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Fisheries > Culture Fisheries > Mussels

Species

Mussels inhabit a wide range of estuarine and marine environments. They are sessile and attach to rocks, jetties and piers, or sometimes form dense beds on sandy flat substrates. Mussels can be found from the low tide level to a depth of 10 metres.

Mussels, like most bivalves (two shelled molluscs), are filter feeders and do not require additional feeding. They strain phytoplankton (microscopic plant-like organisms) from the water. They prefer plankton in the size range of 4 to 120 m (microns), with the majority of food being less than 20 m.

Of the two species of commercially important mussels, the green mussel Perna viridis is widely distributed and found in small beds in Chilka Lake, Visakhapatnam, Kakinada, Madras, Pondicherry, Cuddalore and Porto Novo on the east coast and extensively around Quilon, Alleppey, Cochin, Calicut to Kasargod, Mangalore, Karwar, Goa, Bhatia creek, Malwan, Ratnagiri and the Gulf of Kutch on the west coast. P. viridis occurs from the intertidal zone to a depth of 15 m. On the other hand, P. indica has restricted distribution and is found along the southwest coast from Varkala near Quilon to Kanyakumari and from there to Tiruchendur along the southeast coast. It occurs from the intertidal region to a depth of 10m.

Distinctive characters

The distinctive characters of the two species of Perna are given below:

Character

Perna viridis

Perna indica

External colour

Green

Dark brown

Mantle margin colour

Yellowish-green

Brown

Ventral shell margin

Highly concave

Almost straight

Middle dorsal margin

Arcuate

A distinct dorsal angle or lump present

Anterior end of shell

Pointed, beak-down turned

Pointed and straight

Number and size of hinge teeth

Two small teeth on the left valve and one on the right valve

One large tooth on the left valve and a corresponding depression on the right valve

 

green

Green mussel

indica

Brown mussel

Exploitation

Kerala state can be called as the ‘Mussel fishery zone of India’ since extensive beds of both the green and brown mussels occur in this state, which also accounts for the bulk of the mussel production in the country.

Mussels are exploited during September-April. Good low tide, clear water and sunny days are favourable for fishing. Women and children collect the mussels from the intertidal areas. Mussels are collected by handpicking and a chisel or a knife is used to dislodge the mussels from the rocks. Men either swim or use a canoe to reach the fishing grounds and exploitation is restricted to 5 m depth. They may use masks and carry a nylon bag tied to their waist to keep the catch. Both full time and part time divers are engaged in the mussel fishery.

P. viridis : The major mussel landing centres in the Cannanore-Calicut areas are Koduvally, Mahe, Chombala, Moodadi & Thikkodi, Elathur, Challium and South Beach. The standing stock of the mussels in this area has been estimated at 15,887 t in 555 ha of mussel beds and the density varies from 2.25 to 4.5 kg/m2. The length of the mussels varies from 20 mm to 129 mm with 50-90 mm group contributing to the bulk of the catches.

P. indica : The important fishing centres are Kovalam, Avaduthura, Vizhinjam, Mulloor, Pulinkudi, Chowara, Colachel, Kadiyapatnam and Muttom. The standing stock is estimated to be 1,586 t. Peak landings are during November-January. The population density of mussels is about 5-8 kg/ m2.

Seed collection

Even though hatchery technology is available, mussel seed (10-35 mm spats) in adequate quantities for culture operations is collected from the natural beds or by laying collectors in the farm itself.

It has been reported that profuse settlement of spats of green mussel takes place on granite embarkments and groynes laid along the central Kerala coast for prevention of sea erosion. The density of seed varied from 220 to 248/100 cm2 on the rocks submerged for most of the time and 112 to 170/100 cm2 in less favourable surroundings. Favourable area for spat collection for brown mussel has been the Vizhinjam area.

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