Seasonal abundance of the estimated food consumption by cetaceans in Icelandic and adjacent waters

Abstract

The consumption of fish, cephalopods and planktonic crustaceans by cetaceans in Icelandic and adjacent waters was estimated. The estimates were based on: 1) abundance estimates from recent sightning surveys (NASS-87, 89, 95); 2) seasonal variation in abundance estimated from sightings and/or catch data from whaling vessels; and 3) consumption rates calculated from the estimated biomass of cetaceans in the area throughout the year. A large number of assumptions had to be made, and these calculations were mainly intended to give an idea of the possible magnitude of consumption as well as to be a guidance for further research in this field. The total food consumption was estimated as 6.3 million tons in a smaller area defined as Icelandic and adjacent waters, and 8.8 million tons in the larger area north of 60°N. Considering total consumption, fin whales (Balaenoptera physalus) and minke whales (B. acutorostrata) were the larest consumers in the area, followed by long-finned pilot whales (Globicephala melas) and northern bottlenose whales (Hyperoodon ampullatus). Crustaceans comprise around 50% of the total consumption within the study area while finfish and cephalopods comprised 27% and 22%, respectively, in the large area. Minke whales were the largest consumers of finfish, consuming more than 1 million tons of fish in Icelandic and adjacent waters.