What is a Mooneye?

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  • Written By: Sara Schmidt
  • Edited By: Andrew Jones
  • Last Modified Date: 12 September 2019
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The mooneye is a silvery freshwater fish from North America. The shimmery creature is from the Hiodontidae family. This ray-finned fish gets its name from its large, round metallic eyes. Mooneye fish, commonly referred to as toothed herring, are not considered a valued source of food.

Several different types of fish are known as mooneye fish. These clupeoid fishes are considered primitive, with thin, nearly flat bodies. Mooneyes have prominently forked tails and very sharp teeth. These teeth are arranged on the fish's tongue as well as on the roof of its mouth.

Bellies of mooneye fish feature smooth scales. A small flap known as a pelvic auxiliary process can be found directly above the fish's pelvic fin. The fish's appearance is considered to be similar to that of the herring, providing it with its toothed herring nickname.

These fish are small, growing only up to 12 inches (31 cm) in length and an average of 1 pound (2.2 kg) in weight. Some larger mooneyes may measure up to 19 inches (48 cm) in length, and weigh up to 3 pounds (6.6 kg). Mooneye fish are carnivorous. Their diets consist of several different types of small organisms, such as shrimp, mollusks, insects, and other small fish.


Mooneye fish are a threatened group of animals. Their numbers continue to decline throughout their various habitats. One cause of their reduced population size is thought to be attributed to the siltation of water where the fish are found. Other causes of their dwindling numbers remain unknown.

Two species of the family, Hiodon tergisus, and Hiodon alosoides, remain alive and can be found widely across North America. The mooneye's habitat ranges from southern Canada to the Mississippi River basin. It prefers clear rivers, such as those found in lakes and ponds. Three of the species, Hiodon consteniorum, Hiodon rosei, and Hiodon woodruffi, are extinct.

Hiodon alosoides is also known as the goldeneye fish. While the Hiodon tergisus has a dorsal fin that begins before its anal fin, the goldeneye's dorsal fin is aligned with its anal fin. In contrast to the Hiodon tergisus, the Hiodon alosoides features golden irises rather than silver.

Eggs laid by these fish are similar in appearance and consistency to frogs' eggs. Mooneye fish typically lay their eggs over rocks from March to May. Spawning occurs in the spring. A single female fish can be expected to lay 10,000 to 20,000 eggs.


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