Distribution and abundance of large pelagic predatory bony fishes in the northwestern Pacific over a half-century

Abstract

Large pelagic predatory fishes play an important role in marine ecosystems, occupying the highest position in food webs and accumulating energy and organic matter produced by aquatic organisms of lower trophic levels. Among pelagic predatory fishes, more attention has been given to the sharks, tunas and billfishes inhabiting equatorial and tropical waters, whereas pelagic predatory fishes inhabiting subarctic and temperate waters have been much less studied. We analyzed long-term midwater trawl survey data to investigate changes in the spatial distribution, ranges, and catch rates of the three most abundant large predatory teleosts in the Russian and adjacent waters of the northwestern Pacific, namely, the North Pacific daggertooth Anotopterus nikparini, the longnose lancetfish Alepisaurus ferox, and the Pacific pomfret Brama japonica. The northernmost distributions of daggertooth, lancetfish, and pomfret were observed in summer, spring, and autumn, respectively. All three species were characterized by the greatest northwards occurrence in the 2000s. In the study area, their maximum frequency of occurrence was recorded during the summer, and they were most frequently caught in the 1980s (lancetfish and pomfret) and 1990s (daggertooth). The average catch rates of daggertooth and pomfret were highest in summer, whereas those of lancetfish were highest in winter. The highest average catch rates of daggertooth, lancetfish, and pomfret were recorded in the 2000s, 1990s, and 1980s, respectively. The maximum absolute catch rates of lancetfish were recorded in winter, whereas those of daggertooth and pomfret were recorded in spring and summer, respectively. The maximum absolute catch rates of daggertooth and pomfret were observed in the 1980s, whereas those of lancetfish were observed in the 1990s.