Abstract. Indarjo A, Salim G, Zein M, Septian D, Bija S. 2020. The population and mortality characteristics of mangrove crab (Scylla serrata) in the mangrove ecosystem of Tarakan City, Indonesia. Biodiversitas 21: 3856-3866. The mangrove crab is an iconic species of Tarakan City and is often is used as a souvenir. However, the high demand for this species can cause its population to decline. This study aimed to characterize the mangrove crab (Scylla serrata) population in the mangrove ecosystem of Tarakan City, North Kalimantan, Indonesia. This study was designed using a quantitative descriptive method with a case study model. The samples of mangrove crabs were obtained from 6 different stations using a purposive sampling method. The mangrove crab specimens were caught using 35-50 units of crab traps known as the ambau brackets. The primary data included carapace length, carapace width, carapace thickness, sex, and the total weight of each mangrove crab specimen. The results showed that male mangrove crabs have positive allometric growth when the condition index was fat. However, female crabs exhibited negative allometric growth when the condition index was thin. The Von Bertalanffy growth model analysis showed that the maximum carapace length of male mangrove crab in the mangrove ecosystem of Tarakan City was approximately 11.1118 cm for 189 days, while the female length was 9.6474 cm for 80 days. The total mortality value of male and female crabs was 120.01% and 154.94%, the mortality due to fishing was 84.69% and 135.75%, and natural mortality was 35.32% and 19.2%, respectively. The estimated rate of exploitation of both male and female crabs was 70.57% and 87.61%, respectively. The exploitation of S. serrata in the mangrove ecosystem of Tarakan City was evident, hence, conservation efforts are urgently required.

Abstract. Indarjo A, Salim G, Nugraeni CD, Zein M, Ransangan J, Prakoso LY, Suhirwan, Anggoro S. 2021. Length-weight relationship, sex ratio, mortality and growth condition of natural stock of Macrobrachium rosenbergii from the estuarine systems of North Kalimantan, Indonesia. Biodiversitas 22: 846-857. Giant prawns (Macrobrachium rosenbergii) in North Kalimantan Province, Indonesia are commonly found inhabiting estuarine areas in Salimbatu Village (Bulungan District), Tepian Village (Nunukan District) and Buong Baru and Sesayap Villages (Tana Tidung District). The present study was conducted to analyze the relationship between length and weight, sex ratio, mortality, and growth condition index of the naturally occurring giant prawns in three districts namely Bulungan, Nunukan, and Tana Tidung in the North Kalimantan Province, Indonesia. The samplings were carried out for a period of seven months beginning April to November 2020. The results revealed that the giant prawns in Buong Baru Village, Sesayap Village, and Salimbatu Village were characterized to have negative allometric growth patterns. Interestingly, the male giant prawns in Tepian Village were observed to exhibit positive allometric growth pattern. The ratio sex analysis of the giant prawns in the four villages indicated that female prawns were more than male. In terms of size distribution, Salimbatu Village exhibited 60.1% of prawns measured at 14.02-17.74cm (size range of 10.3-47.5 cm). In Tepian Village, 32.9% of the prawns were observed to measure between 11.20-12.80 cm (size range of 8.0-24.0 cm). In Buong Baru Village, it was observed 18.5% of the prawns measured 22.0-25.5 cm and 29.0-32.5 cm (size range of 15.0-50.0 cm), respectively. Finally, 28.3% of the prawns in Sesayap Village was observed to measure at 12.19-14.02 cm from the overall size distribution between 6.7-25.0 cm. Relative condition factor of giant prawns found in the waters of Salimbatu Village, Tepian Village, and Buong Baru Village waters and Sesayap Village waters was characterized by thin body shape. The maximum length of male prawns was higher than female prawns in Salimbatu Village, Desa Tepian and Sesayap Village, except in Buong Baru Village where female was longer than male. The exploitation rate and fishing mortalities of prawns were higher in Buong Baru Village, Tana Tidung District. Giant prawn fishery contributes to the socio-economic development of the people in North Kalimantan. Hence, sustainable fishery management of this species, particularly in Buong Baru Village is urgently needed so that it can continue to provide livelihoods to the fishermen in the area.

