Pearlspot, Etroplus suratensis, known locally as ‘Karimeen’ (figure 1), is the largest among Indian cichlids, a high-valued food fish endemic to peninsular India and Sri Lanka. The green chromide (Etroplus suratensis) is a species of cichlid fish from freshwater and brackish water in southern India and Sri Lanka. It is also known as the pearlspot or karimeen (കരിമീന്) in Malayalam and koral in Bengali. In India, it is found throughout Kerala, especially in Kerala Backwaters around Alleppey, (Alappuzha), and in western flowing rivers in Karnataka, and backwaters of Andhra Pradesh. It feeds on algae, plant material and insects.
The fish, known locally in Kerala as Karimeen, is considered a delicacy. Some of the prominent dishes are the Karemeen Fry, Karemeen Molly and Karemeen Pollichathu. This fish is fairly expensive and is available throughout the year. It is caught mainly using gillnets. It commonly reaches 20 centimetres (7.9 in) in length, and the maximum length is twice that. In 2010 state fisheries minister of Kerala declared Karimeen as the official fish of Kerala state. Year 2010-'11 was observed as 'The Year of the Karimeen". Karemeen Polichathu is commonly wrapped in banana leaves.
The fish attains maturity at the end of the first year, with sexual dimorphism perceptible only during the breeding season Fecundity of pearlspot is low, varies from 500 to 7550 Breeding of the fish in Vembanad Lake peaks during December–February and June–July. The presence of two peaks in gonadosomatic index and two distinct batches of eggs in the same ovary is corollary to its breeding habit. E. suratensis breeds throughout the year in ponds, with a peak during September.Breeding behaviour includes pairing, nest making, pit nursing and parental care. As a prelude to breeding, the male and female fish form a spawning pair. The breeding pair utilize any stationary solid objects (coconut leaves, husk, roots, stones, bricks, etc. lying at the lake bottom, and along the shallow periphery of the water body, for attaching the eggs. After the eggs (250 to 1573 eggs per brood) are laid by the female and are stuck to the substratum one by one, the male fish fertilizes them immediately.
The process of egg laying and fertilization continues several times and the eggs are cemented closely without touching each other. Spawning is completed within 45 to 60 min. The parents aerate the egg by rapidly fanning with their pectoral fins. The eggs hatch in 70–72 h, and the hatchlings are transferred by the parents to the breeding pit, which is prepared on the shallow pond bottom. Once the eggs are transferred, the female closely guard the pits. During this period, the parents continue fanning the pit with their fins to increase oxygenation required for the hatchlings sheltered in the pit. E. suratensis exhibits a prolonged parental care till the young ones attain a size of 30–40 mm. As the fish hardly eat during parental care, the growth rate of the mature fish is poor in pond rearing conditions.