THE BEHAVIOUR AND PIIYSIOLGOY OF HERRING AND OTHER CLUPEIDS 333
and contranatant migrations, as those described by Russell (1937), and
the reaction in a directed way to gradients of biotic and abiotic factors.
2. Aggregations
What evidence is available for clupeids aggregating in certain areas?
Most work to date has been on Atlanto-Scandian and North Sea
herring. The effect of hydrographic conditions, particularly temperature, on the North Sea herring has been partly reviewed by Hela and
Laevastu (1962). The work of Dietrich et al. (1959) showed that the
herring of the North Sea collected in the core of cold bottom water
(6-7OC) on the Fladen ground in summer and autumn. An example of
their distribution in August 1955 is given in Fig. 14. The time during
which they remained in this area depended on tho temperature, and tho
extent of their vertical migration dopended on the position and steapness of tho thermocline. Rogalla and &hrliage (1960) found a somewhat different picture in early summer 1959 where the herring seemed
to avoid the colder bottom temperatures as they did the cold, lowsalinity outflow from the Skagerak. Schubert (personal communication)
found later that herring particularly concentrated where there were
hydrographical discontinuities in the North Sea. Biryukov (1958)
found a partial tendency for herring to collect in cool water in the
North Sea (for instance in 7-5-8.5"C in June) but also for them to collect
where there were the sharpest temperature gradients (see Fig. 15).
Craig (1960) showed an association between rapid warming of the
surface water and northerly winds with reduced catches of older herring
in the Scottish summer fishery in the north-western North Sea. Steele
(1961) observed that herring leaving their overwintering area in the
Skagerak tended to collect along the outside of the Baltic outflow in t h
late spring, and that they would follow the rnovcmontn arid hakirrg
down of this barrier to some extent. I)wald (]!Nil) and I'olomkij
(1961), for example, showed the now weU-kriowri r f h l , ~ f J r i d ~ ~ p
h 4 , w w l
the Norwegian herring and hydrogralhic corr4tiorrn, Lhc: finh c ~ d l f d , i t t ~
along the " Polar Prorit ".
Cjlortrly tho try(1rogrrtphio nncl pinnkton cotditioiin t m c : o r i t i w t ~ ~ ~ ~ I
f ~ l d p l i L i i k t o i i , trc*itiK HO varicwl iir q)ooicH, iH o f h i ih t)wt iti(lic*af,or of
tho origitl o f wntor tiiwnoN. Tlik iH discuwd by Clovcr (1!)67) uncl
Pavshtiks (1956).
I'avshtiks roviowed much of the cvidence supporting tho correlation between hcrring and plankton as shown by Russian workers and
by British workers such as Praaer, Hardy, Henderson, Lucas, Savage
and Wimpenny; to this evidence should be added Cushing's (1955)
report and the work of Jakobsson (1961). There appear to be well
and contranatant migrations, as those described by Russell (1937), and
the reaction in a directed way to gradients of biotic and abiotic factors.
2. Aggregations
What evidence is available for clupeids aggregating in certain areas?
Most work to date has been on Atlanto-Scandian and North Sea
herring. The effect of hydrographic conditions, particularly temperature, on the North Sea herring has been partly reviewed by Hela and
Laevastu (1962). The work of Dietrich et al. (1959) showed that the
herring of the North Sea collected in the core of cold bottom water
(6-7OC) on the Fladen ground in summer and autumn. An example of
their distribution in August 1955 is given in Fig. 14. The time during
which they remained in this area depended on tho temperature, and tho
extent of their vertical migration dopended on the position and steapness of tho thermocline. Rogalla and &hrliage (1960) found a somewhat different picture in early summer 1959 where the herring seemed
to avoid the colder bottom temperatures as they did the cold, lowsalinity outflow from the Skagerak. Schubert (personal communication)
found later that herring particularly concentrated where there were
hydrographical discontinuities in the North Sea. Biryukov (1958)
found a partial tendency for herring to collect in cool water in the
North Sea (for instance in 7-5-8.5"C in June) but also for them to collect
where there were the sharpest temperature gradients (see Fig. 15).
Craig (1960) showed an association between rapid warming of the
surface water and northerly winds with reduced catches of older herring
in the Scottish summer fishery in the north-western North Sea. Steele
(1961) observed that herring leaving their overwintering area in the
Skagerak tended to collect along the outside of the Baltic outflow in t h
late spring, and that they would follow the rnovcmontn arid hakirrg
down of this barrier to some extent. I)wald (]!Nil) and I'olomkij
(1961), for example, showed the now weU-kriowri r f h l , ~ f J r i d ~ ~ p
h 4 , w w l
the Norwegian herring and hydrogralhic corr4tiorrn, Lhc: finh c ~ d l f d , i t t ~
along the " Polar Prorit ".
Cjlortrly tho try(1rogrrtphio nncl pinnkton cotditioiin t m c : o r i t i w t ~ ~ ~ ~ I
f ~ l d p l i L i i k t o i i , trc*itiK HO varicwl iir q)ooicH, iH o f h i ih t)wt iti(lic*af,or of
tho origitl o f wntor tiiwnoN. Tlik iH discuwd by Clovcr (1!)67) uncl
Pavshtiks (1956).
I'avshtiks roviowed much of the cvidence supporting tho correlation between hcrring and plankton as shown by Russian workers and
by British workers such as Praaer, Hardy, Henderson, Lucas, Savage
and Wimpenny; to this evidence should be added Cushing's (1955)
report and the work of Jakobsson (1961). There appear to be well