Resident trout and movement : consequences of a new paradigm

10 Pages·1995·0.77 MB·English

by  Young, Michael K

Historic, archived document
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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
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USDA
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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
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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
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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
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brook trout (Salvelinusfontitialis) in four small subalpine
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Meyers, L.S., T.F. Thuemler, and G.W. Kornely. 1992. tence ofstream fish assemblages: effects ofenvironmental
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NorthAmericanJournal ofFisheries Management 12:433-
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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.
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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.
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Young, M.K., technical editor. 1995. Conservation assessment
Northcote, T.G. 1992. Migration and residencyin stream for inland cutthroat trout. USDA Forest Service, Rocky
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Platts, W.S., and R.L. Nelson. 1988. Fluctuations in trout Wyomingstreams. CanadianJournal ofZoology.
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