Definition of estuary☼ An estuary is defined as a semi- enclosed coastal body of water, which has a free connection with the open sea and within which the seawater is measurably diluted with the freshwater of land drainage.
• Estuaries are important & distinct component of coastal landscape with highly complex ecosystems,varying physicochemical properties & highly diverse flora & fauna.• Estuaries are of different shapes & sizes, & are known by different names,such as ‘river mouth’,’bays’,’lagoons’,’harbours’ or ‘inlets’.
ESTUARINE RESOURCES OF INDIA• Indian coastline is more than 7500km in length with an EEZ of 2.015 X 106 km2 that accounts for 61% of total land area.
• The country commands a distinct position with more than 55 estuaries,located on East & west coasts• The estuarine resource,including the associated waters,of India has been estimated approx. at 30,000,00 ha.• Amoung the major rivers Ganga, Mahanadi, Godavari,Krishna,Cauveri [east coast] & Narmada,Tapti,Mandovi,Zuari [west coast] forms highly productive esuarine systems esp. in relation to fisheries.
PRESENT STATUS OF FISH PRODUCTION & PRODUCTIVITY• The estuarine fisheries in India are always above the subsistence level,contributing sizably to the inland fish basket in the country.• The fish productivity of various estuaries has been estimated in the range of 45-75 kg/ha.
ECOLOGY AND FISHERIES OF SELECTED ESTUARIES & ASSOCIATED WATERS• HOOGHLY ESTUARY• Largest estuarine systems in India.• width 2-12km.• Salinity : 0.2-31.6 ppt• live estuary supporting rich biodiversity• better known for its profitable winter fishery,the famous sunderban mangroves & Hilsa fishery.
TRENDS OF FISH CATCH• The trend of fish catch in Hooghly indicated significant increase during recent years primarily due to increase in Hilsa catch.• Between 1998-99 & 2002-2003,the average per annum catch of Hilsa has been estimated at 10,382.9t with an impressive increase of 63.3% from previous 5 years [6279.6t]
KRlSHNA ESTUARY• Salinity : 20-35ppt.• fishery dependent on marine migrants.• Mullets are hallmark of Krishna estuary.• Other gps. found in catch include clupeids,perches,catfish,penaid prawns & crabs.
• Annual fish catch during 2004-06 has been estimated at 496.1 – 540t with productivity ranging from 83- 90kg/ha.• Average catch per unit of effort - low & depend on season – 13.6kg/boat [post-monsoon] & 1.74kg/boat[pre- monsoon].
• Godavari estuary as a whole supports 23 prawn sps. Of this Penaeus indicus,P.monodon, P.japonicus etc are impo. from fishery point of view.• Palaemonid prawns like Macrobrachium rosenbergii,M.malcomsonii etc are also impo..
MAHANADl• Comprises 2 impo. estuaries of Odisha viz. Mahanadi & Devi.• Salinity : 0.6-18 ppt.• Fishery include – mullets,prawn,thread fins,perches & others contributed by 96 sps. of fin fish & 10 sps. of shell fish.• Sps. diversity differs with depth & salinity.• However,relatively higher fish catch ,coupled with higher diversity, has been recorded towards seamouth as compared to freshwater stretch
CHILKA• Largest lagoon in the east coast of India.• Lagoon has distinct marine,brackish & fresh water strands but is primarily an estuarine ecosystem.• Ramsar site.• Endangered sps. & migratory birds.• Highly productive with rich fishery resources.• Potential source for high priced prawn & mullet fisheries.
PULICAT LAKE• Second largest brackish water lake in India.• Run //l to Bay of Bengal.• Opens into Bay of Bengal through a narrow passage at its southern end,near Pulicat town.• Shallow lake – average water depth : 0.7m.• Salinity : 7.79 – 28.91 ppt.
• Fishery – largely depend on P.indicus,M.cephalus & Chanos chanos.• However dominant fishery of Chanos chanos in 1980s become rare.• Fisheries of Sardinella,Hilsa,tiger prawn also declined significantly [over fishing].• Penaeid prawns of importance – Metapeneaeus dobsonii,M.monoceros & M.brevicornis.
• The crab fishery – very conspicuous.• The use of destructive gears,esp. small mesh bar nets,has lead to indiscriminate fishing of mullets.• The average catch per fisher per day has been estimated to be poor at 300g-500g/day,mainly of P.indicus
KERALA BACKWATERS• 44 rivers in Kerala,41 flows westwards from W.G to Arabian sea through backwater.• Total area : 500 sq.km• Comprises of vast system – interconnected lagoons,bays & swamps.• Fish landing :14000-17000t
• Vembanad is largest backwater.• Northern part of vembanad – cochin backwater.• River Periyar in north & Pampa in south along with many small channels,streams,irrigation canals etc –freshwater source of cochin backwater.• Salinity : 9-11ppt