Pacific Herring, Clupea pallasii
Pacific Herring, Clupea pallasii. Fish caught from coastal waters off Seattle, Washington, July 2018. Length: 10 cm (3.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
Pacific Herring, Clupea pallasii. Fish caught from coastal waters off Newport Bay, Oregon, February 2018. Length: 22 cm (8.7 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon.
Pacific Herring, Clupea pallasii. Fish caught from coastal waters off Huntington Beach, California, January 2020. Length: 26 cm (10 inches). Catch courtesy of Robert King, Simi Valley, California. Photograph and identification courtesy of Chris Wheaton, Fullerton, California.
The Pacific Herring, Clupea pallasii, is a member of the Herring or Clupeidae Family, and is known in Mexico as arenque del Pacifico. Globally, there are three species in the genus Clupea, with only this species being found in Mexican waters of the Pacific Ocean.
The Pacific Herring has a fusiform compressed body. They are an olive to dark blue in color dorsally transitioning to silver ventrally. The mouth opens at the front with the lower jaw slightly projecting. Their anal fin has a short base and is well behind the dorsal fin has 13 to 20 rays; the caudal fin is deeply forked; their single dorsal fin is located mid-body and has 15 to 21 rays and is located slightly before mid-body. They have 65 gill rakers. They do not have a lateral line and their body is covered with large scales but they do not have scales on their heads.
The Pacific Herring is non-migratory and can be found in freshwater, brackish and marine environments at depths up to 475 m (1,560 feet). They reach a maximum length of 46 cm (18 inches). They are a coastal schooling species that form large schools of similar sized individuals. Mature adults migrate inshore to estuaries to breed. The juveniles remain in large schools in shore for one year and then move to deeper waters. Pacific Herrings are filter feeders that undergo daily vertical diel migrations moving to shallower waters at night for feeding and retreating to the depths for protection at night. The Juveniles consume phytoplankton with adults feeding on zooplankton, copepods and other small crustaceans, fish larvae and fish. In turn they are heavily preyed upon by humans, cod, dolphins, halibut, porpoises, seabirds, sea lions, seals, sharks, tuna and whales. Reproduction is oviparous and occurs in shallow water as a giant sex orgy with thousands of females depositing her eggs on the bottom. Each female may deposit up to 20,000 eggs. As eggs are being deposited, males are releasing milt, fertilizing the eggs. The eggs hatch within 10 days with both the eggs and the juveniles being subject to heavy predation. Only one juvenile per 10,000 eggs will mature into an adult. They have life spans of up to nineteen years. The Pacific 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.
The Pacific Herring is a straightforward identification due to its silvery color, fusiform streamlined body, deeply forked tail and the lack of markings. They are very similar to the Pacific Sardine, Sardinops sagax (prominent black spots on the sides; visible lateral line).
The Pacific Herring is a resident of Mexican waters of the Pacific Ocean and has a limited known range that extends from Guerrero Negro, Baja California, northward along the central and northwest coasts of Baja. With increasing water temperatures of late their populations have become limited in Mexican waters.
From a conservation perspective the Pacific Sardine is currently considered to be Data Deficient. They are widely distributed throughout the southern Arctic and northern Pacific oceans and accurate population assessments have been difficult to obtain and they are subject extreme overfishing. They have been taken in industrial trawl fisheries since the early 1900s and are also caught in small quantities to by-catch in trawl, seine and longline industrial fisheries that target other species. They have experienced catastrophic declines, possibly caused by heavy industrial exploitation during the early 20th century and are believed to be strongly affected by changes in food availability and climatic changes. They are currently caught commercially at a level of 300,000 tons per year. They are heavily regulated in some parts of their range. Due to global water and increasing water temperatures they are moving northward and their populations are becoming more concentrated. Their roe is considered a delicacy in Asia. They are also utilized fresh, frozen, canned, dried or salted, and smoked and baked, broiled or pan-fried. They are also utilized as a live bait fish. Their use in fish oil and fish meal has been discontinued.