Sunday, 20 February 2011

The Black Death – try an eco-remedy

Cormorant - a skilled fisherman that avoids paying the entrance fee, East Warwick gulls, Eider!

I was once escorted out of a fishery conference for suggesting that anglers use Cormorants as a scapegoat for bad fishery management. A trip down to Walthamstow Reservoirs reminded me of the Cormorant-fish controversy, the bird anglers like to call the ‘Black Death’ and claim wipes out fish stocks. Now there is some truth to this complaint in some situations – on many a simple fishery, the Cormorants will be able to simply catch the fish without much effort.  Surely it wasn’t the clearest of thinking to establish a trout fishery on a concrete puddle that had a Cormorant roost in the middle!  Despite this, situations are not always as clear as they seem; most Cormorants nesting at Walthamstow do not fish on site.  I’ve always believed that birders and anglers should be on the same side – we both want to see healthy wetlands.  And the starting point for a solution should be to look at these healthy natural wetlands, particularly the complexity of the underwater habitat.  Provide fish with refuge areas and they will be less easy to catch.  Variation in the topography of the lake bottom, the addition of underwater reefs in the form of fallen trees, rocks or islands of aquatic vegetation, have all been shown to help. These are standard measures that conservationists will employ in creating a new wetland.  But instead of improving fish habitat, the average fishery manager too often rushes for the shotgun and chainsaw.

A second issue at Walthamstow is the apparent decline of breeding duck. In what seemed a good idea at the time (Thames Water have a history of good conservation staff), the formerly scrubby island on the East Warwick was cleared and re-formed, in order to try and create a better habitat for waders and duck. Unfortunately, this did not foresee the surge inland of breeding Herring and Lesser Black-backed Gulls. The gulls took over the island, the duck departed. Predation by the gulls has clearly changed the distribution of breeding duck. Good management of the islands and marginal vegetation would seem to be central to solving the problem.

I first went to Walthamstow Reservoirs exactly 40 years ago. I missed a Shag, but got quite excited by a pair of Goldeneye. There were no roosting Cormorants (this started in 1972 I seem to remember). The first Trout went into No 5 in 1978. Today there were plenty of Cormorants (at least 142 active nests), 7 Ring-necked Parakeets and an Eider.

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