1. Kootenay Lake kokanee (Oncorhynchus nerka) collapse into a predator pit.
- Author
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Warnock, Will G., Thorley, Joseph L., Arndt, Steven K., Weir, Tyler J., Neufeld, Matthew D., Burrows, Jeff A., and Andrusak, Greg F.
- Subjects
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SOCKEYE salmon , *BIOMASS production , *CHAR fish , *FISHERIES , *LAKES , *RAINBOW trout , *PREDATORY animals - Abstract
Kootenay Lake is a large, oligotrophic waterbody in southern British Columbia renowned for recreational fisheries for piscivorous rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus). Long-term datasets showed an increase in large-bodied (>2 kg) piscivore abundance followed by a collapse of the kokanee (Oncorhynchus nerka) prey population in 2013 and subsequent decline of large-bodied piscivores. An unprecedented post-collapse state formed in 2015–2018, characterized by low kokanee spawner abundance and biomass and high catch rates for small-bodied (<2 kg), slow-growing piscivores. Bioenergetics model estimates of average historical (1961–2008) piscivore consumption was 29.3% of the average historical (1993–2008) kokanee prey supply (biomass and production), but increased to 78.7% in 2011, immediately preceding kokanee collapse. From 2015–2018, kokanee did not recover due to persistently poor juvenile survival; estimated piscivore consumption relative to prey supply remained high (73.0%), suggesting that kokanee were trapped in a predator pit. Although the ultimate and interacting causes of the predator build up remain uncertain, overcoming current depensatory dynamics may be aided by kokanee stocking or increasing harvest on still-abundant, unsatiated piscivores. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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