Alligator Gar Reproduction, Growth, and Recruitment in Falcon Reservoir, Texas

Research on alligator gar (Atractosteus spatula) has increased during the last two decades; however, assessments of reproduction, growth, and recruitment remain limited for reservoir populations. We collected a total of 562 alligator gar from Falcon Reservoir, Texas, in 2014 and 2018 to estimate onset of maturity, fecundity, timing of spawning, and growth. Additionally, we modeled the relationship between spawning habitat availability and strong year-class occurrence. Age of maturity (50% mature) was 5.6 years for females and 1.2 years for males. Fecundity ranged from 79,518 to 530,398 and averaged 240,183 eggs per female (SE=16,547). Timing of spawning could not be determined because minimal spawning occurred during our study years and only 2 of 191 mature females had spawned. Females grew faster and larger than males. On average, females attained 152 cm TL in 4.5 years, but it took males 9.1 years to reach this length. Females reached trophy size (≥180 cm TL) in 8.3 years on average. Six strong year-classes were produced over a 17-year period, and strong year-classes were more likely when reservoir size at the start of the spawning season and change in reservoir size over the course of the spawning season increased. Results of our study advance understanding of the species, particularly in reservoirs, and our logistic model allows for assessment of alligator gar recruitment success in Falcon Reservoir without extensive sampling effort.

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