Some Habits of Fish
Some fish feed on plants, others on animals, and still others on both plants and animals. Small fish are the prey of larger fish, which in turn are eaten by still larger fish. Fish also feed on crustaceans, mollusks, plankton, and insects. Large sharks occasionally eat seals. The chiasmodon, a fish that inhabits deep ocean waters, is able to swallow fish twice its size.
A number of fish have unusual methods of capturing prey. The archerfish shoots down flying insects by squirting water at them. Electric eels stun their prey with an electric shock. The common angler attracts other fish with a fleshy bait attached to a flexible spine on its head. When a fish nears the bait, the angler opens its huge mouth and engulfs its prey.
Most shallow-water fish are protectively colored, dark on the back and light on the belly, thus making it difficult to see them from above or below. Flounders and some other fish can change color to match the background.
Many fishes depend on bursts of speed for protection, but few are able to swim far at high speeds. A sudden spurt is more useful to a fish than sustained speed in escaping enemies. Swordfish are capable of bursts of speed up to 60 miles per hour (97 km/h); bluefin tuna of 55 mph (89 km/h); blue marlin of 40 mph (64 km/h); and the great barracuda of 27 mph (43 km/h).
Some fish, such as sea horses and trunk-fish, are heavily armored. Catfish, stingrays, surgeonfish, and many other species are armed with sharp spines, which are venomous in many species. Electric eels, electric catfish, and torpedo rays defend themselves with electrical discharges.
Some fish sleep on the bottom; others rest on various objects, in crevices, or suspended in the water.
A number of species of fish, including shad and salmon, migrate from the sea to fresh water in order to spawn. Others, such as eels, migrate from fresh water to spawn in the sea. Cod, herring, and a number of other species move southward in winter and northward in summer. Many other species migrate from shallow water in summer to deep water in winter. Some of these migrations are made in search of food, others in order to spawn.
Probably the most remarkable of all fish migrations is that of the European eel, which travels about 3,000 miles (4,800 km) to spawn in the Sargasso Sea in the North Atlantic. The eel larvae travel an equal distance to reach Europe. They accomplish the journey in about three years.
Salmon have been caught nearly 2,000 miles (3,200 km) from the rivers from which they entered the sea. The bluefin tuna probably travels farther than any other fish. It is believed to travel constantly throughout its life, seeking warm regions in winter and cool areas in summer.
