UPWELLING AND THE PRODUCTION OF FISH
277
The ratio of radiocarbon production to the quantity of chlorophyll
" a '' was used as a very rough index of the rate of production (i.e.
A stock/stock) ; this ratio was directly related to light intensity as might
be expected, and inversely to temperature at the surface, and so perhaps the algal division rates increase with increased upwelling. Very
roughly, the zooplankton was correlated inversely with chlorophyll ;
Schaefer et al. (1958) show that the pulse of zooplankton occurs a short
time after the algal outburst. The anchovy (Cetengraulis mysticetw)
feeds on diatoms (Melosira, Coscinodiscus and Thalassionemu) (Bayliff,
1963) and spawns in very shallow water in November, December and
January, just before the main upwelling season in February, March and
April (Simpson, 1959). Smayda (1966) has described the distribution of
upwelling, showing that it is found around the head of the Gulf, which
is roughly the area where the anchovy spawns and where the postlarvae and juvenile fish live on the bottom. The Gulf of Panama is a
microcosm and the study of upwelling there illuminates that on the
open coasts and in deep ocean. The most significant result is the connection established between wind strength and upwelling, between upwelling and the rough rate of production (as d stock/stock), between
algal stock and zooplankton and the spawning of the anchoveta. The
detailed mechanisms were not revealed, but the relationships were well
established.
The results from the two studies, that in the California Current and
that in the Gulf of Panama, may be combined. In the Gulf of Panama,
the biological links have been established ; the dependence of production
upon upwelling (as in Monterey Bay) and the correlation of production
rate (as d stock/stock) directly with light and inversely with temperature shows how both rate and quantity of production depend upon
the upwelling. Then the zooplankton was correlated inversely with
chlorophyll, as if it fed on the chlorophyll, and the anchovy spawns at
the head of the Gulf just before the upwelling season, hence the
larvae have the best chance of finding food. Similar animals and
plants live in the upwelling area off California and the systems must
depend upon the upwelling in the same way, and we have seen that the
sardines, anchovies and hakes spawn in the points of upwelling at or
just before the season of upwelling. But the most important point about
the Californian area as a whole is that it appears to be a biological unit.
Upwelling and heavy production occur south of certain capes at about
the same time every year and the spawning of the fishes appears to be
linked to it in time and space. Further, the migration circuits of hake
and sardine are linked t o the current system, so that they migrate north
to feed in summer and south to spawn in winter.
277
The ratio of radiocarbon production to the quantity of chlorophyll
" a '' was used as a very rough index of the rate of production (i.e.
A stock/stock) ; this ratio was directly related to light intensity as might
be expected, and inversely to temperature at the surface, and so perhaps the algal division rates increase with increased upwelling. Very
roughly, the zooplankton was correlated inversely with chlorophyll ;
Schaefer et al. (1958) show that the pulse of zooplankton occurs a short
time after the algal outburst. The anchovy (Cetengraulis mysticetw)
feeds on diatoms (Melosira, Coscinodiscus and Thalassionemu) (Bayliff,
1963) and spawns in very shallow water in November, December and
January, just before the main upwelling season in February, March and
April (Simpson, 1959). Smayda (1966) has described the distribution of
upwelling, showing that it is found around the head of the Gulf, which
is roughly the area where the anchovy spawns and where the postlarvae and juvenile fish live on the bottom. The Gulf of Panama is a
microcosm and the study of upwelling there illuminates that on the
open coasts and in deep ocean. The most significant result is the connection established between wind strength and upwelling, between upwelling and the rough rate of production (as d stock/stock), between
algal stock and zooplankton and the spawning of the anchoveta. The
detailed mechanisms were not revealed, but the relationships were well
established.
The results from the two studies, that in the California Current and
that in the Gulf of Panama, may be combined. In the Gulf of Panama,
the biological links have been established ; the dependence of production
upon upwelling (as in Monterey Bay) and the correlation of production
rate (as d stock/stock) directly with light and inversely with temperature shows how both rate and quantity of production depend upon
the upwelling. Then the zooplankton was correlated inversely with
chlorophyll, as if it fed on the chlorophyll, and the anchovy spawns at
the head of the Gulf just before the upwelling season, hence the
larvae have the best chance of finding food. Similar animals and
plants live in the upwelling area off California and the systems must
depend upon the upwelling in the same way, and we have seen that the
sardines, anchovies and hakes spawn in the points of upwelling at or
just before the season of upwelling. But the most important point about
the Californian area as a whole is that it appears to be a biological unit.
Upwelling and heavy production occur south of certain capes at about
the same time every year and the spawning of the fishes appears to be
linked to it in time and space. Further, the migration circuits of hake
and sardine are linked t o the current system, so that they migrate north
to feed in summer and south to spawn in winter.