Comparison of growth rate and formation of otolith increments in age-0 red snapper

Abstract

For wild red snapper Lutjanus campechanus, mean otolith increment deposition rate after marking with oxytetracycline dihydrate (OTC) was daily (0.97 increments day−1) when growth rates were fast (0.63 mm fork length, LF day−1), but were not daily (0.82 increments day−1) when somatic growth was slow (0.2 mm LF day−1). For reared larvae (n=8), increment deposition rates were daily (0.99–1.03 increments day−1), and growth rates ranged from 0.6 to 0.9 mm LF day−1. Growth rate affected increment deposition rate as a threshold function, i.e. when growth rate was <0.3 mm LF day−1, deposition was less than daily, but above this level increment deposition did not exceed a daily rate. As growth rates increased increment widths increased. Examination of a sub-sample (n=8) of the otoliths from the slowest growing wild fish by scanning electron microscopy did not increase increment counts. Because L. campechanus are late spring-early summer spawners, young fish can expect maximum growth due to warm summer temperatures. Thus, daily ageing methods should be well suited to this species.