Montana's Fish Species of Special Concern

 

 

Fluvial Arctic grayling 

Patrick A. Byorth

  Montana Fish, Wildlife, and Parks

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 project: Annual monitoring report 1992.           Submitted to: Fluvial Arctic Grayling Workgroup.  Montana Department of Fish, Wildlife, and Parks, Bozeman.

_____. 1994.  Big Hole River Arctic grayling recovery project: Annual monitoring report 1993. Submitted to: Fluvial Arctic Grayling Workgroup.  Montana Department of Fish, Wildlife, and Parks, Bozeman.

_____. 1995.  Big Hole River Arctic grayling recovery project: Annual monitoring report 1994. Submitted to: Fluvial Arctic Grayling Workgroup.  Montana Fish, Wildlife, and Parks, Bozeman.

_____. 1996.  Big Hole River Arctic grayling recovery project: Annual monitoring report 1996. Submitted to: Fluvial Arctic Grayling Workgroup.  Montana Fish, Wildlife, and Parks, Bozeman.

Byorth, P. A. and J. P. Magee. 1996.  Big Hole River Arctic grayling recovery project: Annual monitoring     report 1995. Submitted to: Fluvial Arctic Grayling Workgroup.  Montana Fish, Wildlife, and Parks, Bozeman.

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 Montana fluvial Arctic grayling.  Montana Department of Fish, Wildlife, and Parks, Helena.

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.

Back to Species of Special Concern page