GERRITSEN G (2008) Mass fishing in Great Cormorants Phalacrocorax carbo sinensis in the lower River IJssel during adverse summer weather. LIMOSA 81 (1): 30-31.

Since 1996,mass-fishing of up to 4000 Great Cormorants has been observed in the IJsseldelta (Province Overijssel) in 8 out of 12 breeding seasons. The birds originate from the large colony at the Oostvaardersplassen, Flevoland (2500-5500 breeding pairs). The largest distance between the colony and the feeding sites in the delta of the River IJssel is 50 km. All observations coincided with strong winds (4-6 Beaufort), mostly from a NNW or NW direction. Under these conditions, fishing at the usual feeding sites at the large lakes IJsselmeer enMarkermeer is severely hampered by high water turbidity. Previous research has shown that Cormorant breeding success is strongly affected by such conditions since feeding bouts to less turbid waterbodies take too long to raise young successfully. As a result, birds from the large colonies in the southern part of the IJsselmeer andMarkermeer now disperse to smaller colonies in the northern part of the IJsselmeer, where feeding conditions are less affected by adverse weather.

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