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Sungai Mombang banyak dimanfaatkan masyarakat untuk kegiatan sehari-hari. Kegiatan tersebut tentunya memberikan dampak dan tekanan terhadap perairan sungai sehingga dapat menjadi ancaman serius bagi kelestarian dan keanekaragaman hayati ikan di perairan. Penelitian ini bertujuan untuk mengganbarkan keragaman ikan di Sungai Mombang, Kecamatan Batangtoru, Kabupaten Tapanuli Selatan. Titik lokasi pengamatan terdiir dari 4 lokasi. Ikan ditangkap dengan alat backpack electrofishing dengan kekuatan arus lisitrik sebesar 9 ampere. Kondisi habitat yang di surveiyaitu: suhu, DO, BOD, nitrat, fosfat, arus, kedalaman, dan kecerahan. Hasil penelitian di Sungai Mombang Kecamatan Batang Toru Kabupaten Tapanuli Selatan didapatkan 16 spesies ikan, yang termasuk ke dalam 6 ordo, 8 famili. Ikan Jurung dan Ikan Sidat merupakan ikan ekonomis yang terdapat di Sungai Mombang. Ikan-ikan yang ditemukan di Sungai Mombang merupakan ikan asli, kecuali Ikan Nila (Oreochromis niloticus). Diversitas ikan di Sungai Mombang tergolong tinggi dibandingkan dengan sungai-sungai kecil lainnya di Sumatera. Secara umum kondisi habitat ikan di Sungai Mombang termasuk baik dan layak bagi kehidupan ikan.

Fadhilah A, Leidonald R, Susetya IE, Dewinta AF. 2022. Analysis of the relationship between the ENSO phenomenon, Net Primary Productivity and catches of yellowfin tuna in Sibolga Waters, Indonesia. Biodiversitas 23: 4440-4447. The eastern Indian Ocean includes the western seas off of North Sumatra. They have a high potential for catching fish, which is a measure of their degree of primary production. Numerous factors, including oceanic conditions and the El Niño Southern Oscillation (ENSO) phenomena, frequently have an impact on its potential. Additionally, ENSO has an influence on the availability of nutrients that generate chlorophyll, a component of primary production, as well as water mass. It is also responsible for anomalies of sea surface temperature (SST) that occur in the Pacific Ocean. Therefore, this study aims to determine the effect of the ENSO phenomenon on primary productivity as well as the abundance of yellowfin tuna (Thunnus albacares) in the western waters of North Sumatra. Data were obtained from the Aqua MODIS level 3 satellite for analysis of net primary productivity (NPP) using various parameters, namely Vertically Generalized Production Model (VGPM), Ocean Niño Index (ONI), yellowfin tuna catch, winds from ERDDAP, and currents from AVISO. Its relationship with the abundance of yellowfin tuna, and ENSO was then determined using the Pearson correlation. The VGPM calculation showed that NPP for 2016-2020 ranged from 275.169 mgC/m2 to 994.898 mgC/m2. The study also revealed that the ENSO phenomenon has a weak relationship with primary productivity and the abundance of yellowfin tuna with correlation values of 0.262 and -0.191, respectively.

Based on statistical analysis from Dinas Kelautan Perikanan, Deli Serdang Regency in 2018, The capacity for freshwater aquaculture output was recorded at 1328.9 tons / year with a land area of 65.9 ha , which is a problem for the aquaculture community with the decreasing quantity of seed production, limited infrastructure and development management which is still conventional in Desa Perbarakan, Deli Serdang Regency, therefore it is important to implement the required application of science and technology, namely the implementation of semi-natural methods of spawning techniques of koi fish (Cyprinus carpio). Counseling, seminars and practices are the methods of tasks carried out. Extension activities were carried out by illustrating the conceptual awareness of the development of koi fish spawning strategies, the distribution of leaflets, the application of recognition technology, as well as tools and resources, including the dose of gonadotropin hormone (GnH) in broodfish and fish anaesthetic techniques. For female fish, the injected hormone level is 0.5 ml / kg and 0.1 ml / kg for male fish. The weight of the female fish is 1 kg tancho sanke doitsu, 0.5 ml/gr, and the weight of the male fish is 1 kg. At a dose of 0.1 ml / gr and 900 g of shiro, kohaku at a level of 0.09 ml / gr. The result is that the number of eggs is estimated at 10,000, and then the eggs hatch within 2-4 days. Boiled egg yolks are fed to the eggs which hatch into the larvae, then the larvae are transferred to the nursery pon after 10 days of age.

