AbstrakPenelitian yang dilakukan untuk mengetahui morfologi alat reproduksi dan nisbah kelamin jantan-betina pada udang mantis Cloridopsis scorpio telah dilakukan selama 3 bulan, sejak bulan Maret hingga Mei 2019 pada perairan ekosistem mangrove Belawan. Pengambilan sampel udang mantis Cloridopsis scorpio dilakukan menggunakan jaring ambai berbahan nilon polyfilament dengan peletakan posisi jaring melawan pergerakan arus air. Penentuan stasiun pengamatan ditetapkan dengan metode purposive random sampling sehingga diharapkan dapat memperoleh data yang mewakili lokasi. Data nisbah kelamin dianalisis menggunakan analisis chi-square (χ2) (Sugiono, 2006) dan data sebaran frekuensi matang gonad udang dianalisa dengan rumus Walpole (1993). Hasil analisis nisbah kelamin menunjukkan nisbah kelamin jantan C. scorpio lebih sedikit dibandingkan betina dengan perolehan nilai chi-square hitung > chi-square tabel (0,05.10) (63,20 >18,30). Dari hasil analisa data sebaran frekuensi udang ditemukan C. scorpio kategori belum matang gonad (BMG) paling banyak ditemukan pada ekosistem mangrove Belawan dengan selang ukuran panjang tubuh 32 mm hingga 128,72 mm, dan udang mantis yang matang gonad (MG) ditemukan mulai pada selang kelas ukuran panjang tubuh 128,72 mm hingga 298,00 mm Kata kunci: Belawan, Nisbah Kelamin, Cloridopsis scorpio, Reproduksi AbstractThe research was done about information reproductive morphology and sex ratio of mantis shrimp Cloridopsis scorpio. In take of shrimp sample was perform on March until May 2019 in Belawan's aquatic ecosystems mangrove. Sampling the shrimp using seine net/shrimp trawler made of nilon polyfilament material. The nets are placed opposite from the movement of water currents. Determine of sampling area station using purposive random sampling method. Data analysis for sex ratio of mantis shrimp using Chi-Square (χ2) formula analysis by (Sugiono, 2006) and frequency distribution data was analysis by Walpole (1993) formula. Result of sex ratio analysis show that amount of male C. scorpio population found less than female, with value of chi-square (χ2) analysis is chi-square calculation > chi-square table (0,05.10) (63,20 >18,30). The frequency distribution of C. scorpio analysis result is immature gonad category get the highest value was found at 32 mm -128,72 mm interval of body length measuring, and mature gonad of shrimp was found starting at 128,72 mm -298,00 mm interval of body length measuring

Hilsa shad Tenualosa ilishais of the indigenous fish species and the icon of the Labuhanbatu Regency, Indonesia. Presently, a very limited study was done in this species. Hence, the purpose of this study was to analyse the distribution and growth patterns based on the length-weight relationship of Hilsa shad T. ilishaon Bilah River, Labuhanbatu District, Sumatera Utara Province, Indonesia. Sampling was carried out for 3 months starting in February-April 2019 with the exploration method. Determination of sampling locations based on information from local fishermen. Analysis of distribution data used the Morisita index and growth patterns used the Linear Allometric Model (LAM). The analysis results of Hilsa shad distribution indicated that these fish were distributed in groups/clustered with the Morisita index value of 2.211-2.314. The growth pattern of the fish was negative allometric with a value of b3. Correlation analysis showed that DO was closely related to distribution (r2=0.661), meanwhile, light penetration was closely related to growth patterns (r2=0.914). It is concluded that the distribution of Hilsa shad fish in the Bilah River was in groups or clustered, with a negative allometric growth pattern. Keywords: Hilsa Shad, distribution, growth pattern, Tenualosa ilisha

