Theoretical Mechanics of Particle Capture: Predictions for Hydropsychid Caddisfly Distributional Ecology

Abstract

Computer simulations based on equations developed earlier were used to analyze theoretically the effects of six parameters on particle capture by hydropsychid caddisfly nets. If assumptions that form the basis of these simulations are valid, the following statements can be made. (1) Nets with fine meshes capture suspended particles at a higher rate per unit of area than those with larger meshes. (2) Species spinning large meshes have a greater total capture rate because of a correlation between mesh size and overall net area. (3) Capture rates of all nets increase with current speed and temperature. (4) A specific mesh size maximizes the capture rate of a given particle size (for a fixed ambient current velocity and fiber diameter). Finally, (5) nets with larger meshes have a greater tendency to capture larger particles, and nets with smaller meshes have a greater tendency to capture smaller particles. These results are compatible with a particle-size hypothesis, but they compel a modification of a capture-rate hypothesis, suggesting that the particle-capture performance of different net morphologies is not a sufficient basis for explaining empirical correlations between resource concentration and caddisfly community structure.