CONSERVATION OF MARINE RESOURCES 19 



have caused deaths of marine organisms by exposing them to waters of 

 above or below normal temperatures. Intrusions of the warm El Nino 

 current off the Pacific coast of South America frequently are cited as 

 causing mass mortalities of marine organisms. 



Toxic Organisms. Sudden blooms of dinoflagellates, which are micro- 

 scopic free-swimming protozoan organisms, have caused mass mortalities 

 of fish and other marine animals from time to time, probably by some 

 direct poisoning effect. The term ''red tide" is often applied to such 

 blooms because the organisms become so abundant that the water takes 

 on the animal's characteristic red coloration. A bloom of the dinoflagellate 

 Ciymnodinium off Florida in 1946-1947 killed porpoises, barnacles, oysters, 

 and fishes. Dead fish washed ashore were so numerous they had to be 

 buried with bulldozers'^. 



Man-Made Causes. Over-Fishing. Man affects the yields from fisheries 

 in many ways. The most obvious way is by his fishing operations. Fishing 

 most noticeably affects demersal (bottom-dwelling) species which are 

 particularly vulnerable to man because they often are available to capture 

 during most of their lives. Major changes observed in the abundance of 

 the demersal Atlantic haddock and Pacific halibut, for example, can be 

 explained by sizes of catches taken. 



Pacific Halibut Fishery. The history of the Pacific halibut fishery is 

 particularly illuminating for it clearly portrays the course an unrestricted 

 fishery can take and the benefits to be reaped by proper management. 

 The Pacific halibut management program has attracted world-wide 

 attention, since it represents one of the few cases where a sea fishery has 

 been thoroughly managed on an international basis. Since its inception 

 in 1888, the Pacific hahbut fishery has evolved to one of the major 

 longline fisheries in the world. It is prosecuted by both United States and 

 Canadian fishermen who enjoy reciprocal landing privileges. 



By 1910 all readily accessible fishing banks were being exploited, and 

 halibut in protected waters were becoming scarce. Landings of Pacific 

 halibut by United States and Canadian fishermen reached 50 million 

 pounds by 1907. Expansion northward into Alaskan waters and to the 

 deeper banks off Washington and British Columbia resulted in landings 

 of 69 million pounds in 1915. Continued expansion to new fishing grounds 

 and introduction of diesel power to a progressively larger fleet were not 

 accompanied, however, by corresponding increases in catches. On the 

 contrary, the catches subsequently declined, and by 1931 the total 

 Pacific Coast catch of halibut was only 44 million pounds. 



As a result of declining yields, a conservation treaty for halibut was 

 signed by the United States and Canada. Effective regulation, based on 

 holding the catches slightly below additions being made to the popula- 



