Abstract. Taqwa A, Supriharyono, Ruswahyuni. 2013. Primary productivity analysis of phytoplankton and community structure of macrobenthos based on mangrove density in conservation area of Tarakan City,. The studies of phytoplankton primary productivity and macrobenthic fauna community structure in different density of mangrove were carried out from May to June 2009 in mangrove conservation area, in Tarakan

Nomei fish (Harpadon nehereus) is one of the fish that has important economic value in the waters of Tarakan. This species is caught in waters with trawl fishing gear. In this study, H. nehereus fecundity is described based on 1100 female specimens captured in Tarakan waters from November 2016 to October 2017. The spawning season is predicted to occur twice a year, namely December-February and June-August, and reaches peaks in February and June. The average fecundity was 38,731 ± 7,757. The average sex ratio (female / male) was 0.94.

The length-weight relationship of Harpadon nehereus was analyzed. Samples were collected from November 2016 to January 2017, in Juata and Amal at Tarakan, North Borneo, Indonesia. The total length measured using a ruler scale 1mm. The total weight measured using a digital platform scales with an accuracy of 1 gr. The lengthweight equation, based on 600 unsexed individuals, was W = 0.006 * L 2.59 at Juata and W = 0.005 * L 3.00 at Amal where W is the total weight (g) and L is the total length (cm). In general the size of fish in Juata is greater than fish in Amal, but fish in Amal are with more fat. The t-test results in both sites showed that Nomei growth was isometric (α = 0.05). A coefficient of determination value of the length-weight relationship in Juata and Amal has 0.93 and 0.88 respectively.

The Kayan River is the longest in North Kalimantan, inhabited by various types of aquatic biota. However, in recent times there have been established multi-national oil palm plantations and mining around the Kayan River which will have an impact on the Kayan River ecosystem. The aim of this study is to determine the ecological status of the Kayan River based on current conditions. Fish sampling is carried out along the Kayan River starting from the upper reaches of the Bahau River to the downstream. Identification of fish is based on the Fishbase Organization, FAO and Kottelat. Measurement of water discharge using the SNI 8066: 2015 method, Total Suspended Solid refers to SNI 06-6989.3-2004. Determination of species diversity using the Shannon-Wiener Index, while the measurement of dominance index uses the Simson Index. The results obtained 37 species from 16 families during the 2019-2020. The family of Cyprinidae is the largest fund with 32%. Among the 37 species found 9 native species of Kalimantan, 3 invasive species, 1 species of saltwater fish, and 2 species of fish are included in the IUCN red list. Fish that are included in the endemic/native category of the Kayan River are Anguilla borneensis, Hemibagrus capitulum, Nematabramis alettes borneensis, Clupeoides borneensis and Osphrenemus septemfaciatus, and Pangasius rheophilus. Based on the results of the study, it can be concluded that the ecological status of the Kayan River fish is still considered very good and stable during the research period.

Bombay-duck (Harpadon nehereus) was one of economically valuable fish at Tarakan waters. This fish was caught by trawl and jermal. In this study, samples were taken from two fishing area, that were Juata and Amal. 20 characters morphometric was measure carried out on 100 samples from each area. Molecular identification and phylogeny of this species used Cytochrome C Oxidase Subunit I (COI) gene. The phylogenetic tree was constructed used MEGA 5.0 program. There were 5 significantly different characters between sample from Juata and Amal, that were body weight (P = 0.00), distance between pelvic and anal fins (P = 0.001), caudal fin height (P = 0.009), pelvic fin base length (P = 0.015), and dorsal fin base length (P = 0.031). Molecular identification showed that samples were the same species. The genetic distance between samples from Juata and Amal was 0 (zero).