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Waving a Magic Wand(le)


Very hot news just in is that after many months (years!) of assessment, planning, design, negotiation and hard work; permission has just been granted for my design of habitat restoration and enhancement works to go ahead on the upper Carshalton arm of the Wandle.

Many thanks to Bella from the Wandle Trust hosting our E.A. flood risk assessor and putting our case so well and also great effort from Tanya in E.A. fisheries for making the weir removal programme happen.

An extensive array of structures will be installed over around 600 m of river which will create high quality spawning and adult holding habitat along with some additional juvenile habitat to complement the existing opportunities for young trout. When this is coupled with the increased connectivity along this section of the Wandle (through a combination of weir removals and fish pass installation), then the potential for robust self-sustaining populations of wild trout will be greatly increased.
The final piece of this part of the puzzle will come with the hoped-for opportunity to import wild trout parr from nearby in the catchment. Rather than depleting adult brood stock from the donor site - juveniles will be sourced from a population that is producing a natural surplus of parr (mixture of 0+ and 1+ age classes)in a comparable stream. In this way, with the phasing in of sterile "triploid" eggs for use in "Trout in the Classroom" instead of fertile hatchery strain fish - the adaptable and well-prepared wild fish will have the best chance of establishing themselves and successfully breeding in the Wandle once more. The classroom fish have done an admirable job in proving that survival, growth and even a little spawning can happen in stream (they have been the canaries in the cage). The next exciting phase is hoped to be to see how the streetwise wild fish take to their new home.

Comments

Regular Rod said…
Are there absolutely no trout in the Wandle to begin the spawning and regeneration? It would be so much better if no fish had to be brought in from elsewhere...
Paul G said…
The original wild trout of the Wandle were finally lost about 80 years ago.
The presence of a number of impassable weirs has prevented recolonisation via (for example) sea trout.
The only trout in the Wandle at the moment are the product of their great educational efforts using "Trout in the Classroom". These are hatchery strain fish and have at least made some breeding attempts. However, because hatchery fish have only 10% of the survival and reproduction of wild fish, this cannot be the basis of a sustainable population. By 2015 legislation (and best practice) will mean that the classroom fish will be sterile triploids.
Hence the need for a "next nearest" wild parr source.

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