the 25 000 tons of eels annually produced in Europe, 15% come from eel farms.
Most of the farmed eel production (85%) is from the Mediterranean. Out of the
remaining 15%, four per cent is farmed in heated effluents and 11% in
recirculated water (EIFAC, 1987; Heinsbroek and Kamstra, 1990).
common method of eel culture is in pond farms (fig. 19.2), the ponds being
comparatively small. The elver ponds are about 100–350 m2 and the
stocking ponds about 1000–1500 m2. They may be of the still-water
type with occasional exchange of water, or running water ponds with a flow-through
system practised in areas with abundant supplies of warm water from springs is
the tunnel method. Rearing is carried out in concrete tanks of 1 m2
surface area and a depth of 1 m, with an inlet tank and an outlet tank. Water
enters the main tank from the inlet tank through a 23 cm diameter pipe and
drains out through the outlet tank. This system is suited for highly intensive
recirculation system has also been adopted on a limited scale for eel culture,
to enable highly intensive tank culture in areas with a limited water supply.
systems mentioned above are based on the use of fresh water. Making use of the
adaptability of eels, systems of culture in brackish and sea water have also
been developed. The extensive culture in the Mediterranean lagoons (valli) is
based on elvers which are allowed to enter the impounded areas through the
manipulation of tidal flows and which are grown in the fertile lagoon waters.
In ponds supplied with sea water, eels are reported to grow faster, even though
the higher rate of H2S formation in salt-water ponds creates
problems when the oxygen concentration of pH is low.
culture of eels in net enclosures in sheltered bays, back waters, etc., has
been tried to reduce the capital costs of pond construction and avoid problems
of water supply. As eels grow better in warm-water environments, wherever
possible heated water from thermal stations or industrial sources, as well as
from hot springs, has been used.