The Changjiang River discharge affects the distribution of foraging seabirds

Little is known about the effects of river discharge on the distribution of foraging seabirds at sea. Here, we tracked a pelagic seabird, the streaked shearwater Calonectris leucomelas, breeding on an island in the East China Sea, by using a GPS-PTT to examine how its foraging area was related to the river plume area. In the East China Sea, the Changjiang River (i.e. Yangtze River), the largest river in Asia, discharges a large amount of fresh water and nutrients into the sea, with the river plume extending northeastward offshore. Streaked shearwaters concentrated foraging efforts in areas with relatively high chl a concentration (1.70 mg m−3) and sea surface temperatures of around 25°C, conditions which were probably associated with the outflow from the Changjiang River. Primary production and thereby fish stock are known to be enhanced in the Changjiang plume, where a strong vertical thermohaline front exists and schools of forage fish are distributed in the upper layers above the thermocline, which may ensure predictable resource availability for the shearwaters. Our results suggest that large rivers can serve as a large spatial-scale determinant of oceanic physical features and shape oceanic foraging hotspots for marine predators.