Relative Length Frequency: A Simple, Visual Technique to Evaluate Size Structure in Fish Populations

Abstract

I developed a way to rapidly evaluate the size structure of fish populations designed to be readily understood by a wide audience. Relative length frequency compares the length frequency of fish from a particular water body with an average developed for a region. This technique is analogous to relative weight, relative condition, or relative growth, which are used to compare the condition or growth of fish in a particular water body with rangewide or regional standards. Relative length frequency can be used in conjunction with relative weight or relative growth to rapidly identify factors potentially limiting fish production. I demonstrate this method with data on largemouth bass Micropterus salmoides from Washington State and roundtail chub Gila robusta from Arizona that were collected during standardized electrofishing surveys.