Herrings
Herrings
The herrings are a bony fish belonging to the family Clupeidae. There are about 200 species of herring in the family. Herrings are a streamlined, silvery fish with one dorsal fin, a protruding lower jaw and a deeply forked tail. Most species rarely grow over 1.5 lb (700 g) in weight although the tarpon can grow as big as 200 lbs (90 kg). Herrings have a ridge of scales on the belly midline, which is sharp-edged, and they have no visible lateral line.
Herrings eat plankton that they strain from the water with their gill rakers, trapping these organisms as water passes across their gills. Herring are also key parts of the diet of some species of whales, seals, gulls, and predatory fish.
Herrings are widely distributed and found in all oceans except for extremely cold parts of the Arctic and Antarctic Oceans. Although most of the species are marine, a few are anadromous, that is, they spend their lives in the sea and enter rivers to spawn. Other species remain permanently in freshwater.
Spawning times vary in different species but most often occurs in the fall and occasionally in the spring or summer. Each female may deposit 25,000-40,000 eggs, which are heavy and sink to the bottom. On the way down a thick covering of mucus causes the eggs to stick to anything they encounter. It takes up to two weeks for the eggs to hatch; the time depends on such variables as depth and temperature. There is no parental care. In the first year the young may reach a size of 5 in (13 cm), reaching 10 in (25 cm) after two years. In their third year they may have acquired enough fat to be harvested as a source of oil. Herrings become sexually mature in their fourth year.
Herrings represent one of the most important fisheries in the world. They are a large component of the economy of some countries. Wars have been fought for rights to important fishing grounds. Because herrings tend to migrate in enormous schools, they commercial fishers can locate and catch enormous numbers of herring. The Atlantic herring (Clupea harengus) may be the most plentiful pelagic (or open-ocean) fish, and is found on both sides of the North Atlantic Ocean. Due to intensive overfishing, however, the population of herrings has been markedly reduced.
The term sardine is sometimes applied to species of small herrings. For example, the sprat or brisling (C. sprattus) from the European side of the Atlantic is considerably smaller than the Atlantic herring. The term sardine is also applied to the Pacific sardine (Sardinops sagax).
The Atlantic menhaden or mossbunker (Brevoortia tyrannus) is the most numerous of all fish in the mid-Atlantic waters of North America. It has a stubby shape and generally weighs under a pound. Due to its heavy oil content it is not palatable, but makes an excellent fertilizer, fishmeal, and oil. Traveling in massive schools near the surface, these fish can cause a swirling motion of the water. Schools of menhaden may be located by the presence of flocks of seabirds feeding on them.
The American shad (Alosa sapidissima) is one of the largest herring, since it has an average weight of 3
KEY TERMS
Anadromous —Refers to fish that migrate from salt water to fresh water, in order to breed.
Gill rakers —Stiff and thin protrusions on the inner part of the gill arch. Food carried in sea water is strained by gill rakers and made available to the fish.
Lateral line —A line of pores on the side of the fish from the head to the tail containing sensory receptors, especially to sense changes in water pressure.
Roe —A mass of fish eggs.
lb (1.5 kg) and can reach 12 lb (6 kg). It is found in the Atlantic Ocean from the St. Lawrence River south to Florida. Toward the end of the nineteenth century, shad were introduced into the Pacific Ocean and this species now ranges from Alaska to California.
The shad is an anadromous fish. When spawning, the sexes separate with the males entering the river first, followed by the females, known as roe shad. Each female carries a tremendous number of eggs, estimated at 30,000 on average, although larger females can carry several times that number. As with the other herrings, the eggs are dropped at random. Because they are sticky and heavy, they readily sink to the bottom and tend to adhere to objects. The young shad remain in the streams until strong enough to enter the sea. Males are sexually mature at about their fifth year, at which time they return to spawn. Females may take a bit longer to mature and reenter the rivers to spawn. Shad are caught as they are traveling upstream when they are energetic. They are caught commercially as well as for sport, and they are highly prized for human consumption, especially the roe.
The alewife (Alosa pseudoharengus) is a close relative of the American shad but is smaller in size. Ocean-moving alewives are anadromous. Some populations in the eastern United States are landlocked and are found in great abundance in the Great Lakes. Large numbers of alewives die during some summers, resulting in an intolerable, smelly nuisance on beaches. Alewives are caught commercially in seines and nets, and are used for fishmeal and fertilizer.
Resources
BOOKS
Collette, B.B. and G. Klein-MacPhee, eds. Bigelow and Shroeder’s Fishes of the Gulf of Maine. A Complete Guide to the Marine Environment. Washington, DC: Smithsonian Institution Press, 2002.
OTHER
Alaska Department of Fish and Game. “Herring Fisheries Home Page.” August 11, 2006. <http://www.cf.adfg.state.ak.us/geninfo/finfish/herring/herrhome.php> (accessed October 20, 2006).
The Gulf of Maine Aquarium. “Atlantic Herring.” October 20, 2006. <http://www.gma.org/herring/default.asp> (accessed October 20, 2006).