In fisheries, as well as in other natural resource-based industries, there is difference between profit and rent. The former is a basic indicator for gauging the business performance of firms, while the latter is for the evaluation of the contribution of resources and industry to economic welfare. Put simply, resource economists are mainly concerned about rent, including pure resource rent and producer surplus (intra-marginal rent [IMR]). In other hand, business economists are mainly concerned about the profitability of the firms comprising the industry. In the academic literature, there are not always clear definitions of the profit and rent concepts and their use in actual analyses. This article will mainly discuss and clarify differences and similarities in profit and rent concepts. In the classical fisheries economic model with one-dimensional homogenous effort and a constant cost per unit of effort, no rent exists in open-access equilibrium. A simple change in this model, for example by introducing heterogeneous effort, opens it to the existence of rent, specifically IMR, at open-access equilibrium. We estimated resource rent and profit from the data using SNA(system of national accounts) and accounting data methods. RR(resource rent) is composed of value-added, compensation of employees, consumption of fixed capital and normal profit in SNA. RR(resource rent) is composed of EBT, Depreciation of fishing rights, financial costs of fishing rights and calculated interests on equity in accounting data methods. We found that the result of two methods is equal. RR is composed of excess profit, rent and interest expenses. In Korea, the magnitude of RR and profit is not different significantly.