The sustainability of prawn farming in brackish water ponds is controversial because of low yields and a history of mangrove clearing. Low yields are due largely to insufficient preparation of pond bottoms. Mangrove trees are often planted on pond bunds as window dressing. This study examines the effect of three types of liquid compost from vegetable, fruit, and both vegetable and fruit in tanks to which whole or chopped Avicennia marina leaves have been added to mimic local pond conditions. In a split-plot design, 28 square tanks were each stocked with one hundred 15-day-old post-larvae tiger prawns (Penaeus monodon). Four tanks were used as controls and 24 were assigned to the treatments, 12 with whole and 12 with chopped leaves. Of the treatment tanks, 4 received liquid compost from vegetable, 4 received fruit, and 4 received mixed vegetable and fruit. Shrimp were weighed at the start, halfway point, and the end of the 50-day trial, and fed at 5% of the estimated total weight; survival was counted at the end. The survival rates of treatments and controls (65–76%) were not significantly different. Shrimp in water with vegetable compost grew significantly faster (2.7% day−1) than in both treatments with fruit (2.5% day−1), while all treatments were associated with significantly faster growth than were the controls (2.0% day−1). The lower growth rate of shrimp fed fruit compost may have been due to dinoflagellates, which are known to negatively affect shrimp. Shrimp in tanks with chopped mangrove leaves grew slightly better than shrimp in tanks with whole mangrove leaves.

The high organic waste content of river water in Demak, north coast of Java, has caused traditional small-scale pond farmers to stop stocking shrimp. This paper examines whether seaweed and mussel will improve the quality of water these farmers use. The effect of Gracilaria verucosa and Perna viridis on the water quality was assessed by measuring the removal rates (RRs) of total organic material (TOM), total ammonia nitrogen (TAN), nitrite, and nitrate. The specific growth rates (SGRs) of seaweed and mussel were also measured. Thirty-six semi-outdoor tanks containing 800 L of brackish water and 7 cm substrate were randomly assigned to four replications of four densities of G. verucosa: 50 (S50), 100 (S100), 150 (S150), and 200 (S200) g m−2, and of P. viridis: 60 (M60), 90 (M90), 120 (M120), and 150 (M150) g m−2. Weekly, the TOM, TAN, nitrite, and nitrate contents were measured, seaweed and mussel weighted; RRs and SGRs were calculated at the end of the study. The effect of densities on the RRs was significant for both seaweed and mussel. P. viridis was more effective in reducing TOM (by 38%) than G. verucosa (7%); G. verucosa achieved higher RRs for TAN, nitrite, and nitrate. At S200, TOM and TAN decreased by 7.4% and 67%, respectively. At M90, TOM and TAN, decreased by 38% and 49%, respectively. However, nitrite increased significantly at S200 and M150. The SGR of seaweed was significantly lower at S200 than that at S150, S100, and S50. The best performing densities were S100 and M90.

Milkfish is one of the most widely cultivated fish species in Indonesia. The development of milkfish cultivation technology in the community is inseparable from its comparative and strategic advantages because milkfish can be cultivated in brackish water, sea water and even freshwater and tolerant to environmental quality changes. Technology of cultivation and seeding has been done by the community. Milkfish is not susceptible to disease. The prospect of the development of milkfish breeding business in Ulujami District has good potential due to market demand. The purpose of this research is to know the technical aspect, financial aspect, and business feasibility of milkfish cultivation in Ulujami District. This research method is interview that is using questionnaire for data retrieval. The problems that arise in the breeding business of milkfish enlargement is how the efforts to obtain good and profitable results in fulfilling the market demand by spending as less as possible because it affects the profitability of the milkfish farmer income. Data analysis methods are obtained from Payback Period (PP), which is located in Limbangan Village 0.34, Mojo Village 0.98 and Pesantren Village 5.85. Net Present Value (NPV), the farmer's NPV value is positiv.  Benefit Cost Ratio (B / C Ratio) of each village are 2.35 and 4. Results and conclusions are obtained based on the technical aspects of site selection, maintenance, milkfish harvesting and financial aspects of business feasibility it this worth to be. Keywords: Business Feasibility Evaluation, Cultivator In Ulujami District

Abstract. Rejeki S, Middeljans M, Widowati LL, Ariyati RW, Elfitasari T, Bosma RH. 2019. The effects of decomposing mangrove leaf litter and its tannins on water quality and the growth and survival of tiger prawn (Penaeus monodon) post-larvae. Biodiversitas 20: 2750-2757. Shrimp farming in Demak, Indonesia is often practiced in silvo-aquaculture systems in which mangrove trees are planted on pond bunds. As such, mangrove leaves and its substrates may have impact on penaeid shrimp production. In this area, mangrove re-growth proceeded with Avicennia marina while planting is mostly done with Rhizophora apiculata. We compared the effects of decomposing fresh leaves of A. marina and R. apiculata on water quality and on the performance of Penaeus monodon postlarvae (PL). A hundred of PL21 (postlarvae aged 21 days with weight of 0.28 g) were stocked in each of 30 aerated tanks containing 800 liters of brackish water (salinity of 21 ppt) for 37 days. Five treatments with three replicates for each mangrove species were assigned by adding into the tanks of 0.125, 0.25, and 0.5 g L-1 of air-dried leave, 0.125 of g L-1 minced leave and 0.125 g L-1 of leachate of minced leaves. The PLs were fed 3 times daily with pellets at 10 % of initial total body weight. Water quality parameters were recorded daily. Tannin, H2S and NH3-N concentrations were measured every ten days. Prawn's body weight (BW) was measured and specific growth rate (SGR, % day-1) and survival rate (SR, %) were calculated after the end of experiment. Results were analyzed with ANOVA and Pearson's correlation. The results showed that tannin in decomposing mangrove leaf litter up to a concentration of 0.5 mg g-1 did not have a significant effect on water quality and on the growth and survival of P. monodon PL. However, increasing leaf litter concentrations showed an increase in NH3-N concentration due to organic matter degradation. The accumulation of NH3-N may have caused the slow growth of shrimp PL in A. marina treatment. Shrimp PL in leaf litter leachates treatment has a higher growth rate than those PL in regular leaf litter in relation to nutritional value. Survival and growth varied from 62 ±14 to 70 ± 8% and 3.1±2.1 to 5.5±1.2% day-1, respectively. Although decomposing mangrove leaves of A. marina and R. apiculata had no toxic effects on P. monodon PL up to a concentration of 1.25 g L-1, but causing severe mortality for shrimp in tanks without water exchange. As a conclusion, the present of mangrove leaves in brackish water ponds with insufficient water exchange can be harmful to shrimps. However, if the water exchange is good, decomposed mangrove leaves can become organic fertilizer that beneficial for the growth of natural food for the shrimps

The aquaculture industry is developing tremendously over the past two decades following the significant decline of the world’s fish catch. Nevertheless, small scale fish farmers are still one of the most vulnerable communities in Indonesia. In their attempt to carry out successful aquaculture business, small scale fish farmers encounter several challenges that inhibit the fish farmers in ensuring the sustainability of fish products. This research aims to explore challenges and identify internal and external challenges that affect fish farmers’ activities in ensuring fish product sustainability. This research used a quantitative approach by collecting data through questionnaire distribution to small scale fish farmers in Central Java and data was analyzed using statistical analysis package. The findings of this research showed that challenges are classified into nine internal and seven external challenges. Result of statistical analysis indicated that internal challenges influenced product sustainability through water quality examination, whereas external challenges influenced product sustainability through two activities, i.e. giving feed at the right quantity and time, and maintain fish seed quality and availability.