Rhinichthys cataractae
Great Lakes longnose dace
(Also: Longnose dace)

Longnose dace (Rhinichthys cataractae) have the widest geographic distribution of any member of the Cyprinidae family (Jenkins and Burkhead, 1994). The distribution spans much of North America, ranging from the Atlantic coast to the Pacific Ocean and from northern Mexico to the Arctic Circle in northern Canada. (Jenkins and Burkhead, 1994)

Populations of longnose dace use different niches based on local habitat conditions. Different habitat availability as well as the presence or absence of competing species drives populations into different patterns of niche use. Longnose dace are found in fast-flowing, cold water. Most populations are found in stream riffles. When in lakes, they are typically in the turbulent surge zone less than 10 m deep, where outflow from a river mixes with lake water (Brazo, Liston, and Anderson, 1978). Another characteristic of longnose dace habitat is rocky or gravel substrate (McPhail and Lindsey, 1970; Cooper, 1980). Brazo et al. (1978) reported similar substrate preferences in lake-dwelling populations, where longnose dace prefer gravel substrates over sandy habitats. Streams they inhabit tend to be small creeks and rivers with shallow pools as well as an abundance of fast-flowing riffles; similar to "trout streams" (Reed, 1959). Young longnose dace are found in shallow pools for the first four months following hatching (Reed 1959). Pools are also used by adults in the absence of competing species (Edwards, Li, and Schreck, 1983). (Brazo, et al., 1978; Cooper, 1980; Edwards, et al., 1983; McPhail and Lindsey, 1970; Reed, 1959)

Longnose dace are typically dark olive-brown with a lighter yellow-tan venter (Page and Burr, 1991). A dark lateral stripe, present in juveniles, fades as the fish matures. This is a good distinguishing characteristic between longnose dace and their close relatives, blacknose dace (Rhinichthys atratulus), which maintain their dark lateral stripe throughout their lifetime (Page and Burr, 1991). Other identifying characteristics include a sub-terminal mouth with a fleshy snout projecting far beyond the mouth. A small barbel is also present near the corner of the mouth (Goldstein and Simon, 1999). Total length is largely based on local habitat conditions; adults are usually 60 to 90 mm in length (Sigler and Miller, 1963) and reported maximum sizes are around 160 mm for stream dwelling individuals, slightly larger for lake-dwelling longnose dace (Page and Burr, 1991; Brazo, Liston, and Anderson, 1978). Longnose dace have been reported to get up to 225 mm in total length (Gerald 1966). (Brazo, et al., 1978; Gerald, 1966; Goldstein and Simon, 1999; Page and Burr, 1991; Sigler and Miller, 1963)

After fertilization, eggs develop for 3 to 4 days before hatching into protolarva. During this time, the head and tail separate from the yolk sac and the circulatory system begins to develop, as does the spinal cord. Pelagic protolarvae continue to develop, pigmentation begins, and early fin development occurs. By the 9th day after hatching, the sac is absorbed and the larvae are now considered mesolarvae. Fin rays become more defined and pigmentation continues to accumulate. As Rhinichthys cataractae metalarvae develop into juveniles, fin buds develop, the fish takes on the morphology of a juvenile (including an elongated fleshy snout), and pigmentation accumulation is completed (Fuiman and Loos, 1977; Cooper, 1980).

Juvenile longnose dace (Rhinichthys cataractae) continue to grow and develop in streams. Most longnose dace mature at age 2. A small percentage of adults are mature at age 1. This percentage increases slightly in lake-dwelling populations, where growth and maturation is accelerated (Brazo, Liston, and Anderson, 1978). Age 1 spawners are predominantly males, indicating possible shorter maturation times for males than females (Brazo, Liston, and Anderson, 1978). Mature individuals, both male and female, are approximately 75 mm in total length at the time of maturation (Roberts and Grossman, 2001). Females generally become the dominant sex and typically grow larger than males by age 3 (Gerald, 1966). (Brazo, et al., 1978; Cooper, 1980; Fuiman and Loos, 1977; Gerald, 1966; Roberts and Grossman, 2001)

Adult longnose dace are polygynandrous (promiscuous) because both mature males and females have multiple spawning partners. Males are territorial and breed with many females who visit their habitat (Bartnik, 1970). Female longnose dace are capable of spawning 6 or more times during their breeding season and will breed with multiple males during this time (Roberts and Grossman, 2001). (Bartnik, 1970; Roberts and Grossman, 2001)

Some longnose dace are capable of reproducing at age 1, all are mature by age 2 (Roberts and Grossman, 2001; Brazo, Liston, and Anderson, 1978). Mature individuals, both male and female, are approximately 75 mm in total length. While spawning typically occurs only in one year, females are capable of producing 6 or more clutches per year. Total potential fecundity ranged from 1155 to 2534 eggs for females in stream dwelling populations (Roberts and Grossman, 2001) and from 870 to 9,953 eggs per female in Lake Michigan populations (Brazo et al., 1978). Longnose dace larvae hatched 3 to 4 days after fertilization occurred; with an mean length of 5.9 mm (Fuiman and Loos, 1977; Cooper, 1980). Information on mass at the time of hatching was not available. Spawning typically occurs in summer but timing is dependent on latitude and water temperature (Edwards, Li, and Schreck, 1983). Typical spawning season takes place in late June and early July (Brazo, Liston, and Anderson, 1978) but occurs as early as late May (Reed, 1959) and as late as August (McPhail and Lindsey 1970). Peak spawning typically occurs at water temperatures between 14° and 19° C (Brazo, Liston, and Anderson, 1978). (Brazo, et al., 1978; Cooper, 1980; Edwards, et al., 1983; Fuiman and Loos, 1977; McPhail and Lindsey, 1970; Reed, 1959; Roberts and Grossman, 2001)

