Individual-based modelling of hydropeaking effects on brown trout and Atlantic salmon in a regulated river

• Published in: River Research and Applications
• Main Authors: Hajiesmaeili, Mahboobeh, Addo, Louis, Watz, Johan, Steven F., Railsback, Piccolo, John
• Format: Article in Journal/Newspaper
• Language: English
• Published: Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013) 2023
• Subjects: growth; habitat selection; hydropeaking; individual-based modelling; inSTREAM; salmonid; survival; Ecology; Ekologi; Environmental Sciences; Miljövetenskap; Atlantic salmon
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-92253; https://doi.org/10.1002/rra.4037

We developed an individual-based model (IBM) to understand the effects of hydropeaking on growth, survival and distribution of age 0+ to 1+ juveniles for high-conservation value populations of native brown trout (Salmo trutta) and Atlantic salmon (S. salar) in River Gullspång, Sweden. We parameterized and applied inSTREAM (7.2-SD) and calibrated the model by comparing predicted versus observed growth under the current hydropeaking regime (n= > 1,200 model fish for 365 days). Our objective was to model growth, survival and distribution under flow scenarios with and without hydropeaking. We observed that hydropeaking generally resulted in modest (~10%) negative effects on growth and survival of both species. Survival was more affected than was growth, smaller fish more affected than larger fish. On-peak (high) hydropeaking flows resulted in less profitable feeding conditions (less growth) and higher predation (lower survival). Thus, inSTREAM 7.2-SD appears to capture ecologically-relevant behavioral patterns under hydropeaking, e.g., habitat selection, in response to rapid flow changes. Understanding such patterns for large rivers via manipulative field studies, even if possible, would be time-consuming and costly. Our study demonstrates the potential of IBMs as powerful tools for testing research questions and assessing and prioritizing alternative management strategies in regulated rivers.