Round Herring, Etrumeus acuminatus

Round Herring, Etrumeus acuminatus. Fish caught out of the surf by hand with a large flock of birds above. Length: 22 cm (8.5 inches).  A hand collection off the beach as it was one of several that had been chased ashore by underwater predators and then attached from above by Cormorants, Pelicans and Seagulls. “Catch” and photo taken Bahía Santa Rosalillita, Baja California, August 2019. Identification and photo courtesy of Barry Mastro, Escondido, California.

Round Herring, Etrumeus acuminatus. Fish caught from coastal waters off Point Palmilla, Baja California Sur, February 2004. Length: 25 cm (10 inches).

Round Herring, Etrumeus acuminatus. Fish caught from coastal waters off Puerto Peñasco, Sonora, November 2020. Length: 25 cm (10 inches). Catch, photograph and identification courtesy of Chris Moore, Peoria, Arizona.

The Round Herring, Etrumeus acuminatus, that is also known as the Eastern Round Herring and the Pacific Round Herring and in Mexico as sardine japonesa, is a member of the Herring or Clupeidia Family of herrings and shad. There are five global members of the genus Etrumeus, of which two are found in Mexican waters, one in the Atlantic and one in the Pacific Ocean.

The Round Herring has a slender elongated rounded fusiform body 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 and its origin is well behind the dorsal fin with 10 to 13 rays; 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. They are covered with scales.

The Round Herring is a pelagic schooling species found over all types of terrain at depths up to 200 m (655 feet). They reach a maximum of 31 cm (12 inches) in length. The Round Herring 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.

In Mexican waters the Round Herring is a resident of the Pacific but has a limited range and is found along both coasts of Baja and along the west coast of the mainland south to Guaymas, Sonora.

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).

From a conservation perspective the Round Herring is currently considered to be of Least Concern with stable, widely distributed populations. They are a by-catch of the Pacific Chub Mackerel fishery, 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 a quality “cut bait”.