Final Report On The Results Of The 1988 West Coast Groundfish Mesh Size Study

The West Coast Groundfish Mesh Size Study is a multiphase, interdisciplinary research effort. This report focuses on the results of Phase II, the preliminary field study conducted in 1988. In addition to describing field and analytical methods and results, we also discuss the planning process that was used to design and conduct the study, and present the rationale for decisions that were ultimately made. Gross revenues per trawling hour was the key response variable examined; a general methodology for evaluating statistical designs for comparative fishing experiments was developed, and applied to data collected previously. Results of this application were used to select a final experimental design for the field work. The decision was made to test four experimental codend types (3-,4.5- and 5-inch diamond mesh codends, and 5-inch square codends), and to use a randomized complete block design. The results clearly demonstrated that codend mesh size and type have a significant impact on important characteristics of the catch when fishing occurs under commercial production conditions. Specifically, in many instances increases in diamond mesh size resulted in significant decreases in gross revenues per trawling hour, catch sorting time, and discarded catch weight, and increases in mean length of individual species and in the extent of gilling.