Landscape Effects on Growth of Age‐0 Arctic Grayling in Tundra Streams

Abstract

The growth of age-0 Arctic grayling Thymallus arcticus in two adjacent watersheds with differing numbers of lakes was compared. Age-0 Arctic grayling grew faster in the watershed with numerous lakes (eight) than in the watershed with only one lake. The presence of lakes along the stream courses in both watersheds decreased stream temperatures in the spring but increased temperatures in summer. The size of substrates was greater in streams below lakes than in inlet stream reaches. Growth rates of discrete populations of age-0 Arctic grayling were positively related to stream temperature. No relationship between fish growth rate and the biomass of invertebrate drift was apparent. We conclude that the summer increase in stream temperatures attributable to the presence of lakes resulted in increased growth of Arctic grayling in the watershed with numerous lakes. A simulation model of the temperature-dependent growth of age-0 Arctic grayling indicated that the abundance of lakes in one of the watersheds enhanced the potential production of Arctic grayling almost sixfold.

Linking the thermal regimes of streams in the Great Lakes Basin, Ontario, to landscape and climate variables

“…Surface waters (ponds and lakes) inundate outlet reaches with warm epilimnetic water in summer and the thermal inertia of the pond or lake may allow these warmer temperatures to persist into the fall. In the winter and spring cold epilimnetic waters may cool downstream reaches (Mellina et al, 2002;Luecke and MacKinnon, 2008). As previously mentioned, influxes of groundwater cool stream temperatures in the ice-free season but warm temperatures in the winter.…”

“…Ponds and lakes along the continuum may warm and reduce the diel variation in the outlet reaches. These decreases may be most noticeable in the middle reaches where the greatest daily thermal range is normally observed (Vannote et al, 1980;Luecke and MacKinnon, 2008).…”

Seasonal cues of Arctic grayling movement in a small Arctic stream: the importance of surface water connectivity

“…Though lacking gravel substrates, Crea Creek, like many other shallow beaded streams, warms rapidly after ice break-up and may provide the earliest spawning opportunities for Arctic grayling which generally begin spawning as temperatures reach 4°C (Northcote 1995). Furthermore, the unique physical aspects of beaded streams, which often include headwater and flow-through lakes, may provide thermal complexity and favorable growing conditions for young grayling (Luecke and MacKinnon 2008;Arp et al 2015). Though beaded streams are generally not regarded as spawning habitat, our results suggest this notion should be re-evaluated.…”

Do existing ecological classifications characterize the spatial variability of stream temperatures in the Great Lakes Basin, Ontario?

“…At the highest orders, increases in depth lower the surface area to volume ratio and reduce the diel fluctuations of stream temperatures (Vannote et al, 1980). Water from ponds and lakes along the continuum may also warm and reduce the diel variation in the outlet reaches (Luecke and MacKinnon, 2008). This suggests that the variability in temperatures may be best captured using a reach-level classification that incorporates the longitudinal pattern in stream temperatures.…”