BOUDEWIJN TJ, DIRKSEN S, MES RG & SLAGER LK (1989) Current research: Cormorant, an indicator species for the quality of Dutch waters?. LIMOSA 62 (2): 96-97.

At the beginning of this century were in different places along our Great Rivers cormorant colonies. The numbers declined by persecution and ostracism nests as a competitor in the fishing Cormorant saw. The increasing pollution of waters of the Great Rivers was a second important factor. Eventually only two sites on: in Naardermeer and Wanneperveen. after complete protection of the Cormorant in 1965, the numbers gradually increasing. Also emerged a number of new lOals colonies in the Biesbosch Dordrecht, Oostvaardersplassen and along the IJssel and Waal. The return of income and plaster nesting cormorants in the river is a hopeful sign for the ecosystem of the Great Rivers, especially since the increase coincides with an improvement in the quality

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