Mediterranean Seafood - Prospect Books

14 mediterranean seafood
Mediterranean, almost deprived of any connection with the oceans, had been
deteriorating into a series of brackish and shrinking lakes in which the marine
fauna seemed doomed to disappear. The opening of the Strait of Gibraltar literally
saved the life of the Mediterranean and the Strait has remained its lifeline
ever since.
The existence and dimensions of the Strait have other important effects as
well. Besides being narrow (seven miles) it is also shallow (350 metres and less).
It thus forms a raised sill between the Mediterranean and the Atlantic, leaving
the Mediterranean almost sealed off in both dimensions. This is why there are
practically no tides in the Mediterranean, which in turn accounts for many of
the characteristics of the Mediterranean coastline. But the existence of the sill
produces another important phenomenon, which bears on the deep waters.
Wherever you have such a sill separating an enclosed basin such as the
Mediterranean from the open ocean the temperature of the deep water in the
basin, right down to the bottom, will tend to be the same as the temperature at
the lowest point of the sill. As a result all the Mediterranean fauna which live at
depths below 300 metres or so live in a constant temperature of 13°c. This is in
striking contrast to the Atlantic temperature which has already fallen to 5°c at
a depth of 1000 metres. It is therefore easy to see how difficult it would be for
Atlantic deep-water species to settle in the Mediterranean and the
Mediterranean is certainly poor in deep-water species. There is a further point
to be mentioned here. The deep waters of the Atlantic are not only colder, but
also much richer in nutrients. This difference is another factor which (quite
apart from new phenomena such as pollution, to which the smaller sea is
particularly vulnerable) has restricted the fertility of the Mediterranean.
But the Mediterranean is not only connected with the Atlantic. It is also
joined to the Black Sea by the Bosphorus and the Dardanelles. Here too there
is an exchange of waters, but on a less important scale. Here too more flows
into the Mediterranean than out. The Black Sea water, which is low in salt, can
be traced as it fans out through the Aegean.
And there is the Suez Canal. This constitutes a lock-free link with the Gulf of
Suez and the Red Sea, through which water and fish can pass without hindrance.
The volume of water which passes is negligible, but the fish traffic is
important and has become more so in recent years because of a change in the
salinity of the Bitter Lakes in the Suez Canal. Previously they were too salty for
certain species of fish which would otherwise have passed through the Canal
from the Red Sea into the Mediterranean. But the diluting effect of the Canal,
now 100 years old, has gradually lowered the salinity of the Lakes until it has
fallen below the threshold which these fish are willing to cross. One early
example was Siganus rivulatus Forskål, the rabbit fish, which has been establishing
itself in increasingly large numbers in the eastern Mediterranean; and
quite a few others are now thriving there, including the Indo-Pacific relations
MediterraneanSeafood.pdf 14 26/06/2012 10:52