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Bridle Shiner

Bridle ShinerNH Conservation Status: Threatened

 

State Rank: Imperiled

 

Scientific Name: Notropis bifrenatus

 

Distribution: Bridle shiners were once common in suitable habitat from the St. Lawrence River watershed to the Atlantic slope drainages from southern Maine to South Carolina.

 

Bridle Shiner

The bridle shiner (bottom) and the juvenile creek chubsucker (top) are similar in appearance. Note the smaller scales and the downward turned mouth of the creek chubsucker.

Description: The bridle shiner is a small minnow species with a black lateral band that extends from the tip of the snout, through the eye, back to the base of the tail. It is golden in color, with large, diamond shaped scales and a white underbelly.

 

Bridle shiners may be confused with juvenile creek chubsuckers, which also have a prominent lateral band. The mouth of the creek chubsucker is sucker-like and pointed downward, compared to the mouth of the bridle shiner, which is positioned just below the tip of the snout. Juvenile creek chubsuckers, and most other minnow species, also have smaller scales than bridle shiners.

 

Species commonly confused with: Blacknose dace, juvenile creek chubsucker, juvenile fallfish

 

Habitat: Bridle shiners depend on dense communities of submerged aquatic vegetation for survival. This habitat may be found along the shorelines and coves of lakes and ponds, the backwaters of larger rivers, and in slow flowing streams.

 

Life History: The bridle shiner is a short lived species with a life span that rarely exceeds two years. Spawning bridle shiners congregate in open spaces above dense stands of aquatic plants, such as Myrophillum (milfoil). Spawning takes place in late spring and early summer. Aquatic vegetation with thick foliage, including Myrophyllum, ceratophyllum (coontail), and chara (stonewort), appears to provide important spawning habitat for adults and nursery habitat for recently hatched juvenile bridle shiners. Bridle shiners feed on zooplankton and aquatic invertebrates. They move with a distinctive stop and start motion, rarely gliding like other minnow species such as the golden shiner, with which it is often observed. Bridle shiners forage in areas with little or no flow, usually suspended about midway between the surface and the bottom. They are often found in loose groups or clusters. When alarmed, individuals scatter rapidly among the vegetation.

 

Origin: Native

 

Bridle Shiner

Bridle shiners may be surveyed with a dip net due to their habitat of congregating in loose schools among stands of aquatic vegetation.

Conservation/Management: Bridle shiner populations have suffered significant declines over the last few decades. There is only one remaining population of bridle shiners in Pennsylvania, where the species was once considered abundant. Bridle shiners have been extirpated from the state of Maryland and from a number of waterbodies in Massachusetts. Despite an extensive survey effort, the New Hampshire Fish and Game Department (NHFGD) documented bridle shiners at only 6 of 21 sites where they were recorded as present in 1938. The reasons for the apparent extirpations from certain water bodies are not always clear and multiple causes are probable. In some waterbodies, including Winisquam Lake, Canobie Lake, and Shadow Lake, submerged aquatic vegetation has been reduced to just a small fraction of the overall shoreline habitat. The loss of aquatic vegetation is a problem common to lakes and ponds with increasing levels of shoreline development. Even marginal reductions in aquatic vegetation may make bridle shiners more vulnerable to predators, both native and introduced, possibly reducing the population below the numbers required for replacement. Bridle shiners are known to coexist with bass and other introduced predators, like black crappie, in water bodies with intact shoreline habitat.


Water level drawdown has the potential to extirpate bridle shiners from a waterbody. Water level drawdowns occur for dam maintenance, flood storage, dock repair for shoreline property owners, or vegetation control. Drawdowns during winter expose the roots of aquatic vegetation to dessication and freezing, causing temporary die back. The overall reduction in aquatic plants will impact bridle shiners during the growing season. Water level draw downs during winter may have a direct effect on bridle shiners by preventing access to near shore habitat in the early spring. Bridle shiners have been observed using overhanging banks and shrubs as cover in late winter and early spring before the emergence of aquatic plants. Bridle shiners are extremely sensitive to unnatural water level fluctuations during the growing season, when spawning is occurring and juveniles seek refuge in shallow water among submerged aquatic plants. With a life span of only two years, a single draw down event could decimate an entire population.

 

Bridle Shiner

Bridle shiner spawning behavior has been observed over stands of variable milfoil. These two individuals were photographed at the northern end of Lake Winnipesauke in Moultonbourough.

In some cases, bridle shiners have adapted to the impounded conditions upstream of a small dam, culvert, or bridge. Drainage of this upstream habitat may extirpate the local population of bridle shiners. Dam removal, culvert, or bridge replacement should proceed with caution in bridle shiner habitat. Sediment deposition upstream of the dam may have filled in the original wetland, pond, or slow flowing stream habitat that the bridle shiners inhabited before the construction of the dam or road. Rapid draining of the impoundment may result in a narrow channel with riffle habitat that is unsuitable for bridle shiners. Draw down of the impoundment should occur slowly to give aquatic plants time to adjust to the new water level. In some cases, sediment may have to be removed to ensure that adequate habitat for bridle shiners will exist when the project is complete.

 

As visual foragers, bridle shiners are sensitive to water clarity and are therefore susceptible to the effects of eutrophication and siltation. Declines in water quality have been associated with urbanization, which has been shown to alter fish communities. Eutrophication has the combined effect of reducing visibility, altering aquatic plant communities, and reducing oxygen levels. Bridle shiners are known to exist in dark or tea colored water, yet they are unlikely to persist in areas with chronic turbidity issues resulting from landuse activities in the watershed or persistent boat wakes. Naturally vegetated buffers, with a width of at least 15 m, should be maintained along the shorelines of water bodies known to support bridle shiner habitats. It is critical to prevent nutrient and sediment loading into bridle shiner habitat from fertilizers, failed septic systems, and stormwater runoff throughout the contributing watershed.

 

Recommendations:

 

  • Continue to map the distribution of bridle shiners in New Hampshire.
  • Draft a Bridle Shiner Recovery Plan which will identify critical habitat for protection, populations vulnerable to extirpation, potential restoration opportunities, and research needs.
  • Review permit applications and make recommendations to avoid impacts to bridle shiner habitat.

 

Distribution Map: Wildlife Action Plan Species Profile PDF Document