Lake Matano is one of the ancient lakes in Sulawesi where some endemic fish species of Telmatherina, Mugilogobius, Oryziasand Glossogobius matanensis lived. The presence of alien species can be on threat for the loss of biodiversity in fresh waters, including endemic fish in Lake Matano. The research aim to review the threat of louhan fish as alien species to endemic fish in Lake Matano. The study was conducted in Lake Matano at five stations in April and August 2015 namely Lawa, Nuha, Petea, Pantai Impian, and Pantai Kupu-kupu. Sam-ples were collected using experimental gillnet with mesh size of ¾; 1; 1¼; 1⅟2; 2; 2,5; and 3 inches. Fouteen species were found consist of 10 endemic species and red list.These were three of genus Glossogobius, seven species of Telmatherina, and four alien species of the carp (Cyprinus carpio), louhan, gourami (Trichopodus trichopterus), and tilapia (Oreochromis niloticus). The most common species of endemic fish is T. antoniae. Louhan is the result of a hybrid species Amphilopus citrinellus x Cichlasoma trimaculatum. The abundance of louhan is 64 in April and 40 fishes in August, respectively at a time caught. The percentage ratio of louhan to endemic fish was of 8.6% and 18.3%. This indicated that the louhan fish tend to be invasive and certainly threatened endemic fish survival in this lake. The maturity of gonads of louhan is in the level of I - IV that enables the fish to reproduce quickly.

Ranggeh River is one of the inlets of Lake Maninjau (West Sumatra, Indonesia), which has a vital role in supporting the life of native fish. Increasing anthropogenic activities (agriculture and human settlements) around the river can harm benthic macroinvertebrates as natural food for fish. Therefore, this study aimed to analyze and observe water quality changes and their impact on the benthic macroinvertebrate communities in the Ranggeh River. Sampling was conducted from February to August 2019 using the Hess Sampler tool. The results indicate that the anthropogenic impacts around the Ranggeh River on water quality has changed the macroinvertebrate benthic community structures (composition, abundance, and biological index). Furthermore, the Ephemeroptera Plecoptera and Trichoptera (EPT) number of taxa index were superior in reflecting disturbances in the Ranggeh River compared to the Family Biotic Index (FBI) and the Percent Model Affinity (PMA). In conclusion, the anthropogenic effect on the macroinvertebrate community in the Ranggeh River prominently was caused by habitat changes rather than enrichment by nutrients (TN and TP).

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.

Lake Sentarum National Park (LSNP) is a Ramsar site located in the Upper Kapuas Regency, Province of West Kalimantan, Indonesia. This national park is an unique freshwater fish habitat formed by flat basin or floodplain with fluctuated water level throughout the year in response to rainfall and supply of water from the Kapuas River system. This study aims at describing the fish diversity variation in the LSNP caught using gill nets during high water period (rainy season) in March, June, October 2013, and June 2014 and during low water period (dry season) in March 2014. Samples were taken in three locations, i.e. River Tawang (outlet), Lake Pengembung, and Lake Belida. Six orders, 15 families, and 39 fish species were found. The total number of species found during the low water depth period was less (20 species) than that during high water depth period (32 species). ‘Flood-pulse’ cycle and the corresponding rise and drop of water level in the floodplain area, sustained by aquatic productivity and habitat diversity, are considered to be the responsible hydrologically controlled seasonal variation in the study area.

Bada is the local name for Rasbora spp in Lake Maninjau. This fish is an economic fisheries commodity for consumption and has become one of the culinary icons of Maninjau area. Many studies have been carried out related to bada fish in Lake Maninjau, but continuous studies are needed to complete aspects that have not been done or for evaluation purposes, in order to take conservation or management actions. Therefore this study aims to convey the latest status of fish (species distribution of bada fish) and fisheries of bada (fishing activity, relative abundance distribution, and production trend). For species distribution of bada, sampling was carried out in six sampling station of lake waters (Bayur, Kularian, Muara Tanjung, Muko-muko, Sigiran, and Galapung) and four stream waters (Kularian Stream, Muara Tanjung Stream, Koto Gadang Stream, and a stream in Galapung) as inlets of Lake Maninjau in April 2017. For fisheries of bada analysis sampling was carried out in four stations of lake waters (Bayur, Linggai, Sigiran, and Galapung) from April to November 2017. Fish was caught using gillnet and liftnet. Catch data also obtained from some of fishermen as enumerator. In addition, interviews were also conducted with stakeholder from policy maker element. Species of bada were determined based on morphological identification. Three species of bada fish (Rasbora spp) were found in the lake and inlets of the lake, namely Rasbora lateristriata, Rasbora argyrotaenia, and Rasbora cf sumatrana. Rasbora lateristriata has the widest distribution in both lake and inlets. Analysis of Variance result showed that the abundance of bada fish (all types of Rasbora) was relatively same in all locations in Lake Maninjau (p > 0.05). Catch of bada in recent years declined sharply compared to 2008, for example catches in Bayur decreased by 80%. Current fishing activities also experienced a decline as fishermen using gillnet were rarely found. Current fishing of bada are mostly using lukah (trap) which were found in two locations, namely Rangeh stream and Batang stream. Bagan (lifnet) were found in Bayur, Muara Tanjung, Muko-muko, and Sigiran. Recommended management efforts are regulation of fishing (types of fishing gears and locations), maintain the lake and inlets connectivity, habitat improvement through construct fish shelters, and restocking.