08/08/2005 - The Environment
Agency fish farms at Calverton in Nottinghamshire
and Leyland in Lancashire are back in business
nearly one year after a rare disease was discovered
in some of the stocks being bred there.
In the Summer of 2004, we had to deal with
an outbreak of Tench Rhabdovirus in some of
the farm stocks.
The detection of the disease at Calverton
and Leyland meant that both sites, including
all ponds and buildings had to be systematically
cleaned and disinfected. Unfortunately, some
fish could have come into contact with the
disease and a decision was made to destroy
all stocks humanely.
New procedures have been put in place that
will minimise the risk of the disease re-occurring
at Calverton or Leyland.
A new test has been developed which can detect
whether a fish has ever been in contact with
Tench Rhabdovirus. This ‘high tech’ test uses
a small amount of blood and has been used
to screen all fish used for spawning.
Production of fish has re-started at both
farms which is good news for rivers and lakes
throughout England and Wales.
In March 2005, brood dace from the River
Cam and grayling from the River Test were
collected and brought back to Calverton. These
adults were spawned and more than 100,000
larvae were produced.
In May 2005, chub, roach, bream, rudd and
tench larvae were also produced. In all, approximately
500,000 young fish are thriving and growing
in the farm’s ponds. These fish will be stocked
out into rivers and lakes in Autumn 2006.
Over the past 15 years, the production of
fish has increased and most river catchments
in England and Wales have now been stocked
with fish bred at Calverton and Leyland. Nine
different types of coarse fish are now raised
at the Agency farms including roach, chub,
dace, barbel, tench, rudd, crucian carp, grayling
and bream.
The fish are released into the wild at 1½
to 2½ years old as part of a planned
programme to replace fish killed in pollution
incidents, and to create new fisheries, so
that fish populations will increase long term.
Alan Henshaw, our manager of the Calverton
site, says: ‘After the upsetting events of
a year ago, it’s great to see life return
to the farm. This is an extremely significant
event for us and we are all looking forward
to the first stocking of our fish in autumn
2006. The team have all worked very hard to
rebuild stocks at Calverton and I’m confident
we’ll be able to continue with the vital work
producing fish for rivers and lakes throughout
England and Wales"
More information:
Calverton Fish Farm is a major source of
river coarse fish in the UK. It is one of
only two Environment Agency coarse fish farms,
the other being in Leyland, Lancashire. Calverton
was established during the late 1930s, producing
mainly trout until 1986 when it was converted
into a dedicated river coarse fish production
unit. Since then, over 4 million fish from
Calverton have been released into waters the
length and breadth of England and Wales.
Calverton covers 4 hectares and has 35 aerated
mature ponds ranging in size from 100m2 to
5000m2. It is fed by fresh water from a borehole,
which has a fairly constant temperature of
9.5 to 10.50C throughout the year. Fish grow
very quickly due to the warm clean water,
abundant food, and high oxygen levels. The
site also has a research unit and a warm water
hatchery that is used to produce eggs and
larvae in the spring.
The eggs are obtained from selected adult
fish, taken from carefully chosen rivers when
they are ready to breed. Once the eggs have
been harvested, the fish are returned to the
river 2 or 3 days later. Surplus fish larvae
are reared for 2 to 3 weeks before being stocked
back into the same stretch of river to ensure
that the impact of Calverton’s breeding programme
on natural fish populations is minimal.
The remaining fish are raised for 1½
to 2½ years and when they are the right
age and size they are released into the wild,
where they will reach maturity between 2 and
4 years of age. They are graded and counted
using computerised equipment, greatly reducing
handling stress and damage, and enabling the
counting and grading of up to 40,000 fish
an hour.
The fish are delivered to their new homes
using a purpose built 6x6 Land Rover mounted
with 300 litre oxygenated tanks that allow
the fish to be released with the minimum of
netting and handling.
