The emerald shiner belongs to a group of small, similar-looking fish in the genus Notropis that contains nearly 100 species. As a result, it may be difficult to distinguish between the different species. For example, the emerald shiner’s range overlaps the Rio Grande shiner (N. jemezanus) and the sharpnose shiner (N. oxyrhynchus) which are similar in appearance to one another.
To be an emerald shiner, the fish should bear the following traits: it should have a green tint to its body, a silver belly, and clear or white fins. Some individuals have a dark lateral stripe running from their operculum, or gill flap, to their tail. Their mouth is pointed forward, a trait that helps distinguish them from other shiners and similar groups, like suckers (family Catostomidae). Finally, their nose is blunt and rounded.
What Is a Forage Fish?
Emerald shiners are considered forage fish. The term “forage fish” refers to a class of small to mid-sized organisms that are the primary food source for larger predators. These organisms are not necessarily fish and can include organisms like squid and large aquatic invertebrates. Without forage fish, predators like flounder, walleye, pike, and gar would not have a source of food.
Forage fish are a critical part of any food chain, serving to convert small sources of food like zooplankton or insects into substantial protein for larger predators. As a result, forage fish tend to be small enough to eat their preferred prey and reproduce in large numbers to offset the loss of individuals from a population due to predation. Schooling is also a common strategy among forage fish that confuses predators and improves the forage fish’s own prey-finding capabilities.
Are Emerald Shiners Minnows?
Emerald shiners do belong to groups of fish traditionally known as minnows. The minnow family, Cyprinidae, contains many species of small, silver fish like the emerald shiner that consume small aquatic invertebrates and are prey to larger fish.
All minnows are a critical part of their ecosystem by providing a source of food for predators which, in turn, feed even larger predators like piscivorous birds, bears, and more. Some species of fish that eat emerald shiners include steelhead trout (Oncorhynchus mykiss), walleye (Sander vitreus), and sunfish (Centrarchidae) although they are a common prey item for many species. Additionally, birds like the common tern (Sterna hirundo) rely on emerald shiners for food.
Where Do Emerald Shiners Live?
The emerald shiner is native to North America and is primarily found in the Mississippi River drainage system. They prefer large lakes and rivers and are abundant in large waterbodies like the Mississippi River and Great Lakes.
In its native range, the emerald shiner is a vital forage species with naturally fluctuating populations. Their importance in native ecosystems is so great that they are considered a keystone species, or a species with such an impact on an ecosystem that they support multiple facets of that ecosystem and allow other species to flourish.
During the height of their seasonal activity, the emerald shiner migrates to the water’s surface to feed at night and retreats to the depths during the day to avoid predators.
How Long Do Emerald Shiners Live & How Do They Reproduce?
Adults reach maturity between 2 and 3 years of age with females generally being larger than males. They spawn in May to August and the exact spawning time varies by location. During their spawning season, adults will spawn at the surface of the water column at night over gravel beds, sand, or near large rocks.
Multiple males will chase females where they “dance” in chaotic circles just below the water’s surface before releasing eggs into the water which sink to the bottom and are swept into the substrate by the current. Mature females can produce nearly 2,000 to 9,000 yellow eggs which hatch in about a day.
Yearlings primarily eat protozoans whereas small fish and insects are preferentially consumed by adults.
Are Emerald Shiners Popular Sportfish?
Due to their small size, Emerald Shiners are not large enough to be exciting or edible sportfish.
Their utility in sportfishing was not lost on anglers and so this species was introduced outside of its range to serve as a food source for larger predatory fish. They were also introduced illegally as bait. While they have been introduced outside of their native range, there is not enough evidence to consider this species invasive.
