362
J. H. 9. BLAXTER AND F. 0 . T. HOLLIDAY
in which the eggs were matured and spawned in batches, was higher
than in the Murmansk herring which had a total spawning. Naumov
attributed this to the need to spawn enough eggs at any one time to
ensure a successful spawning. Andreu and dos Santos Pinto (1957)
found in Sardina pilchardus that the general stock of oocytes from
which the annual fecundity takes a proportien increased by the fourth
power of the body length.
5. The pituitary
This was studied histologically by Buchmann (1940) and Holliday
(1960a). Both described changes in vascularity and cellular activity
which appeared at certain stages in the maturation cycle. Gonadotrophic activity is apparently localized in the meso-adenohypophysis.
From about gonad Stage I11 onwards this region becomes increasingly
vascular and the cells more abundant and larger in size. After spawning
this area appears relatively inactive. Assay of the whole pituitary
confirmed that the gonadotrophic activity was highest in Stages IV-VI.
Holliday (1960a) studied the maturation of herring in the aquarium.
The ovaries developed to about Stage 111-IV only after a high level of
feeding had been maintained ; they then regressed. The testis developed
normally but in miniature. Histological examination of the pituitaries
showed that they were still in the immature, inactive state, suggesting
that development beyond Stages 111-IV depended on a higher level of
pituitary activity.
6. Timing of maturation in the sea
Naumov (1956) attempted t o correlate the ntntc of m:itmity in tlvr
herring with temperaturo, fkding, .dinity o f t h : wnfrvr t t t r t i m i r j i i t i t , r j f
solar radiation. Although wwh stage WFLR found unt1r.r fairiy well
defined m d differing degrees of thcm environmental variables, it was
difficult to ascribe to any of them the actual control of maturation.
Sahrhage (1954) found that southern North Sea herring were not
ripe in early Deconilm 1952 when sea temperatures were 2 (leg. C below
nornial, whcrcns in early I)ocembc*r 1953, when tcrnpcr:itures werc
2-3 deg. C abovo normal, nioro than 60% of thc herring were ripe.
Devold (1 ‘301) suggested that t h o Norwegian herring, whose spawning
was gradually becoming later each year, might eventually change their
spawning time and grounds completely ; from being spring spawners off
the Norwegian coast, they would spawn in early winter in the Skagerak.
Different “ races ” of herring mature and spawn at different times
of the year, even though they sometimes share the same environment,
for example, Iles (1962) suggested that autumn and winter upawning
J. H. 9. BLAXTER AND F. 0 . T. HOLLIDAY
in which the eggs were matured and spawned in batches, was higher
than in the Murmansk herring which had a total spawning. Naumov
attributed this to the need to spawn enough eggs at any one time to
ensure a successful spawning. Andreu and dos Santos Pinto (1957)
found in Sardina pilchardus that the general stock of oocytes from
which the annual fecundity takes a proportien increased by the fourth
power of the body length.
5. The pituitary
This was studied histologically by Buchmann (1940) and Holliday
(1960a). Both described changes in vascularity and cellular activity
which appeared at certain stages in the maturation cycle. Gonadotrophic activity is apparently localized in the meso-adenohypophysis.
From about gonad Stage I11 onwards this region becomes increasingly
vascular and the cells more abundant and larger in size. After spawning
this area appears relatively inactive. Assay of the whole pituitary
confirmed that the gonadotrophic activity was highest in Stages IV-VI.
Holliday (1960a) studied the maturation of herring in the aquarium.
The ovaries developed to about Stage 111-IV only after a high level of
feeding had been maintained ; they then regressed. The testis developed
normally but in miniature. Histological examination of the pituitaries
showed that they were still in the immature, inactive state, suggesting
that development beyond Stages 111-IV depended on a higher level of
pituitary activity.
6. Timing of maturation in the sea
Naumov (1956) attempted t o correlate the ntntc of m:itmity in tlvr
herring with temperaturo, fkding, .dinity o f t h : wnfrvr t t t r t i m i r j i i t i t , r j f
solar radiation. Although wwh stage WFLR found unt1r.r fairiy well
defined m d differing degrees of thcm environmental variables, it was
difficult to ascribe to any of them the actual control of maturation.
Sahrhage (1954) found that southern North Sea herring were not
ripe in early Deconilm 1952 when sea temperatures were 2 (leg. C below
nornial, whcrcns in early I)ocembc*r 1953, when tcrnpcr:itures werc
2-3 deg. C abovo normal, nioro than 60% of thc herring were ripe.
Devold (1 ‘301) suggested that t h o Norwegian herring, whose spawning
was gradually becoming later each year, might eventually change their
spawning time and grounds completely ; from being spring spawners off
the Norwegian coast, they would spawn in early winter in the Skagerak.
Different “ races ” of herring mature and spawn at different times
of the year, even though they sometimes share the same environment,
for example, Iles (1962) suggested that autumn and winter upawning