368 OCEANOGRAPHY IN THE UNITED STATES 



WHAT DO WE KNOW ABOUT FISHERY OCEANOGRAPHY? 



Our knowledge of oceanography as it affects the distribution and 

 survival of marine resources and the aA^ailability of these resources 

 to fishermen is fragmentary and imperfect. The present state of this 

 knowledge might be compared with our knowledge of the geography 

 of the North American Continent in the 16th century shortly after 

 the voyages of Columbus — a few fairly well established facts pieced 

 together with speculation and considerable myth. We know in gen- 

 eral that temperature is important to marine life ; that each species 

 has its own optimum temperature limits which limit its geographic 

 distribution and its distribution with depth in the sea ; tliat seasonal 

 changes in temperature, and deviations from the normal temperature 

 pattern, affect the migrations of fishes; and that sudden changes in 

 temperature may be lethal to marine life. We know that salinity 

 influences the movement of marine animals and that unusual changes 

 in salinity may cause death. We know that winds and currents have 

 profound effects upon the marine environment, and influence the 

 fisherman's catch in many ways. But these are only the most obvious 

 of a myriad of factors in the ocean that exert an influence upon our 

 marine resources and upon the welfare of those who depend on these 

 resources for their livelihood. 



In order to examine some of these particular features, Mr. Chair- 

 man, with your pemiisison I would appreciate having Dr. McHugh 

 tell you about some of our research and some of the facts of oceanog- 

 raphy which do influence the fisheries resources and our fishing in- 

 dustry. 



Mr. ]\IiLLER. Very well, Dr. McHugh. 



Mr. McHugh. This is a simplified diagram of the major ocean 

 currents of the world. We are concerned primarily with the systems 

 in the North Atlantic and North Pacific Oceans, for these are the areas 

 from which most of our fishery harvest comes. In a general way, 

 these two great ocean systems are remarkably similar. The warm 

 Gulf Stream flows north along our Atlantic coast, then veers diago- 

 nally across the Atlantic to divide into two main drifts, one of which 

 modifies the climate of the United Kingdom and the Scandinavian 

 countries, the other swings southward along the coasts of Portugal and 

 North Africa, returning toward America as the North Equatorial 

 Current. Meeting the Gulf Stream off our New England coast is 

 the cold Laboraclor Current, and the boundary between cold and 

 warm curi-ents in this region separates our fishery resources into two 

 main groups, cliaracterized by such species as haddock, cod, and redfish 

 north of the Gulf Sti-eam system, and bhieiish, tuna, oysters, shrimp, 

 menhaden, and other warm- water species to the south. 



Similarly, in the Pacific the warm Kuroshio flows nortliAvard off 

 the Asian coast, then swings diagonally across the ocean as the North 

 Pacific drift. It also divides as it approaches North America, part 

 flowing northward as the Alaska Current, part swinging south as 

 the California Current. The watei- returns to the westward as the 

 North Equatorial Current. The Laborador CuiTcnt also has its 

 counterpart in the Pacific, the Oyashio, a cold current that flows south- 

 ward off Kamchatka and meets the Kuroshio olf Japan. The boundary 

 between the Aleutian and North l*acilic drifts separates rather sharply 



