BOTSFORD and WICKHAM: UPWELLING INDEX AND DUNGENESS CRAB CATCH 



SUMMARY AND CONCLUSIONS 



The correlation analysis at different lag times 

 indicates a significant correlation of crab catch 

 with upwelling for several years following up- 

 welling. Auto-correlation of crab catch indicates 

 that catch is of a cyclic nature. The same analysis 

 of upwelling does not show a significant cyclic na- 

 ture (although this may possibly be due to incon- 

 sistencies in Bakun's data). These analyses are not 

 rigorous proofs of the indicated characteristics but 

 rather provide impetus and direction for further 

 research. They suggest that the cyclic variation of 

 crab catch may be primarily due to density- 

 dependent biotic factors rather than upwelling, 

 although upwelling does influence catch. Further 

 conclusions regarding the biological basis for the 

 cyclic nature of catch data require research in the 

 natural history and ecology of the Dungeness crab. 

 A specific question to be answered is over what age 

 groups are the niches similar enough for sig- 

 nificant competition to occur. Further conclusions 

 regarding the relationship between upwelling and 

 catch require additional research in the nature of 

 energy transfer from the pelagic to the benthic 

 environment. Research in these directions may 

 provide basis for a more dynamic fishery 

 management policy. For instance, the importance 

 of deciding whether the variations in crab catch 

 are due primarily to density-dependent factors is 

 illustrated by the implication that if competition is 

 occurring between adults and juveniles, limited 

 fishing of females (removing them as competitors) 

 during years of great abundance may provide 

 greater catches in the following years. 



The statistical relationships presented also 

 provide a basis for predicting crab catch. The 

 values of upwelling index and crab catch over 

 several years may be used to predict catch for the 

 ensuing years (Rauch et al. 1975). Additional 

 variables may be added to the basis for prediction 

 such as temperature and results of plankton tows. 

 This type of prediction is based on statistical 



relationships and does not necessarily require 

 causal explanations of the various effects. 



ACKNOWLEDGMENT 



We thank W. E. Ricker for his helpful comments 

 on an early version of this manuscript. 



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