Pacific Herring

Pacific herring have a bluish-green back and silver-white sides and bellies; they are otherwise unmarked. The silvery color derives from guanine crystals embedded in their laterals, leading to an effective camouflage phenomenon. There is a single dorsal fin located mid-body and a deeply forked tail-fin. Their bodies are compressed laterally, and ventral scales protrude in a somewhat serrated fashion. Unlike other genus members, they have no scales on heads or gills; moreover, their scales are large and easy to extract. This species of fish may attain a length of 45 centimetres (18 in) in exceptional cases and weigh up to 550 grams (19 oz), but a typical adult size is closer to 33 centimetres (13 in). The fish interior is quite bony with oily flesh.

Pacific herring prefer spawning locations in sheltered bays and estuaries. Along the American Pacific Coast, some of the principal areas are San Francisco Bay, Richardson Bay, Tomales Bay and Humboldt Bay. Adult males and females make their way from the open ocean to bays and coves around November or December, although in the far north of the range, these dates may be somewhat later. Conditions that trigger spawning are not altogether clear, but after spending weeks congregating in the deeper channels, both males and females will begin to enter shallower inter-tidal or sub-tidal waters. Submerged vegetation, especially eelgrass, is a preferred substrate for oviposition. A single female may lay as many as 20,000 eggs in one spawn following ventral contact with submerged substrates.

Pacific herring fisheries (fishing grounds) had been sustainably exploited by indigenous people for millennia, not only on the Pacific Coasts of North America, but in Japan and the Russian Far East. In all these cases, industrial fishing for herring oil and fertilizer has encroached or seized these fishing areas, leading to collapses in the fish stock.

The Ainu of Ezo (now Hokkaido) caught herring using basic dip nets (hand nets), but Japanese fishermen during the late Edo Period into Meiji Era began to operate increasingly large-scaled capture of herring in these grounds, first using gillnets and later "pound nets" (or traps). Intensive fishing resulted in the so-called "Million-Ton Era" of the late nineteenth century onward. Herring fishery near Hokkaido collapsed in the late 1950s.