Annulus Formation on Otoliths and Growth of Young Summer Flounder from Pamlico Sound, North Carolina

Summer flounder Paralichthys dentatus were collected monthly in Pamlico Sound, North Carolina, and adjacent waters from May 1971 to July 1972 to determine age at first annulus (opaque ring) formation on otoliths and to estimate growth of young‐of‐the‐year and yearling fish. The first annulus formed on yearling otoliths between January and June. It often becomes obscure as fish age, making fish older than 2 years difficult to age from otoliths. A yon Bertalanffy equation with a seasonally varying coefficient closely modeled summer flounder growth during a cohortˈs first 17 months:L max (315.8 mm) is maximum body size; L min (14.4 mm) is size at estuarine immigration; t is age in months; α (0.059) and θ (−3.347) are parameters describing seasonal change in the von Bertalanffy coefficient. Mean total length at the end of the first year was 167 mm for males and 171 mm for females, and differences between sexes were not significant (P = 0.24). After fish moved into the estuary in February, their body weight increased at an estimated 5% per day, but growth rates declined over the following months even as water temperatures increased, and by late fall growth was negligible.