BIODIVERSITAS ISSN: 1412-033X Volume 21, Number 10, October 2020 E-ISSN: 2085-4722 Pages: 4571-4581 DOI: 10.13057/biodiv/d211015 Morphometric and genetic variations of species composers of nike fish assemblages in Gorontalo Bay Waters, Indonesia FEMY M. SAHAMI 1,♥ , RENE CHARLES KEPEL 2 , ABDUL HAFIDZ OLII 1 , SILVESTER BENNY PRATASIK 2 , RIDWAN LASABUDA 2 , ADNAN WANTASEN 2 , SITTY AINSYAH HABIBIE 1 1 Faculty of Fisheries and Marine Sciences, Universitas Negeri Gorontalo. Jl. Jend. Sudirman No. 6, Gorontalo City 96128, Gorontalo, Indonesia. Tel.: +62-435-821125, Fax.: +62-435-821752. ♥ email: femysahami@ung.ac.id 2 Faculty of Fisheries and Marine Sciences, Universitas Sam Ratulangi. Jl. Kleak Bahu, Manado 95115, North Sulawesi, Indonesia Manuscript received: 13 July 2020. Revision accepted: 11 September 2020. Abstract. Sahami FM, Kepel RC, Olii AH, Pratasik SB, Lasabuda R, Wantasen A, Habibie SA. 2020. Morphometric and genetic variations of species composers of nike fish assemblages in Gorontalo Bay Waters, Indonesia. Biodiversitas 21: 4571-4581. Nike is Gobioidei fish at the post-larval and juvenile stages whose habitat is still in seawater before they migrate to the freshwater, grow up, and spawn to fulfill their life cycle as an amphidromous species. This study aims to identify the species composers of Nike fish in Gorontalo Bay waters based on their morphometric and molecular characters. 2,523 samples were collected from the catches of fishermen during three periods of their appearance in Gorontalo Bay waters from January to March 2019. The samples were grouped based on their similarity of melanophore patterns, and morphometric characters of 10 units were then measured. This study found 20 different groups of melanophore patterns; 15 of them were new melanophore patterns. DNA samples from each group of new melanophore patterns were then isolated for molecular analysis. The morphometric analysis grouped the 20 melanophore patterns into three separate clusters that were confirmed through molecular analysis. The results of Gen Cytochrome Oxidase I (COI) sequences indicate that the new melanophore patterns of Nike fish assemblages consisting of six species; five species in the Gobiidae family (i.e. Sicyopterus parvei, S. cynocephalus, S. longifilis, S. lagocephalus, and Stiphodon semoni) and a species in the Eleotridae family (Belobranchus belobranchus). Keywords: Amphidromous, COI gene, Eleotridae, Gobiidae, molecular INTRODUCTION Nike (local name) is a designation for a goby fish group in the post-larval to the juvenile stages that seasonally appear in Gorontalo Bay waters, usually in the last quarter moon phase towards the new moon. The people of Gorontalo catch this fish for consumption as well as in other areas, such as Nike in North Sulawesi (Pangemanan et al. 2020), Penja in West Sulawesi (Nurjirana et al. 2019a; Nurjirana et al. 2019b), and Dulong by the Philippines (Thomas et al. 2013). As a group of amphidromous fish, the catching is usually done when they migrate from the sea to the river. Keith (2003); Yamasaki et al. (2011); Taillebois et al. (2012); and Mennesson et al. (2019) mention that adult amphidromous fish will spawn in freshwater, the eggs are placed on the substrate at the bottom of the water, and the larvae are then carried away by the estuary area into the sea. After the larvae live in the sea, they will then return to the river at the post-larval and juvenile stages. Olii et al. (2017) and Pasisingi and Abdullah (2018) report that Nike fish in Gorontalo Bay will first appear in the sea and move closer to the estuary areas by time until they finally disappear. The local communities and general public believe Nike fish as a single species. Usman (2016) reported that Gorontalo Nike fish has been identified as Awaous melanocephalus Bleeker 1849. Furthermore, Olii et al. (2019) reported that Nike fish is Sicyopterus longifilis de Beaufort 1912. Several studies were then conducted to investigate reality. Sahami et al. (2019b), in her recent study, reported that the composers of Nike fish assemblages in Gorontalo Bay consist of four species (i.e. Sicyopterus pugnans Ogilvie-Grant 1884, Sicyopterus cynocephalus Valenciennes 1837, Bunaka gyrinoides Bleeker 1853, and Belobranchus segura Keith, Hadiaty and Lord 2012). Meanwhile, Nurjirana et al. (2019b) also found similar findings that Nike fish is composed of species in the Gobiidae and Eleotridae family. However, limited studies reported the diversity of similar fish assemblages in other aquatic areas. Nurjirana et al. (2019a) reported Penja fish in West Sulawesi consisting of six genera and nine species (i.e. Sicyopterus lagocephalus Pallas 1770, Sicyopterus longifilis, Stiphodon semoni Weber 1895, Stiphodon atropurpureus Herre 1927, Sicyopus zosterophorum Bleeker 1856, Smilosicyopus leprurus Sakai and Nakamura 1979, Schismatogobius sp., Eleotris fusca Forster 1801, and Eleotris sp.). Furthemore, Pangemanan et al. (2020) reported Nike fish in Tondano Lake to consist of six different melanophore patterns that belong to the same species Ophioleotris aporos. The popularity of Nike fish, which is much favored by the community and its high economic value, has a significant impact on the high level of fishing. However, scientific studies on these fish in bioecological, fishing, and economic are still limited. It is feared that limited information and uncontrolled fishing will reduce diversity if no rapid and appropriate management is carried out. As an initial step, research related to the morphometric and