Coastal Aquaculture and Mariculture

Unit 5- Major groups of Fisheries in India

5.3.6. Flat fishes
Flatfishes belong to the families, Bothidae (Flounders), Cynoglossidae (Tongue soles), Psettodidae (Indian halibut) and Soleidae (Soles). They are bottom dwelling demersal fishes with burrowing habits. Twenty five species under 11 genera contribute to minor or major fisheries along the Indian coast. Most of them are small to medium sized fishes except Psettodes erumei, which attains 60 cm length. They are exclusive benthic fishes, found mainly on muddy or sandy bottom of shelf areas; most of them are restricted to shallow waters of less than 60 m depth. However, P. erumei (Indian halibut) and Cynoglossus bilineatus (Malabar tongue sole) occur up to 100 m and 400 m depth respectively.
Distribution:
Global
West Coast of Africa, seas of India and Malay Archipelago and China, common fishing grounds along the northwest coast of India.
India
They are distributed in seas and estuaries of India. Soles are common along the Malabar coast.
Production trend
The catch of flatfishes increased from 7,891 t in 1961 to 52,197 t in 2000. Soles and tongue soles contributed to 94.4% of the total landings of the flatfishes, followed by the Indian halibut (4.8%) and the flounders (0.8%) during 1961-2000. The substantial increase in the flatfish landings is due to the intensification of trawling. About 90% of the catch of the soles and tongue soles, is from the west coast.

Food and feeding
In general, the food items of flatfishes include benthic invertebrates, including cephalopods and also fishes. The malabar sole prefers polychaetes, amphipods and small bivalves. Perumei is a carnivore, feeding predominantly on fishes and cephalopods with crustaceans and bivalves contributing the subsidiary food.
Size at first maturity
Malabar sole (C. macrastomus) -12cm (1 year old); C. dubius -28. 7cm; C. macrolepidotus -15.7cm (1 year old); P. erumei -41.1 cm
Spawning season
The Malabar sole C. macrostomus has a prolonged spawning period from October to May: C. dubius -October -December: C. macrolepidotus -January -February & August; P. erumei –Short spawning period -September & October.
Fecundity
The relative fecundity of C. macrostomus and P. erumei are 6,540-19,890 and 31,380 - 12,19,080 eggs respectively.
Lifespan
The life span of C. macrostomus is about 3 years and P. erumei is 4 years.
Utilization
Large sized flatfishes, such as P. erumei fetch a good price in the marker compared to small sized soles. About 90% of the small-sized flatfishes are salted and sundried and sold during lean seasons. During glut season, a part of the catch is used for the production of fertilizers.
Conservation and management
There is no sign of over exploitation of flatfishes. However, it is necessary to take precautionary measures for sustaining the stock.