Common Name
Alvarez's Silverside
Year Described
Diaz-Pardo, 1972
Identification
Dorsal Fin: IV; I, 12
Anal Fin: I, 18-24
Pectoral Fin: 12-14
Lateral Line Scales: 35-41
Predorsal Scales:
Circumferential Scales: 18-23
Transverse Scale Rows: 7
Gill Rakers: 20-29 (lower arch)
Vertebrae:
Body elongate, flat dorsally, and compressed laterally, with two dorsal fins. Eye large. Mouth terminal, strongly oblique, and does not reach the orbit. Premaxilla protractile. Distal end of premaxilla expanded. Premaxilla lacks postmaxillary process. Teeth in both jaws. Mesopyerygoid teeth absent. Rostral sensory system present. Anterior portion of sensory system consists of a pair of L-shaped furrows fused medially. Dorsal fins well separated. *Spinous dorsal fin origin behind anal fin origin. Anal fin long. Sheath present on basal half of anal fin. Pelvic fin origin well behind pectoral fin base. Axillary scale present (>half pelvic length). Pectoral fin large and high on body. Caudal fin forked. Scales cycloid.
Color
Body translucent with a yellow to greenish dorsum. A cross-hatched pattern of dark melanophores on the dorsum. Lateral band silvery with darker borders and dark melanophores. Dorsal and caudal fins yellowish.
Size
Maximum size to 80mm SL.
Habitat
Mostly found in freshwater rivers but also in brackish river mouths.
Range
Endemic to coastal drainages of the Bay of Campeche, Mexico.
References
Chernoff, B. 2002. Atherinopsidae (pp 1090-1103). In: Carpenter. 2002. The living marine resources of the Western Central Atlantic. Vol. 2: Bony fishes part 1 (Acipenseridae-Grammatidae). FAO Species Identification Guides for Fisheries Purposes. American Society of Ichthyologists and Herpetologists Special Publication No. 5.