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The average span of life of oil sardines is about 3 to 4 years; they grow to
10, 15 and 19 cm at the end of 1st, 2nd and 3rd year respectively. It is a
plankton feeder, the favourite food being a diatom Fragilaria oceanica. The
sardines are reported to spawn only once in their life span, as they attain
maturity only in the third year. The normal catch (2,350 tonnes) mainly
comprises immature specimens. Sardines are mostly cured, though a small
portion is eaten in fresh condition. When landings are heavy they are used
for extraction of oil (body oil).
(c) THE INDIAN SHAD AND GIANT HERRING
The Indian shad and the giant herring, locally known as ' Palla' and '
Bhing' respectively, are the two species of Hilsa viz. H. ilisha and H.
sinensis belonging to the family Clupeidae. Though these fishes look
similar and are similarly distributed from Persian Gulf to Burma, they
prefer different habitats. H. sinensis inhabits the coastal waters, rarely
coming into estuaries, while H. ilisha ascends into fresh waters. The
former constitutes a sizable fishery (2,000 tonnes p. a.) in the coastal
waters of northern Maharashtra extending up to Bankot creek (Savitri
river). H. ilisha has now been of lesser significance to Maharashtra as it is
available in small qualities only in Ulhas river near Kalyan and in a few
smaller ones up to Savitri river near Bankot, the main abode on the west
Indian coast being the Narbada.
Like Salmon, H. ilisha can be considered a truly anadromous fish,
spending a part of its life in the sea and ascending rivers for the purpose of
spawning. Because of this habit, any obstructions such as dams and weirs
are detrimental to Hilsa fisheries, unless "fish passes" or ladders are
provided for them to continue their spawning migration successfully. In
Mahanadi, Godavari, Krishna and Cauvery rivers, the extent of migration
of Hilsa has been greatly affected on account of the construction of anicuts
or dams. Similar danger exist in the Narbada; the Hilsa fishery in Ulhas
river near Kalyan is on the verge of extinction on account of pollution
caused by factory effluents near Kalyan, in the vicinity of Bombay.
FAUNA 98