Morphometric identification of Tylosurus acus imperialis in the North Aegean Sea

• Main Authors: George Minos, Anastasia Imsiridou, Lambros Kokokiris
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2015-11-01
• Series: Frontiers in Marine Science
• Subjects: Thermaikos Gulf; Morphometric analysis; Aegean Sea; Needlefish; Tylosurus
• Online Access: http://journal.frontiersin.org/Journal/10.3389/conf.fmars.2015.03.00055/full

Increasing numbers of Tylosurus needlefishes together with common Belone needlefishes appeared in Thermaikos Gulf (North Aegean Sea, Greece) from 2012 to 2014, especially from May to August. The Tylosurus individuals were identified because of the absence of gill rakers and the presence of black thin lateral keel on caudal peduncle. From June 2013 to July 2014, 112 specimens of Tylosurus needlefishes were collected from commercial fisheries and a detailed morphometric and meristic analysis was applied for species identification. Measurements were recorded on each specimen, for six distance characters (TL, SL, FL, BL, HL, MBH). The length of fins (pectoral, ventral, dorsal, anal) was measured, various proportions between body and fin length were estimated and the number of fin rays was counted. Total length (TL) ranged from 59.3 to 111.6 cm. The soft rays in ventral fins were 6, in dorsal fin were 23-26 (mainly 24 with 53%) and in anal fin were 21-23 (mainly 22 with 51%). Body length to head length (BL/HL) ranged from 2 to 2.82, BL to pectoral fins length (BL/P) ranged from 8.3 to 10.8, BL to ventral fins length (BL/V) ranged from 10.9 to 17.7, BL to anterior dorsal fin lobe height (BL/D) ranged from 10.5 to 15.3 and BL to anterior anal fin lobe height (BL/A) ranged from 9.3 to 14.3. The anal fin lobe ranged from 4.9 to 7.4% of standard length. Moreover, the specimens had greater size in length, greater values in morphometrics (i.e. BL/P etc) and higher values in meristics than those reported for the congeneric species Tylosurus choram (Rüppell, 1837) and Tylosurus crocοdilus (Péron & Lesueur, 1821). The resulted diagnostic features are in accordance to the literature for the systematics of Tylosurus acus imperialis (Rafinesque, 1810). Thus, specimens were identified as T. acus imperialis confirming its occurrence in Thermaikos Gulf waters appearing the northern geographic expansion in the Aegean Sea.