Species Description: Eucinostomus argenteus is a member of the family Gerreidae. The Eucinostomus genus is distinguished from other members of the family Gerreidae by the interhaemal cone, an unusual cone-shaped structure formed from the first two anal pterygiophores that encloses the posterior end of the air bladder (Matheson and McEachran 1984).
The spotfin mojarra is a small to medium sized fish with a compressed body and protrusible mouth. The body depth is 32.3 to 38.5% of the standard length. It is a silvery fish that is heavily pigmented with a uniform pattern of 7 dorsal bars separated by 6 dark lateral spots. The snout has distinct V-shape pigmentation and the dorsal fin is clear with fine speckling (Matheson and McEachran 1984).
Regional Occurrence: Eucinostomus argenteus occurs seasonally in Chesapeake Bay and other estuaries south to Florida (Kerschner et. al. 1985), to Brazil (Godefroid et al. 2001), the Bahamas, West Indies and the Gulf of Mexico.
IRL Distribution: The spotfin mojarra is common in the Indian River Lagoon during the warmer months and usually found in or around inlet areas (Kerschner et. al. 1985). Schools of juveniles as opposed to adults are encountered more frequently in seagrass beds.
Age, Size, Lifespan: Individuals in the Indian River Lagoon range in size from 10 to 104 mm (Kerschner et. al. 1985). The maximum length of Eucinostomus argenteus is reported to be 150 mm.
Abundance: Eucinostomus argenteus is an abundant, schooling fish that often dominates the transient (seasonal visitors) species in subtropic and tropic estuaries (Stoner 1986). In the Indian River Lagoon, schools of the spotfin mojarra are recorded to make up 11% of the catch in the family Gerreidae (Kerschner et. al. 1985). In a Brazilian estuary at Pontal do Sul, Paraná, E. argenteus makes up 78% of the larval and juvenile catch (Godefroid et al. 2001).
Reproduction: The spawning season of Eucinostomus argenteus occurs during the warmer months of December to June in Brazilian waters (Godefroid et al. 2001).
Embryology: Larval forms and juveniles of the spotfin mojarra are found from December to June in water temperatures of 16-29°C and salinities ranging from 19-34 ppt (Godefroid et al. 2001).
Trophic Mode: Eucinostomus argenteus is a benthic feeder using its highly protrusible mouth to forage for infaunal invertebrates. It feeds primarily on bivalves, polychaetes, and crustaceans (Kerschner et al. 1985, Bronco et al. 1997).
Fishery: Used as live bait in the snapper fishery.
Bayly IAE. 1972. Salinity tolerance and osmotic behavior of animals in athalassic saline and marine hypersaline waters. Annual Review of Ecology and Systematics 3:233-268.
Blaylock RA. 1993. Distribution and abundance of the cownose ray, Rhinoptera bonasus, in lower Chesapeake Bay. Estuaries 16:255-263.
Bronco CW, Aguiaro CT, Esteves FA, and EP Caramaschi. 1997. Food sources of the teleost Eucinostomus argenteus in two coastal lagoons of Brazil. Studies on Neotropical Fauna and Environment 32:33-40.
Godefroid RS, Santos C, Hofstaetter M, and HL Spach. 2001. Occurrence of larvae and juveniles of Eucinostomus argeneus, Eucinostomus gula, Menticirrhus americanus, Menticirrhus littoralis, Umbrina coroides and Micropogonias furnieri at Pontal do Sul beach, Paraná. Brazilian Archives of Biology and Technology 44:411-418.
ITIS. Integrated Taxonomic Information System. Available online.
Kerschner BA, Peterson MS, and RG GIlmore, Jr. 1985. Ecotopic and ontogenetic trophic variation in mojarras. Estuaries 8:311-322.
Matheson RE, Jr. and JD McEachran. 1984. Taxonomic studies of the Eucinostomus argenteus complex (Pisces: Gerreidae): preliminary studies of external morphology. Copeia 4:893-902.
Rookery Bay Field Guide. PDF document available online.
Stoner AW. 1986. Community structure of the demersal fish species of Laguna Joyuda, Puerto Rico. Estuaries 9:142-152.