Identification of Octopus Species and Size Distribution in the Waters Surrounding Seriwe Village, East Lombok Regency, Indonesia

Abstract

Octopus is one of the main sources of livelihood for the community in Seriwe Village and an important fisheries commodity that supports Indonesia’s export activities. This study aimed to identify octopus species and analyze the size distribution of total length and mantle length of octopus in the waters of Seriwe Village, Alas Strait, in order to provide baseline data for sustainable fisheries management. This research employed an accidental sampling technique and was conducted in Seriwe Village, Jerowaru District, East Lombok Regency, West Nusa Tenggara Province, from April to August 2025. Primary data were obtained through direct measurements of 4,150 octopus individuals, including species identification, sex, total length, and mantle length. Species identification was carried out based on morphological characteristics, while size distribution analysis was performed using histograms in Microsoft Excel and compared with the length at first maturity (Lm). The results showed that all sampled individuals belonged to the species Octopus cyanea, consisting of 1,996 (48.1%) males and 2,154 (51.9%) females. The findings also indicated that female O. cyanea had a larger body size than males, with an average total length of 58.16 ± 13.72 cm for females and 57.25 ± 12.26 cm for males. The distribution patterns of both total length and mantle length were unimodal, with dominant size groups of 48–55 cm and 55–62 cm for total length, and 9–11 cm for mantle length. Monthly size distribution demonstrated population dynamics, where the population was dominated by medium-sized individuals from April to June, while from July to August larger individuals approaching the length at first maturity (Lm) began to appear, although in relatively low numbers. Most of the captured population was still below the size at gonadal maturity for both males and females, indicating that the population was dominated by juvenile to sub-adult phases. This condition may indicate fishing pressure on younger individuals due to continuous harvesting activities. If this pattern persists, it could increase the risk of growth overfishing and potentially threaten the long-term sustainability of O. cyanea populations in the waters of Seriwe Village.