Alaska Blackfish can tolerate hypoxic conditions in both summer (ice-free) and winter conditions (Ostdiek and Roland 1959; Ultsch 1989), and have been observed in water of 2.3 ppm oxygen at a temperature of 7.8[degrees]C (Ostdiek and Roland 1959).
In the winter of 2010-2011, a die-off of Alaska Blackfish was observed in the vicinity of Lake Minchumina, Alaska (UTM: Zone 5, E537377, N7084931, NAD83), in 3 separate bodies of water (Table 1).
While Alaska Blackfish are able to survive extreme conditions, it is clear that they often live at the edge of their physiological abilities and consequently may experience die-offs.
The Alaska Blackfish we observed likely died as a result of hypoxia.
Although Alaska Blackfish are air-breathing and hypoxia tolerant, access to sufficient oxygen for respiration may not be enough for survival during winter under ice.