Summer in coastal waters
In April, sand eels swim into shallower waters.
During the summer they live either alone or in large shoals above sandy
bottoms down to 10 or 20 metres. During the night, cloudy days, or in
the morning the shoals depart to shallower waters to find food amongst
the seaweed. Sand eels eat different types of plankton, like fish spawn
and eggs, and bottom living creatures like small crustaceans and polychaetes.
In November they depart to deeper waters where they spend the winter in
large shoals or dug down into the bottom sediment. Most of the time the
sand eels are dug down into the bottom. They dive head first into the
sand and disappear completly, sometimes as deep down as 50cm.
Play in the sand
Sand eels play on sand bottoms at different
times depending on the specie. The eggs, up to 30 000 per female,
are layed in the sand where they stick to the grains of sand. Normally,
the eggs hatch after a few weeks, but some eggs get covered by sand before
they are fully developed. Development of these eggs stops and they lay
in the sand in a sort of hibernation. Eventuelly one day the egg whirls
up again and development continues. In this way new larvae are hatched
over a period of several months. Larvae
and spawn are pelagic, they live in the open water. Sand eels became
sexually mature at between 1-2 years, and live for between 4-5 years.
Hundreds of billions are fished
Sand eels are an important source of food
for other fish and even birds, such as the guillemot, and certain mammels.
Sand eels have even an economic value in the production of
fish meal and fish oil. This type of factory fishing started during the
seventies and is pursued by mainly Danish and Norwegian fleets in the
North Sea using finely meshed trawls in the spring and summer. North
Sea production has annually grossed between 400 000 ton - 1 000 000
ton since mid-1970. Because the average weight of a sand eel is about
10 gram, it would entail that about 100 billion individuals are caught
during a good year! Sand eels are also used as fishing bait.