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1 June 2004 Annual Variation in Diet of Breeding Great Cormorants: Does it Reflect Varying Recruitment of Gadoids?
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Abstract

Great Cormorant (Phalacrocorax carbo) diet was studied during three years (2001-2003) in an area where Arctic Kelp (Laminaria hyperborea) is extensively distributed off the central Norwegian coast. A total of 608 diet samples, 378 (62.2%) chick regurgitations, 22 (3.6%) whole fish, and 208 (34.2%) pellets were collected from the colonies at regular intervals during the chick-rearing period. From these samples a total of 1,013 food items (after pairing the otoliths) were isolated, representing 18 fish species. Gadoids, mainly Cod (Gadus morhua) and Saithe (Pollachius virens) dominated the diet (75% numerically, 86% by biomass). During the first year of the study, Cod represented nearly 50% of the diet, but decreased to 13% in 2003. At the same time, the occurrence of Saithe in the diet increased from 23% to 65%. For Saithe age II-group fish dominated the diet in 2001, and I- and II- group dominated in 2002 and 2003. For Cod 0-group fish dominated the diet in 2001 and 0- and I-group fish dominated in 2002 and 2003. The decrease in Cod in the diet of the Great Cormorant most probably reflected the decrease in the Norwegian coastal Cod population, and that the increase in Saithe in the diet is related to the relative increase in the abundance of this fish prey as the abundance of Cod decreased.

Svein-Håkon Lorentsen, David Grémillet, and Geir Håvard Nymoen "Annual Variation in Diet of Breeding Great Cormorants: Does it Reflect Varying Recruitment of Gadoids?," Waterbirds 27(2), (1 June 2004). https://doi.org/10.1675/1524-4695(2004)027[0161:AVIDOB]2.0.CO;2
Received: 14 October 2003; Accepted: 1 February 2004; Published: 1 June 2004
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