Montana Field Guide

Shortnose Gar - Lepisosteus platostomus

The gar family has only one representative in Montana, the shortnose gar. This fish is native to Montana and is found at only one location--the dredge ponds below Fort Peck Reservoir. Because of its restricted distribution and limited population size, it has been named a Montana state Fish of Special Concern. Gars are predaceous. They are spring, broadcast spawners. They have several unusual features including rectangular scales found only in primitive fishes, and a gas bladder that can function like a lung. All fish have gas bladders, which they use to regulate their buoyancy, but the gas bladder of a gar can extract the oxygen from air that is swallowed. Consequently, gars can survive in waters that have very little oxygen where most other fish would perish. Gar eggs are poisonous to humans.

This prehistoric-appearing fish is cylindrically shaped, with an elongated bony head and snout containing one row of sharp, conical teeth. The dorsal fin is located well posterior and the pectoral and pelvic fins have no spots (Marshall 1996). The skin is covered with diamond shaped ganoid scales arranged in oblique rows, providing a very protective surface armor (Moyle 1993). Scales number 60 to 64 along the lateral line. Color varies from brownish or olive-green on the dorsal surface lightening to yellow on the sides and white on the belly (Holton and Johnson 1996). Young gar less than 10 inches in length process a black stripe along the midline. Shortnose gar may reach a size and weight of about 31 inches and about 3.5 pounds (AFS website 2003).

Montana Range

Shortnose gar are typically found in large rivers, quiet pools, backwaters, and oxbow lakes. It has a higher tolerance to turbid water than the other four gar species found in North America (AFS website 2003).

They are found in dredge cuts below Fort Peck Dam (Holton 2003).

The diet of the shortnose gar is primarily composed of fish. However, crayfish and insects are also utilized (Brown 1971). Young gar are known to feed on small insects and zooplankton, with fish entering the diet when gar are 1.25 inches in length. Gar is known as fierce predators of smaller fish using ambush as a primary hunting technique (Moyle 1993) (AFS website 2003).

Shortnose gar become sexually mature at three years of age and typically spawn in May or June as water temperatures reach the mid 60s (Brown 1971). Adhesive eggs are deposited in quiet, shallow water over aquatic plants or other submerged objects. A sticky, gelatinous adhesive holds clumps of yellowish-green eggs to the vegetation for 8 to 9 days whereupon hatching occurs (AFS website 2003).

The young lead solitary lives floating near the surface (Brown 1971).

Due to low numbers and poor quality flesh, the shortnose gar is not considered a sport fish in Montana (AFS website 2003).