The Mudskipper (P. barbarus) lives in intertidal mud flats and it becomes an indicator of water quality. The transformation of construction and water pollution in this area is important to investigate due to interaction of fishery industry, home residence, and market area surrounding areas. The aim of this research was to analyze the characteristic of Von Bertalanffy growth, allometric, condition index, and mortality of the P. barbarus in KKMB, Tarakan city. The research was designed by using descriptive quantitative method. The sampling process used purposive sampling. The sampling was conducted for 12 times plot.transect-1 in the extension area of KKMB, Tarakan city with a total area is 12 Ha, plot.transect-1area is 10x10 m2, and distance between each transect is 10 m2.  Sampling was carried out in survey area and laboratory to identify the gender and calculate total length and weight. The result showed the growth of male mudskipper (L∞ = 26.545 cm) and female (L∞ = 17.594 cm). Their size and the total population was decreased. The characteristic of male mudskipper growth was positive allometric, then female was negative allometric. The natural mortality and the catch of male mudskipper were higher than female.

This research aims to analyze the allometric growth and condition index of white shrimp (Litopenaeus vannamei) from fishpond and Juata Laut waters, Tarakan (Indonesia). The study was conducted for 3 months, from January to March 2020. The objective method was descriptive quantitative with a case study approach. The determination of the research area by using purposive sampling from fishpond and the catches of trawl fishermen from Juata Laut waters, Tarakan (Indonesia). A sampling of white shrimp (L.vannamei) used survey methods in those two locations. The data collection was done by using a laboratory scale in the Biology Laboratory of Faculty of Fisheries and Marine Science, University of Borneo Tarakan. The data instead of sex, total length, carapace length, and the total weight of white shrimp (L.vannamei). The research variables were sex ratio, allometric growth, and condition index of the male and female white shrimp (L.vannamei). The results study showed that white shrimp (L.vannamei) from ponds had a sex ratio for males and females of 1:3 with a percentage of males by 25% and females by 75%. The allometric growth,i.e.total length, and total weight for both of sex were negative, condition index with a thinner body was not found for male and 1,9% for females; thin body shape was 50% and 53.7%; ideal body shape was 5.6% while females were not found; the fat body was 44.4% and 40.7%; the fatter body for male was not found and females by 3.7%. The results from Juata Laut waters obtained the sex ratio for males and females was 1.68:1 with the percentage of males was 62.71%, and females were 37.29%. The allometric growth like total length and a total weight of males and females was negative with condition index of males and females for thin body shapes were 48.6% and 45.5%; ideal body shape were 2.7% and 9.1%; fat body shape was 45.9% and 45.5%; fatter body shape was 2.7%, respectively and females were not found.

Giant prawns (Macrobrachium rosenbergii) has high economic value with a price range between IDR. 40,000 to IDR. 75,000 that it was one of the main catches of fishing gear used by the society in Muara Tepian Sembakung. This research aims to analyze the growth model composition of giant prawns (M. rosenbergii) in Muara Tepian Sembakung, Nunukan. The objective was conducted for 5 months from October 2019 to February 2020. The research was designed by using quantitative descriptive with a case study approach. The determination of the study location was applied with a purposive random sampling method by following the fishermen who used the bottom fish pots catch. The sampling of giant prawns at Muara Tepian Sembakung was done by taking a survey method adhered to a fisherman with repetition as 10 times of sampling at a different time. The data of Giant prawns that were collected involved sex, total weight, and total length using a laboratory-scale method in the Laboratory of fisheries biology, Fisheries and marine science faculty, Universitas Borneo Tarakan. The research variable was the von Bertalanffy model and age structure of male and female giant prawns. The results obtained that the sex ratio of giant prawns (Macrobrachium rosenbergii) between males and females was 1: 1.83 with a percentage of a male was 35.33% and female was 78.6%. The growth of Von Bertalanffy model in getting the infinitive growth for male giant prawns was 24.185 cm at 132 days then T0 was -1.1088 and growth rate was 0.0877 cm/day with correlation value was 0.88431 (88.431% = very strong correlation) and female giant prawns amounted to 18.470 cm at 101 days whileT0 was -1.0734 days and the growth rate was 0.1019 cm/day with a correlation value was 0.90626 (90.626% = very strong correlation).