Age and growth of southern flounder (Paralichthys lethostigma) from Matagorda Bay, Texas

Abstract

Estimates of age and growth of southern flounder (Paralichthys lethostigma) from Matagorda Bay, Texas were made by analyzing thin sections of otoliths (sagittae) from 892 specimens collected along the Texas coast from May 1992 to January 1995. Marginal increment analysis showed a single annulus was formed on the otolith during January through March. Otolith reading was determined to be very precise in that 99% agreement was attained between two readers. The maximum age differed by bay systems, but ranged from 0 to 4 years for both males and females. Males were generally smaller than females and exhibited asymptotic growth at an earlier age. Back-calculated length distributions were significantly (P < 0.05) different than the observed distributions. This difference was probably due to small sample size of older specimens. The von Bertalanffy growth model equations for both females and males coastwide were Lt = 660.45[l-e-0-208(t + 1.317)] and Lt = 308.67[l-e-0.701(t + 0-421)], respectively. Gonadosomatic index values indicated a spawning period from September to January. All southern flounder were mature at a length of 350 mm and an age of 3 years. Differences in age composition among bay systems probably reflect differences in both fishing pressure and environmental factors.