Torrent Sculpin Research Articles

Distribution, Density, and Size of Migratory and Fluvial Sculpins in Relation to Barriers in Puget Sound Lowland Streams

AbstractWe examined the effects of potential barriers on populations of migratory sculpins (Coastrange Sculpin Cottus aleuticus and Prickly Sculpin C. asper) and fluvial sculpins (Riffle Sculpin C. gulosus, Shorthead Sculpin C. confusus, and Torrent Sculpin C. rhotheus). Barriers can alter sculpin distribution because migratory sculpins have pelagic larvae that drift downstream to calm waters and juveniles and adults migrate upstream. We compared sculpin populations upstream and downstream of a barrier in 19 lowland streams in the Puget Sound region, Washington. Within each stream, we examined the farthest downstream barrier that would be most likely to impact the upstream movements of migratory sculpins. All study streams had populations of migratory sculpins in stream reaches downstream of the barrier. In 8 of the 19 streams with a barrier, at least one species of fluvial sculpin was also present. We also documented the relative distribution of migratory sculpins and fluvial sculpins in one reference stream without a barrier. In all streams examined, the density of migratory sculpins upstream of the barrier was lower than that downstream of the barrier and the differences were statistically significant. In 12 of the 19 streams, migratory sculpins were not present upstream of the barrier. In streams with fluvial sculpin populations, fluvial sculpins were usually rare downstream of barriers and were statistically less abundant than upstream of the barrier. The migratory sculpins collected upstream of barriers were statistically larger than those collected downstream of barriers. In the reference stream, migratory sculpin species dominated the lower stream reaches and were gradually replaced by fluvial sculpin species in more upstream reaches. Overall, barriers appear to have an important effect on the distribution of both migratory sculpins and fluvial sculpins, which should be taken into account when assessing habitat modifications and fish communities in Puget Sound lowland streams.Received November 4, 2016; accepted March 25, 2017 Published online June 12, 2017

Diet of the Torrent Sculpin, Cottus rhotheus, in the Cedar River, Washington: Effect of Season, Habitat Type, and Predator Size with Emphasis on Piscivory

Abstract Torrent Sculpin (Cottus rhotheus) can play an important role in riverine ecosystems in the Pacific Northwest, but factors that influence their feeding ecology are not well understood. To better understand how environmental conditions may influence the diet of Torrent Sculpin in the Cedar River, Washington, we collected diet information from fish across seasons and habitats. Numerically, aquatic insects were usually the dominant prey type for each size class in each sampling effort. Overall, Torrent Sculpin prey on a wide variety of aquatic invertebrates but can also take advantage of other prey types, such as fry of Sockeye Salmon (Oncorhynchus nerka), juvenile Chinook Salmon (O. tshawytscha), and eggs of Largescale Suckers (Catostomus macrocheilus), when these prey become abundant. In February and March, predation on Sockeye Salmon fry was substantially higher in large, deep pools (>2.5-m depth) than in either riffles or slow-water secondary habitats. Besides fry of Sockeye Salmon, the only salm...

Food Habits of Sculpin Spp. in Small Idaho Streams: No Evidence of Predation on Newly Emerged Steelhead Alevins

Abstract Recent declines of anadromous salmonids in the Pacific Northwest have prompted a need to understand the factors limiting populations across habitats and life stages. In the weeks following emergence from the spawning gravel, juvenile salmonids have limited swimming capacity and can be particularly vulnerable to predation by piscivores, such as sculpins (Cottus sp.) which are widespread in Pacific Northwest streams. The objective of this study was to investigate the extent to which sculpin prey on newly emerged steelhead (Oncorhynchus mykiss) in a threatened population in Idaho. Three species of sculpin were present in the watershed, including Paiute (C. beldingii), mottled (C. bairdii), and torrent (C. rhotheus) sculpin. Gut content analyses of 360 sculpin showed that invertebrates were the dominant food source (> 85% of all sculpin preyed mainly on invertebrates), and piscivory was rare (< 2%). None of the samples contained steelhead alevins. We conclude that there was no indication of predation...