Highlights Mangrove sampling was conducted to use the "spot check" method Mangrove ecosystem of Bagan Serdang Village was categorized damaged Diversity of mangroves in the Bagan Serdang Village mangrove ecosystem was categorized moderate, but diversity of aquatic organisms was higher than the mangrove. Pertamina's CSR activities had an impact on environmental sustainability such as a habitat for various fauna and improving the community's economy Abstract Information about mangrove and fauna biodiversity in Bagan Serdang Village is essential to be studied as a basis for assessing the management and utilization potential of mangrove. This information could be used as a reference in sustainable mangrove management. This study aims to determine the biodiversity of flora and fauna in the mangrove ecosystem of Bagan Serdang Village. The research location is divided into three areas, with three observation points. The study was conducted in August-September 2019. The sampling of mangroves was carried out using the Spot Check Method. The results showed that the types of mangroves found were 18 species from 12 families consisting of 14 species of true mangrove and four types of associated mangroves while the fauna found in the mangrove ecosystem of Bagan Serdang Village was 16 species of fish, nine species of crustaceans, 13 species of mollusks, four species of birds, one species of reptile, one species of mammal and one species of horse shoe crab. The results of the mangroves analysis in the Bagan Serdang Village’s mangrove ecosystem, including in moderate heading to damage condition. This could be seen from the death of several trees and the flourishing of A. ilicifolius species as a marker of mangrove, which tends to be damaged. The diversity of mangroves in the Bagan Serdang Village is lower (1.63) compared to aquatic organisms that reach 2.09 - 2.44. Corporate responsibility or CSR that PT Pertamina (Persero) TBBM Medan Group carried out in the village of Bagan Serdang with mangrove planting activities and ecotourism, as well as the development of processed mangrove products, could increase the value of diversity and increase the economy of the surrounding community.

Muhtadi A, Pulungan A, Nurmaiyah, Fadlhin A, Melati P, Sinaga RZ, Uliya R, Rizki M, Rohim N, Ifanda D, Leidonald R, Wahyuningsih H, Hasani Q. 2020. The dynamics of the plankton community on Lake Siombak, a tropical tidal lake in North Sumatra, Indonesia. Biodiversitas 21: 3707-3719. The tidal lake is a very dynamic estuary ecosystem and very vulnerable to environmental stresses and disturbances. Plankton is an aquatic organism that is very easily affected by environmental pressures and disturbances. This study aimed to reveal the phenomenon of plankton dynamics in tropical tidal lakes in Indonesia. The study was conducted at Siombak Lake from September 2018 to August 2019. Data were collected at high and low tides every month during the full month. The data analysis included plankton abundance, diversity index, and the relationship between water quality and plankton with PCA and succession analysis. The results showed that in Siombak Lake was found 66 genera which consisted of 54 phytoplankton genera and 12 zooplankton genera. Plankton abundance is higher in parts of the lake (stations 1-8) than in the river (stations 9-11) at both high and low tide. Temporally it shows that plankton abundance is higher in the rainy season (Feb-Aug, outside May) than in the rainy season (Sep-Jan, and May). Spatially, plankton in Siombak Lake at high tide is more influenced by TSS, phosphate, and salinity, while at low tide, it is influenced by TSS, Water transparency, BOD, silicate, salinity, and dissolved oxygen. Temporally, plankton in Siombak Lake at high tide is more influenced by salinity, conductivity, Debit, TSS, and salinity, while at low tide, it is influenced by salinity, conductivity, turbidity, TSS, TDS, DO, BOD, and COD. Based on the plankton Frontier succession graph, it shows that Siombak Lake is included in stage 1 and stage 2. Stage 1 occurs before the rainy season (August-September) and the peak of the dry season (March-April).

