Ambassis vachellii Richardson, 1846

Zainal Abidin, Danial Hariz, Lavoué, Sébastien, Mohd Abu Hassan Alshari, Norli Fauzani, Mohd. Nor, Siti Azizah, A. Rahim, Masazurah & Mohammed Akib, Noor Adelyna, 2021, Ichthyofauna of Sungai Merbok Mangrove Forest Reserve, northwest Peninsular Malaysia, and its adjacent marine waters, Check List 17 (2), pp. 601-631 : 622-623

Ambassis vachellii Richardson, 1846

Material examined. MALAYSIA • 3, 59– 67 mm TL; Kedah State, Kuala Kedah, Kuala Muda Whispering Market ; 05.578°N, 100.341°E; 6 Dec. 2018; Danial H. Zainal Abidin, Norli F.M.A.H. Alshari leg.; USMFC (30) 00002 . • 5, 59– 64 mm TL; Kedah State, Kampung Batu Lintang, Pompang Batu Lintang ; 05.624°N, 100.395°E; 19 Apr. 2019; Danial H. Zainal Abidin, Norli F.M.A.H. Alshari leg.; USMFC (30) 00003 .

Identification. Small species of Ambassis (maximum TL about 8 cm); body elongated oval-shaped, laterally compressed; mouth terminal; interrupted lateral line; eye diameter larger than snout length; supraorbital spines 4 or 5; nasal spine present and well developed; posterior margin of preopercle serrated; single dorsal fin deeply notched; dorsal fin spines 7; anal fin spines 3; caudal fin deeply forked; body uniformly pale yellowish with scattered melanophores; fins mostly translucent, first 2 or 3 dorsal fin spines blackish.

Tentatively identified as Ambassis vachellii using the identification key of Allen (1999). However, the tax- onomy of small species of Ambassis having more than one supraorbital spine needs revision. Ambassis vachellii can easily be distinguished from the two other species of Ambassidae occurring in Merbok river estuary by the unique combination of two characters: interrupted lateral line and 4 or 5 supraorbital spines. Ambassis vachellii is a typical brackish species and the most common species of Ambassidae in the Merbok river estuary and in other brackish environments in this region (e.g., Tongnunui et al. 2002). Its exact distribution in the Indo-West Pacific region is still unknown.