Host Fish Associations of the California Floater (Anodonta californiensis) in the Yakima River Basin, Washington

Abstract Freshwater mussels play an important role in stream ecosystems but are declining worldwide. The California floater (Anodonta californiensis, Lea 1852), formerly widespread throughout the Pacific Northwest, is listed as a federal species of concern and a candidate species for state listing in Washington (WA). Because freshwater mussels are obligate parasites on fish, conservation and restoration efforts require understanding specific host fish species. We found a previously undocumented population of A. californiensis in the upper Yakima River Basin in WA and determined its host fishes through a combination of laboratory and field studies. Two fish species, speckled dace (Rhinichthys osculus) and torrent sculpin (Cottus rhotheus), were confirmed as hosts for A. californiensis. Two fish species, three-spine stickleback (Gasterosteus aculeatus) and redside shiner (Richardsonius balteatus), were identified as hosts for A. californiensis in the laboratory portion of this study. Our results fill a sign...

The effects of domestication on the relative vulnerability of hatchery and wild origin spring Chinook salmon (Oncorhynchus tshawytscha) to predation

We tested whether one generation of state-of-the-art hatchery culture influenced the vulnerability of Chinook salmon (Oncorhynchus tshawytscha) fry to predators. Size-matched hatchery and wild origin spring Chinook salmon fry were exposed to rainbow trout (Oncorhynchus mykiss) and torrent sculpin (Cottus rhotheus) predators in 10.8 m3 net pens. The hatchery origin fry were the offspring of first generation hatchery-reared broodstock, and the wild origin fry had no history of hatchery culture; both originated from the same stock. Wild origin fry were found to have a 2.2% (p = 0.016) survival advantage over hatchery origin fry during 2 years of predation challenges. The most important findings of this study are (i) domestication can affect the susceptibility to predators after only one generation of state-of-the-art hatchery culture practices, and (ii) the domestication effect was very small.

Responses of Benthic Fishes and Giant Salamanders to Placement of Large Woody Debris in Small Pacific Northwest Streams

Abstract The placement of large woody debris (LWD) to improve or restore habitat for fishes is a common practice in North American streams, and the responses of salmonids to this practice have frequently been examined. In contrast, little information exists on the effects of LWD placement on nonsalmonid fishes and amphibians. In this study, I examined the responses of giant salamanders Dicamptodon spp., juvenile lampreyss Entosphenus tridentatus and Lampetra spp., reticulate sculpins Cottus perplexus, and torrent sculpins C. rhotheus to artificially placed LWD by sampling 29 small streams with paired treatment and reference reaches. Densities and mean lengths of giant salamanders, reticulate sculpins, torrent sculpins, and lampreyss did not differ significantly between treatment and references reaches. I also examined whether the observed responses were correlated with differences in physical habitat between reference and treatment reaches. Lampreys densities (log10(treatment) − log10(reference)) and leng...

Habitat Use by Fishes and Pacific Giant Salamanders in Small Western Oregon and Washington Streams

Abstract The habitat use patterns of juvenile salmonid fishes Oncorhynchus spp., Pacific giant salamanders Dicamptodon spp., torrent sculpins Cottus rhotheus, reticulate sculpins C. perplexus, and larval lampreys Entosphenus tridentatus and Lampetra spp. were examined in 30 small streams in western Oregon and Washington. Fish and salamander densities and sizes were compared between different habitat types (pools and riffles) in summer and winter. Species density, length, and diversity (richness and dominance) were also correlated with physical variables measured at the reach and watershed scales. In the summer, densities of coho salmon O. kisutch, cutthroat trout O. clarki, and larval lampreys were significantly higher in pools than in riffles (P < 0.01), whereas densities of age-0 torrent sculpins were higher in riffles than in pools (P < 0.01). In winter, densities of coho salmon, cutthroat trout, steelhead O. mykiss, and young-of-the-year trout fry were higher in pools than in riffles (P < 0.01). Cutth...

Influence of Substrate Composition and Suspended Sediment on Insect Predation by the Torrent Sculpin, Cottus rhotheus

Studies conducted in laboratory streams showed that torrent sculpins (Cottus rhotheus) congregated in regions of limited cover when exposed to a sand substrate. When cobbles were added, their distribution was more uniform. Various combinations of sand, pebbles, and cobbles significantly influenced sculpin predation on the stonefly Hesperoperla pacifica, the mayfly Ephemerella grandis, and the caddisfly Rhyacophila vaccua. During 24-h tests, each species experienced 95–100% predation when tested on sand substrates. When different combinations of cobbles and pebbles were added, predation was appreciably reduced. Sculpin predation on H. pacifica, Hydropsyche sp., and Heptagenia solitaria was influenced more by substrate than suspended sediments when substrate and suspended sediment (0–1250 mg∙L−1) were tested interactively. Predator avoidance tactics differed among prey species as changes were made in the physical characteristics of the environment.Key words: predator–prey, sculpin, insects, suspended sediment, substrate, turbidity, behavior

