Finescale Dace

Chrosomus neogaeus

finscale daceDistribution: The finescale dace has a northern distribution in North America, inhabiting most of Canada, with isolated populations in the upper Mississippi River watershed, northern New York, Vermont, New Hampshire, and Maine. In New Hampshire, finescale dace populations occur north of the White Mountains, in the Androscoggin and Connecticut River watersheds.

Description: The finescale dace is a medium sized minnow species with a single, black lateral band, a well-developed terminal jaw, and very small scales. It looks very similar to the northern redbelly dace, which has two parallel, black lateral bands. Where they overlap, the two species may hybridize and the offspring retain characteristics from both species. Finescale dace and northern redbelly dace may also be distinguished by the length of their intestines. The intestine of the finescale dace is shorter than the length of its body, with a single “S” turn. The intestine of the redbelly dace is long and coiled. Finescale dace sometimes co-occur with blacknose dace, but may be distinguished by the position of the mouth, which is below the tip of the snout in the blacknose dace and right at the tip of the snout in the finescale dace. Male finescale dace become brightly colored in red or yellow and grow tubercles during the breeding season.

Species commonly confused with: Blacknose dace, northern redbelly dace

Habitat: Finescale dace prefer cool headwater streams and small ponds with sluggish flow and ample cover from over hanging shrubs or aquatic vegetation. They tend to thrive in areas with a history of beaver activity. Individuals may be found in rivers or steams with higher gradients and flow, but they are assumed to have either washed out of or dispersed from areas of more suitable habitat.

Life History: Finescale dace are a carnivorous minnow species. Their large jaws are adapted to feeding on insects, insect larvae, crustaceans, and snails. They are non-territorial and may be observed foraging in small groups in the slower flowing sections of small streams and rivers. They are particularly well adapted to living in streams with beaver dams in various states of activity. This habitat may offer protection from large predacious fish species, with which finescale dace rarely coexist.

Breeding takes place in areas of structure, such as exposed tree roots below an undercut bank, or a submerged tree branch, where the male uses its large pectoral fin to guide the female toward the substrate to deposit her eggs. Spawning takes place in small groups just after ice out. They are one of the first minnow species to spawn in early spring. Adapted to thick ice cover and low oxygen levels, finescale dace are well suited to living in northern climates. Individuals may reach up to 6 years of age and 5 inches in length.

Where finescale dace overlap with northern redbelly dace, hybridization may occur. The offspring tend to be all female and diploid, meaning that they contain a full set of chromosomes from each parent. The hybrids are able to reproduce clonally and they share characteristics from both species, including a more omnivorous diet. Northern redbelly dace usually spawn about two weeks later than finescale dace in warmer water temperatures (190°C/67°F for redbelly dace and 16°C/60°F  for finescale dace). Hybridization occurs in areas where rapid temperature increases in spring may cause more overlap between the spawning seasons of the two species.

Origin: Native

Conservation/Management: Finescale dace are vulnerable to habitat alterations that reduce summer base flows and riparian cover. Populations upstream of dams are also vulnerable to artificial water level fluctuations, especially during the spawning season. The extent of their distribution in New Hampshire is not well understood. Although aquatic habitats in northern New Hampshire are under less pressure from development than those of southern New Hampshire, there may be certain regions that are important for the persistence of the species, which has somewhat limited dispersal abilities.

The biggest threat to finescale dace populations may be the introduction of large predatory fish species, including bass, pike, and sunfish. The brightly colored breeding males, in particular, are not well adapted to avoiding larger fish predators. Preventing illegal fish species introductions may be prove to be an important strategy for protecting finescale dace populations. As a species adapted to cold climates, the range of the finescale dace may be reduced in the future due to the effects of climate change.