Hiodon tergisus
Image of Hiodon tergisus

Photo by John Lyons 

Key Characteristics

The mooneye is a laterally compressed, deep-bodied fish with a small oblique mouth and large eye. This silver fish has a keeled, but not serrate, ventral edge from pelvic fins to the anus.

Status and Rank

  • State Status: T
  • State Rank: S1
  • Global Rank: G5


County NameNumber of OccurrencesYear Last Observed
Presque Isle11943
St. Clair21984
Distribution map for Hiodon tergisus

Updated 5/15/2018. Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


The mooneye occurs in clear large rivers and lakes. They are often found in deep holes of rivers with swift currents and firm substrates. In the Great Lakes they often occur within 1 mile of shoreline and are absent at depths below 10 m.

Specific Habitat Needs

Hard substrates needed in Mainstem Stream (3rd-4th order), Riffle, Mainstem Stream (3rd-4th order), Pool, River (5th-6th order), Riffle, River (5th-6th order), Pool, River (5th-6th order), Run Hard sustrates needed in Mainstem Stream (3rd-4th order), Run

Natural Community Types


For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.


Local populations are highly susceptible to extinction because losses due to natural or human-induced perturbations cannot be replaced by neighboring populations. The mooneye is intolerant of silt and turbidity, and as such agricultural, urbanization, and industrialization practices can be detrimental to this species. Declines have also been attributed to increasing pollution.

Active Period

Spawning from first week of April to fourth week of June

Survey Methods

Page Citation

Michigan Natural Features Inventory. 2007. Rare Species Explorer (Web Application). Available online at http://mnfi.anr.msu.edu/explorer [Accessed Aug 17, 2018]

More Information

See MNFI Species Abstract


Survey References

Technical References

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