USE OF A SPLIT-PLOT ANALYSIS OF VARIANCE DESIGN FOR REPEATED-MEASURESFISHERY DATA

We present a repeated-measures split-plot analysis of variance (ANOVA) design that can be used to analyze fisheries data collected throughou t time from fixed sampling stations. A high percentage (97%) of author s who published papers in the Transactions of the American Fisheries S ociety and the North American Journal of Fisheries Management during t he past 10 years did not use repeated-measures ANOVA for analyzing the ir data when this technique was appropriate. When data are collected f rom fixed stations throughout time, the assumption that independent sa mples are randomly collected from the population is violated for simpl e ANOVA. Fixed stations may display population characteristics specifi c to that location, and environmental change or a management practice may influence stations differently. In addition, multiple measurements collected at a fixed station throughout time will likely be correlate d. For a dependent variable of interest, a repeated-measures split-plo t design will partition the variation due to (1) a treatment or manipu lation, (2) sampling stations, (3) the temporal correlation that may o ccur among repeated measurements, and (4) the potential interactions a mong these class variables. This statistical approach will provide inc reased accuracy and likely provide investigators with new insights on the responses of fish populations to these variables.