OUWENEEL GL (1977) The increase ofthe Cormorant Phalacrocorax carbo on the HoUandsch Diep Haringvliet. LIMOSA 50 (1): 1-5.

Great Cormorant Phalacrocorax carbo Since 1960 the Cormorant Pha/acrocorax carbo has disappeared as a breeding-bird in the south-western part of the Netherlands. Also as a non-breeding visitor in this area, this species decreased quickly during the period 1955-70. Since 1970, however, the number of Cormorants visiting the closed estuaries Haringvliet and Grevelingen during the months July up to September inclusive, is increasing rapidly. 2. The Ventjagersplaat, situated in the Haringvliet, is the central resting place for the Cormorants staying in the area. Numbers increased here from. 130 in September 1970 till 1500 in August 1976. The whole population staying in the Hollandscn Diep-Haringvliet and Grevelingen in late summer, is estimated at at least 1500-2000 birds. 3. The Haringvliet was closed in 1970 and the Grevelingen in 1971. After the closure of the Haringvliet the number of freshwaterfish increased and the water became more clear. These factors can play a role but probably the disappearance of the important fishinggrounds in the IJsselmeer because of the large reclamation is also a principal cause.

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