Thermal habitat for 0-group fish in the Barents Sea; how climate variability impacts their density, length, and geographic distribution

Between 1980 and 2008, the climate changed from cold to warm conditions in the Barents Sea. Warmer conditions have been indicated as favourable for cod, haddock, and herring recruitment and unfavourable for capelin, although during recent years these relationships have weakened and need to be revised. Extensive survey observations of temperature and 0-group cod, haddock, herring, and capelin are explored, a bounded temperature range occupied by similar to 80-90% of 0-group fish (core thermal habitat, CTH) defined for each species, and an analysis made of how climate variability influenced density, length, and geographic distribution. Maximum fish densities were at 6.2 degrees C for cod, 7.2 degrees C for haddock, 7.0 degrees C for herring, and 5.1 degrees C for capelin. The area of CTH for cod, haddock, and herring increased from cold to warm years, as did the occupation area of each species. Capelin underwent a northeast distributional shift from cold to warm years. The 0-group fish were observed in a broad range of temperatures of 21 to 10.5 degrees C. However, fish densities showed a dome-shaped distribution with temperature. Mean fish length was 7.1 cm for cod, 8.9 cm for haddock, 7.0 cm for herring, and 4.6 cm for capelin, with length distributions exhibiting a non-uniform response to temperature.