By 1976 extended fisheries jurisdiction had been declared by most coastal states and territories of the world. The new regime of property rights was expected to affect seafood production costs which, in turn, could impact on seafood trade and the competitive positions of producing countries. In theory this policy should bestow upon coastal nations and territories a comparative advantage in seafoods. Thus, in studying price and nonprice competition as factors that influence seafood trade, a third factor (the effects of extended fisheries jurisdiction EFJ) is added. The best available data are aggregative. These data are used to analyze the influences of the three factors listed above on seafood trade. In the first part of the investigation, Canada and the U.S. are considered. The annual growth of each country's exports of fresh, frozen, and chilled fish to selected countries is computed using the constant market share approach. The calculated annual growth is partitioned into three effects (or components); namely; (1) competitiveness effect, which measures the portion of growth due to (price) competitiveness; (2) market distribution effect, which measures growth due to the (re)direction of exports to more rapidly growing markets; and (3) market size effect, which accounts for growth caused by overall growth in world demand. Both countries have gained substantial shares of the Japanese and European markets, but Canada's share of the U.S. market has declined due to increased competition from U.S. domestic producers. The U.S. share of every considered market has increased, in most cases, substantially. The second part of the study considers eight exporters of fish to the U.S. Various econometric models are used to analyze cause and effect relationships between changes in relative prices and changes in the market shares of pairs of countries/regions. Results indicate significant nonprice influence and symmetrical EFJ effects on product substitution. / Graduation date: 1987