Rohu Farming: A Production Guide

How rohu (Labeo rohita) is farmed: column-feeding biology, role in Indian major carp composite polyculture, pond fertilization and feeding, induced breeding, and growth.

Overview

Rohu (Labeo rohita) is the most important of the three Indian major carps and a leading freshwater food fish of India, Bangladesh, Pakistan and neighbouring countries. A member of the family Cyprinidae, it is native to the rivers of South Asia and is farmed mainly in earthen ponds as part of composite (polyculture) carp culture. Its column-feeding habit makes it a natural partner for surface- and bottom-feeding carps in the same pond.

Biology and feeding

Rohu is an omnivore whose diet shifts with age: young fish take zooplankton, while adults are herbivorous column feeders that consume phytoplankton, decaying vegetation, filamentous algae and periphyton in the middle of the water column. It is a large fish, typically around half a metre but reaching up to 2 m and about 45 kg. It does not feed at the surface or scour the bottom, which is what defines its place in polyculture.

Role in composite polyculture

Indian composite fish culture combines carps that feed at different depths so the pond is used fully. Catla feeds at the surface and in mid-water on zooplankton, rohu feeds in the column, and mrigal (Cirrhinus mrigala) feeds on the bottom; exotic carps such as silver, grass and common carp are sometimes added. FAO records recommended stocking ratios such as catla : rohu : mrigal of about 3:3:4 or 4:3:3, with combined densities commonly in the thousands of fingerlings per hectare.

Pond fertilization and feeding

Ponds are fertilized with organic manure such as cattle dung and with inorganic fertilizer to raise the natural plankton and detritus that the carps eat. Supplementary feed, classically a mixture of rice bran (rice polish) and oilcake, is given to boost growth. FAO composite-culture data report yields ranging from roughly 1,400 to over 4,000 kg per hectare per year for major carps alone, and higher when exotic carps are added.

Reproduction and seed supply

Like the other Indian major carps, rohu is a riverine spawner that breeds in flooded rivers during the monsoon and does not spawn naturally in ponds, so hatcheries rely on induced breeding (hypophysation) of pond-reared broodstock. Fertilized eggs are incubated and fry are nursed through nursery and rearing ponds to fingerling size before stocking into grow-out ponds.

Growth and harvest

Rohu grows well over a single season under good pond conditions and is typically harvested at around one kilogram or more, a size preferred in South Asian markets. Harvest is by seining or by draining the pond, usually together with the other polyculture species, after which the pond is dried, limed and prepared for the next cycle.