Herring

Herring are many species of forage fish in the order Clupeiformes. This article is about the fish itself. For their use as food, see Herring as food. For other uses, see Herring (disambiguation).

Herring often swim in large schools near fishing banks and close to the coast. They live mostly in shallow, mild waters of the North Pacific and North Atlantic Oceans, including the Baltic Sea, and also off the west coast of South America. Fish called herring are also found in the Arabian Sea, Indian Ocean, and Bay of Bengal.

Three species of Clupea (the type genus of the herring family Clupeidae) are recognised. Together they make up about 90% of all herrings caught by fishing. The most common is the Atlantic herring, which makes up over half of all herring caught. The FAO has reported worldwide commercial catches of herring from 1950 to 2010.

Herring were very important to the history of sea fishing in Europe. Early in the 20th century, studying them helped build the foundations of fisheries science.

These oily fish have a long history as an important food fish. They are often salted, smoked, or pickled. In the United Kingdom, herring were also known as "silver darlings."

Species

Many different kinds of fish are commonly called herrings. Most of them belong to the family Clupeidae. The origin of the word "herring" is not completely clear. It may come from the same source as the Old High German heri, which means "host, multitude." This fits, because herrings swim in large groups.

The type genus of the herring family is Clupea. It has only two species. The Atlantic herring is the type species, and it lives in the North Atlantic. The Pacific herring lives mainly in the North Pacific. Scientists have suggested smaller groupings within both species, but it is still unclear what these groupings are based on.

Other fish in the Clupeidae family are also commonly called herrings. The table below lists those that FishBase counts as herrings and that have been checked by the International Union for Conservation of Nature.

Some other fish are also called herrings. They may be related to clupeids, or they may just share some features with herrings. One example is the lake herring, which is a salmonid. The name a fish gets can depend on the place, so a fish called a herring in one area may have a different name somewhere else. Some examples:

Characteristics

Herrings belong to a larger group of fish called Clupeidae. This family includes herrings, shads, sardines, and menhadens. There are about 200 species in this family, and they share many similar features. These silvery fish have a single dorsal fin on their back. This fin is soft, without spines. They have no lateral line, and their lower jaw sticks out a little.

The size of herring depends on the type. The Baltic herring is small, about 14 to 18 cm (5.5 to 7 inches) long. The Atlantic herring can grow to about 46 cm (18 in) long and weigh up to 700 g (1.5 lb). Pacific herring grow to about 38 cm (15 in) long.

Life cycle

At least one group of Atlantic herring spawns every month of the year. Each group spawns at a different time and place, so there are spring, summer, autumn, and winter herrings. Greenland herring spawn in shallow water, 0 to 5 metres (0 to 16 feet) deep. North Sea herring spawn as deep as 200 m (660 ft) in autumn. Females lay about 20,000 to 40,000 eggs, usually about 30,000. They lay them on the sea bed, rock, stones, gravel, sand, or beds of algae. The eggs stick to these surfaces. If the layers are too thick, the eggs do not get enough oxygen and often die, tangled in mucus. The eggs need moving water, usually from wave action or coastal currents. They survive best in sheltered spots, because hungry animals eat eggs that are out in the open. Eggs die in water warmer than 19 °C (66 °F).

The young hatch as tiny larvae, 5 to 6 mm long. Only their eyes have much colour. Their bodies are almost see-through, and over time they grow fins and a forked tail. Herring larvae are very slender. Most other young fish can be told apart from them by the position of the vent near the base of the tail. Telling herring from sprats and other clupeoids when they are very young takes careful study. At one year old, herring are about 10 cm (4 in) long. They first spawn at three years old. In young herring, the otoliths, gut, silvery swimbladder, and heart can be seen through the body. Young larvae that still have their yolk attached can attack a copepod.

Ecology

See also: Hunting copepods

Herring eat tiny sea animals in the open water. These include copepods, arrow worms, pelagic amphipods, mysids, and krill. Herring are also an important food for larger sea animals. During the day, herring usually stay in deep water. At night, they feed near the surface, where predators are less likely to see them. Copepods are their most common food. Young herring often catch copepods one at a time. Adults also catch larger prey, like krill. When copepods gather in large numbers, herring swim with their mouths wide open and catch many at once. Copepods can jump away when they sense a fish coming. Because of this, herring swim in a spaced pattern that matches how far their prey can jump.

See also: Predator avoidance in schooling fish and Bait ball

Many animals hunt herring. These include seabirds, marine mammals such as dolphins, porpoises, whales, seals, and sea lions. Predatory fish also eat herring, including sharks, billfish, tuna, salmon, striped bass, cod, and halibut. Fishermen also catch and eat herring. Predators often work together to push herring into a tight bait ball. Different predators then catch fish from the ball in different ways. These include sailfish, swordfish, thresher sharks, and spinner sharks. Some whales also lunge feed on bait balls. They rush up from below with their mouths wide open. Lunge feeding by rorquals, a family of huge baleen whales that includes the blue whale, is said to be the largest biomechanical event on Earth.

Fisheries

Adult herring are caught for their meat and their eggs. They are also often used as baitfish. Trading herring is an important part of many economies around the world.

In Europe, herring is called the "silver of the sea." Trading herring has been so important to many countries that it is often seen as the most important fishery in history.

As food

Herring has been a staple food since at least 3000 BC. It is served in many ways, and many places have their own recipes. It can be eaten raw, fermented, pickled, or preserved in other ways, such as being smoked as kippers.

Herring have a lot of the healthy omega-3 fatty acids EPA and DHA. They also contain vitamin D. However, water pollution affects how much herring is safe to eat. Large Baltic herring have slightly more PCB and dioxin than is recommended. These are substances that can be carcinogenic, meaning they can cause cancer. Some sources say that the good effects of omega-3 fatty acids are stronger than these harmful effects. The amount of these substances depends on the fish's age, which can be judged from its size. Baltic herring larger than 17 cm (6.7 in) may be eaten twice a month. Smaller herring can be eaten freely. Mercury in fish also affects how much fish women who are pregnant, or who are planning to become pregnant within the next year or two, should eat.

History

Herring has been important in history, both for people and for trade. During the Middle Ages, herring helped lead to the founding of Great Yarmouth and Copenhagen. It also played a key role in the growth of Amsterdam at that time. In 1274, Thomas Aquinas was very ill at the monastery of Fossanova, south of Rome in Italy. When he was encouraged to eat something to get his strength back, he asked for fresh herring.

In Scotland, herring fishing became an important part of life and work in coastal communities along the North Sea. It was at its busiest in the late 1800s, during a herring boom. At that time, Shetland and its town Lerwick became known as the "herring capital of Europe".