Changes in the Diet of Demersal Fish due to Eutrophication-Induced Hypoxia in the Kattegat, Sweden

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Pihl, Leif
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1994
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Kattegat; atlantic cod; Gadus morhua
• Online Access: http://dx.doi.org/10.1139/f94-033; http://www.nrcresearchpress.com/doi/pdf/10.1139/f94-033

The diets of five dominant bottom-feeding fish species, Atlantic cod (Gadus morhua), whiting (Merlangius merlangus), plaice (Pleuronectes platessa), dab (Limanda limanda), and American plaice (Hippoglossoides platessoides), were analysed during spring and autumn between May 1984 and April 1988 in the southeast Kattegat. A general long-term change in the diet of bottom-feeding fish in the Kattegat has taken place since the beginning of the century and, for some of the species, the feeding pattern was different from that in adjacent areas. The observed dietary shift appeared to be due to changes in species composition of benthic macrofauna. Prey species favored by increased organic enrichment were dominant in the diet. Several infaunal species increased in dietary importance during recent hypoxia. In contrast, during hypoxia, a reduction of epibenthic crustaceans was observed in the fish diet. This study emphasizes the potential effects of organic enrichment and hypoxia (due to eutrophication) on trophic interactions in marine benthic communities. Repeated stress from hypoxia might favor small-sized prey species with a short life cycle, which would in turn favor small-sized fishes. Thus, altered food resources and the direct effects of hypoxia might result in shift in dominance among demersal fish species.