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Breeding Cycle of Minnows

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The term minnow commonly refers to any small fish who like to school, feed on insects and serve as prey for larger fish. More than 290 species of minnows exist in North America. They are found in a variety of habitats including rivers, lakes and streams. While species of minnows differ in color and size, all minnows generally breed in the same pattern.

Preparing the Pad

Male minnows initiate the mating process by finding and readying a nesting site for reproduction. This generally occurs between May and September. Mature male minnows select nests on the underside of horizontal objects such as rocks, wood or vegetation. The sites are generally in shallow water, typically on a sandy substrate. Preparing the sites require a male minnows to use his mouth and tubercles to create a depression in the substrate. After the nest is prepared, males become extremely territorial, fighting off other males and potential intruders.

Courting His Mate

A male minnow performs several mating behaviors to attract female minnows to his nest. The male will swim back and forth in the nest area, exhibit close contact with passing females and make his body vibrate when near mature female minnows. The right partners are welcomed into the nest, but females devoid of eggs are driven away. Females without eggs often take advantage of territorial males who are busy fighting by eating eggs already in the nest.

Dropping the Eggs

Once sufficient stimulation is obtained, the male minnow makes contact with the female's urogenital region. To do this, the male usually pushes the female's back end up against a hard surface in the nest. The contact causes the release of the female's eggs along with the simultaneous release of male sperm. Fertilized eggs are then deposited in a single layer on the nest site's ceiling. After the contact, the male minnow aggressively drives the female away. However, the same female may return throughout the day before she is emptied of eggs. Multiple female minnows may visit the same site for mating and egg deposit.

Baby Duty

Male minnows care for the eggs alone. They fan the nest eggs to ensure the unborn minnows receive adequate oxygenation and use their dorsal pad to clean the eggs. Father minnows also defend the eggs against predators until they hatch. In addition, males also remove unfertilized eggs and damaged eggs from the nest. After about a week, the eggs hatch. The baby minnows generally lay at the bottom of the nest for a few days before swimming away to look for food. Male minnows expend extensive energy during mating season, breeding several times, while watching over the eggs. Some male minnows have nests with eggs in various development stages because of breeding with various partners.