Does fish from the Disko Bay area of Greenland possess antifreeze proteins during the summer?

The blood of 21 teleosts and 1 elasmobranch was analysed for antifreeze-protein activity by determining the thermal hysteresis. The fish were caught in the summertime at different locations in West Greenland (Disko Bay area). The difference between the melting and hysteresis freezing point (thermal hysteresis) is a numerical indication of the presence of antifreeze-protein activity. No thermal hysteresis was detected in the blood of the elasmobranch, Raja radiata (thorny skate) and, as expected, its blood was isosmotic to seawater. Of the 21 teleost species examined, 11 were found to have a thermal hysteresis greater than 0.1°C, an indication of the presence of substantial amounts of antifreeze. The remaining 10 species had a hysteresis less than 0.1°C, and thus their summertime possession of antifreeze protein was concluded to be very low or absent. No hysteresis was detected in Gadus morhua (Atlantic cod), but there was a slight faceting of the seed crystal, indicative of a low, possibly physiologically unimportant, level of antifreeze protein. This study is the first time antifreeze-protein activity has been detected in the species Stichaeus punctatus (Arctic shanny).