New light on the migration of the Indian white prawn, Penaeus indicus

Abstract

The tagging experiments conducted on prawns by the NTP at Cochin is described. Loop tag made up of a coloured plastic strip was used through out the experiment. The mark recapture experiments were conducted at sea-as well as in the backwater by evaluating these tagged prawns Tagging experiments were executed in four sequential phases. In the first three phases the tagging operations were carried out concurrently in the sea and at selected centres in the backwaters and in fourth phase it is restricted to the harbour centre. The experiments in phase I to III in which 16,262 prawns were released showed that there was no migration beyond the area from which they were fished, tagged and released. The overall recovery was 0.86%. Of the 28,874 prawns tagged and released from the centres in phases II and III only 11prawns, all of them P.indicus, had been recaptured from the sea and of these prawns, 5 were recovered during February, April and May 1978 and 6 during January, February, March and August 1979, indicating that whatever emigration to the sea that occurs is spread over these months. The larger their size at release in the backwater, the quicker has been their recovery from sea .In phase IV, 8,740 prawns were tagged and released from the harbour centre and from this 7 prawns of P.indicus, were recovered. The present investigation provides the first direct evidence that P.indicus nurtured in the Cochin backwaters would in deed move into the sea and migrate southward along the west coast, skirt round Cape Comorin and proceed further along the southeast coast up to Manappad, which seems to be the end point of the migration of naran chemmeen from Cochin. The average rate prawns during migration is of 0.6 mm/day among the males and 0.98 mm/day in the case of the single female which was recovered.