Sex‐Specific Dynamic Rates in the Alligator Gar: Implications for Stock Assessment and Management
2019
Daugherty, Daniel J. | Buckmeier, David L. | Smith, Nathan G.
Growth and mortality are commonly estimated for fish populations; however, potential differences between males and females receive less attention. Quantifying sex‐specific dynamic rates can be important as they can lead to differential exploitation, altered sex ratios, and reduced reproductive potential. We examined sex‐specific growth, size and age structure, maximum observed age, longevity, and total mortality using total length (TL), age, and sex collected from 549 Alligator Gar Atractosteus spatula from multiple Texas systems. Males (n = 324) ranged from 353 to 2,051 mm TL and 1–61 years of age, whereas females (n = 225) were 385 to 2,420 mm TL and 1–60 years old. We found significant differences in population‐specific size and age distributions between sexes. Greater than 91% of males were less than 1,500 mm TL, whereas over 63% of females sampled were greater than this length. Sixty‐four percent of males were ≤ 10 years old as compared with only 20% of females. Sex‐specific estimates of longevity and total mortality indicated that females lived 10–15 years longer than males and exhibited 25% to 40% lower total mortality. Despite similar growth rates for males and females prior to age 3, female Alligator Gar growth was greater than males at older age‐classes, resulting in a 617‐mm difference in theoretical maximum length based on the double von Bertalanffy growth model. The considerable differences we observed between sexes have important implications for population sampling and stock assessment and highlight the importance of collecting sex‐specific data.
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