Costal fisheries use small boat. The boats are frequently substituted with newly made boat or proper boat. When the boat which is substituted with another one after the fixed date for compensation is estimated for fisheries loss by public project, it is matter that which boat is the object for estimating average catch of fish. There are three ways in practical business. They are based on the date of spot probe, the date of conference for compensation and fixed date for compensation. In case of applying the first and the second ways, as the object of compensation is not fixed, there is problem that estimated result can be changed depending on changing boat tons even after the date of spot probe and the fixed date for compensation. Most of all, these ways are against Attached Form No.4 of the Enforcement Ordinance of Fisheries Law which regulate to calculate average catch of fish applying result of fishery for retroactively counted 3 years from the year before the year in which administrative measure day is. The other side, in applying boat tons based on the fixed date for compensation, estimated result of compensation will not change even boat substituted after the fixed date for compensation. Even though applying tons based on the fixed date for compensation, a problem still remains. If the boat get bigger after the fixed date for compensation, the then boat size must be applied for calculating average catch. But the boat get smaller, the changed boat size must be applied. Because changed small boat would be damaged less than the previous boat. And decrease in catch by changing boat into small one is not due to the project but due to the personal responsibility. This will help to increase objectivity and reliance on the compensation result. As the other objects are fixed based on the fixed date for compensation in the Act on Acquisition and Compensation of Land and Others for Public Project, it can be balanced with other object.