First record of slender red scad, Decapterus smithvanizi (Actinopterygii: Perciformes: Carangidae), from the Philippines

Ten specimens (187.3–226.9 mm standard length) of slender red scad, Decapterus smithvanizi Kimura, Katahira et Kuriiwa, 2013, previously reported from the Andaman Sea, South China Sea, Taiwan, Japan, Thailand, Indonesia, Myanmar, and Pakistan, were collected off Iloilo (Panay Island), the Philippines. The presently reported specimens represent the first record of the species from the Philippines. A detailed description of the specimens is provided, with a comparison to other commonly-caught species of red-fin Decapterus in the area.


Introduction
The carangid genus Decapterus Bleeker, 1851, currently including 11 valid species (Kimura et al. 2013;Fricke et al. 2021), is characterized by having a single finlet behind both the second dorsal and anal fins, absence of scutes on the anterior curved part of the lateral line, two low papillae on the shoulder girdle, and well-developed adipose eyelid (Gushiken 1983;Smith-Vaniz 1999). In 2013, Kimura et al. grouped the Decapterus species with red fins and identified Decapterus smithvanizi as a new species. Four species have been included in the group: was visited in February-May 2020 and additional specimens of D. smithvanizi were obtained. The specimens of D. smithvanizi, used in this study, represent the first records of the species from the Philippines with complete examination and description. This report completes the presence of all red-fin Decapterus in the country.

Materials and methods
Counts and measurements followed Hubbs and Lagler (1947) and Kimura et al. (2013) with additional measurement, from the snout to the central posterior tip of the sideways "W-shaped" margin at the dorsal head. Measurements were made to the nearest 0.1 mm with a digital caliper (≤180 mm) and a manual caliper (˃180 mm). Standard and head lengths are abbreviated as SL and HL, respectively. Curatorial procedures followed Motomura and Ishikawa (2013). Counts of lateral-line scales and scutes followed Kimura et al. (2013) and are defined according to Smith-Vaniz and Carpenter (2007). Characters, such as gill raker, lateral line scale, and scutes, were counted under a dissecting microscope. Identification of specimens followed Kimura et al. (2013). The specimens examined in this study are deposited at the University of the Philippines Visayas Museum of Natural Sciences, Iloilo, Philippines (UPVMI). Kimura Description. Body elongate, compressed, and comparatively slender, deepest between first dorsal and second dorsal fin. Dorsal and ventral profile body slightly convex from tip of snout to caudal-fin base. Mouth terminal, large; posterior tip of maxilla reaching vertical through anterior margin of eye; posterior tip of upper jaw not hooked. Interorbital space slightly convex, with scales. Predorsal scaly area extending to anterior margin of eye. Upper end of pectoral-fin base anterior to vertical through opercular margin; lower end of pectoral-fin base vertical through pelvic-fin origin. Pectoral fin asymmetrical, its posterior tip pointed, reaching beyond vertical through second dorsal-fin origin. Pelvic-fin origin anterior to vertical through dorsal-fin origin. First dorsal fin higher than second; single finlet present both dorsally and ventrally on caudal peduncle. Caudal fin forked; covered with small scales. Body scales small and ctenoid. Lateral line extends downwards from origin of second dorsal fin; running straight from middle of second dorsal fin to caudal-fin base; curved part longer than straight part, covered with ctenoid scales and scutes at posteriormost area; straight lateral line covered with scutes reaching beyond hypural bone. Head covered with scales, except snout area, mandible and anteroventral region of head; posteriormost end of scaly head region anterior to vertical through opercular margin; adipose eyelid developed. Teeth on jaws minute, two rows on upper jaw and single row on lower jaw. Lower jaw slightly protruding. Gill rakers slender, covered with spinules at inner surface.

Decapterus smithvanizi
Color when fresh. Head and body bluish to pale black dorsally, pale white to silvery ventrolaterally; black blotch present on upper edge of opercle; both margins of dorsal, caudal, and pectoral fins and finlet red with fine melanophores; anal fin, pelvic fins and ventral finlet pinkish to white with fine melanophores (Fig. 1A).
Color when preserved. Head and body greyish to brownish dorsolaterally, pale white ventrolaterally; black blotch present on upper edge of opercle; both margins of dorsal, caudal, and pectoral fins and finlet brownish to dirty white with fine melanophores; anal fin, pelvic fins, and ventral finlet brownish to white with fine melanophores ( Fig. 2A-C).
Distribution. Decapterus smithvanizi is distributed in the Andaman Sea, South China Sea, Indonesia, and the western coast of Thailand (Kimura et al. 2013), Taiwan (Smith-Vaniz et al. 2018b), Japan (Iwatsubo et al. 2016;Hata and Motomura 2017), Myanmar (Psomadakis et al. 2020), and Pakistan (Psomadakis et al. 2015). Specimens were collected off Iloilo Province (Panay Island), Philippines. The specimens, used in this study, represent the first record from the Philippines.

Discussion
Decapterus smithvanizi can be distinguished from other red-fin Decapterus by the following combination of characters; lower gill rakers 25-31, curved part of lateral line with 54-62 cycloid scales, body depth 19.4%-22.5% SL, pectoral-fin beyond the level of second dorsal-fin (Kimura et al. 2013). The presently reported specimens were identified as D. smithvanizi agreeing closely with the description of the species given by Kimura et al. (2013). Four species of Decapterus with red caudal fins were grouped by Kimura et al. (2013) Kimura et al. 2013) and D. tabl (Narido et al. 2016;Kimura 2017;Motomura et al. 2017). Decapterus smithvanizi, a newly-described species, is previously known from Thailand, Indonesia, Andaman Sea (Kimura et al. 2013), South China Sea, Taiwan (Smith-Vaniz et al. 2018b), Myanmar (Psomadakis et al. 2020) and Pakistan (Psomadakis et al. 2015). The report of D. smithvanizi in Iloilo Province confirmed its presence in the Philippines and completed all red-fin Decapterus in the country.
Red-fin Decapterus species are similar to each other. It was observed that D. smithvanizi are commonly caught with other species of red-fin Decapterus in Iloilo. Other than the description given by Kimura et al. (2013), it was observed that this species has more melanophores at its dorsal, anal, and pelvic fins compared to other species. Further examination of the specimens showed that their body scales extend on to the head dorsally, forming a sideways "W-shaped" margin in dorsal view. The distance was taken from the snout to the central posterior tip of the margin and showed that D. kurroides has a longer tip compared to D. tabl and D. smithvanizi. These diagnostics characters can help to identify and differentiate the species from each other, which is necessary for effective conservation and management of this group.