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).

Factors affecting the rate of the decomposition are animals and microorganisms such as worms, snails, bacteria, fungi etc. as well as environmental conditions, such as type of soil, pH and salinity of water, etc. This research was conducted at the Deli Belawan River and Forest Cultivation Laboratory, Medan, North Sumatra Sumatera. A study was undertaken to find out the effect of the salinity on : the number of species, the population, the species diversity and the frequency of colonization of the different species of fungi during the process of the composition of the A. marina leaf litter decomposition. The leaf litter of A. marina to be put in a litter bag that is 50 g and it’s 33 litter bags for each level of salinity totally. The level of salinity to be used such as < 10, 10 – 20, 20 – 30 and > 30 ppt. The time series to collect data were 0 (control), 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, and 165 days. The leaf litter of A. marina in a litter bag was taken from each salinity level that was three bags for each time. It was used for isolation and identification of the fungi. There were 21 fungal species isolated from the A. marina leaf litter before being decomposed and from those decomposed at < 10, 10 – 20, 20 – 30 and > 30 ppt. The highest population was found in the leaf litter before being decomposed with an average of 1.6 × 103 cfu/ml. The Species Diversity Indices of the fungi isolated from the leaf litter at < 10, 10 – 20, 20 – 30, and > 30 ppt were 1.96, 1.86, 1.75 and 1,50. The frequency of the fungal colonization ranged from 9.1 to 100 %.

In fishing activity, the success is indicated by the number of catches that extremely influenced by the conditions of fishing ground. Information of the potential fishing ground is needed for fishermen to increase the effectiveness and efficiency in fishing activity. Sea Surface Temperature (SST) and chlorophyll-a in waters are two things that can affect the potential of fishing ground. The research aims to create distribution map of SST and chlorophyll-a and to presume the potentials of fishing ground in Malacca Strait based on distribution of SST and chlorophyll-a in Malacca Strait (2015-2019). The data of SST and chlorophyll-a distribution in Malacca Strait were using Aqua MODIS satellite imagery. Based on the result of SST and chlorophyll-a analysis, potential fishing ground in Malacca Strait is expected located around East Aceh in Western season, Malaysian waters in the Transition I season, between Asahan and Malaysian waters in Eastern season and between Deli Serdang and East Aceh in the Transition II season.

Baung Suat fish (Hemibagrus caveatus) become the newest species in North Sumatera. H. caveatus were collected in Batangtoru downstream. This species has a special mark, specifically a horizontal and vertical strip both on the left and right of the body of this species. The research has been done at Batangtoru downstream, North Sumatera in July 2019. The total amount of this captured fish was53 fish with 170 mm to 394 mm in total length (TL). The value of constant b obtained from the relationship length weight of H. caveatus fish was 3.09 which makes H. caveatus are positive allometric. Condition Factor values obtained based on the relation of body length and weight about 0,8098 – 1,3527. Sex ratio between male and female are 1,41. The male of H. caveatus are at the Gonado Maturity Level (GML) I, II, III, and IV, while the female at GML III and IV. Gonado Maturity Index (GMI) of H. caveatus at 2,46 – 13,07 %. The first size maturity of gonad begins to appear in 291,27 mm length for the male and 303,32 mm length for the female.

Siombak lake (28 ha area) was a salty lake located in Medan coastal, Indonesia. Water fluctuation influenced by the sea tide. Therefore, it needed to do morphometry dynamical study as the first impression of lake physical characteristic. The purpose of this study was to understand the dynamical of Siombak lake morphometry. The research was done in September 2016. Lake mapping was done by making 100 line zig zag and draw with ArcMap. Bathymetry showed that the bottom of the lake was sloping at the center part of west and southeast of the lake, and steeping at north, south and east. Siombak Lake has shoreline length 2,535.78 m, with SDI value 2.70. Maximum length 756 m, with maximum width 246.15 m. Lake maximum depth was 17.7 m at MSL, 18.98 m at highest tide and 16.71 m at lowest tide, with average depth 5.33 m at MSL, 6.30 m at highest tide and 4.30 m at lowest tide. Lake volume was 783,607.16 m 3 at MSL, 829,395.52 m 3 at highest tide and 355,544.14 m 3 at lowest tide, with water debit around 32.50 – 50.17 m 3 s -1 . Water retention time was ± 4.33 – 6.75 hour s

