Arctic Grayling Thymallus Arcticus Research Articles

Notes: Retention of Adaptive Rheotactic Behavior by F1Fluvial Arctic Grayling

Abstract Downstream movements of age-0 Arctic grayling Thymallus arcticus from an indigenous fluvial population (Big Hole River) and two inlet-spawning, lacustrine populations (Upper Red Rock Lake and Ennis Reservoir) were compared in a natural stream. All fish were incubated and reared together in a hatchery and acclimated together in the stream before being released in the stream. All fluvial test fish were F1 progeny of parents originating as gametes from wild fish but reared in a natural lake (1993 trials) or in a hatchery (1994 trials). The F1 fish in four 1993 trials were progeny of parents whose rheotaxis had also been tested as age-0 young. In all four trials of fish with 7–14 d stream acclimation, significantly fewer fluvial than lacustrine fish (P < 0.005) were recovered within 1 d in nets at a weir 1 km downstream from the release site. In two trials of fish with 1 d acclimation, significantly fewer fluvial than lacustrine fish were also recovered in one trial (P < 0.005) but not in the other (...

Management Briefs: Influence of Electroshock on Short-Term Growth of Adult Rainbow Trout and Juvenile Arctic Grayling and Cutthroat Trout

Rainbow trout Oncorhynchus mykiss (330 mm total length) were exposed to pulsed direct current from a Coffelt BP-6 electroshocker for 10 s. Control fish received the same amount of handling but were not shocked. At termination, 35 d after treatment, the control fish had gained an average of 51.3 g (SD, 18.5) and the treated fish had gained 33.7 g (SD, 17.5). The four fish (8.0%) that died during the experiment were all treated fish. The effects of electroshock on growth of juvenile fluvial Arctic grayling Thymallus arcticus and cutthroat trout Oncorhynchus clarki were also examined. These fish were exposed to the same duration of electroshock as described above, After 28 d, average growth in length and weight of electroshocked Arctic grayling was significantly less than that of the control fish. Both the electroshocked cutthroat trout and the control fish lost weight. However, at the end of the study, the weight of the control cutthroat trout was significantly greater than the electrosocked fish, although length was not affected. The long-term effects of reduced growth rate should be further evaluated. Electrofishing is known to cause varying degrees of trauma to fish (Hauck 1949; Collins et al. 1954; Pratt 1954; McCrimmon and Bidgood 1965; Horak and Klein 1967; Spencer 1967; Maxfield et al. 1971; Schreck et al. 1976; Whaley et al. 1978; Hudy 1985; Sharber and Carothers 1988). Broken backs are the most common form of permanent injury noted in large salmonids. Although electroshocking causes some mortality, the effects of nonlethal trauma have not been fully evaluated.

Use of Saline Solutions as Fertilization Media for Arctic Grayling Gametes and Their Effects on Embryo Survival

Abstract Saline diluents improve the fertilization success for several cultured salmonid species. In this investigation, success in fertilizing ova of Arctic grayling (Thymallus arcticus) was enhanced by the use of diluents containing 0.50–1.00% salt compared with fertilization in lake water. We recommend the use of a saline diluent during fertilization as a routine practice for artificial insemination of Arctic grayling ova.

Survival of Arctic Grayling Eggs Water-Hardened in Various Concentrations of lodophor

Abstract Survival of eggs of Arctic grayling (Thymallus arcticus) following water hardening in various concentrations of an iodophor, povidone-iodine, solution was investigated. The treatment is effective in reducing the external bacterial load at the surface of the egg and is thought to reduce the risk of vertical transmission of pathogens from parent to offspring. However, in some cases, the use of iodophor during water hardening of salmon and trout eggs has resulted in significant egg losses. Treatment duration and concentrations similar to those commonly used during water hardening of eggs of other salmonid species were tested with Arctic grayling eggs. Water hardening in 50, 75, and 100 mg active iodine per liter resulted in significantly greater egg losses at eye-up than occurred when eggs were hardened in lake water. Mortality was highest in treatments with the strongest iodine concentrations.

