Gerres oblongus Cuvier, 1830
Slender silver-biddy
photo by Randall, J.E.

Family:  Gerreidae (Mojarras)
Max. size:  30 cm SL (male/unsexed)
Environment:  reef-associated; depth range 0 - 50 m
Distribution:  Indo-Pacific: Red Sea and East Africa to Samoa and Tonga, north to the Ryukyu Islands, south to New Caledonia.
Diagnosis:  Dorsal spines (total): 9-9; Dorsal soft rays (total): 10-10; Anal spines: 3-3; Anal soft rays: 7-7. Scales between 5th dorsal fin spine base and lateral line, 4-4.5. Upper jaw extending almost to the level of anterior margin of dermal eye opening. Second dorsal fin spine longest, 19-26% of SL (mean 23%). Caudal fin dusky (rarely with dark distal margin); lower edge of lower caudal fin hyaline. Dusky stripes absent or very indistinct along scale rows above lateral line (sometimes 4-9 slightly oblique dusky bands in specimens less than about 10 cm SL); 4-9 slightly oblique dusky bands or columns of ovoid dark spots (rarely brownish) immediately below lateral line, but more obvious in preserved or stressed live specimens (Ref. 41108). Adult body plain silver; may have faint dusky bars especially juveniles. Body elongate, depth max 2.8-3.3 in SL. Preopercle lower flange scaleless. Caudal fin forked deeply and with long lobes; pectoral fins do not reach beyond level of anus. (Ref. 90102)
Biology:  Prefers coralline areas (Ref. 30573). Migrates to specific sandy areas near outer reef edge to spawn in late afternoons during full moon. Feeds on small benthic organisms living on sandy bottoms (Ref. 3409, 48635). In Palau, migrates to specific sandy spots near the outer reef edge to spawn in late afternoons around full moon (Ref. 37816). Forms schools. Feeds on small invertebrates found in the sand. Marketed fresh (Ref. 12915).
IUCN Red List Status: Least Concern (LC); Date assessed: 02 March 2015 Ref. (120744)
Threat to humans:  harmless
Country info:   
 

Entered by: Capuli, Estelita Emily - 12.06.92
Modified by: Valdestamon, Roxanne Rei - 15.05.15

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