Do novel ecosystems follow predictable trajectories? Testing the trophic surge hypothesis in reservoirs using fish. Issue 12 (21st December 2016)

• Record Type: Journal Article
• Authors: Turgeon, Katrine; Solomon, Christopher T.; Nozais, Christian; Gregory‐Eaves, Irene
• Is Part Of: Ecosphere. Volume 7:Issue 12(2016)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-12-21
• Subjects: boreal -- catch per unit of effort (CPUE) -- fisheries -- hydroelectricity -- juveniles -- man‐made lakes -- predictive framework -- reservoir -- temperate -- upsurge; Ecology -- Periodicals; Ecology; Periodicals; 577.05
• DOI: 10.1002/ecs2.1617
• Languages: English
• ISSNs: 2150-8925

Abstract

Abstract: Hydroelectric reservoirs are novel ecosystems that provide a variety of important services. To manage these ecosystems and their fish populations effectively, we need to develop conceptual frameworks for predicting their short‐ and long‐term responses. To advance this goal, we revisited and tested the "trophic surge hypothesis, TSH." The TSH has been widely cited in the literature, but has not been empirically tested across numerous reservoirs. The TSH suggests that fish populations should show a hump‐shaped pattern (i.e., the non‐equilibrium phase) after river impoundment. As such, we assembled 40 recruitment and 109 adult fish abundance time series from 19 species distributed across seven reservoirs from temperate and boreal regions, and applied curve fitting analyses and model selection. We found that the hump‐shaped pattern was the predominant pattern across individual time series, providing moderate support for the TSH. Fish recruitment increased substantially during reservoir filling and was followed by an increase in adult fish lagging 3–4 years behind. The non‐equilibrium phase was transient and lasted roughly eight years for recruits, whereas it could be much longer for adults. When time series were combined across regions and sites, the support for the TSH was weaker. However, we observed significant variability in the duration, timing, and magnitude of the surge across individual time series and found that the total flooded area was the most influential predictor to explain this variability. In conclusion, the TSH and related metrics can be a useful and general predictive framework to understand how fish populations may respond to impoundment. In particular, long‐term management recommendations could be short‐sighted if formulated before convincing evidence has emerged to show that the reservoir reached its new trophic equilibrium.