Skip booklet index and go to page content

COSEWIC Assessment and Update Status Report on the Redside Dace in Canada


Aspects of the biology of redside dace have been studied throughout much of its range (Kentucky, Michigan, New York, Ontario, Pennsylvania), but there have been few comprehensive studies. There are still several aspects of its life history that are not well understood.

Life Cycle and Reproduction

The redside dace is relatively short-lived, reaching a maximum age of 4 years (Koster 1939, Schwartz and Norvell 1958). The oldest reported Ontario specimens were 3 year olds (McKee and Parker 1982). Schwartz and Norvell (1958) captured a very low ratio of males to females (1:3.5) in Pennsylvania. The highest number of males (15-50%) occurred in March-June, after which they virtually disappeared. Most were 1-2 year olds. Of 227 individuals there were 118 Age I, 72 Age II, 31 Age III and 6 Age IV.

Redside dace grow quickly and achieve about 50% of their total growth during their first year (McKee and Parker 1982). Growth of fish from pooled Ontario streams analyzed by Parker and McKee (1982) was comparable to growth in populations studied from New York, Pennsylvania and Wisconsin (Koster 1939; Schwartz and Norvell 1958; Becker 1983). Females grow faster, and reach a larger size than males (Koster 1939; McKee and Parker 1982). In a pooled sample of redside dace from Ontario, all 1 year old fish were immature, while most 2 year olds and all 3 year olds were mature (McKee and Parker 1982). Koster (1939) found that redside dace in a New York stream mature at age 2 and that fish apparently spawned every year after reaching maturity. Given that most fish mature at age 2 and live until age 4, generation time is estimated at 3 years.

Redside dace spawn in late May in New York when water temperatures reach 18 °C (Koster 1939). Parker and McKee (1982) captured redside dace in prespawning condition in early May in the East Humber River, Ontario, at water temperatures of 16-19 °C and suggested that spawning times and temperatures in Ontario are likely similar to those observed in New York. The authors have observed redside dace spawning activity in a western Lake Ontario tributary (Fourteen Mile Creek) from 10-29 May at temperatures ranging from 16-18.3 °C.

Eggs are normally laid in riffles in the gravel nests of other minnows (Cyprinidae). Koster (1939) described spawning by redside dace in the nests of creek chub (Semotilus atromaculatus) and common shiners (Luxilus cornutus) in New York. Redside dace spawning activity has also been observed in Ontario streams while these two common species were still active on the nest. Observations indicated that spawning in Fourteen Mile Creek usually occurred at the bottom end of pools, or in the upper part of riffles, where the current was 5-30 cm/sec (E. Holm, unpublished data). Johnston and Page (1992) also included minnows of the genus Nocomis as nest associates. Although the range of redside dace overlaps with two Ontario species in this genus (hornyhead chub [Nocomis biguttatus] and river chub [Nocomis micropogon]), redside dace spawning activity has not been observed in Nocomis nests in Ontario. By spawning in the nests of larger minnow species, which are better at excavating nests, the eggs of the redside dace presumably have a greater chance of survival because they receive better aeration and increased protection from predation (Johnston and Page 1992). Although the practice can result in the frequent production of hybrids (Koster 1939), hybridization does not appear to be a serious problem (Becker 1983). Most nest associates are capable of spawning independently (Johnston, pers. comm. 2001), but this has not been observed in redside dace. Although creek chub and common shiners are ubiquitous in southern Ontario streams, they initiate spawning at slightly cooler temperatures (12-17 °C) than the preferred spawning temperature for redside dace (18 °C) (Becker 1983), although redside dace spawning activity has been observed as low as 16 °C. The temperature differential and the shorter spawning period of redside dace may limit opportunities for communal nesting in some years.

Koster (1939) described the spawning behaviour observed in a New York stream in great detail and most of his observations are consistent with observations from Ontario streams (E. Holm, unpublished data). During the spawning period, males leave their resident pools, and travel short distances to spawning sites, especially in the middle of the day. Prior to spawning, males defend small territories (a few centimetres in each direction) immediately behind creek chub (or common shiner) nests. When ready to spawn, redside dace congregate in dense schools behind the nest. Females then individually move forward into the nest and are followed by groups of up to 4-6 males and spawning takes place. Eggs are broadcast and fertilized in the depression of the nest. Each individual spawns several times with a number of partners. The fecundity of redside dace reported in the literature ranges from 409-1971 eggs/female (Koster 1939; Becker 1983; McKee and Parker 1982). Eggs are non-adhesive and measure 1.2-2.4 mm in diameter (Koster 1939). Koster (1939) found that males remained in spawning condition for a period of 17 days in a New York stream.

There is no direct parental care of eggs, but indirect protection may be afforded by the nest and the presence of the male nest associate. The guarding male keeps the nest free of silt and deters egg predators. Koster (1939) found that male creek chub displayed tolerance to redside dace that had moved into their nest to spawn. Development of eggs and the larval stages of redside dace have not been described. Fish (1932) described a small (23 mm) juvenile, which can be distinguished from Notropis and Luxilus in having 5 (vs. 4) pharyngeal teeth.