Tolerances of Fishes to Dissolved Gas Supersaturation in Deep Tank Bioassays

Abstract Four species of fish were tested for tolerance to dissolved atmospheric gas supersaturation in 10-day bioassays. Based on median times to death at four levels of gas saturation, the fish displayed the following increasing order of tolerance: mountain whitefish (Prosopium williamsoni) < cutthroat trout (Salmo clarki) < largescale sucker (Catostomus machrocheilus) < torrent sculpin (Cottus rhotheus). Increasing hydrostatic pressure due to water depth reduced the levels of saturation of dissolved gases and increased survival. Torrent sculpins typically developed large bubbles of gas which caused them to float and would contribute indirectly to death.

Spawning Migration and Intragravel Movement of the Torrent Sculpin, Cottus rhotheus

Abstract Torrent sculpins (Cottus rhotheus) migrated into the Abernathy Incubation Channel from late January to late April with most fish entering from mid-March through mid-April. Egg laying by captive females was restricted to April. A downstream migration of sculpins occurred in Abernathy Creek in May and June. The sculpins appeared to have entered the incubation channel by intragravel movement.

Increased Predation by the Torrent Sculpin, Cottus rhotheus, on Coho Salmon Fry, Oncorhynchus kisutch, During Moonlight Nights

In stream aquaria, the percentages of coho salmon fry removed by the torrent sculpin averaged 70 in four tests on moonlight nights and 24 in seven tests on dark nights.

Host Relationships of Cryptobia salmositica (Protozoa: Mastigophora) in a Western Washington Hatchery Stream

The periodicity, incidence, and intensity of infection of the hemoflagellate Cryptobia salmositica Katz, 1951, in freshwater fishes corresponds to the biological association between teleost hosts and rhynchobdellid vector: adult and young coho salmon (Oncorhynchus kisutch), the torrent sculpin (Cottus rhotheus), and the salmonid leech (Piscicola salmositica). Adult salmon and leeches occupy Soos Creek, a western Washington stream, only during the fall and winter months. The incidence and intensities of Cryptobia in the maturing salmon increase in response to the period that feeding and infected leeches are carried, and ultimately 80 to 100% of the spawning population acquire the parasites. Young cohos also become infected during the fall and winter, but the incidence is generally less than 5%; the overwintering fingerling population, including the few infected young, emigrates seaward in the spring. The incidence of Cryptobia in the resident sculpin population averages 60%, but significantly lower incidence and higher intensities occur in young fish, those less than 65 mm in length; the sculpins serve as reservoirs of Cryptobia in the study stream.

Transmission of the Hemoflagellate, Cryptobia salmositica Katz, 1951, by a Rhynchobdellid Vector

The transmission of Cryptobia salmositica Katz, 1951, a hemoflagellate of freshwater teleosts, was investigated in experiments involving the rhynchobdellid leech, Piscicola salmositica Meyer, 1946. Uninfected leeches developed metacyclic stages of Cryptobia in their digestive tracts after feeding on naturally infected torrent sculpins (Cottus rhotheus). When naturally infected leeches were fasted and then allowed to engorge on uninfected juvenile coho salmon (Oncorhynchus kisutch) and torrent sculpins, parasitemias developed in the fish as early as 5 days after the leeches had fed. Infections did not appear in uninfected fish after ingesting infected leeches, nor in uninfected leeches after feeding on the blood of uninfected fish. C. lynchi Katz, 1951, is declared a synonym of C. salmositica. Aquatic leeches are recognized as vectors of Cryptobia (= Trypanoplasma) occurring in the blood of European freshwater fishes (Leger, 1904; Keysselitz, 1906; Brumpt, 1906, 1907; Robertson, 1912). Yet, as far as is known, there are no records of leeches as vectors of these hemoflagellates in freshwater teleosts of North America. Infections of Cryptobia salmositica Katz, 1951 (Mastigophora: Cryptobiidae) have been reported in adult and young salmonids and in sculpins of western Washington and Oregon (Katz, 1951; Davison et al., 1954; Katz et al., 1960, 1961). Similar, if not identical parasites, have also been found in various teleosts of northern California (Wales and Wolf, 1955). In the same general localities, the leeches, Piscicola salmositica Meyer, 1946 (Rhynchobdellae : Piscicolidae), are habitual ectoparasites of adult salmonids (Meyer, 1946, 1949; Earp and Schwab, 1954; Haderlie, 1953). Both the hemoflagellates and the leeches are apparently endemic to the Pacific coast of the North