Age and growth of early‐life‐stage Atlantic tarpon ( Megalops atlanticus) from the northcentral Gulf of Mexico

Abstract

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, L S ) 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, L F ) were collected from August through December 2007—2018. Juveniles exhibited a positive allometric relationship (adjusted R 2 = 0.99, P L F ) ranged from 76 to 174 days. Juvenile growth rate was estimated as 1.56 ± 0.11 mm day −1 . Significant ( P R 2 = 0.81) and radius ( R 2 = 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

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