Irish Pompano, Diapterus auratus
The Irish Pompano, Diapterus auratus, whose common Spanish name is mojarra guacha, is a species in the Mojarra or Gerreidae Family, known collectively as mojarras in Mexico. This fish is also known as the Irish Mojarra. There are only four global members in the genus Diapterus, all four found in Mexican waters, two in the Atlantic and two in the Pacific. Its common name of “Pompano” is simply weird, but fortunately it is also known as the Irish Mojarra!
The Irish Pompanos have rhomboidal deep compressed bodies with a depth that is 43 to 47% of standard length. They are uniformly silvery olive in color. Their dorsal fin has a thin black margin and their anal and pelvic fins are yellow. Juveniles have three vertical bars on their sides. Their head has a pointed snout and their lower head profile is significantly concave. Their mouth is extensible and points downward when extended. The margin of their gill cover is serrated. They have 12 to 15 gill rakers on their lower arch. Their anal fin has three spines, the second being thick and longer than the third, and eight rays. Their caudal fin is deeply forked. Their dorsal fin is high on the body with nine spines and ten rays; the second spine is the longest. Their pectoral fins are long and reach past the anal fin origin. Their lateral line is prominent and slightly curved on the front of the body. Their head and body are covered with rough scales.
The Irish Pompanos form schooling species that reside in shallow coastal areas including protected sandy bays, seagrass meadows, lagoons, and freshwater estuaries at depths up to 100 feet. They reach a maximum length of 34 cm (13 inches). They feed on plant materials, copepods, nematodes, ostracods, and other small invertebrates.
In Mexican waters the Irish Pompano are found in all waters of the Atlantic.
The Irish Pompano can be easily confused with a series of other Mojarras noting that they differ in head profiles, gill raker counts, body depths, gill cover serration, and second anal spine thickness. These include the Brazilian Mojarra, Eugerres brasilianus and the Rhombic Mojarra, Diapterus rhombeus (different gill raker counts), the Maracaibo Mojarra, Eugerres awlae (very long second anal fin spine), and the Striped Mojarra, Eugerres plumieri (concave upper head profile).
The Irish Pompanos are very abundant and a major focus of commercial fishermen utilizing cast nets, beach and boat seines, gill nets, trammel nets, beam trawls and traps. In the State of Florida for example, they are sold at a level of 100,000 kg per annum. They are normally sold fresh and whole.
Irish Pompano, Diapterus auratus. Commercial fish courtesy of Soriana’s Mercado, Cabo San Lucas, Baja California Sur, March 2015. Length: 21 cm (8.3 inches). Sold as “Mojarra.” Fish identification courtesy of H.J. Walker, Jr., Scripps Institute of Oceangraphy, La Jolla, CA.