Population Dynamics and Potential Utility per Recruit of Arctic Grayling in Fielding Lake, Alaska

Abstract The population dynamics of Arctic grayling Thymallus arcticus were assessed in Fielding Lake during 1986 through 1992. Estimates of mortality rates were used in a Monte Carlo analysis to assess the potential changes in utility per recruit (satisfaction of the harvest to anglers) if fishing effort or length at first capture were to change, Two formulations of utility were considered: utility based on satisfaction ratings of fish creeled by anglers; and utility based on relative weight (yield) of fish creeled by anglers. Estimates of age and size at age indicate that Arctic grayling in Fielding Lake live longer and grow more slowly than lacustrine stocks in southern Canada, Montana, and Wyoming. Numbers per surface hectare were also less than for stocks at lower latitudes. Total, fishing, and natural mortality rates averaged 0.44, 0.20, and 0.24, respectively, during the study. Utility-per-recruit analyses suggest no potential for increasing utility, at the current level of fishing effort, through ...

Some Effects of Net-Pen-Rearing Methods on Feed Conversion by Age-0 Arctic Grayling in an Interior Alaskan Lake

Abstract Variable results from hatchery and pond rearing of Arctic grayling (Thymallus arcticus) led to an investigation of pen rearing as an alternative for rearing age-0 Arctic grayling. Two experiments were repeated three times each to evaluate the effects of feeding frequency, rearing density, and feed particle size on feed conversion by age-0 Arctic grayling reared in floating netpens. Growth in length or weight was not affected by these factors in any of the trials, possibly because of the short (11–12-d) feeding trials, the method of feeding (to satiation), and the relatively small differences in initial fish densities. When fish were fed to satiation, the optimal interval between feedings was 3 h. The highest initial fish density used (5.6 kg/m3) consistently produced the best feed conversions (1.10–1.51 g feed/g weight gain). Optimal feed size for 60–73-mm Arctic grayling was 1.3–1.5 mm (2.1–2.5% of fork length).

Effects of Current Velocity and Suspended Debris on the Drift Feeding of Arctic Grayling

Abstract We videotaped Arctic grayling Thymallus arcticus feeding on large Daphnia middendorffiana drifting at different water velocities in an experimental stream with and without stream debris. The angle and distance at which fish first located each prey was determined from the videotapes. Both measures were affected by stream velocity and added debris. Location distance was unchanged at the lower velocities (11.6 and 32.3 cm/s) but declined at higher velocities. However, prey encounter rate increased up to water velocities of 45.8 cm/s, and thus water velocity compensated for reduced search area. Added debris always shortened location distance and decreased location angle. These findings have implications for position choice in streams and search strategies.

Autumn Migration and Overwintering of Arctic Grayling in Coastal Streams of the Arctic National Wildlife Refuge, Alaska

Abstract During 1984 and 1985, 67 adult Arctic grayling Thymallus arcticus with surgically implanted radio transmitters were released at their summer feeding areas in three river systems of the Arctic National Wildlife Refuge, Alaska. We tracked the fish from aircraft to determine patterns of autumn migration to overwintering locations. During August or September in each area, fish left the small tundra streams where they were tagged and migrated into larger streams. Migration rates peaked at 5–6 km/d about 1 September and averaged 1 km/d. Fish in two river systems moved into adjacent rivers after passage through estuarine waters. Migration distances from spawning or summer feeding areas to overwintering sites were as great as 101 km. Potential overwintering areas determined from transmitter relocations included deep pools, spring-fed areas, and lakes. Management problems associated with these extensive seasonal migrations may include the maintenance of the species migratory circuit in a region that may f...

