Seasonal variation of oxythermal habitat availability for cisco in southern-edge glacial lakes

Habitat suitability for lentic cold-water fish species may be partially constrained by water temperature and dissolved oxygen concentrations. With the progression of climate warming, challenges linked to these environmental conditions are likely to intensify, especially during the late-summer stratification period. In Indiana, USA, cold-water cisco (Coregonus artedi) have declined precipitously from occupying ~50 lakes in early 1900s, to presently  only inhabiting six glacial lakes. Here, we evaluate the risk of extirpation of these remnant cisco populations a) by exploring variability in temperature and dissolved oxygen patterns to determine habitat suitability and b) by evaluating the sources of nutrient (phosphorous) loading to these lakes. We collected temperature and dissolved oxygen profiles from June to December 2023 and used various oxythermal thresholds to assess seasonal vertical habitat availability. Moreover, we applied L-THIA (Long Term Hydrological Impact Analysis) to estimate the dominant phosphorous loading sources to each lake. Our findings reveal notable declines in available oxythermal habitat between mid-September and mid-October, suggesting aggressive management interventions could target this time period. In the majority of lakes, row crop agriculture within the lake catchment appears to be the dominant source of phosphorous loading. Understanding oxythermal challenge periods for cisco and other cold-water species is essential to their management in a warming climate, particularly in the southern-most portions of their range.

Primary Presenter: Jelsie Kerr, Purdue University (kerrjj@purdue.edu)

Authors:

Matthew Linn, Indiana Department of Natural Resources  (MLinn@dnr.IN.gov)

Ryan McGehee, Department of Agriculture and Biological Engineering  (rmcgehee@purdue.edu)

Bernie Engel, Purdue University Department of Agricultural and Biological Engineering  (engelb@purdue.edu)

Tomas Hook, Purdue University Department of Forestry and Natural Resources; Illinois-Indiana Sea Grant  (thook@purdue.edu)