THE B E H A ~ O U R AND PHYSIOLOOY OF RERSINCI AND OTHER CLUPEIDS 367
habits changing. Devold (1961) pointed to the gradual northward
movements and latening of the spawning herring off Norway in the
spring, and he suggested that this Iatening might eventually result in
the spawning grounds changing from the Norwegian coast to the
Skagerak, giving a “ Swedish herring period ”. Parrish (personal
communication) has suggested that tu~ the southern North Sea (Downs)
herring become older they may sometimes spawn farther and farther to
the north,
Z. Racial characters, the genotype and the environment
The nature of the racial complex in herring, Clupea pa22asii and
Sardiwps caerutea has not been considered to any great extent by
trained geneticists or systematists. Genetical work hardly exists, due
to the difficulty of rearing clupeids. The so-called racial characters are
used in the separation of stocks for the purpose of assessing migration
and the effects of fishing. A great expenditure has been made on
research into scale and otolith types, body proportions and meristic
characters. Reviews of racial investigations are given by Ahlstrom
(1967) in Clupea palhii and by Man- (1967) in Sardinops cuerulea.
Only the meristic characters and their plasticity will be discussed
further, the influence of the environment on them being shown in
Table XI.
TABLE XI
EFFEIJT OP THE ENVIRONMENT ON MERISTIC CHARACTERS
Author
Runnstram (1933)
Le Gall (1936)
Runnetram
(1941a)
Rpccies
Herring
Herring
Herring
PL:0
X.E. Atlantic
N.E. Atlantic