370
J. H. 9. BLAXTER AND F. Q. T. HOLLIDAY
authors suggested that larvae with low counts were selected out,
while Barlow (1961) suggested that selection may take place for factors
connected with high or low vertebral counts, such as sensitivity to
temperature changes giving different metabolic rates or
in
different larvae.
Apart from meristic characters, which appear to have at least some
genotypic basis, Blaxter (1958) has put forward the following as genotypically based characters-egg size, length at first spawning, spawning
season, maximum length attained-to which might be added fecundity
differences. These are discussed in different sections in this review, but
little is known about their control, and so their value in racial and
fisheries investigations remains questionable-do herring change their
spawning season, can egg size and fecundity change out of all relationship to the normal increases which may occur with increasing age, why
do Atlanto-Scandian herring spawn when older than other races? Some
answers may be obtained from Russian experiments on transplanting
herring from the Baltic to Aral Seas (Bibov, 19601, but the question
remains whether they could occur in the normal environment. Graham
(1962) suggested from studies on otolith characters that herring do not
necessarily spawn at the same season as that in which they were
hatched.
Interfertility of spring- and autumn-spawning herring (Scottish
West and East Coasts) and of different spring-spawning races (Scottish
West Coast and Baltic) has been shown by storage of sperm (Blaxter,
1957 ; Hempel and Blaxter, 1961a).
On the basis of a study of tht: characteristics of herring races,
Blaxter (1958) concluded that spring- and autumn-npawning herring
should in general he referred to diffr:rt:n t ~ j J e c h , A I, f,h: (Jtfivr cxf,rwrit),
Russian workers consider &pea p d b x i i t,o ho a NIJ tJnp:cic:fl of' h-wenqu4.
Differences in opinion as to the syetcmatio HtatuH of diffwont olupcidfi,
which are also found in Surdinop~, may Heem academic, h i i t t h y ltavr:
more far-reaching connotations for the k~chaviourint, rtnd phyHiOhJ~ifit.
For instance, what significance ehould bc attachod to the wry di@w:nt,
types of spawning grounds frequcnttd by pallacrii and harengus.
VII. CONULUSIONS
From the point of view of distribution and numbers the clupeids are
obviously a very successful group of fishes. One reason for this is their
unspecialized nature so that they aro able to deal with a wide variety
of environmental conditions. For example, the primitive kidney with
its high glomerular count enables them to exploit a wide range of
J. H. 9. BLAXTER AND F. Q. T. HOLLIDAY
authors suggested that larvae with low counts were selected out,
while Barlow (1961) suggested that selection may take place for factors
connected with high or low vertebral counts, such as sensitivity to
temperature changes giving different metabolic rates or
in
different larvae.
Apart from meristic characters, which appear to have at least some
genotypic basis, Blaxter (1958) has put forward the following as genotypically based characters-egg size, length at first spawning, spawning
season, maximum length attained-to which might be added fecundity
differences. These are discussed in different sections in this review, but
little is known about their control, and so their value in racial and
fisheries investigations remains questionable-do herring change their
spawning season, can egg size and fecundity change out of all relationship to the normal increases which may occur with increasing age, why
do Atlanto-Scandian herring spawn when older than other races? Some
answers may be obtained from Russian experiments on transplanting
herring from the Baltic to Aral Seas (Bibov, 19601, but the question
remains whether they could occur in the normal environment. Graham
(1962) suggested from studies on otolith characters that herring do not
necessarily spawn at the same season as that in which they were
hatched.
Interfertility of spring- and autumn-spawning herring (Scottish
West and East Coasts) and of different spring-spawning races (Scottish
West Coast and Baltic) has been shown by storage of sperm (Blaxter,
1957 ; Hempel and Blaxter, 1961a).
On the basis of a study of tht: characteristics of herring races,
Blaxter (1958) concluded that spring- and autumn-npawning herring
should in general he referred to diffr:rt:n t ~ j J e c h , A I, f,h: (Jtfivr cxf,rwrit),
Russian workers consider &pea p d b x i i t,o ho a NIJ tJnp:cic:fl of' h-wenqu4.
Differences in opinion as to the syetcmatio HtatuH of diffwont olupcidfi,
which are also found in Surdinop~, may Heem academic, h i i t t h y ltavr:
more far-reaching connotations for the k~chaviourint, rtnd phyHiOhJ~ifit.
For instance, what significance ehould bc attachod to the wry di@w:nt,
types of spawning grounds frequcnttd by pallacrii and harengus.
VII. CONULUSIONS
From the point of view of distribution and numbers the clupeids are
obviously a very successful group of fishes. One reason for this is their
unspecialized nature so that they aro able to deal with a wide variety
of environmental conditions. For example, the primitive kidney with
its high glomerular count enables them to exploit a wide range of