Pteronarcys californica

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Range includes the Coast, Cascade, Rocky, and Sierra Nevada Mountains northward to Alaska and Yukon and southward to Mexico where it has been recorded disjunctly in Durango (Stewart and Oswood, 2006). It is found throughout the northern and eastern Basin and Range province of the western U.S. but is conspicuously absent in the western Great Basin, where P. princeps is the sole representative of the genus (Baumann et al., 1977; Kauwe et al., 2004; Sargent et al., 1991; Sheldon, 1979; Stark and Armitage, 2000; Stark et al., 1998; Stewart and Oswood, 2006; Stewart and Stark, 2002).

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Length: 3.2 cm

This is the very largest species of all mayflies, stoneflies, and caddisflies, up to 2.5 inches long. Range only overlaps with two other potentially confusing species; the American salmonfly, Pteronarcys dorsata, and the ebony salmonfly, Pteronarcys princeps. P. princeps is generally darker and typically found in small streams on the west coast primarily but also in isolated mountain ranges of Nevada, eastern Oregon, and southwestern British Columbia. The tenth sternum (= ventral plate; essentially the very last segment) is greatly narrowed ventrally (as opposed to broad like in most species or absent in P. dorsata and P. pictetii). P. dorsata resembles P. californica in coloration but the ninth abdominal sternum (= ventral plate) of males projects over the tenth and is notched on the posterior margin (making the tenth plate appear absent); plus it only gets as far west in the Rocky Mountains as the Mississippi-Missouri drainage basin. In adults, the tenth abdominal tergum (= dorsal plate on the last segment) is rounded with raised lobes (unlike P. dorsata which is not raised) projecting about as high as their width unlike P. princeps where the lobes are plate-like (not rounded) and project higher than the width. In females, the posteromesal processes of the subgenital plate (= projections extending from the tail) are produced backward (unlike P. dorsata where they are reduced) and are about as long as they are wide at their base (unlike P. princeps where they are longer).

In mature nymphs, the prothoracic (= corner) teeth are directed outward and are sharp and longer than their basal width (unlike P. dorsata and P. princeps whose corner teeth are blunt and short and no longer than their basal width).

Habitat Type: Freshwater

Comments: Adults and larvae are associated with fast-moving mountain streams or large to medium sized rivers (2nd to 7th order streams) at relatively low to moderate elevations (Schwiebert, 2007; Stark et al., 1998; Merritt and Cummins, 1996). Streams are often clean and of moderate to high velocity and nymphs are frequently found in medium to large-sized, unconsolidated rocky substrates (Elder and Gaufin, 1973; Kauwe et al., 2004). Freilich (1991) found nymphs most abundant in areas of fast, deep water with large, loosely embedded cobbles, and never in pools or on areas with silty bottoms in the Grand Teton National Park.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Nymphs were found to move a few (perhaps tens) meters each day with the fastest tagged individual moving 40 m in four days (or 22 m upstream in a single day) (Freilich, 1991). Small scale migration is heaviest near dawn and dusk.

Comments: Nymphs are considered major shredders of CPOM (coarse particulate organic matter) in stream systems (Cummins et al., 1973; Short and Maslen, 1977) but are poorly adapted to digest detrital polysaccharides (Martin et al., 1981). Gut content was found to be 75% diatoms, 15% vascular plant material, and 8% animal remains (Freilich, 1991). Richardson and Gaufin (1971) conducted feeding studies.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: Gaufin et al. (1972) cite Montana distribution as Beaverhead (Big Hole River), Flathead (Camas Creek, Kintla Creek, Swan River), Gallatin (Gallatin River, Madison River, West Gallatin River), Glacier (Elizabeth Creek), Granite (Flint Creek, Gilbert Creek, Rock Creek, Stony Creek), Lake (Swan River), Lewis and Clark (Prickley Pear Creek), Lincoln (Fisher River), Madison (Madison River, Spring Creek), Missoula (Blackfoot River, Lolo River, Rock Creek), Park (Yellowstone River), Ravalli (Bitterroot River, East Fork Bitterroot River, Cameron Creek, Camp Creek), and Sweet Grass (Boulder River) Cos. Baumann (1973) recorded it from Utah. Branham and Hathaway (1975) conducted a growth study on a population in the Provo River, Utah. Call and Baumann (2002) cite southern Utah distribution as Beaver Valley, Pine Valley Mountains, Sevier Plateau, Tushar Mountains, Wasatch Plateau, and Capitol Reef. Newell et al. (2006) report it from Glacier National Park in western Montana. Rockwell and Newell (2009) studied mortality in a population on the Jocko River, Montana. Gregory et al. (2000) documented emergence in streams in the Henry's Fork catchment, Idaho. In California, Jewett (1960) cited Butte, Kern, Marin, Mendocino, Placer, Plumas, San Mateo, Santa Clara, Sonoma, and Stanislaus Cos. Kauwe et al. (2004), in an analysis of global phylogeography, examined specimens from California (Lake, Mendocino, Shasta, Siskiyou Cos.), Idaho (Clark, Custer, Elmore, Fremont, Valley Cos.), Nelson and Hanson (1971) documented specimens from California, Colorado, Idaho, Montana, New Mexico, Oregon, Utah, Wyoming, and the Yukon. Montana (Madison, Park Cos.), Nevada (Elko Co.), New Mexico (San Miguel Co.), Oregon (Benton, Grant, Jackson Cos.), Utah (Beaver, Cache, Emory, Garfield, Utah, Weber Cos.), Washington (Walla Walla Co.), and Wyoming (Lincoln, Park, Pine Dale, Sheridan Cos.). Stewart and Ricker (1997) report the species from the Yukon for the first time from Klusha Creek on the Klondike Highway. Townsend and Pritchard (1998) documented it in the Crowsnest River in southern Alberta. Stewart and Oswood (2006) cite occurrences in British Columbia (Clearwater Lake, Okanagan River at Osoyoos Lake, Yellow Lake near Kaleden) and Yukon (Albert Creek, Little Rancheria Creek).

