The eel was once thought to spawn ‘in the entrails of the earth’. That myth has been disproved, but mystery still surrounds the eel’s life-cycle.
The eel (Anguilla anguilla) has a long thin body which is pai’ticularly slimy, giving rise to the saying ‘as slippery as an eel’. The protruding lower jaw is noticeably longer than the upper, the pectoral fins are small and rounded, and the dorsal, anal and tail fins are joined together. It has no ventral fin, and the body is covered with minute scales, unlike the conger, which is scaleless. It grows to a maximum length of 54in (137cm) and it can be as heavy as 20lb (9kg).
Bone and muscle structure It was once believed that there were at least four different species of European eel – long-nosed and short-nosed eels, the frog-mouthed eel and the bull-headed eel. Leading authorities categorized them according to distinct physical differences. In 1896, however, it was shown that the bone and muscle structures were similar in each type and that physical differences were due only to age, sex, and stage of development. Now, all European eels are regarded as belonging to a single species.
An air of mystery has always sur-rounded the eel. This is because its origins and mating habits were, for a long time, not understood. As early as 350BC, Aristotle noted with surprise its apparent lack of seminal fluid or eggs. Seemingly devoid of a reproductive system, the eel was thought to come directly from ‘the entrails of the earth’.
Knowledge of the eel was gradually built up until in the late 19th century the larva Leptocephalus brevirostris was identified as that of the eel. Previously, this had been »^0^ rises to the surface, where it is carried in vast numbers by oceanic currents towards the European Continental Shelf. During the three-year journey it develops and attains a size of about 3in by the time it reaches the European coasts. Here it finally assumes the shape of the elver or young eel we know. It then enters rivers and streams from the Baltic and Scandinavian coasts to the Mediterranean coasts and as far south as Madeira and the coasts of North Africa.
The elver ‘run’ or ‘eel-fare’ takes place at different times in different countries, according to the distances travelled by the larvae. In the Baltic and the North Sea it is between March and April; in the Mediterranean it is between October and December.
Having entered the estuary, the elvers run up river. Many thousands leave the water and travel overland from ditch to ditch, entering lakes, ponds and watercourses totally unconnected with the sea. The elvers travel by night, either in the darker, deeper waters or overland on moonless damp nights during heavy rains, when a heavy dew enables them to remain moist enough to survive. They also take advantage of autumn floods.
The elvers have now become yellow eels, and spend between eight and 18 years in freshwater, feeding on crustaceans, insects, molluscs and fish. They are slow growers, and it is estimated that an eel of 12-15m (30-40cm) is roughly seven to eight years old. Growth rates vary enormously from place to place, the females growing more swiftly than the males and reaching greater ages.
When the eels are sexually mature they take on a silver hue in preparation for their return to the sea. The silver eels begin to move seaward in the autumn, travelling overland as the need arises, and moving mostly at night. Finally, they enter the sea for the final journey across several thousands of miles of the Atlantic Ocean. Their bodies then adapt for the oceanic voyage. The eye enlarges, the gut atrophies, the jaws weaken, and the gonads greatly increase in size.
Previously, it took the eels three years to arrive as leptocephalids, carried largely by currents. Now they must combat the same currents. It is not known how long the journey takes, or indeed whether these eels ever succeeded in spawning. Some authorities consider that the migrating European eels never reach their spawning grounds. They hold the view that the progeny of American mature eels, spawned in the same place, are carried by the currents to renew the contingents of European eels. Other authorities believe that sufficient numbers of the European returners succeed in spawning and so maintain the species. There is still no definite answer to this question.
Capacity to survive
Perhaps the most surprising characteristic of eels is their capacity to survive out of water for long periods. Anglers know that carp and tench can survive for an hour or two when kept in damp grass, but the eel surpasses them. This is largely due to the structure of the gills. Most fish gills collapse when out of water, but those of the eel are rigid enough for the gill plates or laminae to remain largely separated when out of water, and this enables direct gas exchange to take place. Provided the eel is cool and damp, it can survive for up to 10 hours out of water. This characteristic has always been of commercial importance, since it enables eels to be transported alive and fresh. 410
Any angler grasping his catch is soon aware of the copious layer of slime which covers the eel. It is of vital importance, providing a barrier which helps make the eel watertight. It may seem strange that a creature spending its life in water should need to be watertight, but fish like lampreys, salmon, and eels, which migrate from sea water to fresh, or vice versa, depend on such mech-anisms to survive.
When eels are in the sea, water losses due to osmosis occur through the gills and to a lesser extent through the skin. To replace these losses, sea fishes drink considerable amounts of water and this further raises the salt content of the blood and lymphatic systems. Excess salt is therefore removed through the gills, maintaining the osmotic pressure at a balance consistent with the sea water in which they are living.
This balance is upset when the elvers enter the estuary, for they are in a condition in which their body fluids are saltier than the freshwater. The osmotic process is then reversed and water enters through the gills and skin. To counter the excess amount of water in the body, and to maintain a balance, the kidneys have to expel large amounts of diluted urine.
Later, when the eel leaves the freshwater system on its return journey, a reverse process again occurs. In fact, estuarine eels need to be more slimy than river eels, so that the slime acts as a barrier to losses through the skin.
The specimen hunter hopes for large female eels, which grow to far greater sizes than the males. The current record (rod-caught) is a fish of 8 lb 10oz. The record is low, considering the sizes eels are known to attain. Tate Regan mentions an eel of 10lb, and one of 20 lb was reported taken near Norwich in 1893. According to the reporter of this catch, the biggest eels are to be taken in lakes and dykes of the Norfolk Broads, and in the extensive Lincolnshire dykes and drains.
Anglers generally agree that still and sluggish waters, preferably predominantly muddy and highly coloured, produce the best eels. Muddy estuaries are good places for large catches, and the best time for fishing is after dark when the eels are on the move, which is when they are feeding in earnest.
Traditionally, eels have a reputation for damaging game fishing by eating vast amounts of game fish spawn. Water Authority officials spend a great deal of time electrically catching eels on the trout fisheries for it is certain that the eel competes with salmon and trout for food. Whether it damages future stocks is open to conjecture.
Fishing for eels
Certainly, the eel specialist knows that eels will eat almost anything of animal origin, live or dead. A favourite bait for the rod is a dead fish. The countryman seeking eels will often leave a sack of rabbit guts overnight in the river and find eels in the morning.
Tackle needs to be tough – lines of up to 15lb b.s. Are not too heavy if the bait and place are right. The rod should be powerful enough to hold a strong fish hard, because once given its head, the eel will invariably seek refuge in submerged roots, which defeat the best lines. A dead dace or roach is used for bait, but a mackerel slice would do as well, depending on the area fished. Long shanked hooks are preferable because premature striking loses fish and the eel gets the bait well into its throat with a longer hook.
Killing an eel
Once the eel is landed, the best expedient is to cut the line and start again with a fresh hook. The catch is kept in a large damp sack. To kill the eel it is necessary to cut through the vertebral column, usually near the tail, or to cut its head off. Nevertheless, the sack is still needed since the nervous system operates for some time after death, and many an angler will tell of an eel which slithered back into the water minus its head.
Commercial eel fisheries are big business, especially in Holland. In Britain fixed traps are set up every year with the support of the Ministry of Agriculture.