Spotfin Mojarra, Eucinostomus argenteus
Spotfin Mojarra, Eucinostomus argenteus. Fish caught from coastal waters off Key Largo, Florida, November 2020. Length: 9.2 cm (3.6 inches). Catch, photograph, and identification courtesy of Josh Leisen (joshadventures.com), Gaylord, Michigan.
Spotfin Mojarra, Eucinostomus argenteus. Fish caught from coastal waters off Sugarloaf Key, Florida, June 2015. Length: 13.8 cm (5.4 inches). Catch and photograph courtesy of Dean Kimberly, Atlanta, Georgia. Note: This is a difficult fish to correctly identify. This identification should be considered 90% certain. A correct identification is only possible by an examination of the interhaemal cone that is uniquely shaped being formed from the first two anal pterygiophores that enclose the posterior end of the air bladder. This was not done with this specimen as it was returned to the ocean unharmed. The best alternative is the Tidewater Mojarra, Eucinostomus harengulus.
The Spotfin Mojarra, Eucinostomus argenteus, is a member of the Mojarra or Gerreidae Family, that is known in Mexico as mojarra plateada. Globally, there are eleven species in the genus Eucinostomus, all eleven are found in Mexican waters, seven in the Atlantic and four in the Pacific Ocean.
The Spotfin Mojarra has an elongated oval body with a depth that is 32% to 36% of standard length. They are silvery in color with some fish having a unique and very subtle mottling pattern of seven bars separated by six dark lateral spots on their sides. The tip of their dorsal fin is dusky. Their snout has a distinctive V-shaped pigmentation. Their head has a pointed snout, a concave lower profile, and a highly extensible mouth that points downward. Their anal fin has 3 spines and 8 rays; their caudal fin is deeply forked; and, their dorsal fin has 9 spines and 10 rays. They have 7 or 8 gill rakers on the lower arch. Their body is covered with large rough scales.
The Spotfin Mojarra is a schooling species that reside in coastal areas over soft bottoms in bays and shallow inshore areas at depths up to 60 m (197 feet). They are also known to enter freshwater with juveniles found in and around mangroves. They reach a maximum of 15.0 cm (5.9 inches) in length. They are benthic feeders consuming bivalves, crustaceans, and polychaete worms. The Spotfin Mojarra is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
The Spotfin Mojarra is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the Caribbean.
The Spotfin Mojarra is most likely confused with the Mottled Mojarra, Eucinostomus lefroyi (different mottling profile), the Silver Jenny, Eucinostomus gula (wider body depth, 38- 42%), the Slender Mojarra, Eucinostomus jonesii (narrower body depth, 30-32%), and the Tidewater Mojarra, Eucinostomus harengulus (different mottling profile).
From a conservation perspective the Spotfin Mojarra is currently considered to be of Least Concern with stable, widely distributed populations. They are caught commercially with gillnets, beach seines and trawls and are marketed fresh but are not in high demand. They are also processed into fish meal. They can be used as live bait for snappers, snook and tarpon.
NOTE. There are eighteen members of the Mojarra or Gerreidae Family currently Included in this website, ten are from Mexican waters of the Pacific and eight from the Atlantic. They are all very similar in appearance and difficult to identify. As an aide to this challenge I have assembled a Mojarra Body Depth Chart that presents these seventeen mojarras from thin bodied to deep bodied which is useful in identification work. In addition, I have also assembled a Mojarra Maximum Length Chart which I have also helpful in the identification work for these eighteen mojarras. Both charts can be found at the end of the Mojarra Family Page.