Tilapia is a farmed commodity of freshwater fish that can be processed into refined products, e.g. the tilapia fillets. The arising problem in the utilization of tilapia into processed products is its residual waste. The purpose of study is to obtain fish oil from tilapia by-products by wet rendering extraction; to characterize fish oil; to determine the optimum temperature and period of wet rendering extraction; and to determine the fatty acid composition of fish oil. Extraction temperatures were varied i.e. 25, 50, 70, and 90 °C. Extraction periods observed were 15, 25, 35, and 45 min. Quality parameters to evaluate the performance of fish oil were free fatty acid, acid value, peroxide, p-anisidine, total oxidation, and fatty acid composition analysis. The optimum temperature and period of wet rendering extraction were 70 °C for 35 minutes, with the highest yield of 6.44%. Fish oil yield which was obtained using Bligh and Dyer method was 8.12%. Fish oil extracted from wet rendering method contained 1.15% of EPA and 1.03% of DHA.

The research objectives were to investigate the distribution and molluscs community structure in Mertasari beach, Denpasar-Bali. The research area was divided into 2 sites, the first site (I) has sandy substrate and second site (II) has muddy sand substrate. This research used quadrat transects systematic sampling method with 1x1 m2 quadrat. The data of the research were analyzed used Microsoft Excel. It was conducted from January to March 2017. The research result shows that the structure of molluscs in Mertasari Beach was support by 31 species richness of 25 species from gastropods and 6 species of bivalves. The density number of the molluscs was 124.5 ind/m2. The diversity index of the molluscs ranged from 2.29 to 2.58 were category as moderate diversity, the evenness index ranged 0.83 to 0.87 were category as high evenness, the dominance index ranged from 0.09-0.13 were category as low. the index number indicates that the ecological condition at Mertasari beach was in good condition so it is suitable to support the molluscs community livelihood. Which was supported by water quality value of dissolved oxygen at Mertasari beach ranged from 4-6.7 mg/l, pH waters ranged from 7.39-7.74, water temperature ranged from 25.9-29oC, water salinity ranged from 9-29 ppt. The distribution pattern of 31 species of molluscs were in groups (Id>1).

The main causes of ice-ice disease that seaweed production will decline. Bacterial infections occur due to fluctuations in climate change resulted in a decrease in water quality resulting in the durability of seaweed. When seaweed stress will facilitate pathogen infection. Disease pathogens cause damage to internal organs. The spread of bacterial disease in seaweed is generally very fast and can lead to death, so that the loss caused by this disease is quite large. Ice-ice disease occurrence is seasonal and contagious, so the impact on the selling price low. The results showed that there are two types of pathogenic bacteria that can potentially cause disease in which bacteria Vibrio alginoliticus and Pseudomonas aeruginosa. Climate change affects the spatial distribution of micro seaweed bacterial pathogens.

Estuary ecosystem has an important role in supporting the life of shrimp. High productivity and the availability of natural food in the estuary ecosystem, will indirectly affect the growth of shrimp. Penaeus monodon and Penaeus merguiensis were two species of shrimp that had economic value with high demand. The purpose of this study was to determine the biological aspects of Penaeus monodon and Penaeus merguiensis shrimp at estuary of Tukad Aya, Bali. Data collection was carried out in February-March 2019 using quantitative descriptive research methods. The determination of the research station was done by purposive sampling. The results showed the total number of shrimps were caught 1,756 individuals, which consist of Penaeus monodon 151 individuals, Penaeus merguiensis 224 individuals and 1,325 individuals of other shrimp. The composition of Penaeus monodon (8.6%) was less than Penaeus merguiensis (12.76%). Shrimp length measurements were divided into 9 groups with a range of values of 55.15-189.95 mm in Penaeus monodon and 31.3-140.1 mm in Penaeus merguiensis. The results of the length and the weight regression in both species of shrimp obtained the value of b <3 so that the growth pattern of shrimp was categorized as negative allometric where length growth was faster than weight gain.

The objective of this research was to determined the relationship between nitrate and phosphate content on the growth of wet biomass Salvinia molesta in Buyan Lake, and also to know the difference of growth of Salvinia molesta in each station with different treatment. The research was conducted from February to March 2017 at Buyan Lake. Biomass measurements and water sampling were carried out at 4 stations with a plot of each treatment. The measurement of wet-biomass were carried out in situ by measuring at each treatment and for measuring the nitrate and phosphate content performed in the laboratory. The result showed that nitrate correlated with biomass growth of Salvinia molesta at the lowest treatment with R2 value of 0,105 and the  highest at quarter treatment with value R2 of 0,889. The phosphate relationship with the lowest wet biomass growth was at full treatment with the R2 value of 0.042 and the highest in the quarter treatment with the R2 value of 0.936. The highest growth was found in station 1 and the lowest growth at station 4. For each treatment, the highest growth treatment was in a quarter treatment.