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The Predation Action Group Media Coverage – John Wilson's Pyramid

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john wilsons pyramid

1. A HEALTHY PYRAMID IS IMPERATIVE

A Healthy Pyramid, of silver shoal fish, dace, roach, chub etc, as was the case in many of our lowland rivers and lakes back in the 1960's and 70's, prior to the cormorant invasion.

A. Requires millions of fry at the bottom to sustain future generations

B.
These grow into tens of thousands of 4-6 inch fish

C.
These mature into thousands of sizeable fish

D.
Once adult some of these reach specimen-sized proportions, including a few, real whoppers despite natural predation along the way from grebes, herons and pike etc. Because there is sufficient recruitment at each level.



2. AN UPSIDE DOWN-OVER PREDATED PYRAMID IS WHAT WE HAVE TODAY

This is due to massive predation first from three decades of cormorants and now a decade of otters, plus signal crayfish at the bottom of the food chain.

A. Only a fraction of the fry needed to sustain continuing populations of the species actually exist, due to a lack of breeding stock. Not helped [in some rivers] by signal crayfish colonising the river bed and consuming spawn in addition to the invertebrate insect life upon which fish feed.

B and C.
Several generations of silver shoal fish 4inches—2lbs are simply not there to perpetuate their kind. All eaten by cormorants. There is NOTHING to come through.

D.
The few adult fish to make it through can reach huge proportions because they have the entire aquatic insect larder at their disposal. The huge, record-breaking barbel of the upper Ouse at Adams Mill and in the upper Wensum above Norwich from 2003-2009 [NOW NEARLY ALL KILLED BY OTTERS] were a prime example. But this is NOT a healthy situation because once the whoppers have gone, there is literally NOTHING to follow.

IS THIS WHAT WE WANT TO LEAVE AS A LEGACY TO FUTURE GENERATIONS OF YOUNG ANGLERS ???

(John Wilson MBE)


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