The vessels had a permit to catch 1,000 metric tons of pollack and 18 tons of herring, but coast guards found about 5,500 tons of extra undeclared sea catch aboard one of the vessels, according to the Northeast Frontier Department of Russia's Federal Security Service (FSB).
The vessels belong to different affiliated shipping companies, and coast guards have moved to conduct additional checks to verify the permitted amount of catch.
The checks will be conducted on the northeast coast of the Kamchatka peninsular in Russia's Far East.
Poaching disputes between Russian authorities and fishing vessels from Japan have been frequent in Russia's Pacific waters.
An incident near the Kuril Islands, some of which are a disputed territory between Russia and Japan, in mid-August led to the death of one Japanese fisherman. Russian border guards fatally wounded a Japanese crewman, when they made warning shots to make a ship stop. Russian officials accused the vessel of illegally fishing for valuable crab in Russian territorial waters.