>1,000,000 individuals

Comments: Locally, it can be very common in large to medium sized rivers at lower elevations (Stark et al., 1998); likely with millions of individuals worldwide.

Movement patterns and gut content analysis were analyzed by Freilich (2006), who found the species has a three-year life cycle, females are larger than males at all ages, most movements are short as stoneflies stayed within a few meters of their first capture point, significant patch size is a stream reach 24 m long, and guts contained 75% diatoms, 15% vascular plant material, and 8% animal remains with females eating more than males.

Comments: It is on the wing during June, July and August with the easternmost specimen the earliest in season (April 25) (Needham and Claassen, 1925). Although adults, when they hatch, are active during daylight, Elder and Gaufin (1973) indicated this species has nocturnal habits as nymphs and this was supported by Freilich (1991). Elder and Gaufin (1973) stated the aquatic stage lasts three years in the Provo River, Utah, although the basis for this statement is unclear. Branham and Hathaway (1975) used larval body mass and estimated a four-year larval life cycle in the same river. Freilich (1991) reported a three-year larval life cycle in Pacific Creek, Wyoming. DeWalt and Stewart (1995) found a 9- to 10-month egg stage and estimated a 38-month larval life cycle in the Rio Conejos, Colorado. Townsend and Pritchard (1998) concluded embryonic development, incorporating an early diapause, accounts for approximately one year of the life cycle followed by a further four years in the larval stage in Alberta. Examination of genetic differentiation among cohorts from Utah suggests four and five year life cycles comprising an approximate one year embryonic diapause followed by either three or four years of larval development (Schultheis et al., 2008).

This species has a semivoltine (2-, 3-, or rarely 4-year) life cycle including a 9-11 month diapause (Branham and Hathaway, 1975; DeWalt and Stewart, 1995; Freilich, 1991; Gaufin et al., 1972; Stewart and Stark, 2002). After three years in the water, mature nymphs emerge along the shoreline but emergence is earlier with higher water temperature (Gregory et al., 2000). Cold air temperature can kill emerging nymphs as was demonstrated on the Jocko River, Montana; where nymphs emerge earlier (early April through early May) than other streams in the United States (Rockwell and Newell, 2009). Emergence is timed with spring water temperature (Gregory et al., 2000). Small scale migration is heaviest near dawn and dusk. Adults are present in Alaska and western Canada mostly in May and June (Stewart and Oswood, 2006). Emergence time in the contiguous states is generally April to June (Stark et al., 1998), mid- to late May to as late as mid-June in eastern Idaho depending on water temperature (Gregory et al., 2000), early April through early May in northwestern Montana (Rockwell and Newell, 2009), and throughout May in southern Alberta (Townsend and Pritchard, 1998). It is on the wing in western mountains during June, July, and August (Needham and Claassen, 1925). Townsend and Pritchard (2000) studied aspects of egg development.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 15
Species With Barcodes: 1

Rounded Global Status Rank: G5 - Secure

Reasons: Range includes the Coast, Cascade, Rocky, and Sierra Nevada Mountains northward to Alaska and Yukon. The species has been well-studied because it is widely used by the commercial and recreational fly-fishing community at large. Populations have largely been considered secure but recent anecdotal evidence in Montana indicates a significant portion of the state's populations have declined over the last 70 years (particularly last 30 years) mostly through loss of habitat through siltation on increasing water temperatures beyond the species thermal limits. Similar declines have not yet been observed in other populations but studies have not been undertaken in this regard, either.

Intrinsic Vulnerability: Not intrinsically vulnerable

Comments: A recent analysis of gene sequences from populations across North America revealed an eastern North American origin and 2 distinct genetic lineages with most of the current population structure in both lineages explained by a pattern of restricted gene flow with isolation by distance (presumably the result of dispersal via connected streams and rivers), but also some long-distance, overland dispersal (Kauwe et al., 2004). The ability of the species to adapt and survive via long-distance dispersal makes it less vulnerable to random extirpation on a global level.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Comments: Rockwell and Newell (2009) documented mortality due to cold air temperature following early emergence on the Jocko River in Montana.

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

Global Short Term Trend: Relatively stable to decline of 30%

Comments: Throughout Montana, Stagliano (2010) concluded a significant portion of the state's populations have declined to an estimated sum of ~350 river miles (~70 in the past 30 years) mostly through loss of habitat through siltation on increasing water temperatures beyond the species thermal limits. Of particular concern are the Big Hole from Melrose to Browns Bridge and below Melrose, Madison River below Ennis Lake, Smith River above Camp Baker, and the Clark Fork River below the Milltown Dam site and below Missoula; and also sections of rivers (Big Hole, Rock Creek) that have experienced salmonfly decreases during the worst drought years but have rebounded in recent years.

Global Long Term Trend: Increase of 10-25% to decline of 30%

Degree of Threat: Unknown

Comments: Rockwell and Newell (2009) documented mortality due to cold air temperature following early emergence on the Jocko River in Montana. Also, throughout Montana, Stagliano (2010) concluded a significant portion of the state's populations to an estimated sum of ~350 river miles (~70 in the past 30 years) mostly through loss of habitat through siltation on increasing water temperatures beyond the species thermal limits. Otherwise, specific threat information has not been assessed.

Comments: The giant salmonfly is an important food source for trout. As such, both the larvae and adults are used extensively both live and as models by fly fishermen to create natural and artificial lures (Schwiebert, 2007).