Age and growth of the invasive bluegill Lepomis macrochirus (Rafinesque, 1810) from the Howison’s Poort Dam, Eastern Cape, South Africa

Abstract

The present study assessed the age and growth of bluegill, Lepomis macrochirus (Rafinesque, 1810) from Howison’s Poort Dam, Eastern Cape. Precision between readers and structures (burnt and unburnt) of otoliths were estimated, and the aging error was determined by the coefficient of variation (CV, %) and average percentage error (APE, %). The lowest APE (18.73%) and CV (17.28%) were determined for burnt otoliths. Growth for male bluegill was best described by the von Bertalanffy Growth Model of the form L _t = 201.2 (1-e ^{-0.312(t+ 0.61)}) and L _t = 161.8 (1-e ^{-0.409(t+ 0876)}) for females. Growth zone counts on sectioned sagitta showed that L. macrochirus attained a maximum age of 6 years and can grow up to 197 mm TL. A comparison of growth parameters from fish in the present study with those from its native range suggests that the individuals can live for a maximum of 12 years and attain length of 260 mm TL in their native range. Though the species did not attain the same age as with their native range, early reproduction (four years) could have contributed to its establishment success.