Pane Island is one of the tourist destinations in Tapanuli Tengah Regency, visually Pane Island has some of marine ecosystems such as seagrass, mangrove, seaweed, and dead coral ecosystems. Sea cucumbers are invertebrates, it’s have high commercial value and has ecological functions. In this study, sea cucumbers identification, abundance and seagrass cover was investigated in Pane Island. The results showed that 1 sea cucumber species were found, Holothuria leucospilota. Sea cucumber abundance ranged from 0 to 1.2 ind/m2. Based on Principal Components Analysis (PCA), sea cucumber abundance is positively related to temperature, current, pH, salinity, total nitrogen, phosphate, and C-organic content. Furthermore, sea cucumber abundance is negatively related to the parameters of water depth, water transparency, DO and percentage of seagrass cover.

The existence of polychaeta in water is very important to support the life of organisms and illustrate the fertility of the waters. This study aims to measure the content of C-organic in the substrate and determine the relationship of substrate characteristics to the diversity of polychaeta. This research was conducted in the waters of Tanjung Tiram, Batubara Regency, North Sumatra Province in June-July 2019. Determination of the location of sampling using a purposive sampling method at three stations. Intake of C-organic and Polychaeta by placing 3 plots horizontally at each observation station. The results obtained by an average of C-organic content with a range of values of 0.56% - 2.48%, found 12 species of polychaeta and diversity values ranging from 0.52 to 1.92, including the medium category. Pearson’s correlation between polychaeta diversity and C-organic has a negative relationship.

The eastern coast waters of North Sumatra is a fishing ground with a high level of exploitation. One of commodity catches in the eastern coast of Sumatra is mackarel (Rastrelliger kanagurta). By understanding the parameters of oceanography, especially sea surface temperature and chlorophyll-a, it can help to predict fishing area which are used as a guide for the purpose of fishes catching or exploitation. One of the satellites that can detect sea water temperature and chlorophyll-a is Aqua (EOS PM) with a moderate resolution imaging spectro radiometer sensor (MODIS). Mackerel catch data were obtained from ocean fishing port in Belawan. Sea surface temperature eastern coast of North Sumatra based on Aqua MODIS image analysis ranged from 29.55-31.66°C, and chlorophyll-a distribution has a range of 1.56-4.65 mg/m3. Mackerel catches fluctuations every month. The highest average catch is 232.174 tons which occurred in February. While the lowest catch is 201.457 which occurred in May. The results of the correlation between catching mackerel and sea surface temperature of -0.337 have a weak and not direct relationship. Relationship of chlorophyll-a with catches obtained a positive correlation value of 0.660 which indicates that between chlorophyll-a and catches has a strong and direct relationship.

Tidal lakes are unique lakes because of the fluctuations of the water in the lake are influenced by the sea tides. Therefore, Tidal lakes are also called brackish lakes or salty lakes. Thus, the organisms that live in the lake must be able to adapt to the dynamics of brackish water changes. Therefore, the study of the biodiversity of flora and fauna is interesting to study related to organisms that are able to live and adapt to dynamic environments. This research was carried out in Siombak Lake, Medan City, North Sumatra Province from June to July 2018. The data collected were organisms in the form of flora (mangroves and aquatic plants) and fauna (ictiofauna or nekton which were fish, shrimp, crab, and mollusca). The results of research in the Siombak Lake ecosystem found 7 species of mangroves, 5 species of coastal plants, and 2 species of aquatic plant. Fauna found were 14 species of fish, 7 species of gastropods, and 1 species of bivalve, 1 species of shrimp and 1 species of crab.

