MIGRATION OF THE JUVENILE OIL SARDINE, SARDINELLA LONGICEPS (VAL) INTO THE BACKWATERS OF COCHIN

Abstract

The juvenies of oil sardine of the size range 35 to 60 mm were caught
in the stake nets and in the Chinese dip nets operated at Thoppumpady and
Thevara regions of the Codbin Backwater during the last week of August and
the first week of September, 1972. Apart from these, juveniles of oil sardine
in very large numbers have also been caught in the Chinese dip nets operated
at the Fort Cochin area of the backwaters during these weeks. These fishes
were not actively feeding and their stomachs were found empty or only up to
one-fourth full. But the samples of the same size groups examined from the
inshore catches of the same periods showed that their feeding activity was very
high and their stomachs were fuU or three-fourth full. However, there was
similarity in the main items of the stomach contents. The average salinity of
the backwater area from where the samples were collected was only 2.96 %»
with a surface temperature of 28.8°C. Though the causative factor which influences
this unusual migration of oil sardine into the less saline waters of the
backwaters is a inatter of conjecture, it is interesting to note here that the appearance
Of these juveniles in the backwater and their sudden disappearence
coincided with the full-moon and new-moon.