Julung-julung (Hemirhamphodon pogonognathus) merupakan salah satu spesies ikan asli Indonesia. Aek Mailil merupakan salah satu habitat ikan julung-julug (H. pogonognathus) yang berada di Kabupaten Labuhanbatu. Penelitian bertujuan untuk mendapatkan hubungan panjang-berat dan faktor kondisi ikan julung-julung (H. pogonognathus) yang hidup di Aek Mailil. Pengambilan data dilakukan mulai November 2020 hingga Januari 2021 dengan alat tangkap durung. Titik sampling ditetapkan atas informasi dari masyarakat Desa Bandar Kumbul. Hubungan panjang-berat dihitung dengan Linear Allometrik Model (LAM), sedangkan faktor kondisi dihitung dengan rumus Fulton (K) dan berat relatif (Wr). Pola pertumbuhan ikan julung-julung (H. pogonognathus) mendapatkan hasil alometrik negatif dengan nilai b 2,9371 (b<3). Nilai koefisien Fulton (K) 2,57 dan koefisien berat relatif (Wr) 103,07. Hal ini menunjukkan bahwa pola pertumbuhan ikan julung-julung (H. pogonognathus) allometrik negatif dengan panjang tubuh lebih cepat dibandingkan berat tumbuh. Nilai (K) menunjukkan bahwa Aek Mailil masih dalam keadaan seimbang dan baik untuk mendukung kehidupan ikan julung-julung (H. pogonognathus). Kata kunci: faktor kondisi; Hemirhamphodon pogonognathus; pola pertumbuhan ABSTRACTLong-Weight relationship and condition factors of Julung-Julung (Hemirhamphodon pogonognathus) in Aek Mailil, Labuhanbatu Regency, North Sumatera, Indonesia. Hemirhamphodon pogonognathus is one of Indonesia's native fish species. Aek Mailil is one of the habitats for julung-julung (H. pogonognathus) in Labuhanbatu Regency. This study aimed to determine the relationship between length-weight and condition factors of julung-julung (H. pogonognathus) living in Aek Mailil. Sampling was carried out from November 2020 to January 2021 using durung fishing gear. The sampling points were determined based on information from the local community of Bandar Kumbul Village. The relationship of length-weight is calculated using the Linear Allometric Model (LAM), while the condition factor is calculated using the Fulton formula (K) and relative weight (Wr). The growth pattern of julung-julung (H. pogonognathus) got a negative allometric result with a b value of 2.9371 (b <3). The value of the Fulton coefficient (K) 2.57 and the relative weight coefficient (Wr) 103.07. This means that Aek Mailil's waters are in a balanced state and can support the (H. pogonognathus) live.Keywords: condition factor; Hemirhamphodon pogonognathus; growth pattern

Gulamah fish (Johnius trachycephalus) is one type of fish that is widely consumed by the community. Prolonged use of Gulamah fish can have an impact on population decline caused by fishing activities. The purpose of this study was to determine the relationship between length and weight and condition factors of Gulamah fish in the waters of the Barumun River, Labuhanbatu Regency, North Sumatra Province. Sampling points were determined based on information from local fishermen. The Gulamah fish were taken using a net, with a net length of 20 m and a width of 8 m. Sampling was carried out four times for three months. The Gulamah fish that have been caught are then taken to the Ecology Laboratory, Labuhanbatu University, for measuring length, weighing, and separating fish by sex and so on. The number of samples during this study caught 36 fish, with a total length of Gulamah fish of 15.7 cm to 19.7 cm respectively, where the total length of the dominant fish caught averaged 18.16 cm. Meanwhile, the weight of Gulamah fish ranges from 70 grams to 113 grams, with an average fish weight of 95.08 grams. To analyze the relationship between length and weight, the Linear Allometric Model (MAL) was used, by calculating the constants a and b through length and weight measurements. While the condition factor is calculated using a metric system based on the relationship between the length and weight of the sample fish. The results showed that the relationship between the length and weight of Gulamah fish was negative allometric, which means that the length growth of the fish was faster than the weight growth. Then the condition factor states that the Barumun River supports the growth of Gulamah fish.

The purpose of this research was to determine the fish biodiversity in the False Gharial (Tomistoma schlegelii) habitat at Aek Kundur, Labuhanbatu District. This research was conducted from February to April 2019. The sampling locations was determined based on information from local people. Fish samples were caught using gillnets, fishing rods, and durung (trap). The sampling was done one time every month for three months at three sampling stations. The diversity index (H'), Evenness index (J') and similarity index (SI) were analyzed in this study. The results showed that the highest number of fish caught was Anumalura oxygaster (188 individuals) and the lowest number of fish was Monopterus albus (1 individual). The highest diversity index (H') value was at station 1 (2.224) and the lowest at station 2 (2.202) categorized as medium level. The evenness index value at station 1 was 0.867, station 2 was 0.856 and station 3 was 0.826, indicate the high evenness. While the highest Similarity Index (SI) was found at stations 3 and 1 (90%) and the lowest SI was recorded at stations 2 and 3 (80%). It is concluded that the diversity index value in Aek Kundur is categorized as medium level. The Evennes index value is categorized as high uniformity of population, and the fish community was in stable condition.