Reproductive Biology of Nemipterus nemurus (Bleeker, 1857) and Nemipterus furcosus (Valenciennes, 1830) in the North Coast Waters of East Java

Reproductive biology plays a fundamental role in fisheries management, since it provides essential insights into reproductive strategies and the characteristics of fish populations. Studies on fish reproductive biology are important for the effective planning of conservation and management strategies. Successful reproduction is a critical factor in the growth of fish populations in aquatic environments. This study aimed to analyze reproductive aspects of threadfin breams (N. nemurus and N. furcosus) in the North Coast waters of East Java. Fish sampling was conducted at Brondong Fishing Port in Lamongan, from September to October 2023. The samples comprised two different species: N. nemurus with 111 individuals (63 males and 48 females), and N. furcosus with 154 individuals (80 males and 74 females). A balanced ratio of males to females was identified in the reproductive traits (1:1). The relationship between length and weight is negative allometrically. The gonads of both species reached a similar level of maturity. The t-test showed that fecundity and egg diameter were significantly different between the two species (P< 0.05). The majority of the captured threadfin bream exhibited immature gonads (Lc < Lm), which could have implication for the ecosystem conditions in the North Coast waters of East Java. © 2025, Egyptian Society for the Development of Fisheries and Human Health. All rights reserved.