The Sultanate of Oman has 1700 km of coastline extending from the Arabian Gulf south to the Arabian Sea. The demersal fish distributions and assemblages have not previously been well defined. In winter, variations in the oceanography of the area are minimal. In summer, however, the Arabian Sea is strongly influenced by the southwest monsoon. For this study the continental shelf off Oman was divided into eight regional areas and research trawl data on the distribution of demersal fish assemblages was studied using two forms of multivariate statistical analysis: two-way indicator species analysis and detrended correspondence analysis. The study was carried out to examine the influence on the species assemblages of geographical zonation, seasonal variation, and factors such as depth, time of day, and distance from untrawlable ground. There was seasonal variation in the fish assemblages and this variation was greatly influenced by the summer monsoon. Within each regional area depth appeared to be the major factor determining species distribution. In addition to the multivariate analyses, univariate techniques were applied to the catch rate data for forty commercial species to study in detail the influence of time of day and distance from untrawlable ground, factors which could potentially influence stock assessment estimates of fish biomass. Because the data were highly unbalanced, they were analyzed using General Linear Model with five factors, two continuous variables, and ten interaction terms to examine variation in the log-transformed catch rates. The factors time of day and distance from untrawlable ground, in combination with other factors, had significant effects on the catch rates for half of the species. / Graduation date: 1995