Herring

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

Herring often move in large schools around fishing banks and near the coast. They are found especially in shallow, temperate 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 in fisheries. The most abundant of these is the Atlantic herring, which makes up over half of all herring caught. The FAO has reported global commercial catches of herring from 1950 to 2010.

Herring played an important role in the history of marine fisheries in Europe. Early in the 20th century, their study was fundamental to the development 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

A number of different species, most of them in the family Clupeidae, are commonly called herrings. The origin of the word "herring" is somewhat unclear. It may come from the same source as the Old High German heri, meaning "host, multitude," which refers to the large groups they form.

The type genus of the herring family is Clupea. It has only two species: the Atlantic herring, the type species, which is found in the North Atlantic, and the Pacific herring, which is mainly found in the North Pacific. Scientists have suggested subspecific divisions for both, but their biological basis remains unclear.

Other related species in the Clupeidae family are also commonly called herrings. The table below includes those listed by FishBase as herrings that have been assessed by the International Union for Conservation of Nature.

Some other species are also called herrings. They may be related to clupeids or just share some features with herrings, such as the lake herring, which is a salmonid. Which species get the name can vary by place, so a fish called a herring in one area may have a different name elsewhere. Some examples:

Characteristics

The species of Clupea belong to the larger family Clupeidae (herrings, shads, sardines, menhadens), which has some 200 species that share similar features. These silvery fish have a single dorsal fin that is soft, without spines. They have no lateral line and a lower jaw that sticks out.

Size varies between subspecies. The Baltic herring (Clupea harengus membras) is small, 14 to 18 cm (about 5.5 to 7 inches). The proper Atlantic herring (Clupea harengus harengus) can grow to about 46 cm (18 in) and weigh up to 700 g (1.5 lb). Pacific herring grow to about 38 cm (15 in).

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, while North Sea herring spawn down to 200 m (660 ft) in autumn. Females lay about 20,000 to 40,000 eggs, averaging about 30,000, 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 run short of oxygen and often die, tangled in mucus. They need moving water, usually from wave action or coastal currents. Eggs survive best in sheltered spots, because predators feast on eggs that are exposed. Eggs die in water above 19 °C (66 °F).

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

Ecology

See also: Hunting copepods

Herring eat tiny sea animals such as copepods, arrow worms, pelagic amphipods, mysids, and krill in the open water. They are also an important food for larger sea animals. Herring usually stay in deep water during the day and feed at the surface at night, when they are less likely to be seen by predators. Copepods are their most common food. Young herring often hunt copepods one at a time, while 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, so herring swim in a spaced pattern that matches how far their prey jumps.

See also: Predator avoidance in schooling fish and Bait ball

Predators of herring include seabirds, marine mammals such as dolphins, porpoises, whales, seals, and sea lions, and predatory fish such as sharks, billfish, tuna, salmon, striped bass, cod, and halibut. Fishermen also catch and eat herring. Predators often work together to herd herring into a tight bait ball. Different predators then use different methods to catch fish from the ball, such as sailfish, swordfish, thresher sharks, and spinner sharks. Some whales also lunge feed on bait balls by rushing up from below and opening their mouths wide. 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 flesh and eggs, and they are often used as baitfish. Trade in herring is an important part of many economies around the world.

In Europe, herring has been called the "silver of the sea." Its trade has been so important to many countries that it has been seen as the most commercially 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 regions have their own recipes. It can be eaten raw, fermented, pickled, or preserved in other ways, such as being smoked as kippers.

Herring are high in the omega-3 fatty acids EPA and DHA, and they are a source of vitamin D. However, water pollution affects how much herring is safe to eat. Large Baltic herring slightly exceed recommended limits for PCB and dioxin, although some sources say that the cancer-reducing effect of omega-3 fatty acids is statistically stronger than the carcinogenic effect of PCBs and dioxins. The amount of contaminants 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, while smaller herring can be eaten freely. Mercury in fish also affects how much fish women who are pregnant, or planning to become pregnant within the next one or two years, may safely eat.

History

Herring has played a big part in history, both in society and in the economy. During the Middle Ages, herring helped lead to the founding of Great Yarmouth and Copenhagen, and it played a key role in the growth of Amsterdam at that time. In 1274, Thomas Aquinas was dying 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, the herring industry became an important part of life and money-making in coastal communities along the North Sea. It reached its peak in the late 19th century, during a herring boom. At that time, Shetland and its town Lerwick became known as the "herring capital of Europe".