The redside dace is primarily a surface feeder (Schwartz and Norvell 1958). The large upturned mouth of the redside dace makes it ideally adapted to capturing prey from below. Redside dace often leap several centimetres out of the water to capture aerial insects (Koster 1939; Schwartz and Norvell 1958; Daniels and Wisniewski 1994). This type of feeding behaviour relies on vision and would obviously be facilitated in habitats with clear water. The mid-water position maintained by redside dace also helps to facilitate surface feeding.

The redside dace feeds primarily on terrestrial insects, especially adult flies (Diptera) (Schwartz and Norvell 1958; McKee and Parker 1982; Daniels and Wisniewski 1994). Schwartz and Norvell (1958) found that terrestrial insects made up 77% of the diet by volume in a Pennsylvania stream from March to October. Parker and McKee (1982) found that adult flies made up 85% of the food volume consumed by redside dace from Ontario streams in August and September. Adult flies also comprised 85% of the food consumed between April and November in two New York streams (Daniels and Wisniewski 1994). Dance flies (Empididae) of the genus Hilara were the most important prey. Dance flies were not found in drift samples suggesting that redside dace were importing terrestrial energy produced in riparian vegetation into the stream (Daniels and Wisniewski 1994). Although redside dace do consume benthic insects and other invertebrate prey, these organisms are of minor importance in the diet and are more commonly eaten when winged forms are absent (Schwartz and Norvell 1958; McKee and Parker 1982; Daniels and Wisniewski 1994). Terrestrial insects are important to all age classes, although the size of food items consumed increases with age (Schwartz and Norvell 1958).

Predation on redside dace has not been reported in the literature although it undoubtedly occurs. McKee and Parker (1982) identified several piscivorous fishes that were captured infrequently at or near redside dace capture sites – brook trout, rainbow trout (Oncorhynchus mykiss), black crappie (Pomoxis nigromaculatus) and rock bass (Ambloplites rupestris). Piscivorous birds and mammals may also prey upon redside dace. Novinger and Coon (2000) suggest that the close association with cover (overhanging vegetation) and selection for deep water may guard redside dace against aerial attacks.


Only one study has examined the physiological tolerances of redside dace. Novinger and Coon (2000) examined the critical thermal maxima and metabolic rates at various acclimation temperatures. The critical thermal maximum for redside dace from New York acclimated at 20 °C was 32.6 °C. This value is slightly higher than some common minnow species that overlap in range with redside dace, but the data may not be strictly comparable due to differences in determining the end points when estimating critical thermal maxima (Novinger and Coon 2000). Predicted final preferred and optimum temperatures for growth were 24.5 and 24.7 °C, respectively. Tolerance to low oxygen levels have not been examined in the laboratory, but McKee and Parker (1982) reported capturing redside dace from Ontario streams in August and September at dissolved oxygen levels between 4-11.5 mg/L. Dissolved oxygen levels were usually greater than 7 mg/L.


No long distance movements have been reported for redside dace populations. Koster (1939) only noted local movements between adjacent pools and riffles at spawning time in a New York stream. McKee and Parker (1982) noted that pools inhabited in the summer in the East Humber River, Ontario were unoccupied in the spring, suggesting the fish had congregated in spawning areas.

Interspecific Interactions

The fish communities that are normally associated with redside dace populations in Ontario typically consist of common, tolerant coolwater species such as creek chub, common shiner and blacknose dace. The relationship with creek chub and common shiner as nest associates appears particularly important to redside dace. Redside dace do not regularly co-occur with other species at risk.

Redside dace occasionally co-occur with native brook trout but the two are generally not found together. The influence of introduced rainbow trout and brown trout (Salmo trutta) on redside dace has not been investigated experimentally. In one study in the Susquehanna River in New York, however, redside dace, as well as other minnows, were extirpated after the introduction of 12-inch brown trout in 1998 (Stewart pers. comm. 2006).Their influence on redside dace may be conditional on the presence of other predators in the same habitat. Bryan et al. (2002) found that the joint presence of two introduced predators (virile crayfish (Orconectes virilis) and rainbow trout) negatively affected the Little Colorado spinedace (Lepidomeda vittata), a trout-like minnow. Treatments with only rainbow trout did not result in predation of spinedace, but there was a significant reduction of activity level. Treatments with both crayfish and rainbow trout resulted in a decrease in activity rates and a decrease in rates of movements into and out of refuges. An experimental examination of the interactions between rainbow trout and the closely related rosyside dace suggested that interactions between the two species were minimal (Rincon and Grossman 1998). Some authors have identified the redside dace as a problem in that it competes with trout for food and may limit trout production (Greeley 1938; Becker 1983).

The introduction of predatory northern pike (Esox lucius), basses and sunfishes (Centrarchidae) has coincided with the disappearance of the redside dace in at least two creeks (Spencer and Mountsberg). Habitat change from urbanization and agriculture in these two systems has been minimal.


The redside dace does not appear to be able to adapt to habitat alteration as many populations have been extirpated or have declined in the face of habitat change. Artificial propagation and re-introductions have not been attempted with redside dace to date.