Atlantic herring (Clupea harengus) is a herring in the family Clupeidae. It is one of the most abundant fish species in the world. Atlantic herrings can be found on both sides of the Atlantic Ocean, congregating in large schools. They can grow up to in length and weigh up to . They feed on copepods, krill and small fish, while their natural predators are seals, whales, cod and other larger fish.
The Atlantic herring fishery has long been an important part of the economy of New England and the Atlantic provinces of Canada. This is because the fish congregate relatively near to the coast in massive schools, notably in the cold waters of the semi-enclosed Gulf of Maine and Gulf of St. Lawrence. North Atlantic herring schools have been measured up to in size, containing an estimated four billion fish.
Description
Atlantic herring have a fusiform body. Gill rakers in their mouths filter incoming water, trapping any zooplankton and phytoplankton.
Atlantic herring are in general fragile. They have large and delicate gill surfaces, and contact with foreign matter can strip away their large scales.
They have retreated from many estuaries worldwide due to excess water pollution although in some estuaries that have been cleaned up, herring have returned. The presence of their larvae indicates cleaner and more–oxygenated waters.
Range and habitat
Atlantic herring can be found on both sides of the Atlantic Ocean. They range, shoaling and schooling across North Atlantic waters such as the Gulf of Maine, the Gulf of St Lawrence, the Bay of Fundy, the Labrador Sea, the Davis Straits, the Beaufort Sea, the Denmark Strait, the Norwegian Sea, the North Sea, the Skagerrak, the English Channel, the Celtic Sea, the Irish Sea, the Bay of Biscay and Sea of the Hebrides. Although Atlantic herring are found in the northern waters surrounding the Arctic, they are not considered to be an Arctic species.
Baltic herring
The small-sized herring in the inner parts of the Baltic Sea, which is also less fatty than the true Atlantic herring (Clupea harengus harengus), is considered a distinct subspecies, "Baltic herring" (Clupea harengus membras), despite the lack of a distinctive genome. The Baltic herring has a specific name in many local languages (Swedish strömming, Finnish silakka, Estonian räim, silk, Livonian siļk, Russian салака, Polish śledź bałtycki, Latvian reņģes, Lithuanian strimelė) and is popularly and in cuisine considered distinct from herring. For example, the Swedish dish surströmming is made from Baltic herring.
Fisheries for Baltic herring have been at unsustainable levels since the Middle Ages. Around this time, the primary Baltic herring catch consisted of an autumn-spawning population. Cooling in the mid-16th century related to the Little Ice Age, combined with this overfishing, led to a dramatic loss of productivity in the population of autumn-spawning herring that rendered it nearly extinct. Due to this, the autumn-spawning herring were largely replaced by a spring-spawning population, which has since comprised most of the Baltic herring fisheries; this population is also at risk of overfishing.
Life cycle
Herrings reach sexual maturity when they are 3 to 5 years old. The life expectancy once mature is 12 to 16 years. Atlantic herring may have different spawning components within a single stock which spawn during different seasons. They spawn in estuaries, coastal waters or in offshore banks. Fertilization is external like with most other fish, the female releases between 20,000 and 40,000 eggs and the males simultaneously release masses of milt so that they mix freely in the sea. Once fertilized the 1 to 1.4 mm diameter eggs sink to the sea bed where their sticky surface adheres to gravel or weed. They mature in 1–3 weeks; in 14–19 °C water it takes 6–8 days, in 7,5 °C it takes 17 days. They will only mature if the water temperature stays below 19 °C. The hatched larvae are 3 to 4 mm long and transparent except for the eyes which have some pigmentation.
Population
Herrings are most seen in the North Atlantic Ocean, from the coast of South Carolina until Greenland, and from the Baltic Sea until Novaya Zemlya. In the North Sea people can distinguish four different main populations. The different herring families are spawning in different periods: