Length-weight Relationships and Seasonal Variations in the Relative Condition Factor of the Spinycheek Grouper, Epinephelus diacanthus (Valenciennes, 1828), from the Mangaluru Coast, India
Akanksha *
Department of Fisheries Resource Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
S. R. Somashekara
Department of Fisheries Resource Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
H. N. Anjanayappa
Department of Fisheries Resource Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
A. S. Kumar Naik
Department of Fisheries Resource Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
M. Ganapathi Naik
Department of Aquaculture, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
M. Shivakumar
Department of Aquatic Environment Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
Shubham S. Janbandhu
Department of Fisheries Resource Management, College of Fisheries, Mangaluru, Karnataka Veterinary Animal and Fisheries Sciences University, Bidar-575002, India.
*Author to whom correspondence should be addressed.
Abstract
The length-weight relationship (LWR) and relative condition factor (Kn) are important biological indicators for understanding growth patterns and temporal changes in condition of exploited fish populations. This study investigated these parameters in the spinycheek grouper, Epinephelus diacanthus (Valenciennes, 1828), from the Mangaluru coast, India, using 516 specimens collected between December 2024 and May 2026. The sample comprised 405 females and 111 males. Length-weight relationships were estimated using log-transformed linear regression, and differences between the sexes were assessed using analysis of covariance (ANCOVA). The relative condition factor was examined to characterize temporal variation in fish condition. The pooled LWR was described by the equation W = 0.01987L²·⁹⁰⁰⁵ (R² = 0.9724), indicating negative allometric growth based on the estimated exponent. Sex-specific relationships also showed negative allometric growth, with a regression coefficient of b = 2.9147 in females (R² = 0.9636) and 2.5130 in males (R² = 0.8985). ANCOVA indicated significant differences between the relationships for the two sexes. The overall mean Kn was 1.010, with individual values ranging from 0.342 to 2.279. Monthly variations in pooled Kn were statistically significant (Kruskal-Wallis test, χ² = 65.913, df = 15, p < 0.001), reflecting temporal fluctuations in condition. The study provides information on the growth characteristics and seasonal condition of E. diacanthus and contributes to understanding its population dynamics and fisheries management along the Mangaluru coast.
Keywords: Epinephelus diacanthus, growth patterns, temporal variation, regression coefficient, allometric growth, relative condition factor, fish condition