Computing the Importance of Physical and Hydraulic Variables to Fish Habitat Selection Through Multiple Linear Regression

The purpose of this study is to quantify the importance of turbulent kinetic energy, strain, water velocity, fish depth, and fish distance to wood to the decision making process of overwintering coho salmon during habitat selection. Although many studies have evaluated this habitat selection of salmon, few have included hydraulic variables in the equation, while recent research indicates that these parameters could affect salmon behavior. More so, greater understanding of the influence of these parameters can aid in future river and habitat restoration efficiency. Successful coho salmon habitat restoration projects can increase the abundance, biomass, and biodiversity of such salmon. This study was conducted using high resolution (0.1 m) mapping of the flow field through an acoustic Doppler velocimeter array and underwater videogrammetry of fish locations at the Oregon Hatchery Research Center in Alsea, Oregon. Such a study is of even greater importance because studies have shown that overwinter survival success is one of the greatest indicators of annual coho salmon populations 1 . Although inconsistencies were discovered within the multiple linear regression model used, such inconsistencies highlight fish length dependent habitat selections as well as coho salmon affinities for low velocity levels, low distances to wood, deeper depths, and low turbulent kinetic energy values. Introduction: Ecologists and hydrologists have been interested in effective riverine and fish habitat restoration methods for many years. As human population and development has increased, the effect on river systems and habitat stability within such systems has multiplied for the sake of economic and recreational human gain. In addition to increased channelisation, wood removal from rivers has been shown to constrain salmonid populations and biomass. 2 As riverine restoration studies evolve, much focus has been given to habitat preferences of fish in relation to wood debris. Many studies have been conducted in order to determine the effect of depth and water velocity on fish habitat selection, in assumption that these conditions explain fish preference for wood debris. However, some have noted fish remaining beneath cover in shallower and faster conditions than those shown to be preferable to fish. 3 Although turbulence has been shown to be ecologically meaningful and abundant in and near covered areas, it also 1 Howard, C. (2006), Mill Creek Fisheries Monitoring Program: Ten Year Report. Final Report to Savethe-Redwoods League. Stillwater Sciences, Save-the-Redwoods League. Received at http://www.savetheredwoods.org/media/pdf_howard.pdf. 2 Hafs, A.W.(2014).Quantifying the role of woody debris in providing bioenergetically favorable habitat for juvenile salmon. Ecolofy Modelling, 285, 30-38. doi: 10.1016/j.ecolmodel.2014.04.015 3 Ayllón, D., Almodóvar, A., Nicola, G. G. and Elvira, B. (2009), Interactive effects of cover and hydraulics on brown trout habitat selection patterns. River Res. Applic., 25: 1051–1065. doi: 10.1002/rra.1215 3