THE BEHAVIOUR AND PHYSIOLOGY OF HERRING AND OTHER OLUPEIDS 347
were deoompressed at’ a rate of 0.9 kg/oma/8eo without harm. Rates
greater than 1.8 kg/cma/8eo were probably injurious.
There is no reason to suppose that clupeids, which are physostomatous, should suffer from inflated swim bladders on decompression,
but it is possible that decompression might cause embolisms, which
could account partly for mortality of herring caught by trawl at
considerable depths.
It appeared from Brawn’s (19604 work that herring in cages eank
mimming horizontally and rose swimming vertically. The data on
swimming speeds show that upward movement tends to be slower.
This might be partly a gravitational effect and partly a need to compeneate for decreaaing pressure, which might be a more serious problem
than increasing pressure.
8. The “ &rn ”
This h w been discussed in Section VI, V, but it is a phenomenon
pa,rtioularly aaeociated with vertical migration in the shallow waters of
the North Sea (Graham, 1931 ; Balls, 1961).
‘r. ~ffect of the
Probably the first scientific enquiry into the lunar influence on
clupeid catches was that of Fulton (1906), who found the total herring
catch in the Inveraray district of Scotland from 1860-1900 to be 293,035
crms over the new-moon period, and over the full-moon period 215,152
crans. He thought the difference might be due to fishermen fishing less
at full moon as they thought the fish would me the nets. The analysis
of the pre-war southern North 8ca hcrriihg catchaa hy Havago anrl
Hodgson (1934) showed the striking dependence of the catch CHI thr:
moon phase. Around full moon the catch might be double that at other
times, but the course of the seaaon’s fishing waa influenced by the date
of the full moon. If it was in the 2nd week of October good fiRhing could
be expected for about 5 weeks. If the full moon waa near tho end of
October, there tended to be only one peak of good catchee, which made
the fishing more dependent on bad weather. Hickling (1947), however,
found little evidence of the moon phase on the trawl fishery for herring
from Milford Havcn (South Wales) from 1933-1940. It momod that if
the moon waa full in the last part of Scptornher tho trawl firrhcry
suffercd, but them was no effect comparablo with southern North Soa.
Since the war only Jcns (1964) has publiHhed further arialyses of
herring catch statistics baaed on moon phase. He used tho Gorman
lugger drift net catches in the North Sea in 1963, and found a peak
were deoompressed at’ a rate of 0.9 kg/oma/8eo without harm. Rates
greater than 1.8 kg/cma/8eo were probably injurious.
There is no reason to suppose that clupeids, which are physostomatous, should suffer from inflated swim bladders on decompression,
but it is possible that decompression might cause embolisms, which
could account partly for mortality of herring caught by trawl at
considerable depths.
It appeared from Brawn’s (19604 work that herring in cages eank
mimming horizontally and rose swimming vertically. The data on
swimming speeds show that upward movement tends to be slower.
This might be partly a gravitational effect and partly a need to compeneate for decreaaing pressure, which might be a more serious problem
than increasing pressure.
8. The “ &rn ”
This h w been discussed in Section VI, V, but it is a phenomenon
pa,rtioularly aaeociated with vertical migration in the shallow waters of
the North Sea (Graham, 1931 ; Balls, 1961).
‘r. ~ffect of the
Probably the first scientific enquiry into the lunar influence on
clupeid catches was that of Fulton (1906), who found the total herring
catch in the Inveraray district of Scotland from 1860-1900 to be 293,035
crms over the new-moon period, and over the full-moon period 215,152
crans. He thought the difference might be due to fishermen fishing less
at full moon as they thought the fish would me the nets. The analysis
of the pre-war southern North 8ca hcrriihg catchaa hy Havago anrl
Hodgson (1934) showed the striking dependence of the catch CHI thr:
moon phase. Around full moon the catch might be double that at other
times, but the course of the seaaon’s fishing waa influenced by the date
of the full moon. If it was in the 2nd week of October good fiRhing could
be expected for about 5 weeks. If the full moon waa near tho end of
October, there tended to be only one peak of good catchee, which made
the fishing more dependent on bad weather. Hickling (1947), however,
found little evidence of the moon phase on the trawl fishery for herring
from Milford Havcn (South Wales) from 1933-1940. It momod that if
the moon waa full in the last part of Scptornher tho trawl firrhcry
suffercd, but them was no effect comparablo with southern North Soa.
Since the war only Jcns (1964) has publiHhed further arialyses of
herring catch statistics baaed on moon phase. He used tho Gorman
lugger drift net catches in the North Sea in 1963, and found a peak