Montana's Fish Species of Special Concern
Fluvial Arctic grayling
Patrick
A. Byorth
Dillon,
MT 59725
June
1996
Status
The U. S. Fish and Wildlife Service (USFWS) formerly classified fluvial Arctic grayling (Thymallus arcticus) in Montana as
"Category 1" under the Endangered Species Act; that is, enough substantial
information exists to support a proposal to list it as threatened or endangered
(USFWS 1991). This category was
renamed "Candidate" in February 1996 (USFWS 1996). A petition to upgrade the status of
fluvial Arctic grayling to endangered was submitted in October, 1991 (USFWS
1993). A recent finding on the
petition recommended that listing fluvial Arctic grayling was "warranted, but
precluded" by other higher priority species (USFWS 1994). A Memorandum of Agreement between USFWS
and Montana Fish, Wildlife, and Parks (FWP) was developed to maintain, at
minimum, current levels of restoration efforts while expanding a reintroduction
program. This agreement, signed in
February 1996, may affect the classification of fluvial Arctic grayling under
the Endangered Species Act (MFWP Files).
Fluvial Arctic grayling are considered a "species of special concern" by
the American Fisheries Society and FWP (Holton 1980, Williams et al. 1989).
In
contrast to still-common lacustrine/adfluvial populations , fluvial arctic
grayling appear adapted to inhabiting riverine environments year-round (Kaya
1991 and Kaya and Jeanes 1995).
Conserving these fish thus also means retaining their ability to exist as
fluvial populations. They are not
simply replaceable by lacustrine fish.
Presently, fluvial Arctic
grayling are only found in the upper Big Hole River. The fluvial Arctic grayling population
here has stabilized and appears to be increasing. Research has identified limiting factors
and management strategies to protect and enhance the Arctic grayling population
and its habitat. A program has been initiated to reestablish additional
populations throughout its native range.
Under current or expanded levels of effort, potential for recovering
fluvial Arctic grayling in Montana is excellent. However, under terms of the Memorandum
of Understanding with FWP, the USFWS will initiate a status review for listing
if the status of fluvial Arctic grayling should weaken in the future.
Distribution
At the end of the 19th
century, fluvial Arctic grayling were intermittently distributed throughout the
upper Missouri drainage above Great Falls (Vincent 1962). During the 20th century, the range of
fluvial Arctic grayling has been restricted to the Big Hole River of southwest
Montana, about 4% of its native range (Figure 1)(Kaya 1992a). Vincent (1962) attributed the decline of
fluvial Arctic grayling throughout their native range to four factors: habitat
degradation, introduction of non-native salmonids, climatic change, and exploitation by anglers.
Figure 3. Present distribution
(red dot) of fluvial Arctic grayling in Montana.
Life History/Ecology/Population
The fluvial Arctic grayling
population of the Big Hole River is monitored annually in the Wisdom area. The highest documented density of age 1
and older Arctic grayling in index reaches was 70/km in 1983 (Oswald 1990). The population declined to a low of
13/km by 1987 and stabilized at approximately 18/km from 1989 to 1993 (Byorth
1994). Fall surveys indicated that
the population had increased to 39/km by 1994, 42/km in 1995 and 38/km in
1996. In all years, the population
exhibited a balanced complement of age classes (Byorth 1995, Byorth and Magee
1996).
Although fluvial Arctic
grayling inhabit the entire Big Hole River, highest densities occur in the
vicinity of Wisdom. The majority of
spawning occurs near Wisdom in the main stem and several tributaries (Liknes and
Gould 1987, Shepard and Oswald 1989, Byorth 1994). Fluvial Arctic grayling rear in the
vicinity of where they hatch; thus, the Wisdom area provides the majority of
rearing habitat as well. Moderate
densities of Arctic grayling reside between the mouth of the North Fork Big Hole
River and Dickie Bridge. Limited
spawning occurs in lower reaches of several tributaries within this reach. Rainbow trout (Oncorhyncus mykiss) and brown trout (Salmo trutta) increase in abundance
below Dickie Bridge, where Arctic grayling are found in low densities.
Arctic grayling grow quickly
in the Big Hole River, reaching full sexual maturity and nearly maximal size by
age 3. Arctic grayling rarely live
beyond 5 years in the Big Hole River.
In contrast, Arctic grayling in Alaska mature from age 4 to 8 and
commonly live to 12 years (Armstrong 1986). Fast growth rates and short life spans
result in domination of spawning by age 3 and 4 fish. Thus, poor recruitment in a given year
may substantially affect recruitment to the population for several years.
Threats
Factors potentially
threatening survival of Arctic grayling in the Big Hole River include water
quality and quantity, competition with introduced species, predation, habitat
degradation, and impacts of angling.
