It is a pelagic shoaling scombroid fish, widely distributed in the Indo Pacific region. But it is only in Indian Coast, this species is highly exploited. The bulk of the catch comes from West Coast of India between Cape Comorine and Ratnagiri. The contribution from the East Coast (From Tamil Nadu, Andhra and Orissa Coast) is relatively negligible. However, isolated very heavy catches during certain years has been taken on the east coast as well. During the past twenty years, the catch data has shown that the annual mackerel catch in the total marine landings in India is of the order of 8%. But, this is based on the catches varying on 2-19% of total marine landings. The fishery is supported by the species Restrelliger kanagurta (Crivier) mainly. Besides R. Kanagruta, there is one more species, namely, R. Brachysoma (Bleeker) also known as short-bodied Indian mackerel. This has so far been reported from Andaman Islands, where it forms a very small local fishery.
Contribution of the species to all India Marine Landings
In the inshore waters upto 25 meters, the R. Kanagurta is well known to occur all the east and west coast of India. The bulk of the landings to the extent of about 80% comes from the west coast centres, the chief among them being Quilon, Allepey, Cochin, Calicut, Tellicherry, Malpe, Karwar and Malwan. The fishery in general extends on the West Coast from Cape Comorin to Ratnagiri. On the East Coast spordic catches occur near Mandapam, Nagapattinam, Madras, Kakinada, Visakhapatnam and some parts of Orissa coast. The annual landings of the species during 1989 accounted for 213697 tonnes.
Age and size composition of the fishery
The commercial fishery begins to exploit mackerel from about a size of 18 cm., which they attain within six months. Fish below this size are also caught in good numbers in some places. About 80-90% of fish in the commercial catch comes from size below 22 cms., which they attain in the first year of its life. The size groups above 22 cms., contribute a small portion in the commercial catch. The major contribution to the commercial catch comes from the 0 year class. The 1-year and 2 year classes contribute progressively less.
Migration and shoaling behavior
The mackerel of different size groups move in separate shoals. They move in semicircular or arrow head formations and their speed is about 8-10 miles per hour. They scatter, when pursued by seerfish but, when the shoals are chased by sharks or porpoises, the mackerel submerge with the head downwards into a compact mass. When the markerel dive a patch of muddy water is seen at the surface which is due to churning of water by a large mass of fish. The luminescence caused by mackerel shoals passing through a patch of phosphorescent noctiluca off Ratnagiri coast are not unusual.
The fish is a plankton feeder, feeding to a great extent on zooplankton and comparatively to a lesser extent on the phytoplankton.
Mackerel recede from coastal waters during the south west monsoon period for the purpose of spawning. It is believed that the fish after spawning do not permanently retire to deep sea, but come back to coastal waters and their spawning ground are not very far from the coast. The region between Vizhinjam and Cape Comorin off the south west coast of India appears to be spawning ground, as spawners, young mackerel and post larvae have been obtained in this region.
The fishing season starts very early in about August in the southern zone from Cape Comorin to Ponnani and lasts till February. In the Central zone from Ponnani to Mangalore also the season starts at about the same time and lasts till March-April. In the northern zone from Manglore to Ratnagiri, the fishery starts late by about October-November and lasts till about March. Peak catches occur in October-November. In Karwar and south Kanara two peaks are noticed, one at the beginning and the other at the end of fishing season.
Gear and Crafts used
In Konkan, north Kanara and south kanara, the chief gears in operation are shore seine (Rampani), gill net (Pattabale) and cast net (pag). The types of fishing boat are Pandi, Hodi and Dhoni with or without out triggers. In Kerala boat seines (Odam vala, Paithua vala) Ayilakollivala, Thattumvala, Nonvala) shore seines (Karavala) and gill nets (Ayilachalavala) are operated with the help of degout canoes. In Tamil Nadu, masula boats, Tuticorin type of boats, canoes and catamarans are chiefly used for operating different types of shore seines, boat seines, bag nets and gill nets. In Andhra and Orissa more or less similar types of gear are used as is in Tamil Nadu, with masula boats, plank built boats and catamarans.
Mode of disposal
Mackerel is consumed fresh or in cured conditions. About 25% of the catch is salt dried, wet cured and pickled by colombo method using salt and tamarind. When the catches are big, they are impounded for, short period, in shallow waters, by Rampani nets, before they could be disposed off in a satisfactory manner.
In India 20% of the catch is salt cured or pickled and approximately 5% are canned. A negligible portion of the salt cured mackerel is exported to Sri Lanka and Far East, while canned mackerel is entirely sold with in the country. The remaining 75% are consumed in fresh form in the country. Sometimes unsold mackerel are beach dried and then converted into manure for use in coconut, coffee and tea plantations.
The importance of mackerel fish meal as cattle and poultry feed is well known. It has easily digestible proteins, vitamins and minerals and is obtained by pressing the cooked fish and sundrying the same. It is also prepared by beach drying of fish in the open sun without being cooked. In both the cases it is then powdered, sieved and stored in tins.
Pickling of mackerel in brine fortified with 0.5% and 0.25% propionic acid levels has been recommended to keep the fish in good condition for about a year and upto 5 months respectively. Curled mackerels used to export mostly to Sri Lanka. The export of dried fish declined in recent year due to the increase in internal demand for fresh fish with the provision of more and more ice and cold storage facilities and due to poorer catches of the fishery.
Canning of mackerel was attempted by the Tamil Nadu Govt. near Calicut, which is proved to be a commercial failure due to lack of regular supply of fish, high cost of cans and ground nut oil.
There is considerable potential for the export of canned mackerel in the world markets and this trend is likely to continue in the future. Indias export of this item has been practically nil. In view of the large market potential and abundant resources available, we have to ensure a steady supply of mackerel by:
The variation in the pattern of the coastal current in relation to mackerel fishery and the co-relation between the coastal currents and occurrence of the fishery may be identified in order to be able to predict the fishery prospects from year to year.