mid to late increased abundance of trout in structurally summer in small Colorado streams. Investigations enhanced reaches ofsix Colorado streams to of these species, as well as rainbow trout (0. greater retention ofmobile fish arriving from mykiss) in Idaho (Middle Fork Salmon River, outside the treated reaches. This implies that the Bjornn and Mallet 1964; Silver Creek, Young, absence ofa critical habitat outside an “enhanced” unpublished data), continue to demonstrate that reach may be responsible for suboptimal trout movement is far more commonplace among adult densities within the reach. Consider that suitable trout than previously believed. edge habitat for fry of Colorado River cutthroat trout was usually unoccupied unless spawning habitat was nearby (Bozek 1990). Consequences of Movement The possibility of fish movement is frequently ignored when building in-stream structures not intended to enhance trout populations (e.g., water Many aspects of resident trout biology implicitly diversions or dams). One consequence is that fish rest on the assumption ofimmobility. If this may be blocked from seasonally critical habitats assumption is invalid, it challenges several tenets up- or downstream (e.g., spawning or over- ofcurrent trout management and research. wintering sites). Alternatively, such barriers may — cause the extinction ofmobile life history forms, Special regulations. Restrictive regulations are and if these forms are genetically distinct, their usually designed to reduce harvest ofsome or all genetic contribution to the population will be lost. ofa trout population. These regulations presume A genetic contribution to mobility is plausible but that the protected groups will remain within speculative Qonsson 1985; Northcote 1992). designated stream reaches. But this presumption is Regardless, these structures fragment populations not always correct; Clapp et al. (1990) noted that that then run a greater risk of extinction without some large brown trout, originally tagged in a no- the opportunity for natural recolonization. kill section of the South Branch of the Au Sable River, spent most of their time in a standard- Up- and downstream effects are not limited to regulation reach. In Wyoming, a slot limit has physical disruptions. The stocking ofnon-native mm protected 254-406 trout in the North Platte trout has led to the eventual loss ofmany indig- River since 1982 (Mike Snigg, Wyoming Game enous trout populations, except where barriers and Fish Department, personal communication), prevented migration of the invading species (see and this may have led to increases in the abun- Young 1995). For example, a single stocking of dance ofspawning adults in the tributaries during brook trout in a headwater lake apparently led to the spawning run. The tributaries, however, are their eventual replacement of Colorado River under standard regulations, and fluvial fish are cutthroat trout in most of the Battle Creek, Wyo- unprotected once they enter the tributaries (often ming watershed, except where a polluted stream as early asJuly). Ifanglers harvest these large fish prevented their invasion into unpolluted tributar- in the tributaries (and anecdotal evidence suggests ies (Eiserman 1958). Ironically, the relatively that they do), future gains to the overall popula- rapid spread ofintroduced populations was tion may be limited.__ apparently disregarded as evidence that trout were mobile. Page 2 FHR Currents Samplingfish abundance and population the North Eork Little Snake River and could have — characteristics. Most estimates of fish abundance been thought to represent the putatively isolated in streams are derived from one or a few short populations in any of the three streams. Because of reaches ofa stream, typically only once each year the potential seasonal and annual variability in (or less often). Movement of fish through these , population composition, we should consider the reaches would render counts suspect, in part by consequences of one-time sampling for describing violating an assumption ofmark-recapture esti- population genetic structure (Eausch and Young, mates. Decker and Erman (1992), after repeatedly in press). electrofishing adjoining reaches of one stream — throughout a summer, noted that the abundance Habitat modelling. Modelling may also be ofseveral trout species varied asynchronously. confounded by trout movement. Many habitat- They attributed this variability to species-specific based models, constructed from physical or movements, and questioned the value of one-time biological data often collected at a single point in sampling for estimating fish abundance. Over 50 time, attempt to predict the abundance or biomass years earlier, Shetter and Hazzard (1938) similarly ofsalmonids (see Eausch et al. 1988 for ex- concluded that “populations ofstream fish are amples). The