Ranching of anadromous species
The strong homing behaviour during spawning migration of anadromous species makes them the most suitable aquatic animals for ranching. Successful ranching of anadromous species on a sufficiently large scale, however, relates only to two groups of temperatezone fishes: the salmon and sturgeons.
The maintenance or revival of salmon fisheries in countries of the northern hemisphere has, to a very large extent, been due to the successful hatchery rearing of smolts, regular release of smolts into the open seas and their subsequent return to the home streams for spawning. Attempts have been made to introduce certain species of salmon in some countries of the southern hemisphere. In recognition of the merits of ranching, as opposed to intensive rearing of species in confinement, there is interest in identifying a suitable species for ranching in the tropics. Though the shad Hilsa ilisha has often been considered a possible candidate, its short-range migrations and ability to propagate and form riverine populations above dams and other obstructions in rivers, as well as the lack of a well-established technology for the hatchery rearing of young Hilsa, have stood in the way of even experimental work.