Morphometric relationship of otolith, length, and weight of rainbow runner, Elagatis bipinnulata (Quoy and Gaimard, 1825) from Gunungkidul Coastal Waters

Rainbow runner, a high-value commodity caught by fishermen in southern Java, is not the main catch target. This research aimed to determine the morphological characteristics and morphometric relationship of otoliths with the length-weight of fish in rainbow runner. A total of 120 individual samples taken in October-November consisting of 68 females and 52 males from local fishermen at Sadeng Coastal Fishing Port were extracted and measured according to the Otolith shape index method with six descriptors: Form Factor (FF), Roundness (RO), Rectangularity (Rt), Circularity (C), and Aspect Ratio (AR). The otoliths were tested using the T-test, and the results showed substantial differences in the width, area, and periphery of the left and right otoliths. The results of the regression test showed that the highest relationship was between the weight of the otolith and the length of the rainbow runner, which had an R-value of 0.70, and the relationship between the weight of the otolith and the weight of the rainbow runner had an R-value of 0.51. Rainbow runner otoliths have an irregular surface, are not circular, and tend to be elongated. Otolith size varies between species, influenced by differences in calcium carbonate deposition rates, growth, age, and environmental factors.