inability to incorporate temporal relatively unstable in specific areas ofa stream variation in stream characteristics has been during the summer months, and ... calculations of recognized as a shortcoming ofsuch models i.e., stream populations from counts made on one or habitat characteristics change seasonally without two short sections ofstream at only one period of apparent concurrent changes in fish abundance the year are not reliable.” Long-term modelling of (Conder and Annear 1987). Yet rarely considered population fluctuations (Platts and Nelson 1988) is the potential temporal variation in fish abun- or community composition (Ross et al. 1985) are dance produced by mobility, which could add especially sensitive to annual or species-specific substantially to the unexplained variation insuch variation in mobility. Even one-time basin-wide models. Additionally, that species (e.g., brown inventories cannot account for trout mobility. trout) may not be in feeding positions when Merger et al. (in review) performed two basin- sampled by electrofishing (Young, personal wide surveys one month apart on each of two observation) may further degrade the performance streams, and noted that the redistribution of of these models. Colorado River cutthroat trout led to different — estimates ofhabitat-specific densities and overall Arbitrary definition ofpopulations. Perhaps trout abundance within each stream. because ofa perceived lack ofmobility in fishes, biologists often attempt to geographically, but not This unreliability can extend to other kinds of biologically, define populations. That is, we often sampling. Eor example, meristic and morphomet- designate the trout in a small stream as a single ric analyses were used to determine the genetic population (in a sense, isolated by immobility). purity of Colorado River cutthroat trout from two Yet rarely is this designation merited, because tributaries and the mainstem of the North Eork trout may immigrate to the small stream (to Little Snake River in southern Wyoming (Binns reproduce, feed, or escape floods) or emigrate - 1977). The analyses indicated that fish in the from it (to overwinter or escape desiccation). That mainstem were genetically pure, fish from the range ofa single population may include far Harrison Creek were obviously contaminated by more waters than the “type location” is consistent hybridization, and fish from Green Timber Creek with the emerging concept ofmetapopulations. were assumed to be intermediate. However, in Metapopulations consist ofa collection ofsub- movement studies conducted in 1992 (Young, in populations that are linked by immigration and review), a single radio-tagged adult occupied all emigration (Hanski and Gilpin 1991). The indi- three locations within 23 days. Moreover, nearly vidual subpopulations may thrive, suffer losses of all the fish originally captured in Harrison Creek genetic variation, or go extinct, but individuals and Green Timber Creek eventually migrated to from other subpopulations within the Page 3 / FHR Currents metapopulation can contribute to the growing Clapp, D.F., R.D. Clark,Jr., andJ.S. Diana. 1990. Range, subpopulations, restore genetic variation to small activity, and habitat oflarge free-rangingbrown trout in a Michigan stream. Transactions oftheAmerican Fisheries subpopulations, or found new subpopulations Society 119:1022-1034. after extinction. To persist, metapopulations must consist ofperiodically mobile individuals in Conder, A.L., andT.C. Annear. 1987. Test ofweightedusable habitats without continuous barriers to movement area estimates derived from a PHABSIM model forinstream flow studies on troutstreams. NorthAmericanJournal of (Gilpin 1987). Whether metapopulation theory Fisheries Management 7:339-350. explains trout population structure remains to be investigated, but it seems likely that most popula- Decker, L.M., and D.C. Erman. 1992. Short-termseasonal tions ofsalmonids have been founded by mobile changes in composition andabundance offish in Sagehen individuals from large populations (cf. Milner and Creek, California. Transactions oftheAmerican Fisheries Society 121:297-306. Bailey 1989). Eiserman, F. 1958. A fisheries surveyofthe Little Snake River drainage. Wyoming Game and Fish Commission, Cheyenne. Conclusions Fisheries Technical Report 6. Fausch, K.D., C.L. Hawkes, and M.G. Parsons. 