Water quantity issues include drought and recruitment limitation due to
sudden runoff events. Sudden
increases in stream flows during hatching and emergence of larval Arctic
grayling may decrease survival and limit recruitment in the Big Hole River
(Shepard and Oswald 1989). Clark
(1992) reported similar detrimental effects, of high flows during swim-up, on
Arctic grayling recruitment in the Chena River, Alaska. Oswald (personal communication)
hypothesized that extreme flood flows severely impacted Arctic grayling
recruitment in the Big Hole River during 1984 and 1985.
Conversely, extreme low flows
during severe drought decrease survival of older Arctic grayling due to high
water temperatures, increased susceptibility to predation, and diminished
habitat volume. Diversion of water
for agriculture has exacerbated persistent drought conditions. All salmonid species in the
upper Big Hole River declined in abundance during the drought (Byorth
1993). During drought years, water
temperatures have surpassed lethal limits for Arctic grayling documented by Lohr
et al. (1996).
The distribution of Arctic
grayling in the Big Hole basin suggests that they are displaced by non-native
brown and rainbow trout. Recent
studies indicate overlap in microhabitat preferences between Arctic grayling and
rainbow trout (Magee and Byorth 1995).
Brook trout and Arctic grayling are sympatric in the upper Big Hole basin
near Wisdom, but appear to segregate according to microhabitat preferences
(Skaar 1989, Magee and Byorth 1994, Magee and Byorth 1995). However, predation on juvenile Arctic
grayling by all non-native species is also a potential limiting factor (Kaya
1992a).
Historically, angling may have
impacted fluvial Arctic grayling populations in Michigan and Montana (Vincent
1962). Arctic grayling are easily
caught by anglers and are susceptible to over-harvest. However, recent research suggests that
catch-and-release-only regulations enacted in 1988 in the Big Hole River
sufficiently protect the Arctic grayling population from over-exploitation
(Byorth 1993, MFWP unpublished data).
Another factor potentially
limiting grayling in the Big Hole River is habitat degradation. Degradation of riparian vegetation and
stream banks by cattle grazing, mass willow removal, and dewatering the river
for agricultural uses have negatively impacted fish habitat. High levels of fine sediments, high
mid-summer water temperatures, and loss of suitable habitat volume have impacted
Arctic grayling in the Big Hole River.
Management
The Fluvial Arctic Grayling
Workgroup (FGW) developed a plan to research, protect, and restore fluvial
Arctic grayling (FGW 1995). A
primary objective was to develop a brood stock from wild Big Hole River Arctic
grayling to preserve their genetic identity. Gametes were collected from spawning
Arctic grayling in the Big Hole River between 1988 and 1992, until a sufficient
founding population was represented (Leary 1991). Progeny of the brood stock with genetic
diversity equivalent to the wild stock were available in 1995. Arctic grayling derived from the brood
may be used to augment the Big Hole River population, if necessary, and to
reestablish other populations within their native range.
Another objective of FGW is to
expand the range of fluvial grayling beyond the Big Hole River basin. Kaya (1992b) identified streams suitable
for reintroductions of fluvial grayling.
Experimental reintroductions have occurred in Cougar Creek, Yellowstone
National Park, and in the West and East Gallatin rivers using progeny of the
brood stock. Intensive
reintroduction efforts are scheduled in 1997 for the Ruby River of southwestern
Montana and the Firehole and Gibbons rivers in Yellowstone National Park in the
near future.
Water quality and quantity
problems are being addressed in the Big Hole basin. Efforts are underway to develop
groundwater to supply livestock water while preserving minimum instream
flows. Supplementation of instream
flows through storage and water leasing have been investigated. Water conservation efforts in
conjunction with water users were successful in preserving flows during severe
drought in 1994.
A habitat inventory conducted
in 1994 will provide baseline information necessary to identify degraded
habitats and potential rehabilitation projects (OEA 1995). Projects will be oriented toward
riparian rehabilitation, decreasing peak water temperatures, and identifying and
protecting critical habitats. While
catch-and-release-only regulations protect grayling from over-harvest, angling
regulations will also be used to exert pressure on non-native trout. More liberal regulations may inhibit
encroachment of rainbow and brown trout into key grayling habitat.
REFERENCES
Armstrong, R. H. 1986. A
review of Arctic grayling studies in Alaska, 1952-1982. Biological Papers of the University of
Alaska, 23:3-17.
Byorth, P. A. 1993. Big Hole
River Arctic grayling recovery
_____. 1994. Big Hole River
Arctic grayling recovery
_____. 1995. Big Hole River
Arctic grayling recovery
_____. 1996. Big Hole River
Arctic grayling recovery
Byorth, P. A. and J. P. Magee. 1996. Big Hole River Arctic
Clark, R. A. 1992. Influence of stream flows and stock size
on recruitment of Arctic grayling (Thymallus
arcticus) in the Chena River,
Alaska. Canadian Journal of
Fisheries and Aquatic Sciences 49(5):1027-1034.
