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.

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.

Environmental DNA (eDNA) methods are increasingly viewed as alternate or complementary approaches to conventional capture-based surveys for marine conservation and fisheries management purposes, especially at large spatial scales in mega-biodiversity regions such as Indonesia. Decapod crustacean distribution and diversity across Indonesia are still poorly known, even for economically important fisheries commodities. This study assessed coral reef associated decapod diversity and distribution by sampling 40 sites in three regions (West, Central, East), representing 17 provinces and 10 Fisheries Management Areas (FMAs) across Indonesia, with a special focus on the blue swimming crab Portunus pelagicus. DNA sequencing (Illumina iSeq100) data were analysed in mBRAVE (Multiplex Barcode Research And Visualization Environment) yielded 406 OTUs belonging to 32 families, with 47 genera and 51 species identified. The number of families identified was highest in the Central region (25), while the most genera (31) and species (36) were identified in the West region. Alpha diversity did not differ significantly between regions or provinces, while Beta diversity differed significantly between provinces but not between regions. Our results also showed 31 species are possibility native based on the distribution meanwhile 12 species do not appear to have been recorded based of SeaLifeBase or WorMS. While providing a reference for further exploration of Indonesian coastal and small island decapod biodiversity, the high proportion of unidentified taxa calls for concerted efforts to develop and maintain reference specimen and sequence repositories and expand species conservation status assessments. The economically important decapod crustaceans identified in this study included three crabs (Charybdis anisodon, Charybdis japonica, Portunus pelagicus), a freshwater prawn (Macrobrachium nipponense), a lobster (Panulirus stimpsoni) and two penaeid shrimps (Mierspenaeopsis hardwickii and Trachysalambria aspera). For most decapod taxa, observed patterns indicate management under existing provincial and/or FMA level management structures is appropriate. Furthermore, the data can inform science-based fisheries management strategies, in particular for P. pelagicus.

Research about seagrass in Central Tapanuli is still very limited. This study aimed to assess E. acoroides density and coverage in Jago Jago coastal area, Central Tapanuli. The seagrass beds in Jago Jago coastal area are monospecific beds that formed by Enhalus acoroides, a species that has bigger morphological size than other species. Seagrass sampling was conducted in July 2020 in three observation stations. The assessment of seagrass coverage and density was conducted using line transect method and placing 50 cm x 50 cm quadrats every 10 m along the transect. The lowest coverage and density were found in Station I which was 26.06% and 39 shoots/m2. Meanwhile, the highest coverage and density were found in Station II which was 42.12% and 80 shoots/m2. This research outcome is expected to be basic data for future seagrass management in Central Tapanuli.