Rheotactic Differentiation between Fluvial and Lacustrine Populations of Arctic Grayling (Thymallus arcticus), and Implications for the Only Remaining Indigenous Population of Fluvial "Montana Grayling"

Rheotactic behavior of young Arctic grayling (Thymallus arcticus) from fluvial (Big Hole River) and lacustrine (Red Rocks Lake) populations in Montana was assessed in an artificial stream to see if fluvial grayling are adapted to life-long residence in streams by having an innately greater tendency to hold position and lesser tendency to go downstream. Responses of young tested at 0–10 d post-swimup contradicted the hypothesis; the fluvial grayling had strong downstream responses similar to or greater than those of the lacustrine grayling. When tested 18–31 d post-swimup, however, rheotactic responses of the fluvial and lacustrine grayling were consistent with the hypothesis, at three light intensities (full and dim lighting and darkness). Rheotactic differences were even greater in trials at 47–72 d post-swimup (conducted only under full lighting). Big Hole River grayling appear to be adapted to permanent stream residence. Such adaptation reinforces the importance of conserving this last indigenous fluvial population of the geographically disjunct, genetically identifiable "Montana grayling."

Rheotaxis of Young Arctic Grayling from Populations That Spawn in Inlet or Outlet Streams of a Lake

Abstract Rheotactic behavior of young Arctic grayling Thymallus arcticus from two populations that spawn in inlet or outlet streams of a lake and from reciprocal crosses between the two populations was tested in an artificial stream at flow velocities up to 7 cm/s. Fertilized eggs from wild fish and the resulting young from the two populations were incubated and reared under identical conditions in a hatchery before being tested. Young fish from both populations (referred to as inlet and outlet young) were tested at the time of initial swim-up and at 11–41 d after swimup. Outlet young had a significantly greater tendency to swim upstream than inlet young at temperatures of 10 (newly emerged but not older young), 12, and 16°C under both full (10.1–15.6 μmol·s−1·m−2) and dim (0.03–0.05 μmol·s−1·m−2) light conditions. Young from reciprocal crosses had intermediate responses at 12 and 16°C. However, both outlet and inlet young had similar, very weak, upstream responses when tested in darkness or (except for n...

Genetic Relationships of Arctic Grayling in the Koyukuk and Tanana Rivers, Alaska

Abstract Electrophoretic data were used to examine the stock structure of Arctic grayling Thymallus arcticus collected from the Yukon River drainage, Alaska. Arctic grayling were sampled from Grayling Lake in the Koyukuk River drainage and from three tributaries (Caribou Creek, Goodpaster River, and Volkmar River) entering a 60-km stretch of the Tanana River. Of 30 protein-coding loci examined, three (Mdh-2, Pgm-1, and Sod-2, coding for malate dehydrogenase, phosphoglucomutase, and superoxide dismutase, respectively) were polymorphic. Differences in allele frequency between the Koyukuk and Tanana drainages accounted for about 5% of the observed variability, whereas differences among the collections from the Tanana drainage accounted for less than 1%. The difference observed between collections from the Koyukuk and Tanana rivers, major tributaries to the Yukon River, suggests that genetic comparisons are useful for biogeographical studies of Alaskan Arctic grayling. The small divergence exhibited among the...

Introduced Salmonids: Where are They Going in Quebec Watersheds of the Saint-Laurent River?

Abstract Salmonid fish (Salmonidae) are among the most important sport and commercial species in North America. Numerous attempts to extend their range have been made over the past 100 years. In Canada, Quebec was among the first provinces to be involved in such attempts. Rainbow trout (Salmo gairdneri), brown trout (S. trutta), cutthroat trout (S. clarki), kokanee (Oncorhyncus nerka), Arctic grayling (Thymallus arcticus) and huchen (Hucho hucho) were experimentally introduced in various lakes and rivers of the southern part of the province. Some of these species, along with pink (O. gorbuscha), chinook (O. kisutch), and coho salmon (O. tshawytscha), were also stocked intensively in neighbouring states and provinces. Rainbow, brown, and cutthroat trout species are now established in southern Quebec. Present data also indicate that rainbow and, to a lesser extent, brown trout gradually increased in numerous rivers flowing into the Gulf of Saint-Laurent, along the North Shore and the Gaspe Peninsula. Pink s...

