This study investigated the effect of the number of meshes in the protective bag circumference on size selectivity of a demersal trawl codend. Circumferences of 50-mesh (NMPB50) and 215-mesh (NMPB215) protective bags rigged on the 44mm diamond mesh codend were tested. Fishing experiments were carried out on the commercial trawler Hapulolu' between 20 and 27 August 2010, using a modified trawl net. Data were collected using the covered codend method and analyzed using the logistic equation with the maximum likelihood method. Mean selection curves were analyzed and compared using the between-haul variations model. The mean L-50 values of NMPB50 and NMPB215 were, respectively, 16.4 +/- 0.1mm and 16.5 +/- 0.1mm carapace length for deep-water rose shrimp, 10.7 +/- 0.1cm and 12.2 +/- 0.1cm total length for hake, and 16.0 +/- 0.1cm and 16.7 +/- 0.1cm total length for horse mackerel. In conclusion, increasing the number of meshes around the protective bag resulted in a 14% and 4% increase in the L-50 for hake and mackerel, respectively; however, these differences were not statically significant (P>0.05).