Abstract. Dersita, Rambey R, Muhtadi A, Onrizal O, Mamurung VR, Hasibuan JS, Tamba IS. 2022. Biodiversity of nekton in the Barumun Watershed, Labuhanbatu District, Indonesia. Biodiversitas 23: 2426-2432. Biodiversity is a very valuable source of germplasm for science and sustainable development. Therefore, research on freshwater biodiversity is very important to support the sustainability of this development. The research investigated three rivers in South Labuhanbatu District, North Sumatra, Indonesia: Barumun, Tasik, and Titi Kembar rivers. This investigation aims to ascertain the composition, distribution, and variety of nekton. From April to August 2020, the trial lasted five months. Nekton samples were collected with the aid of nets and fishing nets. While installed in the afternoon, the nets are removed the following day. Additionally, at each observation point, stocking nets were operated three times. The investigation discovered 38 fish species and one shrimp species. Two species of fish discovered, are protected by the government of the Republic of Indonesia. Both fish species are Tenualosa terubuk, a fish with little protection, and Fluvitrygon signifer, a ray fish with complete protection. The study site's sole shrimp species was the gigantic prawn Macrobrachium rosenbergii in the Barumun river. The index of nekton diversity discovered in the three rivers was not identical. Compared to other rivers, the Tasik river station has a high diversity. This makes the Tasik river rich in fish compared to the Barumun and Titi Kembar rivers. The Tasik river is recommended as water suitable for fish life from these results.

Tinfoil barb is one of the fish caught in the Tasik river. The purpose of this study was to determine the morphology and weight-length relationship of tinfoil barb. This research was conducted in July-August 2020 in the Tasik river using a net with a mesh size of 1.25 inches. The number of fish caught was 96 fish with a total weight (TW) of 2-47 g and a total length (TL) of 60-125 mm. Meristic characteristics of tinfoil barb consecutively are as follows: 31-33 Linnea Literalis (LL), 24-26 Body Circular Scales (BCS), 12-14 Dorsal Front Scales (DFS), 12-14 Tail Scales (TS) a total of 12 pieces, the dorsal fin formula (DF) is DI. 8-9, the ventral fin formula (VF) is V8-10, the pectoral fin formula (PF) is P12-14, the anal fin formula (AF) is AI. 5-6 and the caudal fin formula is (CF) C14. The results of the length-weight relationship indicate that the growth pattern of fish is negative allometric (b =3.221) where the weight gain is faster than the length gain.

The purpose of this study was to determine the morphometric and meristic characteristics, growth of Signal barb fish in the Tasik river. The method used in this research is a survey method. Morphometric characteristics of Signal barb fish Bodyweight (BW) ranges from 4-73 gr, Total Length (TL), Standard Length 6.3-15.5 mm (SL), Head Length (HL) 1.8-2.5, Snout Length (SL) 0.5, Dorsal Fin Height (DFH) 2.3, Dorsal Fin Length (DFL) 3-7, Eye Diameter (EM) 0.8, Tail Trunk Height (TTH) 0.8-1.8, Body Height (BH) 2-4.5, Pectoral Fin Length (PFL) 2 cm and Belly Fin Length (BFL) 2 cm. The meristic characteristics of Signal barb fish are the number of Linnea Literalis (LL) as many as 35-38 scale, 13 Circular Body Scales (CBS), 11-13 Front Fin Dorsal Scales (FFDS), the Scales Around the Tail (SAT) a total of 5, Dorsal Fin (DF) of DI. 23-26 fin radii, Ventral Fin (VF) of 9 fin radii, Pectoral Fin (PF) of 11-14, Anal Fin (AF) a total of 7 fin radii and a Caudal Fin (CF) a total of 20-22 fin radii. The growth pattern of signal barb fish in the Tasik River is negative allometric with the condition factor value an average value of 0.42

Indian Mackerel (Rastrelliger kanagurta) is one of the main catch fishery at Tanjung Beringin’s Auction Place, Serdang Bedagai, Sumatera Utara. The purpose of this research is to analyze the stock status of indian mackerel landed at Tanjung Beringin. This research was conduted in July – September 2021. The method of research used purposive sampling method. The total sample fish of indian mackerel were 272 individuals. The research showed Indian mackerel’s sex ratio was 1: 1.060. Indian mackerel’s growth pattern was negative allometric. Value estimation of male and female’s L∞ was 268.80 mm and 295.05 mm. Value K of male mackerel was bigger than female. But value of Lc and Lm male mackerel were smaller than female. The total rate of mortality was 2.466/year, natural mortality was 0.684/year and fishing mortality (F) was 1.782/year. The rate of exploitation was 0,723 classified as high exploitation level (overfishing).

Stingrays are a group of fish that have high economic potential landed at TPI Tanjung Beringin. The dominant type of stingray landed at TPI Tanjung Beringin is the Dwarf Whipray (Brevitrygon heterura) or commonly called Tuka-Tuka by the local community. This research wa carried out during July and September of 2021 at TPI Tanjung Beringin, survey method with a census technique, namely a method by seeking various information and various facts regarding the biological aspects. This study aims to determine the growth and exploitation rate of the dwarf whipray. There were 82 dwarf whipray, which were then measured for length and weight. The results of the study concluded that dwarf whipray (Brevitrygon heterura) which landed in TPI Tanjung Beringin had a negative allometric growth pattern, namely length growth was greater than weight growth. The exploitation status of the dwarf whipray (Brevitrygon heterura) in the waters of the Malacca Strait is classified as overfishing.