Depth and temperature drive patterns of spatial overlap among fish thermal guilds in lakes across Ontario, Canada

Background/Question/Methods

As fishes are ectothermic, their spatial distributions are strongly dependent on the temperature of their environments. In temperate lakes, fishes with different thermal optima can become spatially segregated during summer stratification. This habitat partitioning, or niche complementarity, may play a role in the coexistence of trophically similar species; however, the extent of partitioning is dependent on the resources available within each habitat. Although habitat partitioning of fish thermal guilds has been studied in individual lakes, broad-scale patterns of spatial overlap and segregation are not yet understood. In this study, we explore the patterns and drivers of spatial overlap among thermal guilds (cold-, cool-, and warm-water) in 438 lakes found in Ontario, Canada.

Results/Conclusions

We identified five clusters of lakes exhibiting different patterns of spatial overlap among the three thermal guilds. Temperature (growing degree days) and maximum lake depth were strong drivers of the spatial overlap patterns. The proportional abundance of each thermal guild was similar among the clusters but there was some evidence of species turnover within the warm-water guild. These findings not only provide a better understanding of broad-scale patterns of spatial overlap, but also allow us to predict how spatial overlap, and ultimately species interactions and competition, may change under a warming climate.