The upstream of Wampu Waters is a habitat for various fish species including Tor spp fish. Fluctuating conditions of habitat will greatly affect the existence of fish as diversity, uniformity, dominance, and abundance of fish. This research was conducted to determine of the condition of habitat and diversity of Tor spp fish in the upstream of Wampu waters. Measurement of habitat conditions by measuring current velocity, depth, temperature, visibility, DO and pH. The method was used n this research is descriptive post facto with fishing using backpack electrofishing units, 12 volts and 9 amperes of battery with the multiple-pass depletion operation technique. Habitat conditions in both research locations are good and appropriate to support the life of fish of Tor spp. Tor fish species was found are Tor soro and Tor tambroides with low fish diversity index of Tor spp of 0.5 for the Bahorok River and 0.61 for the Berkail River, lowest evenness index of 0.09 was found in the Bahorok River and 0.11 in the Berkail River and lowest dominance index of 0.17 were found in the Bahorok River and 0.2 in the Berkail River.

Gastropod was one of the class from mollusca in mangrove ecosystem. Lubuk Kertang Village's mangrove forest was been converted into tourist areas, agricultural land and settlements. The purpose of this study was to analyze the structure of gastropods at Avicennia lanata, Rhizophora apiculata and Sonneratia alba. This research was conducted at Lubuk Kertang Village in February-March 2017. Gastropod were collected in 1 m × 1 m transect in mangrove. Examples of biota were taken by using shovel, then the biota was inserted into a plastic bag sample, wrote date of sampling and identified. The results showed there were 15 species Gastropods, namely Achatina fulica, Cerithidea alata, Cerithidea cingulata, Cerithidea obtusa, Chicoreus capucinus, Cymatium pileare, Ellobium aurimisdae, Ellobium aurisjudae, Littoraria melanostoma, Littoraria scabra, Murex tribulus, Nerita balteata, Nerita planospira, Pugilina cochlidium, Stramonita gradata, Telescopium telescopium and Terebralia sulcata. Diversity index ranged 1.702 to 2.165 was in medium category, Similarity index ranged 0.676 to 0.799 was in low category and Dominance index ranged 0.142 to 0.282 that categorized was low. The highest gastropod density was 31 individuals/m2 in the Sonneratia alba. The conclusion of the research is the existing mangrove ecosystem in Lubuk Kertang Village in a stable state.

Limnological Status of Lake Siombak, Medan, North Sumatra. Lake Siombak is located in the coastal area of Medan city, making its waters influenced by the tides. The lake serves as a water catchment, flood control, fishing area, and tourist destination. Various activities in the lake have led to changes in the environmental quality of the lake. To maintain the sustainability of the lake, efforts are needed for proper management. Lake management should begin with a good understanding of the nature and characteristics of the waters. This study aimed to determine the limnological status of Lake Siombak through morphometric analysis, aspects of physics, chemistry, and biology, as well as trophic status of the waters. Morphometry included dimensions of water surface and subsurface. Physics parameters included temperature, Total Suspended Solid (TSS), water clarity, electrical conductivity (EC), and salinity. Chemical parameters included pH, dissolved oxygen (DO), Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), nitrates, and phosphates. Biological parameters included community structure of nekton and benthos. Measurement of lake morphometry was performed in April 2014 at high and low tides. Measurements of water quality and biological sample collection were conducted in May-July 2014 at high and low tides. The results showed that Lake Siombak has an area of 41.44 ha with a maximum depth of 5 m at high tide and 4 m at low tide. Based on the aspects of physics, chemistry, and biology of the waters, Lake Siombak was categorized as an open waters influenced by the tides and was saline with high level of oxygen. The lake water retention time (Rt) was 15.65 hours and discharged (Q) 3.7 x 107 m3/h of water at high tide and 3.0 x 107 m3/h at low tide. High phosphate concentration indicated these waters have already been polluted. However, the water quality of Lake Siombak was still suitable for fishing activities. Benthos and nekton communities were relatively unstable. Benthic community was dominated by Blue Mussel (Mytilus edulis) at high tide (57%) and Red-rimmed Melania (Melanoides tuberculata) at low tide (41.34%). Nekton community was dominated by Blue Panchax (Aplocheilus panchax) at high tide (74.07%) and low tide (64.79%). In general, Lake Siombak was classified as eutrophic.