Age Determination and Body Length Relationship of Two-Spot Red Snapper (Lutjanus bohar)

Abstract

Otolith study on fifty two-spot red snappers (Lutjanus bohar) in Davao Gulf, Philippines, was conducted to describe their growth pattern, determine the age structure, and estimate their age at sexual maturity. Fish samples were obtained from Toril and Bankerohan Public Markets in Davao City from February to June 2015 where fish morphometrics, otolith extraction, and age determination followed. Length-weight relationship showed that L. bohar follows isometric growth pattern (b = 3.0015). Somatic and otolith morphometrics gave significant correlations where otolith length and total length relationship had the highest R2 value (R2 = 0.9382). Out of fifty fish samples, twenty-one of the sagittal otoliths had ages ranging from three to seven years old. The parameters obtained from the age-at-length data fitted to von Bertalanffy growth function were K = 0.81 and L∞ = 28.9 cm, with an estimated age at maturity of six years old. The growth performance index (φ = 2.83) also revealed that L. bohar in Davao Gulf has faster growth rate compared to other locations. Faster growth rate leading to earlier maturity and smaller size-at-maturity may indicate the compounded effects of environmental factors and fishing pressure to slow-growing fishes. Thus, we recommend studying the population ecology of L. bohar in Davao Gulf and considering a larger sample size in future researches.