Desrita, Muhtadi A, Tamba IS, Ariyanti J, Sibagariang RD. 2018. Community structure of nekton in the upstream of WampuWatershed, North Sumatra, Indonesia. Biodiversitas 19: 1366-1374. River is a habitat for many aquatic organisms. Water quality is themain river characteristic that strongly influences distribution pattern, biodiversity, and abundance of aquatic organisms. Nekton isaquatic organism that swims and moves actively on their desire, for example, fish, shrimp, amphibian and also big aquatic insects. Thepurpose of this research was to know the habitat condition and biodiversity of nekton in the upstream of Wampu watershed. The habitatcondition was measured by examining the temperature, visibility, flow velocity, depth of waters, dissolved oxygen, pH, kind ofsubstrate, the width of the river, body width of river and rate of flow of the river. The type of nekton was determined by catching thenekton using a backpack of electrofishing unit with an electric flow of 12 Volt and 9 Ampere. The upstream habitat condition of Wampuwatershed was characterized by big stone, pebble, sandy type of substrate with moderate to strong current flow, and the clear aquatic.Physical and chemical parameters in upstream of Wampu watershed were still sustainable and appropriate as habitat for fish and shrimp.The result of this research showed a variety of nekton collected, comprised of 27 species of fish, five species of shrimp of inland water.Two species of fish from Tor genera, i.e., T. soro and T. tambroides were also found in this study. The highest diversity (H´) in thisresearch site was the Bahorok River (2.12), followed by Landak River (1.93) at the second, and the lowest was Berkail River with onlyabout 1.50 diversity index.

Abstract. Desrita, Muhtadi A, Leidonald R, Sibagaring RD, Nurfadillah 2020. Biodiversity of nekton in Batangtoru River and its tributaries in North Sumatra, Indonesia. Biodiversitas 21: 2344-2352. Batangtoru River which flows from the Tapanuli highlands (i.e., Sipirok, Tarutung, Siborong-borong, and Silangit) to the southwestern Indian Ocean is an important habitat for aquatic organisms in the western region of North Sumatra. This research was done to provide basic data on biodiversity of aquatic organisms in Indonesia, especially North Sumatra. The study was conducted in July-August 2019. Nekton was captured using backpack electrofishing units (12 volts and 9 Amperes), traps, nets, and bamboo trap. This study found 68 nekton species, consisting of fish (57 species), crab (3), shrimp (6), lobster (1), and 1 freshwater turtle (1). In general, nekton found in the Batangtoru River and its tributaries are native and economically valuable fish (Tor and eel), including the newly discovered species, which was, Hemibagrus caveatus. Invasive fish found consisted of 6 species, i.e., Cyprinus carpio, Oreochromis mossambicus, Oreochromis niloticus, Xiphophorus helleri, Hypostomus plecostomus, and Trichogaster pectoralis. The only invasive crustacean found was freshwater crayfish (Cherax quadricarinatus).

The Shortfin Mako Isurus oxyrinchus is one of the major shark bycatch species in the longline fishery for tuna Thunnus spp. in the Indian Ocean; however, its biological information is still little known. This study estimated the age and growth of Shortfin Makos in the southern Indian Ocean. In total, 178 specimens (72 females and 106 males) were opportunistically collected by the scientific observers onboard Taiwanese large‐scale longline fishing vessels from February 2013 to September 2016 in the southern Indian Ocean. The relationship of gutted weight (GW; in kg) to curved fork length (CFL; in cm) for both sexes combined was estimated as GW = 0.00001 × CFL2.517 (n = 170, r2 = 0.85). Growth band pairs (including translucent and opaque bands) were counted based on sectioned vertebral centra from the caudal peduncle region. The periodicity of band‐pair deposition on vertebral centra was estimated to be 1 year, with opaque bands deposited around August based on edge analysis. On this basis, the maximum observed ages of females and males were 18 and 14 years, respectively. The von Bertalanffy growth function best fitted the observed sexes‐combined length‐at‐age data, with growth parameter estimates as L∞ = 267.6 cm CFL, k = 0.123/year, and t0 = −2.487 years (n = 159). The growth model could be improved for future stock assessments by increasing the sample size, particularly on very small (neonates and small subadults) and very large female Shortfin Makos.

Dumai is one of the coastal waters of Indonesia that has the potential for the biodiversity of microorganisms including anoxygenic photosynthetic bacteria (APB). Anoxygenic photosynthetic bacteria are bacteria that carry out decomposition activities even though oxygen levels in water and sediment are very little or even absent. This study aims to determine anoxygenic photosynthetic bacteria from aquatic and sedimentary ecosystems in the coastal waters of Dumai, Indonesia. This research was conducted by an experimental method using modified mineral media. The APB was isolated from six different places in sequence, namely Dumai sea station, river prayer room, harbor, shrimp pond area, fish auction place, and, Purnama tour. All bacteria obtained were then characterized by their morphological and physiological characteristics. The isolation results showed that 15 different bacterial isolates were obtained after being determined based on Bergey’s Manual of Determinative Bacteriology. All isolates contained different pigments such as carotenoids, xanthophylls, and, chlorophylls. Thus, further utilization of APB bacteria can be carried out in various microbiological applications such as bioremediation, aquaculture, biofuel, food, and medicines.

This study aimed to determine the concentrations of heavy metals (Cd, Cr, Pb, Zn, Fe, and Cu) in gills, muscles, kidney, bone, liver, and reproductive organs of Notopterus notopterus from the Sail River. The results shown that the concentrations of heavy metals in each tissues of fish were as follow: muscles > reproductive organs > liver > kidney > gills and bone for Cd; liver > bone > kidney > muscles > reproductive organs > gills for Cr; gills > kidney > bone > muscles > liver > reproductive organs for Pb; gills > bone > reproductive organs > kidney > liver > muscles for Zn; gills > muscles > liver > kidney > reproductive organs > bone for Fe; bone > liver > kidney > muscles > gills > reproductive organs for Cu. Concentrations of Cr (95.62 mg/kg) was highest than 5 others heavy metals. The average of metal concentrations of Pb (35.62 mg/kg), Zn (88.47 mg/kg), and Fe (2.35 mg/kg) were highest in the gills. The estimated concentrations of Cd, Cr, Pb, Fe were higher and Zn, Cu were lower than the limits permitted.