Coastal marine pollution and fish

Abstract

Abstract Most of the marine pollution problems lie in the coastal zone, where sewage and industrial wastes are discharged and various developments are changing the configuration of the coastline. It is on the continental shelf and in the upwelling areas of the nearshore zone, constituting 10% of the world oceans, that over 90% of world marine fish are taken. The species most sensitive to depradation by man are those dependent on streams, lakes and estuaries for spawning and early-life feeding and those which dwell in the intertidal zone. Marine life may be damaged by pollution and the consequences of other activities of man in a number of ways: (1) destruction of habitat; (2) acute poisoning by toxic wastes; (3) adverse alteration of water quality; (4) sub-lethal effects of pollutants causing impairment of feeding, growth, migration, resistance to disease and parasites, and interference with reproduction; (5) bacteriological and viral contamination; (6) bioaccumulation of toxic metals and organic substances; and (7) tainting and/or discoloration of the flesh by organic and/or metallic substances. The economic effects of pollution and other environmental changes introduced by man on the world fisheries are difficult to assess at the present time. However, the elimination of shellfish resources alone by sewage can involve hundreds of millions of dollars per year. This can only be overcome by costly cleanup of sewage and industrial waste disposal in contaminated areas, depuration (purification) of shellfish by transplanting to clean areas, or artificial depuration with ultra-violet light or chlorine in an installation designed for the purpose. The rejection of fish products because of high metals content, e.g., mercury in swordfish, of high chlorinated hydrocarbon concentration, e.g., DDT in California jack mackerel, can pose a hardship to fishermen, an economic burden on governments which may have to pay compensation to fishermen for their losses, and of course, a loss of protein urgently needed in a hungry world. It is obvious that in spite of the most aggressive conservation policies, backed by strong national legislation, many of the productive coastal areas will be lost to fisheries. Either factors of national importance, other than marine conservation, will outweigh fisheries needs to support preservation, or costs will be too high to warrant full-scale restoration. Yet the demand for protein will not diminish. Hence, the only recourse is mitigation with: (1) intensification of fish propagation by enhancement techniques, e.g., hatcheries and spawning channels, in areas still unpolluted and generally unaltered by man, with a potential for higher fish production; (2) transplantation of desirable species into waters suitable for their propagation; (3) aquaculture with protected water quality in partially enclosed areas of the sea, or in enclosures with controlled seawater input; and (4) environmental improvement, e.g., artificial reefs, in those areas which could be attractive for fish, but at present are unproductive because of the nature of the bottom, lack of food and undesirable water characteristics. In regard to (4) above, it is conceivable that some of the wastes of man, which are now pollutants, could be put to productive use in the sea. These include: (a) sewage, which might be used for controlled fertilization of unproductive coastal waters; (b) cooling waters for increasing water temperatures in temperature regions, where certain introduced warm-water species could thrive, or indigenous species living at the bottom of their temperature range, could increase their productivity; (c) selected solid refuse for building reefs in flat-bottomed sea areas; and (d) suitable pulverized solid wastes, e.g., mine tailings, for developing bottom material of a desirable character for burrowing molluscs, such as clams and cockles.