Bombay duck fishery

The Bombay duck fishery, supported by a single species, Harpodon nehereus, contributes to about 10% of the estimated average annual marine landings of India. With a peculiar discontinous distribution of the species, the fishery is of utmost importance in two maritime States of India, Gujrat and Maharashtra, where over 98% of the all-India Bombay duck catches are landed. In fact, from the bulk of the landings and the economic returns, the Bombay duck fishery in Gujrat and Maharashtra is equivalent to oil sardine and mackerel fisheries in Mysore and Kerala States.

As already stated it has wide discontinuous distribution along the coast of East Africa, Indian subcontinent, Malaysia, Indonesia and China. In India it is taken in large quantities on the south and southeast coasts of Saurashtra, on the Gujrat coast and the Konkan coast of Maharashtra. It is also taken in appreciable quantities on the Andhra Orissa coasts and from the estuaries of Bengal. The discontinuous distribution of Bombay duck along the coasts of India has been attributed to various factors, the principal ones being the distribution and movements of various food components, variation of salanity along the coast, the 70⁰F isotherm barrier of July etc. It is felt that the presence of low surface temperature in the area of occurrence is primarily responsible for peculiar distribution of the species.

In view of peculiar distribution of the fishery, it is essential to determine, whether, Bombay duck occurring on the east and west coasts of India belong to the same stock or they originate from more than one stocks; in order to avoid depletion of the fishery due to intensive exploitation.

From an examination of samples from the four localities, it appear that the Bombay duck fishery is supported by three independent stocks. The fishery at Versova and Janjira Murud is supported by a single and closely related stocks whereas the fisheries of Jaffrabad and Masulipatnam are supported by two independent stocks.

The catch statics indicate a remarkable increase in landings from 7262 tonnes in 1951 to 1,28,618 tonnes in 1956. In 1958 and 1959 recorded poor landings. The fishery revived in 1960 and since then it has more or less stabilized around 80,000 tonnes comprising 80% of the catch of immature fish. 80% of total Bombay duck landings come from the west coast of India, which exclusively from the States of Gujrat and Maharashtra. In 1989, 1,30,689 tonnes have been landed.

A study of sex ratio indicated that females predominated the catches throughout the year except in the month of July and August, when male predominates.
In view of the continuos breeding habits, the recruitment to the stocks is also continuous and is not restricted to definite periods.
The fish appears to attain an average length of 127mm at the end of the first year and 210mm at the end of the second year. The frequent appearance of the '0' class shows that the recruitment is continuous and is more pronounced during the post monsoon period i.e. September-December.

The wanderings of the Bombay duck, which bring about fisheries of much regional importance along certain coasts seem to be influenced by two main factors i.e. the availability of food and the favorable condition of the water temperature. The low surface temperature in the areas of occurrence is probably responsible for the peculiar distribution of the species to a great extent than the other factors.

In south and southeast coast of Saurashtra, about 400-500 boats operate in the area during the fishing season, each boat carrying 7-9 fishermen. They operate 'Dol' nets 6-12 miles from the coasts in water of 10-15 fathoms deep. The majority of fishermen operate two nets at a time from each boat, but some units operate three nets.

The fishermen of Gujrat coast from Kosmba to Kolak fish for Bombay duck by gill nets along a stretch of 10 miles of coast line in inshore water during the months of June to September. These gill nets are 30 feet long and 3 feet high with a mesh of one inch from knot to knot.

The fishermen of Konkan coast from Kalai(South of Daman) to Waroda operate 'Dot' nets of various sizes in waters ranging in depths from 6-10 fathoms.

The fishermen of Andhra-Orissa coast harvest Bombay duck in boat seines and fixed bag nets operatedby two catamarnas.

A portion of the catch is used as a food when fresh, but the bulk of it is sun dried. Being a very soft fish it is easily spoiled. When the landings arrive late the catch is very often not in fit condition for human consumption and is forced to be converted into manure. The fish is sun dried on specially erected bambo scaffoldings.

Non laminated Bombay duck

Sundrying of Bombay duck on scaffolds is the traditional method of preservation of the fish on the Maharashtra and the Gujrat coasts. The fish after being washed in sea water, is locked in pairs at the jaws and hung on ropes tied between poles to be dried in the natural breeze and heat. Complete drying of the product requires 3-5 days depending on the weather conditions. After 3-4 days the fish is removed from the scaffolds and further dried by spreading on palmyra mats.

Fresh fish are washed in water containing 1-2 per cent salt and 0.05-0.1 per cent citric acid. The fish flattened by longitudinal cuts to remove entrails and vertebral column and spread over wire mesh trays on bamboo platforms and dried in sun till the moisture content is brought down to 10%. The laminated fish is pressed individually by passing through a roller press. The individual pieces are trimmed into uniform size and shape.

Ag.
Technologies
(Fisheries)