304
D. H. UUSHING
published durations of some copepodite stages at different temperatures
and so a relationship between stage duration and temperature was constructed. Marshall and Orr (1955) also provide some data on the
duration of maturation and of hatching and so the length of a full
generation can be roughly worked out at different temperatures. It is
not a very precise estimate, but it does not differ very much from the
estimates of Heinrich (1961). The generation time estimated in this
way has been arbitrarily lengthened by one-third to take account of the
intermittent character of upwelling, due to variation in wind stress
(California Department of Fish and Game, 1953). The zooplankton
distributions off California (Thrailkill, 1956, 1957, 1959, 1961, 1963)
reflect the transient structures of an upwelling region, possibly because
the animals are vulnerable t o food lack in the periods between upwellings. The same procedure should really be applied to the algal
production, but a short halt of a week or so would only reduce the rate
of increase of production (and of course is taken up in the average radiocarbon estimates), but it might cause the local failure of a brood of
nauplii. Then when upwelling returned, it would take half a generation
for the new brood t o get under way. The estimate of one-third of a
generatjon was taken from the seasonal picture of intermittent upwellings off southern California (California Department of Fish and
Game, 1953) but there is no evidence of the real dynamic effect upon
the secondary production. I n Table IV, the secondary production is
estimated in two ways, with and without the lengthened generation
time.
It is possible that the intermittent halts in the upwelling process
(which are not confined to the California Current) really sustain greater
levels of production. The rate of increase of algal production is temporarily halted and the zooplankton production is perhaps stopped.
When the upwelling is resumed, the rate of algal production is resumed,
but the grazing restraint on the populations is absent. Consequently,
during the delay until the grazers grow again, a form of algal outburst
takes place. Hence a considerable degree of patchiness in time and
space is generated. Ivlev (1961) showed that animals convert, and
grow more effectively, on food which is distributed in a patchy way,
than on food which is distributed evenly. Thus the effects of intermittent upwelling on the possible destruction of the zooplankton may
be mitigated by the manner of their exploitation of the algal production. There is no evidence t o support these speculations.
Lovegrove’s (1962) data show that copepods, dried to a constant
weight, contain 5.6% of carbon ; Beers (1966) found the same value
for copepods, but 5.8% for pteropods, 6.4% for euphausids and 6.7%
D. H. UUSHING
published durations of some copepodite stages at different temperatures
and so a relationship between stage duration and temperature was constructed. Marshall and Orr (1955) also provide some data on the
duration of maturation and of hatching and so the length of a full
generation can be roughly worked out at different temperatures. It is
not a very precise estimate, but it does not differ very much from the
estimates of Heinrich (1961). The generation time estimated in this
way has been arbitrarily lengthened by one-third to take account of the
intermittent character of upwelling, due to variation in wind stress
(California Department of Fish and Game, 1953). The zooplankton
distributions off California (Thrailkill, 1956, 1957, 1959, 1961, 1963)
reflect the transient structures of an upwelling region, possibly because
the animals are vulnerable t o food lack in the periods between upwellings. The same procedure should really be applied to the algal
production, but a short halt of a week or so would only reduce the rate
of increase of production (and of course is taken up in the average radiocarbon estimates), but it might cause the local failure of a brood of
nauplii. Then when upwelling returned, it would take half a generation
for the new brood t o get under way. The estimate of one-third of a
generatjon was taken from the seasonal picture of intermittent upwellings off southern California (California Department of Fish and
Game, 1953) but there is no evidence of the real dynamic effect upon
the secondary production. I n Table IV, the secondary production is
estimated in two ways, with and without the lengthened generation
time.
It is possible that the intermittent halts in the upwelling process
(which are not confined to the California Current) really sustain greater
levels of production. The rate of increase of algal production is temporarily halted and the zooplankton production is perhaps stopped.
When the upwelling is resumed, the rate of algal production is resumed,
but the grazing restraint on the populations is absent. Consequently,
during the delay until the grazers grow again, a form of algal outburst
takes place. Hence a considerable degree of patchiness in time and
space is generated. Ivlev (1961) showed that animals convert, and
grow more effectively, on food which is distributed in a patchy way,
than on food which is distributed evenly. Thus the effects of intermittent upwelling on the possible destruction of the zooplankton may
be mitigated by the manner of their exploitation of the algal production. There is no evidence t o support these speculations.
Lovegrove’s (1962) data show that copepods, dried to a constant
weight, contain 5.6% of carbon ; Beers (1966) found the same value
for copepods, but 5.8% for pteropods, 6.4% for euphausids and 6.7%