The complementary role of lentic and lotic habitats for Arctic grayling in a complex stream‐lake network in Arctic Alaska

Abstract

Lakes can be important to stream dwelling fishes, yet how individuals exploit habitat heterogeneity across complex stream‐lake networks is poorly understood. Furthermore, despite growing awareness that intermittent streams are widely used by fish, studies documenting the use of seasonally accessible lakes remain scarce. We studied Arctic grayling (Thymallus arcticus) in a small seasonally flowing (June–October) stream‐lake network in Alaska using PIT telemetry. Overall, 70% of fish visited two lakes, 8% used a single lake, and 22% used only stream reaches. We identified five distinct behavioural patterns that differed in dominant macrohabitat used (deep lake, shallow lake or stream reaches), entry day into the network and mobility. Some juvenile fish spent the entire summer in a shallow seasonally frozen lake (average 71 days), whereas others demonstrated prospecting behaviour and only entered the stream channel briefly in September. Another group included adult and juvenile fish that were highly mobile, moving up to 27 km while in the 3‐km stream‐lake network, and used stream reaches extensively (average 59 days). Lentic and lotic habitats served differing roles for individuals, some fish occupied stream reaches as summer foraging habitat, and other individuals used them as migration corridors to access lakes. Our study emphasises the importance of considering stream‐lake connectivity in stream fish assessments, even to shallow seasonally frozen habitats not widely recognised as important. Furthermore, we demonstrate that individuals may use temporary aquatic habitats in complex and changing ways across ontogeny that are not captured by typical classifications of fish movement behaviour.

Ice roads through lake-rich Arctic watersheds: Integrating climate uncertainty and freshwater habitat responses into adaptive management

“…At least twelve species of fish inhabit the freshwaters of the FCW (Whitman et al 2011) and their presence and abundance in ACP lakes and ponds is strongly linked to ice regime and connectivity (Haynes et al 2014a;Jones et al 2017). Species richness increases greatly with lake depth and connections to other water bodies, yet even bedfast-ice lakes can provide important summer foraging habitats (Haynes et al 2014a;Heim et al 2018). Although shallow waters freeze solid through the winter, if connected to stream systems or rivers during breakup flooding they readily become recolonized during the openwater season by fish, such as ninespine stickleback ( Figure 7D), to take advantage of high productivity from abundant large-bodied zooplankton, such as Daphnia middendorffiana ( Figure 7C; Laske et al 2017;Beaver et al in review).…”

A general model of temporary aquatic habitat use: Water phenology as a life history filter

“…The increased habitat complexity created by TAHs is likely to facilitate diversity in life history strategies, within and across populations, generating stabilizing portfolio effects (Den Boer, ; Schindler et al, ). If some fish used TAHs, while others did not, stranding risk would be spread across individuals with different behavioural strategies (Baldock et al, ; Heim et al, ). At the metapopulation scale, TAHs can contribute substantially to overall production in some years (Table ), while perennial spawning populations could sustain production in times of poor conditions in TAHs.…”

“…Although a general theme is that inundation periods must be quite long (i.e., long enough for embryonic development) and temporally (2013) Growth Arctic grayling 70% of tagged fish used a shallow, seasonally frozen solid lake during the summer; juvenile fish used this habitat for an average of (71 days), nearly the entire ice-free period Heim et al (2019) predictable for TAHs to serve as spawning habitats (Figures 3 and 4), there are several exceptions. Several highly specialized fish species including the capelin (Mallotus villosus, Osmeridae) are adapted to spawn synchronously with high tides and deposit offspring on beaches (Gibson, 2003;Martin & Swiderski, 2001).…”

“…This can be especially important for young fish with higher thermal optima relative to adults (Morita, Fukuwaka, Tanimata, & Yamamura, 2010), or during periods of high prey abundance where rapid assimilation of energy is required before the next foraging bout (Armstrong & Schindler, 2011). Shallow lakes in Arctic Alaska that freeze solid in the winter thaw in the spring an average of 17 days earlier than deeper lakes that do not freeze (Arp, Jones, Liljedahl, Hinkel, & Welker, 2015), providing early access to food and warm temperatures for migratory fishes (Heim, Arp, Whitman, & Wipfli, 2019). At daily timescales, juvenile coho salmon (Oncorhynchus kisutch, Salmonidae) feed to satiation in the cold thalweg of a river, but move to warm off-channel TAHs to digest food more rapidly (Baldock et al, 2016).…”

“…If some fish used TAHs, while others did not, stranding risk would be spread across individuals with different behavioural strategies (Baldock et al, 2016;Heim et al, 2019). At the metapopulation scale, TAHs can contribute substantially to overall production in some years (Table 1), while perennial spawning populations could sustain production in times of poor conditions in TAHs.…”