Responses of Arctic Grayling (Thymallus arcticus) to Acute and Prolonged Exposure to Yukon Placer Mining Sediment

Underyearling Arctic grayling (Thymallus arcticus) from the Yukon River system were expsed for 4 d to suspensions of fine inorganic (≤ 250 g∙L−1) and organic (≤ 50 g∙L−1) sediment and for 6 wk to inorganic sediment (≤ 1000 mg∙L−1) under laboratory conditions. The test sediments were collected from an active placer mining area near Mayo, Yukon Territory. The exposures evoked sublethal responses but did not cause gill damage. Mortalities (10 and 20%) occurred only in experiments at 5 °C with inorganic sediment concentrations ≤ 20 g∙L−1. Six weeks of exposure to sediment concentrations &gt; 100 mg∙L−1impaired feeding activity, reduced growth rates, caused downstream displacement, colour changes, and decreased resistance to the reference toxicant pentachlorophenol, but did not impair respiratory capabilities. Stress responses (elevated and/or more varied blood sugar levels, depressed leucocrit values) were recorded after short exposure (1–4 d) to organic sediment concentrations as low as 50 mg∙L−1. Inorganic sediment strengths ≥ 10 g∙L−1caused fish to surface. The lethal and sublethal responses of Arctic grayling to pentachlorophenol were similar to those determined for other healthy salmonid fishes.

Otolith, Pectoral Fin Ray, and Scale Age Determinations for Arctic Grayling

Abstract Ages determined from scales, otoliths, and fin rays of a selected sample of Arctic grayling (Thymallus arcticus) from Marshall Creek, Yukon Territory, were compared. Ages determined from scales were lower than those estimated from either otoliths or fin rays. Otolith and fin ray age determinations were within 1 year of each other for 94% of the fish. Otolith ages were generally higher than either scale or fin ray ages. Otoliths were the preferred material for aging Arctic grayling from Marshall Creek. Ages determined from scales may underestimate the true age of grayling and should be used cautiously unless validated.

Proliferative Branchiitis due to Tetraonchus rauschi (Trematoda: Monogenea) in Captive Arctic Grayling (Thymallus arcticus)

The monogenetic trematode Tetraonchus rauschi was diagnosed as the cause of severe proliferative and inflammatory gill disease among captive Arctic grayling (Thymallus arcticus). Grayling captured from the wild had few flukes and very limited pathologic lesions when compared to captive fish.

Movements and Growth of Arctic Grayling (Thymallus arcticus) and Juvenile Arctic Char (Salvelinus alpinus) in a Small Arctic Stream, Alaska

Fish movements were monitored in a small arctic stream that drains into the Kavik River near Prudhoe Bay, Alaska. The stream, which flows only during summer, served as a spawning and nursery area for Arctic grayling (Thymallus arcticus). Adult grayling entered the stream shortly after breakup and left again after spawning. Juvenile grayling also entered soon after breakup and many remained throughout the summer. Grayling fry emerged from the gravel in late June or early July and remained until freeze-up (mid-September). Small numbers of Arctic char (Salvelinus alpinus) juveniles also entered the stream to feed.The growth rate of grayling in the study stream was among the fastest recorded for arctic populations. Otolith-based age determinations were preferred as scales tended to underestimate the ages of old fish. Maximum observed age was 16 and age at sexual maturity ranged from 5 to 8.

Geographic Variation in the Lateral Line Scale Counts of the Arctic Grayling, Thymallus arcticus

An examination of Arctic grayling (Thymallus arcticus) collected on either side of the continental divide (Brooks Range) in Alaska revealed that lateral line scale counts were significantly higher on the North Slope than in the Yukon Basin to the south. An examination of geographic variation in this character within the North American range of the species suggested a division into three geographic areas: an area of uniformly low mean counts in the Bering Sea–North Slope of Alaska; an area of uniformly high counts in the remainder of Alaska and parts of the Yukon Territory and British Columbia; an area of variable mean counts in the Northwest Territories. Only two glacial refugia need be postulated to explain this pattern if it is assumed that populations in the first and last of these areas have a similar Mississippian origin and the high count populations a Beringian origin.