Identifying Cisco Refuge Lakes in Minnesota under Future Climate Scenarios.

The ciscoCoregonus artediis the most common coldwater stenothermal fish in Minnesota lakes. To project its chances of survival under future warmer climate conditions, an oxythermal habitat variable, i.e., the water temperature at 3 mg/L of dissolved oxygen in stratified lakes (TDO3) was calculated from simulated daily temperature and DO profiles in 30 lake types under past (1962–2008) climate conditions and two future climate scenarios. The mean daily TDO3 values over a 31-d fixed benchmark period were calculated for each of the simulated years and then averaged over the simulation period for each lake type. The multiyear average TDO3 was used to identify cisco refuge lakes in Minnesota. Six hundred twenty known cisco lakes in Minnesota were divided into three groups, tier 1 refuge lakes having the most suitable habitat for ciscoes, tier 2 refuge lakes having suitable habitat for ciscoes, and tier 3 or nonrefuge lakes supporting ciscoes only at a reduced probability of occurrence. The multiyear average TDO3s for tier 1, 2, and 3 lakes were ≤11°C, 11–17°C, and >17°C, respectively. Projected increases in the multiyear average TDO3 under the two future climate scenarios averaged 2.6°C to 2.9°C. About one-third of the 620 lakes that are known to have cisco populations were projected to maintain viable cisco habitat under the two future climate scenarios. These lakes have a Secchi depth greater than 2.3 m (mesotrophic and oligotrophic lakes) and are seasonally stratified. Received November 9, 2011; accepted July 13, 2012 [ABSTRACT FROM PUBLISHER]