Common minnow facts for kids

Quick facts for kids Common minnow
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Synonyms
List Cyprinus phoxinus Linnaeus, 1758 Leuciscus phoxinus (Linnaeus, 1758) Cyprinus aphya Linnaeus, 1758 Salmo rivularis Pallas, 1773 Cyprinus rivularis (Pallas, 1773) Phoxinus rivularis (Pallas, 1773) Cyprinus morella Leske, 1774 Cyprinus isetensis Georgi, 1775 Cyprinus galian Gmelin, 1789 Cyprinus chrysoprasius Pallas, 1814 Phoxinus laevis Fitzinger, 1832 Phoxinus varius Perty, 1832 Phoxinus marsilii Heckel, 1836 Cyprinus lumaireul Schinz, 1840 Phoxinus lumaireul (Schinz, 1840) Phoxynus montanus Ogérien, 1863 Phoxinus csikii Hankó, 1922

The Eurasian minnow (Phoxinus phoxinus) is a small freshwater fish. It belongs to the carp family, called Cyprinidae. You can find these minnows all over Eurasia, from Britain and Spain to eastern Siberia. They usually live in cool streams and well-oxygenated lakes and ponds. Minnows are known for living in large groups, called shoals.

What Does a Minnow Look Like?

The common minnow is a small fish. It usually grows to about 7 centimetres (3 in) long. The longest they get is about 14 centimetres (5+1⁄2 in). It has fins on its back and belly. The back fin is called the dorsal fin, and the belly fin is the anal fin.

Minnows have a brownish-green back. Their underside is whitish-gray. A stripe or blotches run along their sides. These markings separate the darker back from the lighter belly.

Where Do Minnows Live?

Common minnows live across northern Eurasia. You can find them from Ireland in the west to Korea in the east. They live as far north as Scandinavia and Russia. In Western Europe, they are found as far south as the Garonne and upper Rhone rivers.

They have also been found in the Volga and Ural river areas. Minnows are also in Lake Balkhash. In some places like Scotland and Ireland, they are not native. This means people likely brought them there.

Minnow Homes: Their Habitat

Common minnows live in many different places. They need cold water with lots of oxygen. Often, they share their homes with salmonid fish. They can live in small streams with fast currents. In colder regions, they also live in large lowland rivers.

Minnows also live in still waters. This includes small mountain lakes and large, clear lakes. For laying eggs, they need clean gravel areas. These spots must have good water flow or waves. They also need deep pools with slow currents for winter. These pools must have rough bottoms where they can hide.

How Minnows Behave

Minnows shoaling in large groups in shallow water.

Living in Groups: Shoaling

Common minnows start living in groups very early. They begin to shoal as soon as they can swim. This group behavior becomes very strong by three to four weeks old. Living in a shoal helps minnows in many ways. It helps them avoid predators and find food.

However, there are also downsides to living in groups. There can be more competition for food. Also, there's a higher risk of getting sick. Minnows change their shoaling behavior based on what's happening. For example, they might group closer if predators are nearby.

Staying Safe from Predators

Minnows form groups to protect themselves. This idea is called the "selfish herd effect." It means each minnow tries to be safer by moving closer to others. They try to get to the center of the group. This is where the risk of being eaten is lowest. When more predators are around, minnows group together even more.

Alarm Signals

Minnows can tell their friends about danger. They use a special chemical signal. This chemical is released if a minnow gets hurt or caught. Other minnows can smell this "alarm substance." It tells them that a predator is near.

This alarm signal helps the whole group. It's like a warning system. The minnows then know to be more careful.

Checking Out Predators

When a predator comes near, some minnows take a risk. They swim closer to the predator to check it out. This is called "predator inspection." It helps them figure out how dangerous the predator is. It's risky, but it helps the minnows react faster if the predator attacks.

Minnows can recognize predators by how they look. They also seem to know if a predator is ready to attack. If a minnow checks a predator that is about to attack, they become more alarmed. This shows they can sense the predator's mood.

Different Ways to Avoid Danger

Minnows from different places might act differently. Minnows from areas with many predators often inspect predators more. They start inspecting sooner and form bigger groups to do it. They also approach the predator less closely.

Some of these behaviors are passed down. Young minnows raised in a lab show these behaviors even without seeing predators. But, early experiences with predators can also change their behavior. If they meet predators early, they might inspect more and shoal more.

Finding Food Together

Living in a shoal helps minnows find food. When more fish are looking, they find food faster. This is true for common minnows. A larger group usually finds food more quickly.

Choosing Friends: Shoal Choices

Minnows don't just swim with anyone. They prefer to be with minnows they know. They also like to group with others who are not as good at finding food. This is because even though group foraging helps, it also means more competition for food.

Minnows tend to stick with familiar friends. But new groups can form when different shoals meet. Over time, minnows might start associating with new individuals.

Breeding Minnows in an Aquarium

Eurasian minnows can breed in cold freshwater aquariums. They need plenty of oxygen, so air bubblers help. A good water current is also important. They also need a gravel bottom for their eggs. Clean water and plants help them thrive.

Breeding usually starts around late May. The fish become more active and change colors. Females don't change color much, but their bodies get rounder. Males change a lot. Their colors become stronger, and their fins and throat turn red. Their gills become pale with blue patches.

Males chase females, rubbing against them. This gets very active before mating. Mating happens when the female releases her eggs. The male then fertilizes them.

The fertilized eggs sink into the gravel. Other fish might try to eat the eggs. The male minnow will guard the eggs fiercely. After a few days, the eggs hatch into tiny fry. It's important to have many plants for the fry to hide in. Adult fish might eat the fry, especially if they are hungry.

Baby fry eat tiny organisms called infusoria and algae. As the fry grow, their diet changes. When they are about 1⁄2 inch (13 mm) long, they can eat small creatures like daphnia. Soon, they will eat the same food as adult minnows and grow quickly.

Images for kids

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  A Eurasian minnow.

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  Another view of the Eurasian minnow.