DYNAMICS IN LENGTH-WEIGHT RELATIONSHIP AND CONDITION FACTOR OF BRACKISH WATER POPULATIONS OF SILVER THERAPON Leiopotherapon plumbeus (KNER, 1864) IN BATAAN, LUZON ISLAND, PHILIPPINES

The silver therapon (Leiopotherapon plumbeus, Kner 1864) is an endemic freshwater fish species and the only known freshwater terapontid in the Philippines. It was first described in Laguna de Bay, largest inland water bodies in the Philippines, but it has been translocated to various lakes in Luzon Island, Philippines. It is regarded as an important fish commodity, with a market price of $4-$6 per kilo. Unknown to many, L. plumbeus is also thriving in the brackishwater environment with feral population in brackishwater fishponds in the provinces of Pampanga and Bataan. Several studies have been done to evaluate the diet preference, early development and aquaculture potential of this terapontid. Despite of such scientific efforts, baseline information on morphometrics, length and weight relationship, and condition factor of naturally occurring brackishwater populations of
L. plumbeus during wet and dry months have not been studied. To fill-up the scholarly gaps, the objective of this study is to characterize the two populations of L. plumbeus based on their morphometrics, length-and-weight relationship, and condition factor, with emphasis on spatio-temporal and sexual variability.

Hence, this study evaluated the length-and-weight relationship, (W = aTLb) and condition factor dynamics based from two brackishwater populations. Fish specimens were sampled in fishponds located in Sampalucan, Orani, Bataan (n = 500), and in Almacen river (n = 380) in Hermosa, Bataan. Length and weight was observed to be affected by sex, sites and seasons. The sexual variation in growth rate as inferred by length-and-weight relationship was significant, with female being positively allometric (b = 3.11), whilst male being negatively allometric (b = 2.877). Spatial variation on growth rate was significant between Sampalucan (b = 3.07) and Almacen (b= 3.017) despite of being both isometric. Growth coefficient in wet season displayed isometry (b = 3.052), whereas dry season was negatively allometric (b = 2.712). Values of condition factor were close to ideal score of 1.0. Mean condition factor was significantly influenced by sex (female = 1.023 ± 0.015; male = 0.949 ± 0.006), sampling sites (Sampalucan = 0.991 ± 0.005; Almacen = 0.983 ± 0.007), and season (wet season = 1.017 ± 0.008; dry season = 0.974 ± 0.014). Mean condition factor in each month were statistically varied, ranging from 0.974 to 1.04.