294
J. 11. S. BLAXTER A N D F. 0. T. HOLLIDAY
Little can be said about changes in the habits of clupeids after
metamorphosis. Certainly herring at this stage start to shoal and are
found inshore in large numbers. Whether there is a need to move into
water of low salinity is not clear, though such a need has been correlated
in other fish species with increase in thyroid activity. It may be that
feeding conditions are more suitable, but there can be no doubt that
young herring are particularly heavily preyed upon at this time.
VI. POST-METAMORPHIC STAQES
A. Establishment
The general delicacy of clupeids was the reason given by such
workers as Parr (1927), Spooner (1931), Loukashkin and Groody (1965)
and Parrish et a2. (1958) for the lack of experimental work on this
important group of fish. Clupeids have not often been established in the
aquarium. However, a number of attempts have been made not merely
to keep the fish, but also to determine the reasons for the success or
failure of the attempts and to perform expcriments on them. These
are summarized in Table V. Loukashkin ancl Groody (1955), Verheijen (1950), Farrin et al. (1957) and I’arrish et al. (1958) reviewed tho
problems of establishing clupeids in aquaria, listing the factors that
contributed to mortality at each of the stages of capture, transport,
initial establishment and long-term maintenance and feeding. In
general these authors concluded that epidermal damage was the principal cause of initial mortality. Parrish et al. suggested that osmotic
dehydration followed the damage and these mortalities could be
overcome by careful handling and keeping the fish in sea water of
salinity roughly isotonic with the blood-about IS%,. It is interesting
that, much earlier, Elmhirst (1908) accidentally di~covcrcd that
herring survived best in an equal mixture of sea water and frcsh water.
The size and structure of the aquarium, the rapidity with which the
herring start to feed and the prevention of disease were the main
factors controlling the long-term establishment of the herring (Parrhh
et al. 1958). SUCCeHSfUl experimental handling waH h i t carrkd out
under anaesthesia with tricainr: mcthane Hulphonata. ‘I’ho Ircrring
always appeared very senRitive to ditjturbances, ancl thowcd no &gnn
of becoming conditioned (or “ tame ”) in any way. ‘1’hr:y werct influenced by thc size of the tunk, an fcc:ding could not trr: i i l i t i i i k d if‘ tho
fish length: tank spaco ratio was too nmall.
Both Verheijen (1956) working on Sardina p i l c h r d w and I’arrinh
et at. (1958) on herring, found that feeding fish (in the cam of herring
also feeding Gadus virens) influenced non-feeding fish and caused them
to begin feeding.
J. 11. S. BLAXTER A N D F. 0. T. HOLLIDAY
Little can be said about changes in the habits of clupeids after
metamorphosis. Certainly herring at this stage start to shoal and are
found inshore in large numbers. Whether there is a need to move into
water of low salinity is not clear, though such a need has been correlated
in other fish species with increase in thyroid activity. It may be that
feeding conditions are more suitable, but there can be no doubt that
young herring are particularly heavily preyed upon at this time.
VI. POST-METAMORPHIC STAQES
A. Establishment
The general delicacy of clupeids was the reason given by such
workers as Parr (1927), Spooner (1931), Loukashkin and Groody (1965)
and Parrish et a2. (1958) for the lack of experimental work on this
important group of fish. Clupeids have not often been established in the
aquarium. However, a number of attempts have been made not merely
to keep the fish, but also to determine the reasons for the success or
failure of the attempts and to perform expcriments on them. These
are summarized in Table V. Loukashkin ancl Groody (1955), Verheijen (1950), Farrin et al. (1957) and I’arrish et al. (1958) reviewed tho
problems of establishing clupeids in aquaria, listing the factors that
contributed to mortality at each of the stages of capture, transport,
initial establishment and long-term maintenance and feeding. In
general these authors concluded that epidermal damage was the principal cause of initial mortality. Parrish et al. suggested that osmotic
dehydration followed the damage and these mortalities could be
overcome by careful handling and keeping the fish in sea water of
salinity roughly isotonic with the blood-about IS%,. It is interesting
that, much earlier, Elmhirst (1908) accidentally di~covcrcd that
herring survived best in an equal mixture of sea water and frcsh water.
The size and structure of the aquarium, the rapidity with which the
herring start to feed and the prevention of disease were the main
factors controlling the long-term establishment of the herring (Parrhh
et al. 1958). SUCCeHSfUl experimental handling waH h i t carrkd out
under anaesthesia with tricainr: mcthane Hulphonata. ‘I’ho Ircrring
always appeared very senRitive to ditjturbances, ancl thowcd no &gnn
of becoming conditioned (or “ tame ”) in any way. ‘1’hr:y werct influenced by thc size of the tunk, an fcc:ding could not trr: i i l i t i i i k d if‘ tho
fish length: tank spaco ratio was too nmall.
Both Verheijen (1956) working on Sardina p i l c h r d w and I’arrinh
et at. (1958) on herring, found that feeding fish (in the cam of herring
also feeding Gadus virens) influenced non-feeding fish and caused them
to begin feeding.