Broadhead, G.C., and I. Barrett. 1964. Some factors 

 affecting the distribution and apparent abundance 

 of yellowfin and skipjack tuna in the eastern 

 Pacific Ocean. Inter-Am. Trop. Tuna Comm. Bull. 

 8:419-473. 



Sea surface temperatures and thermocline 

 topography were considered as possible regu- 

 lating factors of tuna abundance and distri- 

 bution. Abundance patterns were modified at 

 the northern and southern extremes during 

 major changes in the sea surface temperature. 

 The coincidental movement of both isotherms 

 and contours of skipjack abundance during 

 spring and summer months was particularly 

 evident off Baja California. Off Ecuador and 

 Peru the seasonal warming and cooling had no 

 pronounced effect on skipjack distribution. 

 No relationship was evident between yellowfin 

 tuna abundance and depth of the mixed layer. 



KEY WORDS: tunas, yellowfin, skipjack, sea 

 surface temperature, thermocline topography, 

 abundance, season, distribution. 



Brown, R. P., and K. Sherman. 1961. Oceanographic ob- 

 servations and skipjack distribution in the North 

 Central Pacific. Jji J.C. Marr (editor). Pacific 

 Tuna Biology Conference, August 14-19, 1961, Hono- 

 lulu, Hawaii, p. 22. U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. Fish. 415. 



Abstract only. Results of five oceanographic 

 cruises. The summer season skipjack appear- 

 ances were concentrated in boundaries between 

 two adjacent water types. Frequency of oc- 

 currence of skipjack schools suggested move- 

 ment of large fish from the west into the 

 Hawaiian Island area. Authors suggested a 

 relation between skipjack larvae occurring in 

 summer and zooplankton abundance, both attri- 

 butable to the spawning periodicity of adult 

 skipjack . 



KEY WORDS: tuna, skipjack, season, area, mi- 

 gration, larvae, water types, current bounda- 

 ries . 



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