A Bayesian Belief Network, validated using past observational data, is applied to conceptualize the ecological response of Lake Maninjau, a tropical lake ecosystem in Indonesia, to tilapia cage farms operating on the lake and to quantify its impacts to assist decision making. The model captures ecosystem services trade-offs between cage farming and native fish loss. It is used to appraise options for lake management related to the minimization of the impacts of the cage farms. The constructed model overcomes difficulties with limited data availability to illustrate the complex physical and biogeochemical interactions contributing to triggering mass fish kills due to upwelling and the loss in the production of native fish related to the operation of cage farming. The model highlights existing information gaps in the research related to the management of the farms in the study area, which is applicable to other tropical lakes in general. Model results suggest that internal phosphorous loading (IPL) should be recognized as one of the primary targets of the deep eutrophic tropical lake restoration efforts. Theoretical and practical contributions of the model and model expansions are discussed. Short- and longer-term actions to contribute to a more sustainable management are recommended and include epilimnion aeration and sediment capping.

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Lake Poso has high eel potential and a strategic position in supporting the development of eel fisheries in Sulawesi. Lake Poso is out of 15 national priority lakes in natural resources and environmental management programs. The catch of eel from Lake Poso is reported to have been decreasing for the last twenty years. Several factors causing the decline in eel populations are fishing activities, disruption in migration routes, and other factors such as changes in habitat and environmental conditions. The sustainability of the life of the Poso eel is determined by the success of the eel migration process. The migration of adult eels to the sea and young eels from glass eels to freshwater habitats must continue. The perspective plans that can be done to manage Poso's eel resources include 1) Socializing the eco-biological characteristics of eels as catadromous fish; 2) Establishing conservation areas and regulation of eel fishing; 3) Increasing eel population through restocking 4) Integrating fisheries and aquaculture activities; 5) Developing eel culture technology through size segmentation production; 6) Developing an eel migration monitoring system; 7) Building a cross-sectoral forum and put a joint action program; 8) Proposing the Poso eel Research and Conservation Center.

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High-frequency measurement provides a sophisticated insight in capturing environmental patterns. Compared to traditional discrete measurement, high-frequency sensors allow a better understanding of any processes particularly those with temporal scale characteristics. Lake metabolism is one of the exemplars getting advantage of such better resolution measurement. The dynamics of dissolved oxygen concentration (DO) observed in an hourly manner, even in minutes, may explain the balance of photosynthetic activity as expressed by gross primary production (GPP), respiration (R), and atmospheric exchange. Using a coupled thermistor-chain and oxygen sensor, we computed lake metabolism of the eutrophic Lake Maninjau. Characterized by high phytoplankton productivity fueled by the abundance of nutrient availability, DO concentration in Lake Maninjau is likely to be supersaturated. On the other hand, floating cage aquaculture operated in the lake may have a consequence in increasing water column heterotrophy, that is oxygen demanding community. Through a simple mathematical model, we revealed that water column respiration in Lake Maninjau is higher than gross primary production (R > GPP) with an average of 12.1 mg O2 L-1 day-1 and 9.0 mg O2 L-1 day-1 , respectively. Our findings highlight that as heterotrophy in eutrophic lakes may relatively be high, oxygen depletion in the water column may occur in any instance, especially in lakes where dense floating cage aquaculture is in place.