The Indian Mackerel belongs to Family- Scombridae Genus- Rastrelliger A total of 3 species are found in Indian waters-I. R. kanagurtaII. R. brachysomaIII. R. faughni More than 95% of the total mackerel catch is contributed by Rastrelliger kanagurta. Nearly 90% of world catch of Indian Mackerel is contributed by India alone.
Distinguishing features of R.kanagurta Head length equal to the height of the body. First dorsal spinous, first spine shorter than second. Second dorsal soft rayed. Caudal deeply forked with pointed lobes. Few golden yellow bands present along and below lateral line. Dorsal and anal finlets 5 or 6 in number.
So how would u differentiate R.kanagurta, from R.brachysoma & R.faughni R.brachysoma can be easily differentiated from R.kanagurta by its short head which is much shorter than greatest depth of body and is marked by the absence of longitudinal yellow bands and by the presence of black spots. R.faughni has even shorter head, with shorter mandible & maxilla with shorter and fewer gill rakers. Absence of both longitudinal bands and black spot differentiates it from other other two.
Rastrelliger kanagurta is extensively found in tropical indo-pacific regions between 30°N and 30°S latitudes and 30°E and 160°W longitudes. Countries it occurs are- coastal waters of Eastern Africa north of Durban, Seychelles, Madagascar, Mauritius, countries bordering red sea and Persian gulf, Pakistan, India including Andaman & Nicobar islands, Sri Lanka, Myanmar, Malaysia, Thailand, Indonesia, Cambodia, Northern Australia, Polynesia, Micronesia, New guinea, China, Taiwan, Philippines and Hawaiian islands.
R.brachysoma is also found in Indian waters however its presence is restricted to the southern African waters, Andaman sea, Malaysia, Thailand, Indonesia, Philippines and solomon islands. Occurrence of R.faughni has been recorded from Taiwan, Philippines, Indonesia and east coast of India. R.brachysoma R.faughni
Surface feeders of inshore waters Ingestion is mainly through straining by well developed feathery gill rakers. Food items- phytoplankton and zooplankton. Phytoplankton- comprises mainly diatoms, Coscinodiscus, Pleurosigma, Chaeotoceras, Eragillaria, Thalassionema, Nitzschia, Rhizosolenia, Skeletonema and Biddulphia and dinophyceae, Ceratium, Peridinium, and Dinophysis.
Zooplanktons mainly comprises of :- Copepod crustaceans represented by- Oithona, Acrocaianus, Eucalanus, Temora, Euterpina and Acartia. Other food organisms include Cladocerans, Cirripede larvae, mysids, sergestids (Acetes), amphipods, decapod larval stages of nauplius, protozoea, zoea, and mysis stages of prawn, alima larvae, polychaete worms, foraminiferans and molluscan larvae.
REGION SIZE AT AGE FIRST MATURITYR.kanagurta of 19-22.4cm 2 yearswest coast ofIndiaR.Kanagurta of 25-25.9cm 3 yearsAndaman sea
R.kanagurta is heterosexual However sexual dimorphism is not distinguishable from external characters. Sexes can be separated from gonadal examination only after attaining size of 12cm. As stated before the general age of attaining maturity is about 2years. There is strange regional difference in the spawning patterns, explained in next segment.
The Indian Mackerel has been found to have 2 spawning season depending upon monsoon season:- Intensive spawning and Supplementary spawning seasons. The spawning seasons not only varies along south-west and south-east coast but also along the south-west coast from South Canara and Mangalore coast in karnataka to Vizhingam in Kerala. Eggs are pelagic in nature and contains a single oil globule.
AREA SPAWNING SEASONWest coast (in general) Corresponds with southwest monsoon July-August(intensive spawning) Nov-Dec(supplementary spawning)East coast (in general) Corresponds with northeast monsoon Oct-Dec(intensive spawning) April (supplementary spawning)Andaman sea October-April (1st spawning) No other data available
No of batches and amount of eggs liberated by Mackerels in 1 spawning season remained unknown for a long time. It was later established that a 28cm R.kanagurta releases its eggs in 3 batches in 1 spawning season. Eggs released in each batch and total fecundity is given in the following table:- Batch no. Eggs Total released fecundity 1 45,000 2 27,000 1,10,000 3 38,000
After extensive research work from CMFRI from year 2002-2005, the sex ratio in R.kanagurta was found to be 1:1. i.e 1 female per every single male.
