Food in Abzmdmzce
33
sampling depth—10 metres—and in taking only plankton samples.
Now machines are being built which undulate between depths of
10 and 100 metres as they move through the water. At the same time
these machines record other oceanographic data enabling a more
complete survey of the zone of the sea populated by the plankton.
Studies based on the collections made with the conventional
plankton recorder have already proved of considerable importance
to the commercial sheries. In a herring survey which has been
carried out since 1947 by the Oceanographic Laboratory in con—
junction with the Aberdeen Marine Laboratory, uctuations in the
abundance of some planktonic organisms have been related to
variations in the number of sh available. Other research has
revealed differences in the feeding habits of important food sh,
information which may ultimately help in the analysis of the uctua—
tions which occur in the populations of these sh. The better
scientists can understand the marine food web, the greater are the
possibilities for more efcient exploitation of the sh stocks and the
brighter the prospects for developing marine farms.1
Hunting for sh
Catching sh must rank among man’s oldest ways of exploiting
the sea and yet, in spite of a wide range of edible marine sh, only a
few Species such as cod, haddock, plaice, anchovy, herring and tuna
support really large commercial sheries. Generally speaking, these
sheries belong to one of two groups: one catching demersal
(bottom—living) sh and the other catching pelagic (surface—living)
sh. By far the most important demersal shery is that for cod——
over three million tons of cod are caught each year in the North
Atlantic alone. The haddock and atsh such as plaice, sole and
ounder are other examples of demersal sh. Of the pelagic sherics,
the Peruvian one for the anchovy, which shoal in the fertile waters
of the up—welled Humboldt Current, has already been mentioned.
The tuna and the herring also support large pelagic sheries.
Whereas pelagic shing can be done anywhere around the world
where sufcient sh are found, demersal sheries can only operate
in shallow regions such as the continental shelf or where great banks
rise up from the sea bottom. Because the greater proportion or
continental shelf is found in the temperate regions Of the northern
hemisphere, the demersal sheries predominate in the temperate
‘
Chapter 2 for a treatment of marine farming.
33
sampling depth—10 metres—and in taking only plankton samples.
Now machines are being built which undulate between depths of
10 and 100 metres as they move through the water. At the same time
these machines record other oceanographic data enabling a more
complete survey of the zone of the sea populated by the plankton.
Studies based on the collections made with the conventional
plankton recorder have already proved of considerable importance
to the commercial sheries. In a herring survey which has been
carried out since 1947 by the Oceanographic Laboratory in con—
junction with the Aberdeen Marine Laboratory, uctuations in the
abundance of some planktonic organisms have been related to
variations in the number of sh available. Other research has
revealed differences in the feeding habits of important food sh,
information which may ultimately help in the analysis of the uctua—
tions which occur in the populations of these sh. The better
scientists can understand the marine food web, the greater are the
possibilities for more efcient exploitation of the sh stocks and the
brighter the prospects for developing marine farms.1
Hunting for sh
Catching sh must rank among man’s oldest ways of exploiting
the sea and yet, in spite of a wide range of edible marine sh, only a
few Species such as cod, haddock, plaice, anchovy, herring and tuna
support really large commercial sheries. Generally speaking, these
sheries belong to one of two groups: one catching demersal
(bottom—living) sh and the other catching pelagic (surface—living)
sh. By far the most important demersal shery is that for cod——
over three million tons of cod are caught each year in the North
Atlantic alone. The haddock and atsh such as plaice, sole and
ounder are other examples of demersal sh. Of the pelagic sherics,
the Peruvian one for the anchovy, which shoal in the fertile waters
of the up—welled Humboldt Current, has already been mentioned.
The tuna and the herring also support large pelagic sheries.
Whereas pelagic shing can be done anywhere around the world
where sufcient sh are found, demersal sheries can only operate
in shallow regions such as the continental shelf or where great banks
rise up from the sea bottom. Because the greater proportion or
continental shelf is found in the temperate regions Of the northern
hemisphere, the demersal sheries predominate in the temperate
‘
Chapter 2 for a treatment of marine farming.