Age and Growth of Early-Life-Stage Atlantic Tarpon (Megalops atlanticus) From the Northcentral Gulf of Mexico

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Coastal Sciences, Gulf Coast Research Laboratory


Ocean Science and Engineering


Age and growth of early-life-stage Atlantic tarpon Megalops atlanticus collected from Mississippi coastal waters in the northcentral Gulf of Mexico (GOM) are described using otolith microstructure analysis. Tarpon leptocephali (n = 95, 16.0—27.8 mm standard length, LS) collected from June throughOctober 2013—2018, ranged in age from 22 to 43 days (mean = 30.9 ± 0.5 days). Leptocephalus somatic growth rates ranged 0.46—1.24 mm day−1 (mean = 0.76 ± 0.02 mm day−1), and leptocephalus otolith growth rates ranged 1.78—3.97 μm day−1 (mean = 2.58 ± 0.04 μm day−1). Growth rates were inversely correlated to leptocephalus age, indicating the shrinkage phase associated with leptocephalus metamorphosis. Juvenile tarpon (n = 358, 50—359 mm fork length, LF) were collected from August through December 2007—2018. Juveniles exhibited a positive allometric relationship (adjusted R2 = 0.99, P < 0.001) between length and mass. The age of 100 juveniles (71—277 mm LF) ranged from 76 to 174 days. Juvenile growth rate was estimated as 1.56 ± 0.11 mm day−1. Significant (P < 0.001) linear relationships were found between juvenile age and otolith metrics, including otolith mass (R2 = 0.81) and radius (R2 = 0.68). Evaluation of the backcalculated hatch dates suggests that specimens in the collection hatched from late May through mid-September with slight peaks during July and August. A Rao's Spacing Test of Uniformity indicates the presence of significant lunar periodicity in leptocephalus hatch dates (n = 95, U = 250.1, P < 0.05), with 50% of the leptocephali hatched within 5 days (before or after) of the full moon. This study fills critical gaps in the scientific knowledge of tarpon and provides estimates of early-life-history metrics for an iconic game fish at the northernmost extent of its GOM range.

Publication Title

Journal of Fish Biology

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