In this brief section discussion is confined to a description of damage to fisheries caused by oil pollution and outbreaks of red tide in recent years; a more detailed account has been precluded since damage to fisheries by these two causative agents has been accurately assessed only in the past few years.
Outbreaks of red tide were once generally characterized by their occurrence on a relatively small scale during the summer season in partially enclosed or sheltered bodies of water such as the Seto Inland Sea, Ise Bay, Mikawa Bay and Tokyo Bay. In more recent times, however, the incidence of seasonal red tide outbreaks has increased considerably as a result of progressive eutrophication of some marine environments, due to an increase in the discharge of municipal and industrial waste materials. Twenty-seven cases of red tide-related damage were reported in 1973, costing a total of 591 million yen (approx. US$1.97 million). Although this figure is staggering, it does represent a decrease in comparison to 1972, when 33 cases costing 7 386 million yen (approx. US$24.6 million) were reported.
A total of 58 cases of damage due to oil pollution of fishing grounds were reported in 1973, of which 41 resulted in damage totalling 1 768 million yen (approx. US$5.89 million). This figure, however, represents a decrease compared with those reported in 1971 and 1972. In 1973 pollution damage in marine regions caused by oil was 43 percent of the total number of pollution cases, and represented 47 percent of the total cost of the damages. In order to protect fishing grounds from oil pollution, the discharge of waste oil and oily ballast from ships has been strictly regulated by the Port Regulation Law and the Marine Pollution Prevention Law. However, damage to fisheries caused by oil spills resulting from grounding or collision of tankers is still on the increase and has become more of a serious problem in view of the increased flow of traffic (including “super-tankers”) in ports and coastal waters.