Pool Availability and Arctic Grayling System Capacity

This function was adapted to be used for Arctic Grayling in the Upper Peace River Basin by Hagen et al. (2026) from Hubert et al. (1985). The relationship describes the hypothesized effect of pool frequency on Arctic Grayling system capacity in adult/subadult summer rearing habitats.

Hagen et al. (2026) justifies pool availability as a stressor for Arctic Grayling as so:

"Access to pool habitat within clear stream reaches of moderate gradient appears to be a key habitat requirement for adult and subadult Arctic Grayling within the Williston watershed (Mathias et al. 1998; Blackman 2004; Bottoms et al. 2023) and elsewhere (e.g., Lower Nelson River watershed: Stewart et al. 1982; Big Hole River, Montana: Lamothe and Magee 2004; Kaya 1990). Adult and subadult Arctic Grayling (Figure 4) in the Parsnip River watershed utilize pool and glide habitats of >80 cm depth generally, with preferred locations being deeper water adjacent to the food-delivering thalweg flows (Blackman 2004). Using drone-based thermal mapping of the Anzac River, combined with reach- and landscape-scale snorkeling surveys, Bottoms et al. (2023) were able to demonstrate strong associations between Arctic Grayling and pool habitats. As described in Section 5, animations of hourly temperatures at the reach scale highlighted the spatial importance of pools as thermal refugia during temperature extreme events."

Hagen et al. (2026) describes the basis for the stressor-response curve using the following logic:

"An index of pool habitat quality was developed by Bottoms et al. (2023) based on scoring criteria for pool size, internal thermal heterogeneity, effects of shade, and relative depth. Future CEMPRA applications would benefit from pool index scores estimated across adult/subadult Arctic Grayling summer rearing habitats, but these data are unavailable currently. The stressor-response curve (Figure B 9) is a placeholder, adapted from Hubert et al. (1985)."