Table 3.-Comparison of this work with literature values for the concentration of PCB's and DDT 

 residues in surface films and subsurface waters. All values in nanograms per liter, and are the sum 

 of filtrate and filter from Table 2 where applicable. 



The primary aim of this work has been to es- 

 tablish open ocean concentrations of PCB's and 

 DDT residues in surface films and subsurface 

 waters in oligotrophic regions of the ocean such as 

 the North Central Pacific Gyre. The PCB content 

 of open ocean waters are significantly lower rela- 

 tive to inshore waters, and represent the first such 

 numbers for an open ocean environment in the 

 Northeast Pacific. 



Acknowledgments 



We thank H. Bezdek for collection of the surface 

 film samples from the Mexican coastal waters (M 

 1-4). 



This work was supported by AEC Contract 

 AT(11-1)GEN 10, P.A. 20. 



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P. M. Williams 

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Institute of Marine Resources 

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HATCHING SURVIVAL OF HYBRIDS OF 



ONCORHYNCHUS MASOU WITH 

 SALMO GAIRDNERI AND WITH NORTH 

 AMERICAN SPECIES OF ONCORHYNCHUS 



The cherry salmon, Oncorhynchus masou, which is 

 native only to Asian watersheds discharging into 

 the northwestern Pacific Ocean, is a recent in- 

 troduction to North America. While cherry salmon 

 have been crossed with some Asian salmonids, in- 

 formation on their ability to hybridize with North 

 American salmonids has not been reported in the 

 literature. The primary purpose of these 

 experiments was to determine hatching survival 

 of some interspecific crosses involving cherry 

 salmon, leading to a sound basis for predicting 

 their effects on indigenous salmonid species and 

 their potential value in salmon management. 



447 



