Spotted gar grow to a maximum length of 91 cm, the average length is 76 cm. The body is cylindrical and often mistaken for a log lying in shallow waters. They are covered with hard, diamond-shaped scales and spots on the top of the head and fins. Females are generally larger than males.
Spotted gar are found throughout the rivers and streams that feed into Lake Michigan and Lake Erie, the Mississippi River, and rivers along the northern coast of the Gulf of Mexico from Texas east to Florida.
Spotted gar prefer shallow open waters, usually 3 - 5 m deep, as well as stagnant backwater. They are often found near the surface basking near fallen logs, trees, or brush. This species is also shoreline-oriented, meaning it can be found near banks that include some sort of brush covering. Spotted gar are rarely found in areas that do not include some form of brush covering. (Snedden, et al., 1999)
Larval spotted gars hatch from eggs, and are about 2.5 cm long when they first emerge. They are slender and have a thread-like extension of the tail that vibrates, helping them to swim when they are small. They become fully developed by age 2. Females and males grow at different rates.
Males gather in shallow (1.5 m) water with plants growing in it to compete for the largest females to mate with. Females allow more than one male to fertilize their eggs.
Most eggs are laid in October, when females lay about 14,000 eggs. Larger females lay more eggs.
Females deposit a lot of energy in the form of nutrients in their eggs to fuel the development of young. There is no parental care after the eggs are laid.
It is not known how long spotted gar can live, but one study showed males living up to 8 years and females up to 10.
Spotted gar are mainly active at night. Often, this species will remain still near fallen trees or brush throughout the day. At night they emerge and search for prey. Occasionally, they go to the surface of the water to take air into their specialized swim bladder. This specialized bladder acts as a primitive lung and allows them to live in waters with low levels of oxygen.
Home range sizes change with the seasons in spotted gar because water depths change. In spring, home ranges are about 20 times larger than in other seasons. Spotted gar move away from their home areas to spawn.
Methods of communication among spotted gars aren't well-studied. They have a lateral line system that may help them sense prey in the turbid waters they live in.
Spotted gars are ambush predators, eating mainly crayfish (47% of diet in one study). They forage at night under the cover of floating logs or vegetation. Spotted gar also eat other species of fish including sunfish, gizzard shad, crappies, bass, catfish, and shiners.
Adult spotted gars do not have many natural predators, except for other types of gars. Eggs and juvenile spotted gars are probably attacked by a number of fish predators, although the eggs of gar are potentially toxic to many species. The spotted pattern on these fish may act as camouflage.
Spotted gars are important predators of crayfish, other crustaceans, and smaller fish in the low-oxygen level waters they inhabit.
Spotted gars sometimes attack popular game fish species, but there is no evidence that they effect populations of game fish. Existing studies show they prey on mainly non-game species.
Juvenile spotted gar eat mosquito larvae. The species is not particular popular for sport fishing, although gars are considered good fish for eating.
Spotted gars are not generally considered in need of special conservation efforts, except at the edges of their range, where numbers have shrunk due to habitat destruction. They have not been evaluated by the IUCN. Spotted gar are Species of Special Concern in Michigan, Threatened in Canada (Ontario Province), and may have protected status in other states on the northern, eastern, and western limits of theirrange.
George Hammond (editor), Animal Diversity Web.
Lana Hall (author), Radford University, Thomas Meade (author), Radford University, Drew Paulette (author), Radford University, Josh Albert (author), Radford University, Karen Francl (editor, instructor), Radford University.
Stephanie Givinsky (author), University of Michigan-Ann Arbor.
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