The response of the diets of four carnivorous fishes to variations in the Yellow Sea ecosystem

The stomach contents of Spanish mackerel (Scomberomorus niphonius), snailfish (Liparis tanakae), anglerfish (Lophius litulon), and Pacific cod (Gadus macrocephalus) from the Yellow Sea during 1985–1987 and 2000–2002 were analyzed. The diets of these four carnivorous species changed over time, showing that the importance of the previous major prey, Japanese anchovy (Engraulis japonicus), had greatly decreased, owing to its declining abundance, and that intake of Crangon affinis had increased. Spanish mackerel foraged for more food, particularly for other small pelagic species in addition to Japanese anchovy, causing an increase in its niche width in recent years, whereas the other three demersal carnivorous species had mainly targeted the small benthic shrimp C. affinis, and their niche widths had reduced in the later years. This phenomenon may be an adaptive response to changes in the food availability of the ecosystem, indicating a change in the food web and community structure of the Yellow Sea ecosystem. Changes in the composition of the diet of major predators may be an indicator of changes in a marine ecosystem.