Environmental influence on the behaviour of Indian mackerel and their availability to fishing gear along the Malabar coast

Abstract

The upwelling phenomenon observed along the Malabar coast regularly fromMarch to October, produces a plankton bloom. This helps in increasing thereproductive output of mackerel and effect successful spawning and recruitment.During the monsoon period the new recruits concentrate at the surfaceas the thermocline is very shallow. During this period they become highlyvulnerable to the surface gear. With the sinking of thermocline they move todeeper waters reducing their vulnerability. Mackerel prefers a temperaturearound 27°C and hence stays immediately above the thermocline. Hence, thereis a demersal phase in the life history of the fish during summer. The fishis a prolific breeder always ready to make use of a favourable environmentfor spawning