The Indian mackerel Rastrelliger kanagurta exists widely

distributed in the Indo-Pacific region supporting good fisheries in many countries including India

Noble, A

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f j \ CENTRAL MARINE FISHERIES I ^ Q ^ 1 RESEARCH INSTITUTE \i^ ^ fiRNAKULAM, COCHIN-e82 031, INDIA R & D SERIES FOR MARINE FISHERY RESOURCES MA^ ACaBSimNT 2. THE INDIAN MACKEREL Che Indian mackerel Rastrelliger kanagurta exists widely distributed in the Indo-Paciik region supporting good fishoies in many countries including India. Prodncttra Though found all along Indian waters including Andamsa ft Nioobar Islands, high concentrations occur only in the south'west coast. Large^cale exploitation tixus takes place m Kerala, Kama* taka and Goa. The annual average catch in the country according to 196S-'84 data is 66,189 tonnes and 87% of it is fished from the west coast. In east coast maximum catches were recorded ttom Tamil Nadu and Pondicherry. During last 35 years for which all-India annual estimates are availaole, the catch fluctuated between 16,431 tonnes of 1956 and 204,575 tonnes of 1971. Two other species viz,, R. brachysoma and R. faughni also occur in these waters in small numbers. Contribution of mackerel to the marine fish catches in the country, during 1965-'84 ranged from 2 to 20% with an average of 6%. In Goa and Kamataka, the mackerel contri-butes to high proportion in the marine fish catches. In Kerala, in spite of h i ^ production, it accounts only for 7%. On the contrary^ in Andaman St Nicobar Islands, the catch is less, but in marine fish produce it forms 8%. Till recently, the mackerel was exploited only by country crafts and gear. Today these implements are being replaced at many places by mechanised purse seiners. Karnataka alone has a large fleet of it now and the traditional Rampan net of the State is soon becoming out of fashion. Thsi cotton nets, in the meanwhite, gave way to nylon materiab. The mackerel at the consumer rate of Rs. 6/- per kg fixed by Governmental Agency adds on an average of about Rs. 40 crores annually to the national income. The fish is consumed mostly in fresh or iced condition. Processing and export are negligible. Reseuch In view of high commercial importance, detailed information on its biology, fishery and resource has been collected. The mackerel is migratory in habit and its fishery is seasonal. High catches occur during September-November on the west coast and March-April in the east coast. The ofT-season^oichroniscs with the peak of southwest monsoon in July-August. It breeds on shetf ' waters outside the conventional fishing area during pre^ and post-monsoon months. The species lives in the upper layers of sea in shoals, and in calm weather they arc visible at surlwe as patches of ripples during day time and by bioluminescence at night. TfaJs is being taken advantage of for their exploitation. Mackerel feeds on the small plants and animals called plankton pesent in water. No item is recognised as its staple food and none identified as indicator f species. ' The commercial catches depend mainly on fishes of 18^24 cm sizes and its bulk comprises of a single year class. Success of the ' fishery in a season rests on recruitment of this year class into the ( fishing grounds and annual replenishment of its stock. It was estimated that the total mortality (Z) of the mackerel in the popu-lation is around 3 of which 2 die due to fishing (F) and 1 due to natural causes (M); and the rate of exploitation (U) is thus 0.6335. Besides annual variations in landings, the mackerel fishery shows a 10-year cycle with alternating ups and downs in its long-term fluctuations. During the unit of cycle in nineteen seventies, ; the average annual yield (Y) was around 87,200 tonnes. The average annual stock (Y/U) accordingly is 137,650 tonnes and the average standing stock (Y/F) available for exploitation by F 1 is 43,600 tonnes. Studies on yield per recruit (Yw/R) indicate the exploitation would be at its best when the fish is I} year old, 20 cm in length and 80 g in weight. Fishing has not affected the stock leading to overfismng and depletion. Yield is good between F 2 and F4.The potentialstock hence waver between 87,200 and 174,400 tonnes. As there is a sort of stagnation in yield beyond F 4, an increase in effort will go waste without economic escalation in pro-duction. Furtherance of fishing effort hence has to be restricted. However, fixing F max as 5, the maximum sustainable yield (MSY) in India would be around 218,000 tonnes. Recoramoidi^oiis Introduction of purse seining has increased the area of fishing grounds, but failed to enhance production. Fluctuations in the catches therefore are due to fishery independent environmental factors such as the coastal drifts; up welling; monsoon and rainfall; and temperature, salinity, pH, fertility and productivity of the water. The breeding, growtib, density of population, migration and recruitment to the fishery come directly under tiieir influence. Continuous monitoring of data on the fish and its surroundings is inevitable ^ understand the dynamics behind it md to evolve appropriate prediction systems on production. Developmental agencies have gone ahead with mechanisation of fishing. Pufse seining has not but succeeded even in maintain-ing the level kept up by the traditional sector in the past. Inadver-tently, conflicts between them cropped up for fishing rights. Resul-tant competitions in exploitation will one day affect the resource detrimentally. It becomes imperative at this juncture to avoid indiscriminate fishing and proliferation of purse seining. Regula-tions earmarking areas of fishing for the indigenous and mechanised fishery have already come. Closed season for purse seining during June-August as a measure of conserving spawners is a welcome gesture. But exploitation and research should go hand in hand. The fishing industry should take cognisance of the results and recommendations of research particularly on conservation of resource, and provide valuable feed back data on what, where and when they fish, how and howmuch they get, and the effort put in to fish them. Rational exploitation would then be a reality promising maximum catch without endangering' this valuable resource. Prepared by Shri A. Noble, edited by K. Rengarajan and published by Dr. P. S. B. R. James, Director, C.M.F.R.I., Cochin-682 031. The conclusions/recommendations made in this series are subject to revision with addition of further information on the resource. February 1986 

Indian Mackerel

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Indian Mackerel

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