Silver Jenny

Silver Jenny, Eucinostomus gula

The Silver Jenny, Eucinostomus gula, whose common Spanish name is mojarra española, is a species in the Mojarra or Gerreidae Family, known collectively as mojarras in Mexico. Globally, there are 11 species in the genus Eucinostomus, all of which are found in Mexican waters with seven in the Atlantic and four in the Pacific.

The Silver Jennies have oval, compressed, and fusiform bodies with a depth that is 38% to 42% of standard length; they have the deepest body of any of the Mojarras. They are silvery with light pigmentation on their snout. Their head has as strongly concave lower profile, a pointed snout, and a highly extensible mouth that points downward. Their anal fin has three spines, the second of which is the longest, and seven rays; their caudal fin is deeply forked; and their dorsal fin has nine spines and ten rays. They have seven or eight lower gill rakers. Their body is covered with large rough scales.

The Silver Jennies are an abundant schooling species found seasonally in shallow coastal waters over muddy bottoms in mangrove-lined lagoons and creeks at depths up to 175 feet and in waters between 11oC (52oF) and 28oC (82oF). Juveniles are found in seagrass beds. They may also enter freshwater. They reach a maximum length of 23.0 cm (9.1 inches). They are known to make seasonal migrations to warmer offshore waters during cooler months for wintering and hibernation and return to coastal waters in the spring for breeding. They are benthic feeders that probe the bottom with their protrusible mouth and consume bivalves, crustaceans, ostracods, and detritus. They are a poorly studied species and very limited information is available about their behavioral patterns.

In Mexican waters the Silver Jennies are found in all waters of the Atlantic. They are very abundant on a seasonal basis within the Ria Lagartos National Wildlife Refuge on the northern tip of the Yucatán Peninsula.

The Silver Jenny is fairly similar to a series of other mojarras including the Mottled Mojarra, Eucinostomus lefroyi, the Slender Mojarra, Eucinostomus jonesii, the Spotfin Mojarra, Eucinostomus argenteus, and the Tidewater Mojarra, Eucinostomus harengulus, but these all have significantly thinner bodies. The Yellowfin Mojarra, Gerres cinereus has a similar body depth but has seven or eight dark bars on its sides.

The Silver Jennies are generally too small to be of interest to most. They are marketed fresh in some South American countries but are not in high demand. They are used on a limited basis as live bait. From a conservation perspective, they are considered of Least Concern with stable and widely distributed populations, however, the loss of estuaries and seagrass beds from coastal environments is of concern in the long-term.

Silver Jenny, Eucinostomus gula. Fish caught from coastal waters off the Silver Palm Park, Boca Raton, Florida, January 2017. Length: 16.5 cm (6.5 inches). Catch, photo, and identification courtesy of George Brinkman, Guelph, Ontario, Canada.