Relationships Between Length and Weight of the Six Hairtail Species (Trichiuridae) in the Coastal Waters of China, with Special Attention to Trichiurus japonicus Temminck & Schlegel, 1844

Hairtail fishes are the most important fishery species in the China Seas, supporting approximately 10% of the total marine capture fisheries production over the years, and China has consistently ranked top in the world for hairtail landings. Specimens were collected along the coastal waters of China in autumn 2016 and 2017. A total of 6 species, Trichiurus japonicus, Trichiurus nanhaiensis, Trichiurus brevis, Lepturacanthus savala, Eupleurogrammus muticus, and Tentoriceps cristatus, were sampled, of which T. japonicus is the most widely distributed common species and the South China Sea has the richest species diversity. Length-weight relationships (LWRs) were determined, and the spatial variation in T. japonicus is discussed. The values of parameter b ranged from 2.506 to 3.075, which remained within the normal range of 2.5-3.5. Positive allometric growth (b>3) was observed for T. japonicus, and negative allometric growth (b<3) was observed for T. nanhaiensis, T. brevis, L. savala, and E. muticus. Significant spatial differences in the LWR of T. japonicus were found along the coast of China, which showed an increase in a and a fluctuating decline in b from south to north. The specimens of T. japonicus in the north was heavier for a given length than those in the south. This study discusses the LWRs and growth performances of hairtail fishes from south to north in the China Sea, which will be useful for hairtail fishery management and protection. In particular, it will be an important reference to improve hairtail aquaculture technology in the future.