Mackerels are shoaling fish. They do not move in small schools or in few numbers but in millions or even billions! Shoals are differentiated into fish of same size groups comprising a single shoal moving together steadily in the same direction. Shape of the shoals- crescentic or arrow head formation Shoal size- 100metres – a few kilometres Moving speed- 8-10miles/hr During day they can be spotted as a long dark patch moving in water During night they emit luminiscence which helps them in moving , but also helps in scouting for the fishermen
Fishing is mainly carried out in neritic waters along the west coast up to a depth of 25metres. Fishery is mostly supported by juveniles of size range 16-18cm. Main landing centres are- Ratnagiri, Malvan, Goa, Karwar, Malpe, Tellicherry, Calicut, Cochin and Alleppey on west coast, Mandappam, Nagapattinam, Kakinada, Vizag & some parts of Orissa and West Bengal on east coast (accidental catch). West coast contribute a mammoth 73% of total Mackerel catch, while east coast contributes 27%.
Basic Crafts used for fishing on west coast are:- Dug-out canoes Canoe boats Plank-built boats, & CatamaransTypes of gears used are:- Boat seines Beach seines or drag nets Gill nets- comprising mainly drift nets, & Cast net
REGION CRAFTS USED GEARS USEDMAHARASHTRA DUG OUT CANOES- Pagar Beach Seine-Rampani payawada and Thoni Drift Gill net- Bongdajal CANOE BOATS-Akada hodi Cast net- PagKARNATAKA DUG OUT CANOE- Thoni Drift Gill net- Kandadi bale, Patta CANOE BOAT- Pandi Beach seine- Rampani, KairampaniKERALA DUG OUT CANOE- Odam Drift Gill net- Ozhuku vala, Ayila- and Thoni chala vala CANOE BOATS- Vallam Beach Seines- Karamadi&kara vala CATAMARAN- Kattumaran Boat Seines-Ayilla koli vala, Thangu vala, Odam vala, Madi vala, Paithu vala.TAMIL NADU PLANK BUILT BOAT- Boat Seines- Thuri Valai, Madi Valai Vallam Beach Seines- Kara & Peria Valai CATAMARAN- Kattumaran, Drift net- Vazhi & Vala Valai Periamaran, ChinnamaranANDHRA PRADESH PLANK BUILT BOATS Beach seines- Pedda Vala CATAMARANS- Padava Boat Seines- Iraga Vala Gill nets and cast netsORISSA PLANK BUILT BOAT- Ber Beach Seine- Ber jal
YEAR OF LANDING CATCH (IN ‘000’TONNES)1961-1970 52.041971-1980 85.601981-1990 95.351991-2000 190.472001-2005 113.59
Year of maximum landing-2,91,080 tons(1989) Year of minimum landing- 20,780 tons(1968) Potential yield- 2,95,000 tons Current landings- 1,25,420 tons(2005) Region wise contribution of total catch:- REGION PERCENTAGE NORTH-EAST 3.5% SOUTH-EAST 31.1% SOUTH-WEST 55.2% NORTH-WEST 10.2%
MIGRATION of Rastrelliger kanagurta:- The mackerel shoals enter the inshore waters of west every year during post-monsoon period. The reasons for this migration is still a debatable issue. Some of the possible reasons under considerations are:-i. For feeding purposes. However this may not be right, as they do not migrate when the planktonic population are at its peak in off south-west coast .ii. Changes hydrological and meteorological parameters. Mackerels seem to have higher susceptibility to changes in temp. than salinity and hence may migrate to cooler inshore waters. Migrations into the estuaries and backwaters upto as much as 1.5 miles have also been noted in the summer months.
RELATIONSHIP BETWEEN Mackerel and Oil Sardine Fisheries of India:- The geographical distribution and the fishing season of the 2 mainstay of Indian fisheries coincides with each other. There exists an inverse relationship between the two fisheries, i.e. lets say, a successful year of Mackerel fishery coincides with the failure in catch of Oil sardine fishery and vice versa. There are various factors that may lead to this-I. Competition for food- this is the most obvious assumption. However conclusive evidence has not been found to supplement this theory.II. Competition for space- it is assumed that the spawning grounds for both fishes are in the same regions, so there may exist a competition for space for survival.
MANAGEMENT and CONSERVATION practices in Mackerel Fishery The large scale exploitation of mackerel juveniles along the southwest coast has lead to concerns about the sustainability of the Mackerel stock in the country. 42% of the catch comprises of juveniles of size groups 14-16cm. This has led to development of precautionary and conservative strategies by limiting the fishing of mackerels during monsoon months of July-September. Increasing the mesh size up to a minimum of 35mm is another regulation that has been recently employed to control overfishing of Mackerels.