304
J. H. 9. BLAXTER AND F. a. T. HOLLIDAY
between the growth of a fish and the salinity of the water in which it
lived (all other things being equal). Graham (1956) showed that marine
Pornolobus had a more rapid rate of growth than the freshwater form
of this fish, and Hoar (1952) thought that this was related to the high
energy requirements of osmo-regulation in the freshwater environment
(see Section VI, H).
4. Growth of herring in the North Sea
During and after 1950 a large increase in the growth rate of the
herring of the North Sea and English Channel occurred (e.g. Ancellin,
1953; Gilis, 1954; Andersson, 1954; Cushing and Burd, 1957; Parrish
and Craig, 1957). The increase in growth rate has been correlated with
an increase in the abundance of Calanua in the North Sea (Cushing and
Burd, 1956, 1957 ; Glover, 1958 ; Cushing, 1962). If this change in the
growth rate is in fact a real one (and not an error in aging the fish, due
to a change in the pattern of scale growth), it poses many physiological
problems. For instance, was the herring " underfed " prior to 1950,
retarded and living below its physiological limits? Has it now reached
these limits or could it show an even higher growth rate? Waa there
any increaaed pituitary activity from 19501
5. Growth and maturation
Burd (1956, 1958, 1962) studied the relationship betweengrowth and
the maturation cycle. He concluded that there was a minimal length,
irrespective of age, that a herring must reach before maturation of the
gonad commenced. Burd termed this the " Critical Length " (21.6 cm
for herring of the southern North %a). OhviouHly t-incc? the increased
growth rate of 1950, herring have roached t h i H lurigtti Hoortcr tharr
before 1950, and hence the age at first maturity hae been advanced (by
1 year).
6 . Effect of age and sex
Hickling (1940) showed that the male herring of the southern North
Sea grew faster than the female. He found a disharmony of growth
between the fish as a whole and the growth of the gonadH, uc) that an
increasing strain was put on older fish as they matured. Because of
their better growth rate the Atrain wae leeu on the malee, h u t Hickling
found no significant difference in mortality betwc:c:ll malr: and fi:male
fish at any age. However, Wynne-FXwardH (1029) nhowed that in tht,
Manx herring growth of the body and the gonads was in harmony, and
that spawning did not draw on the reserves of the fish more than could
be replaced each year.
J. H. 9. BLAXTER AND F. a. T. HOLLIDAY
between the growth of a fish and the salinity of the water in which it
lived (all other things being equal). Graham (1956) showed that marine
Pornolobus had a more rapid rate of growth than the freshwater form
of this fish, and Hoar (1952) thought that this was related to the high
energy requirements of osmo-regulation in the freshwater environment
(see Section VI, H).
4. Growth of herring in the North Sea
During and after 1950 a large increase in the growth rate of the
herring of the North Sea and English Channel occurred (e.g. Ancellin,
1953; Gilis, 1954; Andersson, 1954; Cushing and Burd, 1957; Parrish
and Craig, 1957). The increase in growth rate has been correlated with
an increase in the abundance of Calanua in the North Sea (Cushing and
Burd, 1956, 1957 ; Glover, 1958 ; Cushing, 1962). If this change in the
growth rate is in fact a real one (and not an error in aging the fish, due
to a change in the pattern of scale growth), it poses many physiological
problems. For instance, was the herring " underfed " prior to 1950,
retarded and living below its physiological limits? Has it now reached
these limits or could it show an even higher growth rate? Waa there
any increaaed pituitary activity from 19501
5. Growth and maturation
Burd (1956, 1958, 1962) studied the relationship betweengrowth and
the maturation cycle. He concluded that there was a minimal length,
irrespective of age, that a herring must reach before maturation of the
gonad commenced. Burd termed this the " Critical Length " (21.6 cm
for herring of the southern North %a). OhviouHly t-incc? the increased
growth rate of 1950, herring have roached t h i H lurigtti Hoortcr tharr
before 1950, and hence the age at first maturity hae been advanced (by
1 year).
6 . Effect of age and sex
Hickling (1940) showed that the male herring of the southern North
Sea grew faster than the female. He found a disharmony of growth
between the fish as a whole and the growth of the gonadH, uc) that an
increasing strain was put on older fish as they matured. Because of
their better growth rate the Atrain wae leeu on the malee, h u t Hickling
found no significant difference in mortality betwc:c:ll malr: and fi:male
fish at any age. However, Wynne-FXwardH (1029) nhowed that in tht,
Manx herring growth of the body and the gonads was in harmony, and
that spawning did not draw on the reserves of the fish more than could
be replaced each year.