Population Dynamics of Alligator Gar in Choke Canyon Reservoir, Texas: Implications for Management

Historical eradication efforts, increasing fishing pressure, and growing anthropogenic impacts have resulted in decreased abundance or extirpation of the alligator gar (Atractosteus spatula) throughout much of its historic distribution. Current population status has prompted states to actively manage stocks; however, efforts are hindered by a lack of data necessary to make informed management decisions. To begin addressing these data needs, we investigated alligator gar population dynamics and exploitation in Choke Canyon Reservoir, Texas. A total of 754 fish (total length [TL] range, 678 to 2275mm) was collected with multifilament gill nets from 2008 through 2013; 656 individuals collected from 2011 through 2013 were tagged and released as part of a mark-recapture study to estimate abundance and exploitation. Alligator gar age ranged from 0 to 27 yrs. Growth in length followed a typical von Bertalanffy function with greatest growth occurring through age 5, then considerably slowing among older age classes. Growth in weight, per unit length, was greatest in fish ≥ 1700mm TL. Length-at-age of females was significantly greater than male length-at-age; TL of female fish was about 278 mm greater than male fish of the same age. Adult alligator gar (TL ≥ 1100 mm) abundance was estimated at 5437 (95% CI; 3215 to 9195) individuals, conferring a density of 0.5 (0.3 to 0.9) fish ha-1 at conservation pool. Annual exploitation based on tag returns was less than 3%; bowfishing tournament data indicated a bow angler harvest rate of 0.01-0.02 fish angler hour-1. Results of our study provide important information for the management of alligator gar populations in Texas and throughout its distribution.

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