SECKEL and YONG: SEA-SURFACE TEMPERATURES AND SALINITIES 



1974) do not correlate with the salinity changes, 

 and variations in the meridional component of 

 flow appear to cause the seasonal and long-term 

 salinity changes. 



On the basis of the long-term temperature curve 

 at Koko Head (Figure IB) one might conclude that 

 interannual changes in environmental processes 

 are unimportant. The Koko Head salinity curve 

 (Figure 2B) shows such an inference to be incor- 

 rect and illustrates the value of monitoring more 

 than one property at a location. 



An understanding of the processes governing 

 the temperature and salinity changes is pertinent 

 to fishery management problems. Our specula- 

 tions about these processes illustrate that good 

 correlations between environmental properties 

 and biological concentrations do not necessarily 

 imply causal relationships. An example is the 

 good correlation between skipjack tuna captures 

 in the eastern Pacific yellowfin tuna regulatory 

 area and central equatorial Pacific temperatures 

 or the southern oscillation index, the skipjack 

 tuna catches lagging about 18 mo. 5 Do these corre- 

 lations mean that temperatures in the central 

 equatorial Pacific determine larval survival and 

 year-class strength or do they mean that the cur- 

 rents affect the concentration and distribution of 

 skipjack tuna in the eastern Pacific with the tem- 

 perature variations being ancillary? These ques- 

 tions are important if environmental factors are to 

 be included in fishery population models. 



ACKNOWLEDGMENTS 



We thank A. Bakun, Pacific Environmental 

 Group, NMFS, for helpful discussions; T. P. Bar- 

 nett and W. C. Patzert, Scripps Institution of 

 Oceanography, and J. Hayes, Fleet Numerical 

 Weather Central, for reading the manuscript and 

 making many useful comments; and M. J. Vitou- 

 sek, Hawaii Institute of Geophysics, for making 

 Christmas Island temperatures available to us. 



5 Bi-monthly report, November-December 1974. Inter-Am. 

 Trop. Tuna Comm., La Jolla, Calif. 



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