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Egg-citing times down on the Fish Farm

Posted by: , Posted on: - Categories: Fisheries and biodiversity

Every year we breed thousands of fish to stock into rivers and still waters around the country.  Up to half a million are used to replace fish killed in incidents, to improve fish stocks, and to develop new fisheries.

Spring is a really busy time of year for me and my team based at our fish farm in Calverton, Nottinghamshire. Family life has to take a bit of a back seat as we’re on the road as early as 5.30am travelling around the country to collect fish to breed from.  We always use wild fish as the quality of their eggs is better. In the last couple of weeks we’ve been catching dace from the River Snail in Cambridgeshire and grayling from the Derbyshire Derwent and Yorkshire’s Wharfe, Ure, and Nidd rivers.

When we arrive back at Calverton with the fish they are placed in tanks and injected with hormones.  This mimics the hormone surge which happens naturally in fish at spawning time.  Males and females are kept separately in warm water until ovulation takes place.

The males and females are then dry stripped and the eggs are treated with a solution to improve the rate of fertilisation.  After 10-30 minutes the eggs are gently poured into mesh trays and placed inside troughs, where they receive a regularly changing water supply. The eggs are  incubated for between seven and 30 days depending on species and temperature.

The eggs are stripped from the female fish, fertislised and then poured gently into trays.
The eggs are stripped from the female fish, fertilised and then poured gently into trays.


The adults are given a couple of days to recover and then they are all taken back, in tip top condition, to the rivers they came from.  Last year it was a bit chilly as we were doing this and Rab got the short straw and had to wade into a very cold river!

James Rabjohns, Fish Farm Technical Officer releasing adult Grayling back into a very cold River Derwent near Hathersage
James Rabjohns, Fish Farm Technical Officer releasing adult Grayling back into a very cold River Derwent near Hathersage

Once the dace and grayling eggs are developing nicely we have a short respite, time to win back some brownie points with our family before we get to May and an even more bonkers few weeks as we breed another seven species of fish. We’ll let you know how that goes...


Alan Henshaw is the Team Leader at the Environment Agency's Fish Farm at Calverton in Nottinghamshire. His manager Louise Johnson tweets about their work.

The work at Calverton is funded by rod licence sales, this film created in association with Online Fishing TV gives a unique insight to the work of the Environment Agency to protect and improve fish stocks in England

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  1. Comment by Stewart Taylor posted on

    If you were catching fish on a river in the last couple of weeks you must have been fishing in the close season!

    • Replies to Stewart Taylor>

      Comment by Environment Agency posted on

      Hi Stewart, the fish were caught on 14 March, just before the start of the coarse fishing close season. We hope you enjoyed reading about our work at Calverton fish farm. ^Jo

  2. Comment by paul mclinden posted on

    I wish they could stock grayling in and around the Coventry area.

  3. Comment by Michael Squire posted on

    I'm hoping to do my work based learning from hadlow college, with your good people at calverton. Which my head lecturer and his colleagues will be helping me to apply for with yourselves, in the next few weeks. Given good fortune and grace, it'd be fantastic to be able to assist and learn more about what you do there.

  4. Comment by Kevin Grozier posted on

    I am a member of a small syndicate with access to a lake in Ringood area. It is 2.5 acres and has a depth range of approx. 1.6 metres at one end (damned) and .8 of a metre at the shallow end. It has several lily pads and much overgrowing bankside vegetation (marsh sedge) etc grass. It has a small number of carp and I put some true Crucian carp (50 7.5- 10 mm) on advice from peter Rolfe into the pond 5 years ago. I am a member of The Crucian Carp conservation group and as the small number of fish weren't sufficient to impact upon breeding I would be interested to know if the EA @ Claverton would be prepared to seed this lake/pond?

  5. Comment by paul searle posted on

    can i buy grayling from you?

    • Replies to paul searle>

      Comment by kathrynbooth posted on

      Hi Paul

      We don’t sell fish to the general public. We only supply fish in-house as part of our statutory duties and these are stocked free-of-charge by our fisheries teams throughout the country.

      Many Thanks

  6. Comment by ian coxon posted on

    Please say hello to Alan Henshaw, great work they are doing up at Calverton. Hopefully he will remember the ginger Brummie

  7. Comment by Rich Green posted on

    Hi, I have a surplus of small roach and Rudd. Would these be of interest to you FOC.

    • Replies to Rich Green>

      Comment by kathrynbooth posted on

      Hello Rich
      Please either call our customer services on 03708 506506 or email into our enquiries team at . We would need further information from you so we will be able to contact our fisheries team in your area, for their advice.
      Kind regards

  8. Comment by Mark Parry posted on

    A huge thank you for Calverton in supplying our club with Crucian Larvae.

    We have some lovely old farm ponds to grow them on.

  9. Comment by Paul Woodings posted on

    You carry out vital work at Calverton. Well done to everyone involved and keep up the great work.
    Question: Im genuinely interested. Do you permit members of the public to visit to see the process and ask questions?


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