Trophic status and trophic interactions of common predatory fish species of the West Kamchatka shelf

Abstract

Feeding and trophic relationships have been studied for the common benthic predatory fish spe cies of the West Kamchatka shelf in 2008-the Pacific cod Gadus macrocephalus, great sculpin Myoxoceph alus polyacanthocephalus, plain sculpin M. jaok, sea raven Hemitripterus villosus, and whitespotted greenling Hexagrammos stelleri. Crustaceans and fish are the main food components of the great sculpin, plain sculpin, Pacific cod, and whitespotted greenling; sea raven feeds on the fish mostly. The ontogenetic changes of the food spectra have been tracked for all the studied species. The indexes of the food similarity evidence to the possible food competition between the Pacific cod and all the other species; however, the dissimilarity of the ecological niches may serve as the adaptation to decrease the food competition. The trophic levels of all the studied predators vary from 3.41-4.50; i.e., they are the tertiary consumers. It is justified that the Pacific cod, whitespotted greenling, plain sculpin, and great sculpin are the facultative polyphagous predators, and the sea raven is the obligate bentho and ichthyophagous species on the West Kamchatka shelf.