1988. Models A new paradigm for stream-dwelling trout consid- thatpredictstanding crop ofstream fish from habitat ^ variables: 1950-85. USDA Forest Service, Pacific Northwest ers (but does not mandate) mobility as one of the Research Station, Portland, Oregon. General Technical Report possible responses to food, growth, competition, PNW-GTR-213. ^ - predation, environmental disturbance, and daily and seasonal cycles. Movement may be minimal Fausch, K.D., and M.K. Young. In press. Movement of under some circumstances e.g., abundant residentstream fishes and managingESU’S: a cautionar)^ tale. In Proceedings ofthe conference on evolution and the aquatic macroinvertebrates, complex habitats, and envi- ecosystem: definingunique units in population conservation. ronmental stability (cf. Bachman 1984). But American Fisheries Society, Bethesda, Maryland. because most streams are spatially and temporally heterogeneous, trout may elect to move frequently Gerking, S.D. 1959. The restrictedmovement offish popula- tions. Biological Review 34:221-242. and extensively. The challenge for managers and researchers is to recognize when and where Gilpin, M.E. 1987. Spatialstructure and populationvulner- movement will be advantageous or necessary for ability. Pages 125-140 in M.E. Soule’, editor. Viable popula- maintaining wild trout populations. tions for conservation. Cambridge UniversityPress, Cam- bridge. Cowan, C., M.K. Young, K.D. Fausch, andS.C. Riley. In Literature Cited press. The restricted movement ofstream-resident salmonids: a paradigm lost? CanadianJournal ofFisheries andAquatic Sciences. Bachman, R.A. 1984. Foragingbehavior offree-rangingwild and hatcherybrown troutin a stream. Transactions ofthe Hanski, L, and M. Gilpin. 1991. Metapopulation dynamics: American Fisheries Society 113:1-32. briefhistory and conceptual domain. BiologicalJournal ofthe Linnean Society42:3-16. Binns, N.A. 1977. Present status ofindigenouspopulations of cutthroat trout, Salmo clarki, in southwestWyoming. Heggenes,J., T.C. Northcote, andA. Peter. 1991. Spatial Wyoming Game and Fish Department, Cheyenne. Fisheries stability ofcutthroat trout (Oncorhynchusclarki) in a small, Technical Bulletin 2. coastal stream. CanadianJournal ofFisheries andAquatic Sciences 48:757-762. Bjornn, T.C., andJ. Mallet. 1964. Movements ofplanted and wild troutin an Idaho river system. Transactions ofthe Merger, L.-G., W.A. Hubert, and M.K. Young. In review. American Fisheries Society 93: 70-76. ^ Evaluation ofa basin-wide inventory ofcutthroat trout habitat insmall mountain streams. North AmericanJournal Bozek, M.A. 1990. Generalityofhabitat models for Colorado ofFisheries Management. River cutthroat trout fryand the influence ofadults on habitat choice and behavior. Doctoral dissertation. University Hoover, E.E., and M.S.Johnson. 1937. Migration and ofWyoming, Laramie. depletion ofstockedbrook trout. Transactions ofthe Page 4 . FHR Currents 1022385269 American Fisheries Society 67:224-227. Riley, S.C., K.D. Fausch, and C. Gowan. 1992. Movement of brook trout (Salvelinusfontitialis) in four small subalpine Jonsson, B. 1985. Life history patterns offreshwater resident streams in northern Colorado. Ecology ofFreshwater Fish andsea-run migrant brown trout in Norway. Transactions of 1:112-122. theAmerican Fisheries Society 114:82-194. Ross, S.T., W.J. Matthews, andA.A. Echelle. 1985. Persis- Meyers, L.S., T.F. Thuemler, and G.W. Kornely. 1992. tence ofstream fish assemblages: effects ofenvironmental Seasonal movements ofbrown trout in northeastWisconsin. change. American Naturalist 126:24-40. NorthAmericanJournal ofFisheries Management 12:433- 441. Shetter, D.S., andA.S. Hazzard. 1938. Species composition by age groups andstability offish populations in sections of Miller, R.B. 1957. Permanence and size ofhome territory in three Michigan troutstreams during the summer of 1937. stream-dwelling cutthroat trout.Journal ofthe Fisheries Transactions oftheAmerican Fisheries Society 68:281-302. Research Board ofCanada 14:687-691. Stefanich, F.A. 1952. The population and movement offish in Milner, A.M., and R.G. Bailey. 1989. Salmonid colonization Prickly Pear Creek, Montana. Transactions ofthe American ofnewstreams in GlacierBayNational Park, Alaska. Fisheries Society 81:260-274. Aquaculture and Fisheries Management 20:179-192. Young, M.K., technical editor. 1995. Conservation assessment Northcote, T.G. 1992. Migration and residencyin stream for inland cutthroat trout. USDA Forest Service, Rocky salmonids: some ecological considerations and evolutionary Mountain Forest and Range ExperimentStation, Eort Collins, consequences. NordicJournal ofFreshwater Resources 67:5- Colorado. General Technical Report RM-GTR-256. 17. Young, M.K. In press. Brown trout mobilityin south-central Platts, W.S., and R.L. Nelson. 1988. Fluctuations in trout Wyomingstreams. CanadianJournal ofZoology. populations and their implications for land-use evaluations. North AmericanJournal ofFisheries Management 8:333-345. Young, M.K. In review. Telemetry-determined movementand habitat use ofColorado River cutthroat trout (Oncorhynchus Riley, S.C., and K.D. Fausch. In press. Trout population clarkipleuriticus) CanadianJournal ofEisheries and Aquatic response to habitatenhancement insix northern Colorado Sciences. streams. 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