Otolith ⁸⁷ Sr / ⁸⁶ Sr identifies natal origin, movement and life history of Burbot Lota lota in the Kootenai River following 45 years of impoundment

Journal Article · 03 March 2023 · Ecology of Freshwater Fish

DOI: https://doi.org/10.1111/eff.12712 · OSTI ID:1968971

Dunnigan, James L.  ^[1]; Linley, Timothy J. ^[2]; Janak, Jill M.  ^[2]; Nims, Megan K. ^[2]; Garavelli, Lysel ^[3]; McMichael, Geoffrey A. ^[4]

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1. Montana Fish Wildlife and Parks Libby Montana USA
2. Pacific Northwest National Laboratory Richland Washington USA
3. Pacific Northwest National Laboratory Seattle Washington USA
4. Mainstem Fish Research Port Townsend Washington USA

Abstract Hydropower has long been an effective form of renewable energy, but the development of the resource has negatively impacted fishes throughout the world. Formulating recovery plans to mitigate these effects requires a firm understanding of species‐specific provenance, life history and life stage habitat requirements. However, the importance of this information is often only recognised after a substantial population decline, when obtaining it becomes demographically challenging. We provide a case study for this scenario and present a post hoc approach to gain insight into these critical data gaps for Burbot Lota lota in the upper Kootenai River in Montana and British Columbia. The population once supported a robust tribal and recreational harvest but declined following impoundment and these fisheries have remained closed or curtailed for nearly 20 years. The reasons for the decline are unknown and actions to assist recovery have been constrained by limited information regarding natal origin, life history and habitat use. We addressed this issue using strontium isotope ratios ( ⁸⁷ Sr/ ⁸⁶ Sr) in otoliths collected over four decades in Lake Koocanusa, the reservoir on the Kootenai River above Libby Dam. Due to the geologic heterogeneity of the basin and resulting variation in water ⁸⁷ Sr/ ⁸⁶ Sr, the assignment probability for Burbot to their region of natal origin approached unity. Otolith ⁸⁷ Sr/ ⁸⁶ Sr also indicated the population was comprised of mainstem‐ and tributary‐origin forms and their relative abundance changed over time. Mainstem Burbot was most abundant during the 1970s and 2000s, whereas tributary forms dominated between these periods. We suggest ecosystem changes following impoundment contributed to this shift in life history forms and the overall decline of the population. Our findings underscore the need for additional investigations of these impacts to guide restoration efforts.

• Sponsoring Organization: USDOE
• OSTI ID: 1968971
• Journal Information: Ecology of Freshwater Fish, Journal Name: Ecology of Freshwater Fish Journal Issue: 3 Vol. 32; ISSN 0906-6691
• Publisher: Wiley-BlackwellCopyright Statement
• Country of Publication: United Kingdom
• Language: English