Round Herring, Etrumeus acuminatus
The Round Herring, Etrumeus acuminatus, whose common Spanish name is sardine japonesa, is a member of the Herring or Clupeidia Family known collectively as sardinas in Mexico. This fish is also known as the Eastern Round Herring and the Pacific Round Herring. There are only five global members of the genus Etrumeus, two of which are found in Mexican waters, one in the Atlantic and one in the Pacific.
The Round Herrings have slender elongated rounded fusiform bodies with a depth that is 18 to 23% of standard length. They are blue dorsally and silvery on the rest of their body. Upon collection their color changes rapidly to a deep blue-black and their scales become highly visible. They have a small mouth that opens at the front. Their anal fin has a short base with 10 to 13 rays and its origin is well behind the dorsal fin. Their dorsal fin is located mid-body and has 18 rays. Their pectoral fins have 15 to 17 rays and their pelvic fins are behind the dorsal fin. They have 41 to 46 gill rakers.
The Round Herrings are a pelagic schooling species found over all types of terrain at depths up to 200 meters (655 feet). They reach a maximum length of 31 cm (12 inches). The Round Herrings are a poorly studies and very little is known about their behavioral patterns.
In Mexican waters the Round Herring have a limited range in being found along both coasts of Baja and along the west coast of the mainland south to Guaymas.
The Round Herring is most likely confused with the Pacific Sardine, Sardinops sagax (series of black dots along sides; compressed body) and the Pacific Chub Mackerel, Scomber japonicus (patterned back).
The Round Herrings are a by-catch of the Pacific Chub Mackerel, a targeted baitfish in the greater Los Cabos area, during cold water episodes and are caught by the thousands from December to February utilizing Sabiki rigs (known locally as “Lucky Joe rigs”) off the bottom in deep water over sandy terrain. They do not survive baits well and thus are of diminished value but can be kept frozen and used year round as a slow-trolled dead decoy to attract large surface fish, being a favorite of Dorados, or sent down deep with a bottom rig attached to a 7/0 hook and a cut on each side to expose their meat. They can also be utilized as “cut bait”.