(Migration of grey mullet (Mugil cephalus Linnaeus, 1758 sensu latu) in south coast of Brazil)

Abstract

After examining 5941 grey mullets wich had been tagged between 1954 and 1962, they were considered to belong to the species circum-tropical Mugil cephalus Linnaeus, 1758, sensu lato, considering the fact that our fauna is made up of more than one species of grey mullet 12% of the tags were returned giving us important information as to the breeding migrations (reproduction) of these fishes. The reproduction period lasts ten months (February to November) with peaks in May-June in RS, and June-July in SC, PR, SP, and RJ. The migration begins and is stimulated by meteor-hydrologic factors characterized by the passage of a cold front: strong SW winds, sudden drop of temperature, precipitation, and high tides. The shoal which form in this pre-reproduction period, probably remain intact during the entire migratory movement, going out together to the ocean, migrating to N/NE direction along the coast, and scattering in different routes and speeds to the place where they will spawn. The migration seems to begin in Uruguayan and Argentine waters and near Cabo Frio at 23°S adjacent to the zoogeographic limits of the subtropical coastal waters. During the migration the shoals are reinforced constantly by other shoals that mix in, coming from the mixed (salt and fresh) waterways, and thinning out as the shoals that have spawned return to their former grounds. The movement related to meteor-hidrologic factors is intermittent, interrupted by brief stops in the estuaries and coastal waters. The exact spawning grounds were not detected, assuming that they are distributed some distance from the beaches along the coast. The farther distances registered in the migrations of the tagged fish at the bar of Rio Grande were 790 miles, and in Cananéia were 180 miles NE. In spawning areas there are marine water flows toward opposite direction of the migration, which transport mullet eggs and larvae until South Brazilian coast and so restocking the habitats.