UPWELLING AND THE PRODUCTION O F FISH
257
which is already being taken. Nearly 10 million tons are taken from the
Peru current and there are catches being made now in nearly all of the
areas. Therefore there is a limit to the expansion of the present world
catches (of 60 million tons). Further, the possibility of feeding the expanding world population from conventional fisheries is distinctly
limited, if only because most of the present catch is taken by the
developed countries, as fish meal or as frozen fish. In the deep ocean,
the tuna or fourth level is already well exploited, which leaves the
tertiary level such as myctophids ; there are large quantities of these,
but rz new technology is needed to exploit them.
There are three by-products of the investigation. Tho first is a
rough model of production in upwelling water which suggests that, if
upwelling is too fast, the production becomes vulnerable to grazing too
early in the cycle and so the total production in a time period is less
than it might have been. The second by-product is an analysis of the
relation between phosphorus in the water and production ; it is suggested
that the well-known correlation between phosphorus and zooplankton
occurs because the quantity of nutrients in the sea may depend upon
production and not the other way round, as has been so often suggested.
The third by-product is a comparison of transfer coefficients from primary to secondary production, which suggests that the coefficient decreases with increasing primary production.
11. THE PHYSICAL BACKGROUND
In each of the three major oceans, the largest structures are the two
subtropical anticyclones, one north and one south of the equator. In
each, the western boundary current (for example, the Kuroshio, the
Gulf Stream and the Somali Current in the northern hemisphere) is
swift and narrow (up to 4 knots in the northern hemisphere) and the
eastern boundary current is broad and slow (about 4 knot) and tends
to be somewhat reduced in salinity because it originates in rainy areas.
In the Pacific, the eastern boundary currents are the California Current
and the Peru Current and they are linked to the equatorial currents
directly and also by the California Extension and the Peru Oceanic
Current. In the Atlantic, the analogous currents are the Canary
Current and the Benguela ; in the Indian Ocean, the monsoons dominate
the upwelling structures, but there are minor eastern boundary currents
on the Malabar coast of India, off the Andaman Islands and off N.W.
Australia. There is upwelling in the eastern boundaries because the
winds tend to blow parallel to the coast towards the equator (Wooster
and Reid, 1963) ; in summer time, the high pressure systems lie very
roughly above the subtropical anticyclones and so the winds, which,
257
which is already being taken. Nearly 10 million tons are taken from the
Peru current and there are catches being made now in nearly all of the
areas. Therefore there is a limit to the expansion of the present world
catches (of 60 million tons). Further, the possibility of feeding the expanding world population from conventional fisheries is distinctly
limited, if only because most of the present catch is taken by the
developed countries, as fish meal or as frozen fish. In the deep ocean,
the tuna or fourth level is already well exploited, which leaves the
tertiary level such as myctophids ; there are large quantities of these,
but rz new technology is needed to exploit them.
There are three by-products of the investigation. Tho first is a
rough model of production in upwelling water which suggests that, if
upwelling is too fast, the production becomes vulnerable to grazing too
early in the cycle and so the total production in a time period is less
than it might have been. The second by-product is an analysis of the
relation between phosphorus in the water and production ; it is suggested
that the well-known correlation between phosphorus and zooplankton
occurs because the quantity of nutrients in the sea may depend upon
production and not the other way round, as has been so often suggested.
The third by-product is a comparison of transfer coefficients from primary to secondary production, which suggests that the coefficient decreases with increasing primary production.
11. THE PHYSICAL BACKGROUND
In each of the three major oceans, the largest structures are the two
subtropical anticyclones, one north and one south of the equator. In
each, the western boundary current (for example, the Kuroshio, the
Gulf Stream and the Somali Current in the northern hemisphere) is
swift and narrow (up to 4 knots in the northern hemisphere) and the
eastern boundary current is broad and slow (about 4 knot) and tends
to be somewhat reduced in salinity because it originates in rainy areas.
In the Pacific, the eastern boundary currents are the California Current
and the Peru Current and they are linked to the equatorial currents
directly and also by the California Extension and the Peru Oceanic
Current. In the Atlantic, the analogous currents are the Canary
Current and the Benguela ; in the Indian Ocean, the monsoons dominate
the upwelling structures, but there are minor eastern boundary currents
on the Malabar coast of India, off the Andaman Islands and off N.W.
Australia. There is upwelling in the eastern boundaries because the
winds tend to blow parallel to the coast towards the equator (Wooster
and Reid, 1963) ; in summer time, the high pressure systems lie very
roughly above the subtropical anticyclones and so the winds, which,