The herring family is an ancient, successful, and highly productive one, and for centuries was the animal food on which much of northern Europe subsisted. Its various species school throughout the world’s oceans in large, easily netted numbers and are relatively small, often just a few inches long but sometimes reaching 16 in/40 cm and 1.5 lb/0.75 kg.
Members of the herring family feed by constantly swimming and straining tiny zooplankton from the seawater. They thus have very active muscle and digestive enzymes that can soften their flesh and generate strong flavors soon after they’re harvested. Their high fat content, upwards of 20% as they approach spawning, also makes them vulnerable to the off-flavors of easily oxidized polyunsaturated fats. Thanks to this fragility most of these fish are preserved by smoking, salting, or canning.