Reproductive Biology of Longtail Tuna (Thunnus tonggol) in the Bali Strait

The research aimed to determine the gonad maturity level, gonadal maturity index, fecundity, and length of first maturity of the species. Fish samples were obtained from the catches of fishermen in the Bali Strait, which landed at PPP Muncar from December 2018 to February 2019. The gonad maturity level of longtail tuna in December 2018 was mostly found in immature conditions (TKG I). However, TKG III and IV were most commonly found in February. The highest gonadal maturity index (IKG) value was found in February 2019 (0.017), indicating that longtail tuna experienced peak spawning and was actively reproducing in February. The sex ratio of gray tuna was dominated by males. Fecundity at TKG III ranged from 18,800 to 33,200 grains, while at TKG IV, it was 154,000 grains. The length of first maturity of longtail tuna was 495 mmFL for males and 487 mmFL for females. The study found that the reproductive biology of longtail tuna in the Bali Strait was influenced by the gonad maturity level, gonadal maturity index, and fecundity. The research used a simple random sampling method to collect fish samples from the catches of fishermen in the Bali Strait. The gonad maturity level was determined based on the morphological structure of the gonad, while the gonadal maturity index was calculated using the formula IKG = BG / BT. Fecundity was calculated using the gravimetric method, and the length of first maturity was determined using the Spearman-Karber method. The study's findings provide valuable information on the reproductive biology of longtail tuna in the Bali Strait, which can be used to support the sustainable management of the species. The research highlights the importance of understanding the reproductive biology of longtail tuna to ensure the long-term sustainability of the species and the ecosystem it inhabits. The study's results can be used to inform fisheries management decisions, such as setting catch limits and establishing protected areas. Additionally, the research can be used to develop conservation strategies for longtail tuna and other marine species in the Bali Strait. The study's findings can also contribute to the development of sustainable fishing practices and the promotion of eco-tourism in the region. The reproductive biology of longtail tuna in the Bali Strait is influenced by various factors, including the gonad maturity level, gonadal maturity index, and fecundity. The study's findings provide a comprehensive understanding of the reproductive biology of longtail tuna in the region, which can be used to support the sustainable management of the species.