In stream and lake-dwelling populations, spawning occurs over gravel. Male longnose dace construct a small nest in the pebbles where eggs are deposited (McPhail and Lindsey, 1970). Males are territorial and defend their spawning habitat, which is visited by multiple females (Brazo, Liston, and Anderson, 1978). After spawning, little or no parental care is given the eggs. They are are categorized as benthic spawners who broadcast their eggs over gravel. The eggs are not hidden (Helfman, Collette, and Facey, 1997). Embryos temporarily adhere to the gravel for 7 to 10 days and then the hatched fry become pelagic (McPhail and Lindsey, 1970; Cooper, 1980). (Brazo, et al., 1978; Cooper, 1980; Helfman, et al., 1997; McPhail and Lindsey, 1970)

Longnose dace have a maximum reported lifespan of 5 years, but lifespan is typically only 3 years for male individuals (Reed and Moulton, 1973; Brazo, Liston, and Anderson, 1978). (Brazo, et al., 1978; Reed and Moultan, 1973)

While faster areas of a riffle are typically inhabited by adults, both adult and juvenile longnose dace prefer fast velocity (40 to 50 cm/s) areas in the riffles they inhabit. Mullen and Burton (1998) found that, in the presence of adults, juveniles will generally use medium velocity (25 to 35 cm/s) areas, but show niche expansion into faster velocity areas when adults are removed from the site. Neither adults nor juveniles made use of riffles where the water velocity was below 10 cm/s (Mullen and Burton, 1998). This aspect of niche distribution is thought to be caused by intra-specific competition for faster velocity areas in the riffle and is referred to as size-specific habitat segregation (Mullen and Burton, 1995). Mullen and Burton (1995) suggested that this microhabitat segregation was a strategy to reduce intra-specific competition between individuals in different life history stages by reducing niche overlap. Grossman et al. (1998) also found that intra-specific competition, driven by food limitation, was the primary factor influencing habitat choice by longnose dace rather being dispersed due to inter-specific competition or predator avoidance. (Grossman, et al., 1998; Mullen and Burton, 1995; Mullen and Burton, 1998)

During the breeding season, males are territorial and stay near their spawning area; females are more mobile during this time and move throughout the stream. Exact territory size has not been determined. (Bartnik, 1970; Brazo, et al., 1978)

Detailed information on Rhinichthys cataractae communication and perception is not available.

Longnose dace are primarily nocturnal feeders (Brazo, Liston, and Anderson, 1978). This nocturnal foraging strategy is different from most cyprinids, but Rhinichthys cataractae is well adapted for this method (Beers and Culp, 1990). Longnose dace have dark-adapted vision for night foraging. Beers and Culp (1990) studied how changes in light intensity changed foraging efficiency when predators were removed. All factors indicative of foraging ability were greatest under low light conditions, such as around dusk. However, most foraging occurs at night where they are slightly less efficient. Therefore, this nocturnal strategy is thought to be a combination of minimizing predation risks while still increasing efficiency in low-light conditions (Beers and Culp, 1990). (Beers and Culp, 1990; Gerald, 1966)

Longnose dace are well adapted for feeding on bottom dwelling insects (Gerald, 1966). At night, they use benthic-rooting behavior; it is thought they locate prey by olfaction using their barbels to probe into the substrate (Beers and Culp, 1990). Brazo et al. (1978) determined through stomach analysis that longnose dace depend primarily on invertebrates as their primary food source. As in previous studies, their invertebrate diet consisted of midges, black flies, and mayflies (Reed 1959) as well as leaf hoppers, aphids, and small cicadas. Small, juvenile longnose dace feed primarily on algae and diatoms until they were large enough to consume the same diets as adults. Larger adults shifted their diet toward larger terrestrial insects as well as fish eggs from other Cyprinidae (Brazo, Liston, and Anderson, 1978). (Beers and Culp, 1990; Brazo, et al., 1978; Gerald, 1966; Reed, 1959)

Longnose dace are potential prey species for fish-eating birds, such as herons, and predatory stream fishes including many salmonid species (Brazo, Liston, and Anderson, 1978). (Brazo, et al., 1978)

Rhinichthys cataractae is a wide-ranging freshwater minnow that is an important part of the food chain in many stream habitats. One of the important functions these fish provide are consuming terrestrial insects, bringing them into the aquatic food chain. Longnose dace are a potential prey species to predatory stream fishes including many salmonid species. This is especially believed to occur when alewives (Alosa pseudoharengus) undergo substantial population crashes (Brazo, Liston, and Anderson, 1978).

Longnose dace are also hosts to 13 parasitic species, including individuals from 6 larger taxonomic groups: 1 monogenean fluke, 2 flukes, 2 cestode species, 4 nematodes, 1 spiny-headed worm, and 3 protozoan species) (Muzzall, Whelan, and Taylor, 1992). (Brazo, et al., 1978; Muzzall, et al., 1992)

Direct anthropogenic interactions are minimal with longnose dace, but in some areas they are used as bait for fishing (Scott and Crossman, 1998). (Scott and Crossman, 1998)

There are no known negative affects of Rhinichthys cataractae on humans.

Longnose dace (Rhinichthys cataractae) are not listed as a species of special concern, endangered, threatened, or regionally extirpated in any of the following conservation lists: IUCN Red List, CITES appendices, or the United States Endangered Species Act.