Pearl oysters are a marine aquaculture commodity with high economic value. However, there are still many obstacles in pearl oyster cultivation activities, such as the need for quality seeds. This study aims to determine the effect of immersing pearl seeds in natural feed tanks of Chaetocheros sp. with different immersion periods on the growth and survival rate of pearl oyster (Pinctada maxima) seeds. The method used in this study is an experimental method using a completely randomized design (CRD), with 5 treatments and 3 replications, namely A (control/without immersion), B (0.5 hours), C (1 hour), D (1, 5 Hours) and E (2 Hours). The results showed that soaking the seeds in natural feed tanks had a significant effect on the growth of the shell (dorsal-ventral) of the pearl oyster Pinctada maxima (p<0.05). The highest growth was achieved in the 2-hour immersion period with an absolute growth value of 1.67 mm, a relative growth of 68.49% from the initial size, and a daily specific growth rate of 3.31% per day. This method must be tested on larger pearl oyster seeds and using other natural feed species and various natural mixes (multi-species).

Cantang grouper is one of the leading NTB commodities that have high economic value. Cantang grouper (Epinephelus fuscoguttatus) has a wide distribution, one of which is in Penyambuan Village, North Lombok Regency. The disease that often attacks grouper fish is VNN (Viral Nervous Necrosis). One of the methods that can be used to detect VNN is the histopathological method. The purpose of this study was to determine the suspected cases and levels of infection with the VNN (Viral Nervous Necrosis) virus in grouper fish (Epinephelus fuscoguttatus) cultivated in Penyambuan Hamlet, Tanjung District, North Lombok Regency by using the histopathological method. The research method used is descriptive by explaining the results obtained from the histopathological test of 3 samples taken by looking at the presence or absence of necrosis in the eye and brain organs of the test sample. The results of observations using a microscope on the test sample after the histopathological process showed that the second sample (S2) of cantang grouper from the KJA in Pemambuan was suspected to be positive for VNN infection, as seen from the presence of necrosis in the form of vacuoles in the brain and eye organs in the level of chronic infection. From the results of this study, it is suggested that further research be carried out in the form of confirmation of the results using a more accurate method, namely real-time PCR. This study can serve as a detection guide for samples of suspected VNN.

Vannamei shrimp is a shrimp that has high economic value in Indonesia. The poor aquatic environment can reduce shrimp growth rates and stress and cause death, and efforts to improve water quality by giving Probiotics EM4. Probiotic EM4 contains beneficial bacteria that can improve shrimp's digestive system, decompose organic matter in the waters, control the growth of pathogenic bacteria, and improve water quality. The experimental parameters included total hemocyte count (THC), differential hemocyte count (DHC) consisting of hyaline cells, granule cells, and semi-granule cells, and phagocytic activity (AF). The study was carried out for 69 days using vanamei shrimp with PL 30. This study used four treatments and three replications, namely treatment P0 (without giving probiotic EM4), P1 (giving probiotic EM4 at a dose of 0.5 ml/L), P2 (giving probiotic EM4 at a dose of 1.5 ml/ L), P3 (giving probiotic EM4 dose of 2.5 ml/L). The study's results proved that the administration of probiotic EM4 on the maintenance medium had a significant effect (P<0.05) on THC, DHC, and AF. At THC, the highest value was at P3 with a value of 19.44 x 10 6 cells/ml, and the lowest was at P0 with a value of 11.01 x 10 6 cells/ml, then the DHC values such as hyaline cells ranged from 51.34 – 65.81%, granule cells ranged from 21.33 – 30.4%, semi-granular cells ranged from 12.84 – 18.24%. And then for the highest AF value at P3 with a value of 67.97% and the lowest P0 with a value of 49.34%

Seed is essential in aquaculture activities, but tilapia hatcheries often suffer from disease attacks caused by Aeromonas hydrophila bacteria, causing losses for hatchery businesses. One of the natural ingredients for treating Aeromonas hydrophila is betel leaf extract. This study aims to analyze the effect of betel leaf extract (Piper betle L.) on Aeromonas disease hydrophila on fish fry tilapia (Piper betle L.). This study used a completely randomized design (CRD) with 5 treatments and 3 replications. The treatment used was a dose of betel leaf extract (P1) 0.4 ml, (P2) 0.6 ml, (P3) 0.8 ml, (P4) positive control, (P5) negative control. The parameters observed were survival rate, specific growth rate, feed conversion ratio, absolute length growth, erythrocytes, hemoglobin, hematocrit, leukocytes, differential leukocytes, total bacteria count, and water quality. The results of this study showed that before and after the challenge test, the best average values were P3 leukocytes (1.06 and 1.4 x 10 5 ), erythrocytes (0.90 and 0.93 x 10 5 ), hemoglobin (10.9 and 9.7), hematocrit (10.7 and 10.3), total bacteria (7 x 10 1 ). Then the worst value on P1 leukocytes (0.74 and 0.87 x 10 5), erythrocytes (0.86 and 0.75 x 10 5 ), hemoglobin (10.7 and 7.7), hematocrit (10.3 and 9.3), total bacteria (74 x 10 2 ). The study concluded that the best treatment was found in treatment 3 with a dose of 0.8 ml of betel leaf extract, which significantly increased the immune system in tilapia seeds.