Age-Growth Parameters of Crescent Grunter, Terapon jarbua (Forsskål 1775) in Mindanao, Philippines


by: Maybelle A. Fortaleza, Reena Cyndi L. Uy, Merlene E. Elumba, Cleto L. Nañola, Jr.


Otolith studies provide a breadth of information valuable in investigating the life history of reef fish species. When incorporated with analysis on length-weight relationships, this biological information becomes useful in understanding the population dynamics of economically important reef fishes. This study looked into the lengthweight relationship and age-growth parameters of Terapon jarbua, a euryhaline fish species that is commonly harvested in coastal areas of Mindanao, Philippines. The length-weight relationship for 160 T. jarbua individuals (9– 22.4 cm, standard length) collected from Davao Gulf (n=105) and Iligan Bay (n=55) is given by the equation W = 0.0428 x SL2.8484, with an R2 value of 0.85. Results of Student t-test identified that T. jarbua from these areas exhibit a negative allometric growth pattern, where the fish grows more in length than in weight. High R2 values were obtained from linear regressions between the fish standard length and otolith length (R2 = 0.85), standard length and otolith weight (R2 = 0.83), and standard length and otolith mass (R2 = 0.82), indicating feasibility of otolith measurements in predicting fish size. Based on the pooled age data from all readable otoliths (n = 86) fitted to the von Bertalanffy growth function, this study provides a theoretical maximum length (L∞) of 21.720, curvature parameter (K) of 0.259, theoretical age at length zero (t0) of 0.522, and growth performance (Ф’) of 2.086 for T. jarbua collected from Iligan Bay and Davao Gulf in Mindanao, Philippines. Moreover, the age estimates of T. jarbua reported in the current work presents the first attempt of providing age-growth parameters using sagittal otolith microstructure.

Keywords: age, growth, length-weight relationship, otolith, Terapon jarbua