Introduction: The largehead hairtail (Trichiurus lepturus) is an economically important species widely distributed in tropical and subtropical marine ecosystems, including the coastal waters of Makran. Investigating biometric parameters along with feeding and growth patterns in fish is a vital tool for fisheries management and for understanding dietary habits from juvenile to adult stages. Moreover, understanding the biological characteristics of this species in local habitats lays the groundwork for developing effective strategies for sustainable fisheries management and biodiversity conservation in marine ecosystems. Therefore, the present study aimed to investigate the biometric features, growth patterns, and feeding habits of T. lepturus to enhance fishery management practices in the coastal waters of Makran.
Materials and Methods: For this purpose a total of 120 specimens of T. lepturus were collected seasonally over one year, from autumn 2021 to summer 2022, from three fishing sites along the Makkoran coast in Sistan and Balouchestan Province, namely Chabahar, Beris, and Ramin. The specimens were immediately fixed in 10% formalin and transported to the laboratory. In the lab, biometric parameters including total length, body weight, and growth pattern were measured. The digestive tracts were dissected to identify stomach contents for dietary analysis. Additionally, the relative gut length index was calculated by dividing gut length by total body length to assess dietary characteristics.
Results: The average total length and body weight of the samples were estimated at 73.53 ± 21.33 cm and 501.72 ± 270.7 g, respectively. The highest and lowest mean values for length and weight were recorded in autumn and summer, respectively, although no significant seasonal differences were observed (p > 0.05). Length and weight distribution analysis indicated that the highest frequency was within the 73–83 cm length class and the 150–250 g weight class. The length-weight regression yielded a b value of 2.293, indicating negative allometric growth. Stomach content analysis revealed a diverse diet composed of digested material, fish, crustaceans, and mollusks. Digested material accounted for the highest dietary proportion (58%), while mollusks had the lowest (9%). The relative gut length index varied across length groups and seasons, with the highest value recorded in fish over 107 cm in length. These findings suggest feeding plasticity and a consistent growth pattern in this species.
Discussion: The results indicate that T. lepturus in the coastal waters of Makran exhibits negative allometric growth, wherein weight increases at a lower rate than length. This pattern is commonly observed under nutritional, habitat, or physiological constraints. The species' diverse diet, with a substantial portion of digested material and notable contributions from fish and crustaceans, reflects an opportunistic and active feeding strategy consistent with its role as a top predator in the food web. This feeding flexibility plays a crucial role in seasonal adaptability and coping with fluctuating food availability. Furthermore, variations in the relative gut length index with body size and season support potential changes in metabolic requirements and diet composition across growth stages. These findings, combined with the uniform distribution in length and weight, provide useful indicators for monitoring population health and establishing guidelines for size and season-based fishing regulations.