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Conservation & the Environment


Fish are vital for maintaining a rivers ecosystem a look into Calverton Fish Farm


ALAN HENSHAW


Fish re-stocking is a vital element in the restoration of a rivers ecosystem, it restores the aquatic and wildlife habitats and can bring nature back into balance.


Fish numbers can decline for any number of reasons - it could be the effects of spillages, the adverse effects of water control structures, such as weirs and dams or naturally occuring events such as drought or floods. As the fish numbers decline so too can the natural ecosystem causing a knock on effect for wildlife and plants alongside the channels.


Calverton plays as essential role in the well being of our rivers and lakes. In England and Wales, as many as half a million fish are stocked into rivers and still waters, each year from the Environment Agency's national coarse fish rearing unit at Calverton.


about Calverton


Calverton fish farm is based a few miles North of Nottingham and is funded by the anglers rod licence duty. The service provided is all part of the the Agency's work to protect and improve fisheries throughout England and Wales.


It has been under the control of several operating authorities, starting life under the control of the Trent River Board, which later became the Severn Trent Water Authority. It then came under the control of the National Rivers Authority (NRA) before the role of the the NRA was brought under the Environment Agency , created in 1996.


1939 - Calverton began life as a trout farm supplying Brown and Rainbow trout to rivers and still waters throughout the midlands.


1975 - half of the site was converted into a coarse fish experimental unit and techniques were developed for producing cyprinids in larger numbers.


1985 - the whole site was converted to coarse fish production.


1992 - the NRA, doubled the size of the farm giving the space needed for future developments that included, new ponds, extensive pond reconstruction, purpose- built recirculation systems, holding facilities and a warm water hatchery.


1996 - Calverton came under the operating control of the newly created Environment Agency


Present day - The farm now covers 4 Hectares, has 32 mature ponds ranging in size from 250m2 to 5000m2 and is recognised a national and international centre of excellence in rearing Cyprinids. They also provide R&D support to various Universities, Colleges and research institutes.


36 Brood female Barbel from the River Trent.


Carefully selected adults in spawning condition are taken by electric fishing from carefully chosen sites. They are quarantined in holding tanks and injected with various hormone preparations that mimics the natural hormone surge, which happens naturally in the fish at spawning time.


Close up of Barbel eggs.


The eggs are taken and 2 to 3 days later the adults are returned to their native river in tip- top condition.


Newly hatched Barbel Larvae with yolk sac.


When the larvae have been stocked into the growing ponds, the surplus fry are reared for 2 to 3 more weeks before being stocked back into the same stretch of river that the adults came from. This ensures that there is no impact on the population from the brood stock collection activities.


Two essential ingredients that we all rely upon are water and oxygen, fish require the same – a good supply supply of oxygenated water. Water to the farm is supplied via of a borehole. The borehole is capable of supplying 1 million galls/day and provides all the water that the farm requires, the advantage being that no "second hand" water is used and the risk of parasitic, bacterial and viral infection is removed. The quality of the water is very good, but the low oxygen content at 65% saturation, means that oxygen is added to bring the saturation level up to 100%. The ponds are using large diameter porous pipe linked to an underground air supply, for the smaller ponds (up to 350m2) and single or multiple "air


www.fadsdirectory.com The fish farming process


Firstly, for a fish farm..you need fish, or more specifically fish eggs. Calverton does not keep adult fish so all brood stock are collected from the wild – this is because egg quality is usually poorer when captive brood fish are used and there would be no genetic variation if the same adult fish were repetitively spawned.


The fertilised eggs are placed inside incubation troughs for between 7 and 30 days depending upon on species and incubation temperature. When they hatch, the larvae then spend up to 7 days absorbing their yolk sacs before swimming up to commence feeding, at which point the larvae must be fed or stocked out.


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