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  • Jens Hegg

New Research: Climate change may exacerbate steelhead density dependence in Idaho, CJFAS


A new paper published in the current issue of the Canadian Journal of Fisheries & Aquatic Sciences indicates that increasing temperatures due to climate change may increase the likelihood that density-dependence will affect the demography of of steelhead in Idaho streams.


The paper is authored by former LIFE Lab Ph.D. student Knut Marius Myrvold and co-authored by Dr. Kennedy. The abstract is below, and the full text can be found here, as well as on the Lab Publications page of this site.


ABSTRACT:

We studied the potential effects of predicted climate change on the energetic demands of juvenile steelhead (Oncorhynchus mykiss) and their consequences for local population size and structure in Idaho, USA. Projected increases in water temperature incurred on average a 10% higher energetic cost by 2040 (range 7.0%–12.5% among study reaches in the watershed) and a 16% increase (range 8.5%–21.3%) by 2080 following the A1B scenario. The predicted increase in energetic cost was largest in the coolest stream reaches, where the proportional increases in energetic cost exceed that of temperature. Energetically, and in absence of increases in food supply, local densities were consequently expected to decline. We examined which factors best described the shape of current size distributions to explore future size distributions as temperatures increase. Mass distribution skewness was best explained by local biomass (positive relationship) and water temperature (negative relationship). The results suggest that local steelhead cohorts will approach a platykurtic, slightly negatively skewed distribution with increasing temperatures and demonstrate that temperature can exacerbate demographic density dependence in fish populations.


Canadian Journal of Fisheries and Aquatic Sciences, 2018, 75(6): 897-907, https://doi.org/10.1139/cjfas-2016-0497



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