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

Maybelle A. Fortaleza, Cleto L. Nañola Jr.

Abstract


Otolith study on fifty two-spot red snappers (Lutjanus bohar) in the Davao Gulf, Philippines, was conducted to describe their growth pattern, determine the age structure, and estimate their age at sexual maturity. Samples were obtained from Toril and Bankerohan Public Markets in Davao from Februay to June 2015. 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 the samples, twenty-one of the sagittal otoliths ranges 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 estimated age at maturity of six years old. The growth performance index (φ = 2.83) revealed that L. bohar in Davao Gulf has a faster growth rate. Faster growth rate leading to earlier maturity and smaller size-at-maturity may indicate the effects of environmental factors and fishing pressure to slow-growing fishes. We recommend studying the population ecology of L. bohar in Davao Gulf and considering a larger sample size in future researches.


Keywords


age; growth; length-weight relationships; Lutjanidae; Lutjanus bohar; otolith; two-spot red snapper

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