Fishery and biological characteristics of the pearly hairtail Trichiurus auriga (Klunzinger, 1884) in the South-eastern Arabian Sea

The pearly hairtail Trichiurus auriga, a little-known deep-sea ribbonfish, has recently emerged as a commercially relevant resource in southern India due to expanding deep-sea trawling and increasing demand from the fishmeal and fish oil industry. Scientific information on its biology, growth and fishery characteristics remains scarce, limiting management interventions. This study presents the first comprehensive account of fishery trends, age, growth, and reproductive biology of T. auriga using specimens (n=895) collected from the Neendakara (Kerala), Colachel and Jeppiar (Tamil Nadu) landing centres between 2022–2024. Length and body weight ranged between 190–420 mm TL (total length) and 20.8–28.4 g respectively. Length–weight relationship (LWR) parameters indicated negative allometric growth (b = 2.88), though the deviation from isometry was not statistically significant (p>0.05). Sagittal otolith microstructure analysis revealed ages ranging from 107 to 267 days, with corresponding daily growth rates of 1.34–1.85 mm day⁻¹. Female fecundity ranged between 320 and 710 ova, and maturity indicators confirmed sexual maturity at or below 190 mm TL. Large-scale landings and frequent misidentification of T. auriga as juveniles of Trichiurus Lepturus, pose regulatory challenges, particularly in the enforcement of under minimum legal size (MLS) regulations. The findings of the study provide baseline biological information and highlight the need for species-specific identification and management strategies to ensure the sustainable exploitation of this emerging deep-sea fishery.