Our observations indicate that disease is a fac- 

 tor to be considered in evaluating the decline of 

 the San Francisco area crab population. The re- 

 productive capacity of the population must be af- 

 fected by this epibiotic fouling condition especially 

 if it can also infest the larval stages as indicated by 

 the studies on other crustaceans (Fisher et al. 

 1975). 



The variety of fouling organisms and the geo- 

 graphical trends observed in this disease situation 

 suggest a complex relationship with external en- 

 vironmental factors. In view of the saprophytic 

 nature of the fouling organisms, their major 

 source of nutrients is probably external. As such, 

 the growth of the contaminants are affected by the 

 nutrient level in the seawater. 



It appears that the external factors involved 

 may originate in the San Francisco Bay effluent. 

 This is suggested by the decreasing trend of mor- 

 talities and fouling heading north from this area, 

 presumably reflecting the dilution of the effluent 

 waters. The normal water currents in this area 

 flow in a southerly direction; however, during the 

 period from November through February, the pre- 

 vailing inshore flow is the northerly Davidson 

 Current (Reid et al. 1958). During the egg-bearing 

 season, the effluent from San Francisco Bay is 

 carried northward. 



The observations of this study were limited by 

 the collection of samples during only the 1974-75 

 crab season. Because of the potential relationship 

 of these findings to a valuable natural resource, 

 we felt that it was important to communicate the 

 available information. It is clear that further stud- 

 ies during the next season will enhance our under- 

 standing of the situation. 



Acknowledgments 



We thank Robert Shleser for his support under 

 California State Legislature funds and in the 

 preparation of the manuscript; Edgar Nilson for 

 his assistance and suggestions; Louis Cavellini, 

 Earl Carpenter, Tom Burke, and the crab fisher- 

 men of northern California who obtained egg 

 samples. 



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