Individual growth in Jack mackerel (Trachurus murphyi) of the Southeastern Pacific Ocean using sagitta otolith weight, daily rings, and annual rings

Abstract

We estimated the growth of Jack mackerel (Trachurus murphyi) using increments of daily growth, otolith weight and annual ring reading in sagittal otoliths. The daily micro-increments were used to fit ring density to the otolith radius (n = 4481) and then to estimate the age of the individual in days. The parameters of the von Bertalannfy growth equation were: maximum theoretical fork length, FL_∞ = 75 cm; individual growth coefficient, K = 0.16 year^-1; theoretical age at which fish length is zero, t₀= –0.19 years. The growth parameters of T. murphyi estimated using annual rings reading were: K = 0.10 year^-1, FL_∞ = 74.7 cm, t₀ = –0.50 years. The growth parameters estimated using otolith weight were: K = 0.15 year^-1, FL_∞ = 75.0 cm, t₀ = –0.48 years. The parameter K estimated with the daily micro-increments was similar to the K estimated using sagittal otolith weights. We constructed a size-age key for T. murphyi using otolith weight, OW (milligrams) as a variable was: OW= 0.0323*t-15.197 (r²= 0.68). We recommend using otolith weight to estimate age in T. murphyi due to this technique is statistically reliable, but also cheap and fast.