Montana's Fish Species of Special Concern

Shortnose Gar

Wally McClure

Gallatin National Forest

P.O. Box 130

Bozeman, MT 59771

May 2003

Description

The shortnose gar (Lepisosteus platostomus) is the lone Montana representative species of the Family Lepisosteidae.  The scientific name Lepisosteus translates in Greek to “bony scale” and platostomous means “broad mouth”. 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 60-64 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.  

Distribution

The shortnose gar is widely distributed throughout North America within the Missouri and Mississippi River system.  However, it’s distribution within Montana is very limited with presence being documented primarily in the Missouri River dredge cuts downstream of Fort Peck dam (Brown 1971). The only other documented observation of shortnose gar in Montana is a single specimen collected on the Yellowstone River approximately 15 miles upstream of it’s confluence with the Missouri River in 1998 (K. Kapuscinski, MFWP, personal communication, February 2003).  The gar family as a whole ranges from southern Canada to as far south as Central America (Page and Burr 1991).  

Life History and Ecology

Due to their limited distribution little is know about shortnose gar within the State of Montana.  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.  Gar also have the unique ability to supply a high vascularized swim bladder with supplemental oxygen by engaging in a behavior of “breaking” where air is gulped at the surface (Pflieger 1975).  This allows gar to occupy waters with extremely low dissolved oxygen concentrations, which would not be suitable for most other fish inhabitation.

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. Gar eggs are documented as being poisonous to mammals (Smith 1994).

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).

Threats and Management

Due to low numbers and poor quality flesh the shortnose gar is not considered a sport fish in Montana.  However, bow fishing for gar in the southern states has become increasingly popular, with competitive tournament fishing common for longnose and alligator gar.  The Montana state record shortnose gar was caught in 1977 in the Fort Peck Dredge Cuts and weighed 3 pounds 1 ounce.

References

Brown, C.J.D.  1971.  Fishes of Montana.  Big Sky Books.  Montana State University Bozeman.

Holton, G.D. and H.E. Johnson. 1996.  A field guide to Montana Fishes. Second edition. Dave Books editor. Montana Fish Wildlife and Parks.  Helena, Montana.

Marshall, N.B.  1966.  The life of fishes. Universe Books. New York, New York.

Moyle, P.B.  1993. Fish an enthusiast’s guide. University of California Press.  Oxford, England.

Page, L.M. and Burr, B.M.  1991.  A field guide to freshwater fishes.  The Easton Press.  Norwolk, Connecticut.

Pflieger, W.L.   1975.  The fishes of Missouri.   Missouri Department of Conservation, Jefferson City.

Smith, C. L.  1994.  Fish watching: an outdoor guide to freshwater fishes. Cornell University Press.

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