Fluvial Arctic Grayling Workgroup.
1995. Restoration plan
for
Holton, G. D. 1980. The riddle of existence: fishes of
special concern. Montana Outdoors
11(1):2-6.
Kaya, C. M. 1991. Rheotactic differentiation between
fluvial and lacustrine populations of Arctic grayling (Thymallus arcticus), and implications
for the only remaining indigenous population of fluvial �Montana grayling�. Canadian Journal of Fisheries and
Aquatic Sciences 48:53-59.
_____. 1992a. Review of the decline and status of
fluvial Arctic grayling (Thymallus
arcticus), in Montana.
Proceedings of Montana Academy of Sciences 52:43-70.
_____. 1992b. Restoration of fluvial Arctic grayling
to Montana streams: assessment of reintroduction potential of streams in the
native range, the upper Missouri River drainage above Great Falls. Prepared for: Montana Chapter of the American
Fisheries Society and Montana Department of Fish, Wildlife, and Parks,
Bozeman.
Kaya, C. M. and E. D.
Jeanes. 1995. Retention of adaptive rheotactic
behavior by F1 fluvial Arctic grayling. Transactions of the American Fisheries
Society 124:453-457.
Leary, R. F. 1991. Establishment, maintenance, and use of a
genetic reserve of Big Hole River Arctic grayling. Wild Trout and Salmon
Genetics Laboratory Report 91/5.
University of Montana, Missoula.
Liknes, G. A., and W. R. Gould. 1987. The distribution, habitat, and
population characteristics of fluvial Arctic grayling (Thymallus arcticus) in Montana.
Northwest Science 61(2):122-129.
Lohr, S. C., P. A. Byorth, C. M. Kaya, and W. P. Dwyer. 1996. High temperature tolerances of fluvial
Arctic grayling and comparisons with summer water temperatures of the Big Hole
River, Montana. Transactions of the
American Fisheries Society 125:933-939.
Magee, J. P. and P. A. Byorth.
1994. Competitive
interactions of fluvial Arctic grayling (Thymallus arcticus) and brook trout (Salvelinus fontinalis) in the upper Big
Hole River, Montana. Submitted to:
Fluvial Arctic Grayling Workgroup.
Montana Department, of Fish, Wildlife, and Parks, Bozeman.
_____. 1995. Competitive interactions of fluvial
Arctic grayling and sympatric species in the Big Hole River drainage,
Montana. Submitted to: Fluvial
Arctic Grayling Workgroup. Montana
Fish, Wildlife, and Parks, Bozeman.
Oswald, R. A. 1990. Big Hole
grayling work report: Fall field season 1990. Report to Fluvial Arctic Grayling
Workgroup. Montana Department of Fish, Wildlife, and Parks, Dillon.
Shepard, B. B., and R. A. Oswald. 1989. Timing, location, and population
characteristics of spawning Montana Arctic grayling (Thymallus arcticus montanus [Milner]) in
the Big Hole River drainage, 1988. Montana Department of Fish, Wildlife, and
Parks, Bozeman.
Skaar, D. 1989. Distribution, relative abundance, and habitat utilization
of Arctic grayling (Thymallus
arcticus) in the upper Big Hole River drainage, Montana, July 5 to September
8, 1988. Report to: Montana Natural
Heritage Program, Beaverhead National Forest, and Montana Department. of Fish,
Wildlife, and Parks, Bozeman.
U.
S. Fish and Wildlife Service.
1991. Endangered and
threatened wildlife and plants; animal candidate review for listing as
endangered or threatened species, notice of review. Federal Register
56(225):58804-58836.
_____. 1993. Endangered and threatened wildlife and
plants; 90-day finding and commencement of status review for a petition to list
the fluvial population of the Arctic grayling as endangered. Federal Register 58(11):4975-4976.
_____. 1994. Endangered and threatened wildlife and
plants; finding on a petition to list the fluvial population of the Arctic
grayling as endangered. Federal
Register 59(141):37738.
_____. 1996. Plant and animal notice of review. Federal Register 61:7596.
Vincent, R. E. 1962. Biogeographical and biologic factors contributing to
the decline of Arctic grayling (Thymallus
arcticus [Pallus]) in Michigan and Montana. Ph.D. Dissertation, University
of Michigan, Ann Arbor.
Williams, J. E., J.E. Johnson, D. A. Hendrickson, S. Contreras-Balderas,
J. D. Williams, M. Navarro-Mendoza, D. E. McAllister, and J. E. Deacon.
1989. Fishes of North America
endangered, threatened, or of special concern: 1989. Fisheries 14(6):2-20.
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