Biological Insights into Length–Weight Relationship and Relative Condition Factor of Frigate Tuna A. thazard (Lacepede, 1800) Landed at Veraval Fishing Harbour, Northwest Coast of India

Abstract

The present study was carried out during March, 2025 and February, 2026 at Veraval Fishing Harbour along the northwest coast of India to evaluate the length–weight relationship (LWR) and relative condition factor (K_n) of frigate tuna, Auxis thazard. A total of 300 specimens were collected between March 2025 and February 2026. The sampled fish ranged from 26.5 to 46.5 cm in total length and weighed between 205 and 1353 g. The length–weight relationship was analysed separately for males, females, and pooled samples using the allometric growth equation. The estimated b-values were 3.4737 for males, 3.4951 for females, and 3.4827 for pooled specimens, indicating positive allometric growth, where body weight increased at a faster rate than length. High coefficients of determination (R²>0.94) revealed a strong relationship between length and weight. The relative condition factor (K_n) remained close to 1 throughout the study period, suggesting that the fish population was generally in good health and adapted well to its environment. Minor seasonal fluctuations were observed, with slightly lower values in some months, particularly among females during November, which might be associated with reproductive energy expenditure. Overall, the results indicated healthy growth and favourable physiological condition of A. thazard in the study area. These findings provided useful baseline information for stock assessment, fisheries management, and the sustainable utilization of this commercially important tuna species.