486
D. H. CUSHING: The Transfer from the Primary to the Secondary Level
bed. So the animals which need hardly swim from algal cell to algal cell generate the
basic inefficiency of the system; even the vertical migration of the herbivores is likely
to be less in the somewhat more turbid waters of the upwelling areas. In the quasi
steady-state cycle in the deep ocean, the delay period is probably very short indeed, if it
exists at all, and from the low amplitude of the predator-prey oscillation one would
expect efficient transfer. Indeed with searching, vertical migration and the need to
reproduce, the transfer coefficient can be as high as 20 - 25%. Of the various constraints
to efficiency, it is possible that the reproductive load is the heaviest. But the details of
the mechanism may be in the feeding-that the particulate material is small (because
the ocean is clear) and that organic material is transferred downwards in depth by
vertical migration and predation (VINOGRADOV, 1953).
llI. Discussion
In biological oceanography, a study of production is the study of a whole ecosystem in
terms of the flow of energy, material ornumbers through it. In fisheries biology itis the study
of the same ecosystem in terms of the output of edible fish. In this paper it is considered
that most of the edible fish occur (except tuna-like fishes) in the upwelling areas or
along the coastal reefs. The estimates of tertiary producers are of fish in the main and
some use could be made of them.
Fish populations, however, depend upon the production of herbivores directly, in
that recruitment may be partly determined during the larval stages in the plankton.
Hence greater variability in recruitment might be expected in the upwelling areas than
in the open ocean -that is, if recruitment depends upon the match or mismatch of larval
production to that of their food in time. As most of the fish in upwelling areas are
sardine-like and hence not able to stabilize their numbers very well (CUSHING, 1971 a),
the variability of recruitment to the fish stocks may be high. It remains, however,
that commercial fisheries are found in areas which are productive and with inefficient
transfer, because the fish concentrate. Elsewhere, where transfer is efficient, fish do not
concentrate and can only be caught with gear like pelagic long-lines.
D. H. CUSHING: The Transfer from the Primary to the Secondary Level
bed. So the animals which need hardly swim from algal cell to algal cell generate the
basic inefficiency of the system; even the vertical migration of the herbivores is likely
to be less in the somewhat more turbid waters of the upwelling areas. In the quasi
steady-state cycle in the deep ocean, the delay period is probably very short indeed, if it
exists at all, and from the low amplitude of the predator-prey oscillation one would
expect efficient transfer. Indeed with searching, vertical migration and the need to
reproduce, the transfer coefficient can be as high as 20 - 25%. Of the various constraints
to efficiency, it is possible that the reproductive load is the heaviest. But the details of
the mechanism may be in the feeding-that the particulate material is small (because
the ocean is clear) and that organic material is transferred downwards in depth by
vertical migration and predation (VINOGRADOV, 1953).
llI. Discussion
In biological oceanography, a study of production is the study of a whole ecosystem in
terms of the flow of energy, material ornumbers through it. In fisheries biology itis the study
of the same ecosystem in terms of the output of edible fish. In this paper it is considered
that most of the edible fish occur (except tuna-like fishes) in the upwelling areas or
along the coastal reefs. The estimates of tertiary producers are of fish in the main and
some use could be made of them.
Fish populations, however, depend upon the production of herbivores directly, in
that recruitment may be partly determined during the larval stages in the plankton.
Hence greater variability in recruitment might be expected in the upwelling areas than
in the open ocean -that is, if recruitment depends upon the match or mismatch of larval
production to that of their food in time. As most of the fish in upwelling areas are
sardine-like and hence not able to stabilize their numbers very well (CUSHING, 1971 a),
the variability of recruitment to the fish stocks may be high. It remains, however,
that commercial fisheries are found in areas which are productive and with inefficient
transfer, because the fish concentrate. Elsewhere, where transfer is efficient, fish do not
concentrate and can only be caught with gear like pelagic long-lines.