Flatiron Herring, Harengula thrissina
The Flatiron Herring, Harengula thrissina, whose common Spanish name is sardina plumilla, is a member of the Herring or Clupeidia Family known collectively as sardinas in Mexico. There are only four global members of the Harengula Genus with all four found in Mexican waters, three in the Atlantic and one in the Pacific.
The Flatiron Herrings are moderately deep bodies that have a depth of 27 to 31% of standard length. They have iridescent blue backs and silvery sides. There is a faint yellow stripe on the upper sides and a black spot behind the gill cover. The mouths open at the front and the lower jaw is stlightly projecting. They have 28 to 34 gill rakers. The anal fin base is short and the anal fin has 15 to 17 rays, with its origin well behind the dorsal fin; the caudal fin is deeply forked; the dorsal fin is mid-body with 17 or 18 rays; the pectoral fins reach the dorsal origin; and, the pelvic fins are directly under the dorsal fin..
The Flatiron Herring reach a maximum of 18 cm (7.3 inches) in length and are virtually weightless. They are a pelagic coastal schooling species that form very large schools and they are found near and within protective rock cover on the surface in the surf zone to depths of 7 meters (25 feet). The Flatiron Herring is found in Mexican waters along the Pacific side of the Baja south of Guerrero Negro, throughout the Sea of Cortez and along the coast of the mainland south to Guatemala.
The Flatiron Herring cannot be easily confused with any other sardine or herring due to its “wide body” and lack of elongated dorsal fin rays.
Note: this species is routinely referred to incorrectly as a “sardina” or “sardine” and this small beast is THE mainstay of the live bait industry in the Los Cabos area and as a rule of thumb if you have Sardines in your Panga you will have a highly productive day and if you don’t you won’t! Having said that the virtually disappeared from the greater Los Cabos area from 2011 to 2015 but seem now to be making a small comeback.