Spatial variation and temporal stability of littoral water temperature relative to lakeshore morphometry: environmental analysis from the view of fish thermal ecology

Lakeshore developments change the physicochemical properties of the underwater environment by altering shore morphometry, which may have significant effects on spatial variation and temporal stability in water temperature. Spatiotemporal temperature changes are costly to fish in terms of subsequent thermoregulatory behavior and acclimation; therefore, thermal conditions have a heavy impact on the biological function of fishes. Spatiotemporal variation and stability of water temperatures along cross-shore transects in the littoral zone (within 100 m from shore) were monitored and compared on two lakeshores with different cross-shore depth profiles. One shore was associated with a retaining wall and a relatively deep, flat bottom (steep shore), whereas the other extended offshore at a gentle gradient (gentle shore). Water temperature was more spatially variable on the gentle shore than the steep shore [1.44 +/- A 0.47 and 0.20 +/- A 0.14A degrees C (mean +/- A SD), respectively], but a stable temperature range (i.e., the range of temperatures continuously observed on each shore for 48 h) was maintained only on the gentle shore during seasonal temperature decline. These results suggest that gentle shores have higher potential to provide a wider range of thermal options, allowing fish to fine-tune thermoregulatory behavior and acclimate more efficiently to temperature changes.