Vertical distribution and metabolism in Antarctic mesopelagic fishes

Abstract

1. 1. Vertical distributions, oxygen consumption rates and activities of intermidiary metabolic enzymes were examined in several species of Antarctic mesopelagic fishes as part pf the AMERIEZ (Antarctic Marine Ecosystem Research at the Ice Edge Zone) program to study ice-edge biology in the Scotia-Weddell Sea region. 2. 2. Sixteen mesopelagic fish species were captured, nine in sufficient numbers to determine their vertical distribution. Seven of the nine exhibited a diel vertical migration. 3. 3. Oxygen consumption rates ( VO 2) declined with increasing depth of occurence and ranged from 0.159 μl O 2/mg wet weight/hr in a fish living at the surface to 0.016 μl O 2/mg wet weight/hr in a fish living at 500 m. 4. 4. Activities in white skeletal muscle of lactate dehydrogenase (LDH) and cutrate synthase (CS), representing the anaerobic and aerobic pathways of intermediary metabolism, declined in a similar manner to oxygen consumption rate with depth. 5. 5. Comparison of Antarctic and California mesopelagic fishes reveals a similar VO 2 at normal habitat temperature. When extrapolated to the same temperature Antarctic fishes show the elevated VO 2 commonly called “cold adaptatio”. 6. 6. Cold adaptation is reflected in the activity of the aerobic pathway (CS) but not in the anaerobic (LDH).