Coastal Aquaculture and Mariculture (2+1)

Unit 1 - Shore based aquaculture and mariculture

1.4.2. Shellfish seed resources
Shrimp seed resources: Although 11 species of shrimps are available in India only three species namely, Penaeus monodon, P. indicus and P. semisulcatus are cultivable.These species breed in offshore waters, but their seeds enter lagoons, creeks, estuaries and backwaters from where they can be easily collected.

The following table lists the occurrences and abundance of seeds of the two most important cultivable species of shrimps.

Factors affecting shrimp seed abundance
Tidal amplitude, lunar phases, current, water depth, river discharges, rain, substratum, suspended matter, pollution etc. affect the availability of shrimp seed. P. monodon has wider salinity tolerance, therefore, available in a wide variety of habitats. The seed are particularly abundant during full moon and new moon night tides.
Crab seed resources
The seeds of mud crab, Scylla serrata have a wider distribution in the east rather than the west coast of India. They are available in Sundarbans, Chilka lake, Vizag, Pulicat, Parangipettai and Tuticorin. In the West coast they are available in Cochin Backwaters. Seed abundance has been reported during June-August in Tuticorin and October-January in Chilka Lake.

Lobster seed resources
Detailed studies on the distribution of lobster seed resources in different coastal areas are lacking. Lobsters spawn throughout the year in deeper waters. Peak breeding is during November to December.

Molluscan seed resources

Mussel seed resources
The spats of green mussel Perna viridis are found both along the east and west coast of India. Gthey are found in rocky open coasts, harbours and mouth of estuaries where the salinity is as much as that of the seawater. They attach themselves to rocks, pilings and other hard objects from intertidal zone to a depth of 15 m depth.
The spats of brown mussel Perna indica have restricted distribution. They are abundant from quilon to Cape Comorin in the south west coast and from Cape Comorin to Tiruchendur in the south east coast of India.

Resources of edible oyster seed
The spats of Crossostrea madrasensis are abundant in Deltas of Godavari and Krishna, Pulicat, Chennai, Porto Nov, Mandappam, Keral and Port Blair. The spat are available in the south east coast from late September to early May.

Pearl oyster seed resources
The seeds of pearl oyster are very scanty and are not available in sufficient quantities. Aquaculture of this group needs to depend solely on hatchery produced seeds.