Quantification of Barrier Effects on Stream Fish Movement: Understanding Fish Behavior and Optimizing Sampling Design

We present a study describing a modeling framework of stream fish dispersal in the presence of obstacles to passage. A major strength of the approach is that ecological process (dispersal model) and sampling design (observation model) are incorporated simultaneously into the analysis to provide accurate estimates of dispersal and barrier permeability from mark-recapture data. Simulation of various plausible scenarios indicated that detectability of barrier effects was strongly dependent on the features of sampling design, such as spatial configuration of the sampling area, barrier extent, and sample size. The main contributions of our modeling framework are that it can 1) efficiently use data from mark-recapture field trials to quantify the permeability of potential barriers to fish dispersal; 2) assess, via simulation, the statistical power of candidate sampling designs; 3) help identify changes in sampling design that could lead to increased power with little or no additional cost. Extensions accounting for the behavior of fish that encounter barriers, as well as alternatives to current sampling designs will be discussed at the symposium.

Keywords: fish dispersal behavior; road crossings