Is the Increasing Popularity of Alligator Gar Fishing threatening the resource?

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Young alligator gar apparently grow very fast; in Sam Rayburn Reservoir, Texas, fish thought to be young-of-year in 1965 averaged 1.1 kg by July 30 and 2.9 kg by October 6 (Toole 1971). Growth of older fish is much slower, taking about 10 years to attain a total length of 1 m and 30 or more years to reach a length of 2 m (Figure 1). Alligator gar mature between 950 and 1,400 mm total length (at age 10-14), with males maturing earlier than females (Ferrara 2001; Garcia de Leon et al. 2001). Although young fish grow fast, alligator gar are believed to be long-lived. Ferrara (2001) estimated annual survival of adult alligator gar exceeded 90% and found fish up to age 50 in an Alabama population receiving little harvest. However, maximum age of a heavily-exploited population in Lake Pontchartrain, Louisiana was only 28 years. Maximum age of alligator gar in Lake Texoma, Oklahoma, was recently estimated to be greater than 30 years (E. Brinkman, Oklahoma State University, personal communication). Length-
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weight relationships for male and female alligator gar are similar (log10 W = 3.176 log10 L – 2.540; Garcia de Leon et al. 2001).
Relative to other gar species, alligator gar have the greatest capacity to overcome complete or partial year-class failures because they mature at the oldest age, are the most fecund, and have the highest adult survival (Ferrara 2001). However, low intrinsic rates of population increase indicate alligator gar are vulnerable to over-exploitation. Marine researchers have recommended setting the target levels of exploitation at < 10% for species similar to alligator gar that are long-lived and have very low rates of natural mortality (Walters and Pearse 1996; Codling et al. 2005). Ferrara (2001) postulated that mid-size adult alligator gar had the greatest influence on population growth rate and should be protected; limited harvest of older fish (> 25 years) did not cause population growth rates to decline substantially. Occupation of shallow spawning areas makes alligator gar highly vulnerable to sight fishing techniques such as bow fishing during spring and early summer. Male alligator gar may be especially vulnerable, because it is thought that they remain in the spawning area for extended periods (Suttkus 1963; Garcia de Leon et al. 2001).

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Atractosteus spatula, with Recommendations for Management
Prepared by:
David L. Buckmeier
Heart of the Hills Fisheries Science Center
Texas Parks and Wildlife Department, Inland Fisheries Division
5103 Junction Highway
Mountain Home, TX 78058
July 31, 2008

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