THIRTY-NINTH BIENNIAL REPORT 37 



Pismo clam investigations were suspended during the war. However, 

 one of our staff members was able to make a few observations on Mexican 

 beaches while on vacation. 



Sea Lions: In response to an intensification of the usual com- 

 plaints of sea lion depredations on fishing gear and fishery resources, 

 the Bureau of Marine Fisheries in cooperation with the Bureau of 

 Patrol made a survey of the numbers of sea lions present along the entire 

 California coast in June, 1946. The assistance of the United States Navv 

 in placing dirigibles and crews at our disposal is gratefully acknowledge. 



The survey revealed that sea lions have indeed increased sub- 

 stantially in numbers since the last previous complete count, which was 

 made in 1938. The 1946 survey listed 12,506 sea lions, an increase of 

 4,645. Of these, 7,338 were observed south of Point Conception. It is in 

 Southern California that the greatest increase has taken place. 



Keafizing that the increase in numbers of sea lions constituted a 

 menace to the fishing industry, the Bureau recommended that a reduc- 

 tion in the herds was desirable. 



Undersea Oil Exploration : The ever-increasing demand for petro- 

 leum products has led the oil industry to seek new deposits far from 

 shore beneath the ocean bottom. Exploration methods involve the detona- 

 tion of explosive charges under the surface of the water, with echoes 

 of oil-bearing strata being picked up on sonic detection devices. Inasmuch 

 as the use of explosives can cause damage to marine life, any undersea 

 exploration is subject to regulation by the Fish and Game Commission. 



Supervision of the exploratory work insofar as it may affect the 

 fisheries resources is the responsibility of the Bureau of Marine Fisheries. 

 Not only have the operations been closely observed and supervised, but 

 independent studies have been conducted to determine the effect of 

 explosives on fish, mollusks, and crustaceans. These studies, which are 

 the subject of a forthcoming publication, indicate that the use of explo- 

 sives as conducted in oil surveys is only moderately harmful to marine 

 life, and only within a restricted range. If the ' ' shots ' ' are buried under 

 the sand, harmful effects are minimized, it was noted. As a result of 

 these observations, the oil companies are required to operate only where 

 fish are not abundant at the time, and furthermore they must bury their 

 charges in the sand when operating in shallow water. 



Ocean Sportfishing : Deep sea sport fishing was greatly curtailed 

 during the war, largely because of stringent security measures and to 

 some extent because party boat operators and crews entered the armed 

 forces or were engaged in commercial fishing. Activity increased in 1945 

 as security restrictions were lifted. By the spring of 1946 the sport 

 fishery from San Francisco to San Diego was operating on a prewar 

 scale. In fact, many new boats were built and newcomers to the business 

 were eagerly reaping the golden harvest of postwar easy money. 



The bureau's survey of sport fishing boat catches was suspended 

 until early 1946 when an increase in research personnel had made 

 resumption possible. 



The interests of commercial fishermen and anglers overlap, as both 

 groups fish in the same waters and for the same species of fish. Both 

 commercial and sport fisheries have expanded at a sensational rate, the 



