Northern Redbelly Dace - Chrosomus eos
The Northern Redbelly Dace is another of Montana's small minnows. During the spawning season, this species becomes quite colorful with red flanks. Its maximum size is about 3 inches. In some locations in the northern U.S. and Canada, the Northern Redbelly Dace hybridizes with its close relative, the Finescale Dace. The resultant hybrids are very unusual in that they are all females and produce offspring that are likewise all female. Eggs from the hybrids are "fertilized" by the sperm of Northern Redbelly Dace. It appears that this "fertilization" is necessary for egg development to begin, but curiously none of the genetic traits of the male are incorporated into the fertilized embryo. This type of reproduction is known as gynogenesis and is found in only a few fish and amphibians. Here in Montana we have the Northern Redbelly Dace and the hybrids, but no Finescale Dace. Because of its genetic uniqueness, the Northern Redbelly Dace x Finescale Dace hybrid is a Fish of Special Concern in Montana.
The Northern Redbelly Dace is olive to dark brown above; the lower side and belly are yellow or silvery except on adult males during summer when the lower side is red. The side has two dark stripes with a light band between them; the upper stripe often breaks into spots toward the tail. The lower stripe is broader and extends from the snout to the base of the tail fin where it may end in a spot. These two lateral stripes are sometimes connected by a dark, oblique line or crossband. The eyes are large. The body is almost round in cross section. The front of the dorsal fin is behind the front of the pelvic fins. The lateral line is incomplete and not distinct and there are no barbels (Brown 1971, Holton and Johnson 1996).
Northern Redbelly Dace range across Canada from British Columbia through the Northwest Territories to Nova Scotia, and from Montana to Maine, primarily in the Atlantic, Great Lakes, Hudson Bay, upper Mississippi, Missouri, and Peace-Mackenzie river drainages, with populations in the west south to northern Colorado.
Summary of Observations Submitted for Montana
Number of Observations:
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Not studied in Montana. In a 7.3 hectare lake in Quebec, Northern Redbelly Dace swam in shoals in the shallow littoral zone during the day and migrated to the deeper pelagic regions at sunset, where shoals broke up into single fish, then regrouped as individuals returned to the shallow littoral areas at sunrise; migrations began in late May (Naud and Magnan 1988). Patterns of movement in streams is apparently not well-documented, but probably includes moves of several hundred meters.
Not well-studied in Montana. Northern Redbelly Dace are found in clear, cool, slow-flowing creeks, ponds and lakes with aquatic vegetation, including filamentous algae, and sandy or gravelly bottoms interspersed with silt (Brown 1971). In Stink Creek of northern South Dakota (Morey and Berry 2004), dace were found in a single unconstrained and low-gradient prairie channel with little surface flow at the time (early June). Pools were 26 to 84 cm (1.0 to 3.3 inches) deep in a wetted area about 1.3 m (4.3 ft) wide. Water temperature was 16.6 C, filamentous algae and rooted macrophytes were abundant. In western South Dakota, the range of this species appears to be limited to perrenial streams with slow, clear water and abundant macrophytes and algae (Morey and Berry 2004). In Colorado (Bestgen 1989), the presence of cool springs or cool tributary flow was a consistent feature of Northern Redbelly Dace habitats in prairie streams and marshes. Strong thermal stratification existed in some heavily vegetated ponds. In water < 0.3 m (0.9 ft) deep, surface temperature was 27 C when bottom temperature was 18 C; water < 22 C was present in all occupied habitats. Individuals were usually found in water 0.25 to 1.3 m (0.8 to 4.3 ft) deep and congregated near the shores of ponds >3.0 m (9.8 ft) deep. Substrate in all habitats ranged from black anoxic silt to sand.
Diet has not been studied in Montana. In a Quebec lake (Naud and Magnan 1988), 95% of the food items in 78 stomachs consisted of two species of cladocerans (Daphnia and Holopedium). Contents (frequency of occurrence) in 40 stomachs from Michigan (Cochran et al. 1988) included green algae (100%), diatoms (68.4%), blue-green algae (10.5%), dinoflagellates (42.1%), zooplankton (42.1%: rotifers, copepods, Daphinia, Chaoborus, Bosmina), macroinvertebrates (5.3%: flies, caddisflies, beetles, mayflies) and miscellaneous (89.4%: sponge gemmules, pollen, macrophyte fragments).
Not studied in Montana (but see Habitat comments). Age structure of collections from Colorado in August and September (Bestgen 1989), respectively, were Age Class 0 (13-35 mm standard length): 82% and 82.5%, Age Class 1 (33-46 mm): 12% and 15%, Age Class 2 (45-52 mm): 6% and 2.5%; some populations from Canada are reported to include fish living 5 to 8 years. In Colorado (Bestgen 1989), Northern Redbelly Dace were absent from sites when Green Sunfish and Largemouth Bass were present. Risk of predation appears to be an important agent for Northern Redbelly Dace in Canadian Shield lakes. Northern Redbelly Dace are also subject to predation by Brook Trout in Canada, and appear to be sensitive to chemical alarm cues, by which they are able estimate the risk of predation (Dupuch at al. 2004). In Quebec (Dupuch et al. 2009), results of a study of 13 lakes showed that 1) mean abundance of dace in the littoral zone was positively related with the relative risk of predation in the pelagic zone, 2) dace preferentially used structured over open water habitats in the littoral zone, and 3) this preference was not related to the relative predation risk in the littoral zone, but decreased as the relative risk of predation increased in the pelagic zone. It was concluded that, at the lake level, dace appear to enter the littoral to avoid pelagic predators; at the littoral zone level, the results indicate flexibility in antipredator tactics (shelter versus shoaling). Movements to pelagic habitat at night for feeding and returning to littoral habitats during day may also be a way to reduce predation risk to themselves while increasing encounters with preferred prey (Naud and Magnan 1988).
Not well-studied in Montana. The Northern Redbelly Dace is sexually mature at 1 year and spawns May through August. Incubation is 8 to 10 days at 70 to 80 degrees F (Brown 1971). In Colorado (Bestgen 1989), spawning appears to occur from late June to early August, although spawning is not necessarily synchronous in geographically close habitats, probably due to differences in water temperatures between spawning sites. In Alberta (Das and Nelson 1990), spawning extends from mid-June to late July at surface water temperatures of 13.0 to 18.0 C. Female gonads are ripe from early June to late July, fully ripe from mid-June to late July, and spent from mid-June to mid-August. The number of eggs carried by 50 female dace 39.4-54.5 mm standard length was 146-1030 (mean = 654). Fully ripe eggs are 0.91 to 1.24 mm diameter and golden yellow. Eggs are scattered among aquatic vegetation over gravelly substrates and abandoned. A protracted spawning period in Ontario (and elsewhere), the patterns of fecundity to size relationships (lack of a relationship between female length and number of eggs carried), and egg size distributions with no apparent age (size) differentiation, suggest that Northern Redbelly Dace is a fractional (multiple, serial, or batch) spawner in at least some parts of its range (Powles et al. 1992).
No management activities specific to Northern Redbelly Dace are currently occuring in Montana. Surveys to assess population status and life histroy throughout the state would be useful. Most assessments have been to determine status and genetic structure of hybrid Northern Redbelly X Finescale Dace. Presence in livestock watering ponds in Colorado (Bestgen 1989) indicate an ability to coexist with livestock under certain conditions.
Threats or Limiting Factors
As with many small native stream fishes, Northern Redbelly Dace could be adversely effected by stream channelization, reductions to discharge, changes in water quality and temperature, and introductions of non-native predatory fishes.
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