A COMPUTER-ASSISTED PLANKTON ANALYSIS SYSTEM FOR THE MACINTOSH

CAPAS (Computer-assisted Plankton Analysis System), an application sof tware developed for Macintosh computers, was designed for the analysis of taxonomic and size composition of zooplankton. We based CAPAS on t he zooplankton analysis system of Mills and Confer (1986), but instead of using electronic calipers, CAPAS requires a digitizing surface for making one-dimensional plankter measurements. Advantages of CAPAS ove r Mills and Confer's system (1986) include (1) freedom from caliper-as sociated mechanical error; (2) increased flexibility regarding sample magnification changes, taxonomic lists, measurable size ranges, precis ion level, and output format; and (3) increased file editing abilities . Moreover, prey taxon- and size-dependent selectivities (Manly-Chesso n preference index cc and Strauss's linear index L) of planktivorous p redators can be calculated using plankton samples from an ''environmen t'' (e.g., lake, pond, tank) in which a predator was feeding and sampl es from either the predator's stomach or from the ''environment'' afte r the predator had been feeding. Though designed primarily for the ana lysis of zooplankton, CAPAS can be useful in a variety of other analys es in which taxonomic or size composition is needed (e.g., phytoplankt on enumeration, measurement and enumeration of morphological character istics of zooplankton such as leg spines and setules, antennae segment s, etc.).