The lower mortalities from the adjacent Pacifica 

 and Russian River regions confirm the suggestion 

 of the original study that the heavy mortalities 

 were substantially confined to the Drakes Bay 

 region. This is consistent with the suggestion that 

 the northerly Davidson Current may be sweeping 

 harmful effluent from San Francisco Bay into 

 Drakes Bay. The intermediate mortality levels of 

 the Pacifica region could simply be a result of 

 proximity while the Russian River region might 

 remain relatively unaffected due to blockage and 

 dispersion caused by the Point Reyes land mass 

 and to dilution of the harmful effluent. 



The similarity between the peripheral and 

 overall mortalities found for the Pacifica, Russian 

 River, and Eureka regions show a constant 

 mortality distribution throughout the egg masses 

 in these areas. The Drakes Bay region, however, 

 showed considerably higher peripheral mor- 

 talities (39.4%) compared with the overall mor- 

 talities (27.6% ■). It is surmised that the peripheral 

 mortalities are the primary difference between 

 the high number of mortalities found in Drakes 

 Bay and the lower numbers in other regions. This 

 parallels the distribution of mortalities caused by 

 epibiotic fouling in the laboratory (Fisher 1976) 

 which were found to decrease with increased depth 

 into the egg mass and further supports the 

 proposition that epibiotic fouling contributes to 

 egg mortalities in the Dungeness crab population 

 of Drakes Bay. 



There are several similarities between this egg 

 disease and that of the blue crab, Callinectes 

 sapidus, caused by the fungus, Lagenidium cal- 

 linectes (Couch 1942; Sandoz et al. 1944). Both 

 conditions are geographically selective, cause 

 peripheral mortalities, cause greater damage on 

 older egg masses, and coincide with increased 

 nemertean worm populations (Rogers-Talbert 

 1948; Fisher and Wickham 1976). It is interesting 

 to note that some epibiotic microorganisms were 

 also observed on the blue crab eggs (Rogers- 

 Talbert 1948). These similarities may indicate a 

 common factor such as environmental stress or 

 physiological impairment of the eggs that 

 supercedes the importance of the respective 

 etiological agents. 



It is difficult to ascertain the effect of the 

 Dungeness crab egg mortalities in Drakes Bay on 

 the recruitment of the commercially important 

 adult stages. Specific production data for Drakes 

 Bay and migration patterns for the species are un- 

 known. Although no attempts have been made to 



bear out the suggestion, Rogers-Talbert (1948) felt 

 that 25% mortality found on the blue crab eggs 

 could not be regarded as a factor in (adult) popu- 

 lation fluctuations. Recently, larval stages of the 

 Dungeness crab have also been found susceptible 

 to epibiotic microbial infestation in the laboratory 

 (Fisher and Nelson 3 ) although no field data are 

 available. It can at least be speculated that the 

 combined losses of egg and larval stages have 

 decreased the adult population of Dungeness crabs 

 in Drakes Bay. This decrease is reflected by the 

 collapse of the fishery in central California since 

 1960 while northern California production, al- 

 though fluctuating, has been maintained (Orcutt 

 et al. 1975). 



Acknowledgments 



We thank Harold Ames, Tom Burke, Earl 

 Carpenter, Bill Genochio, Tony Anello, Willie 

 Ancona, Tom Estes, and Charles Fagg for their 

 sampling efforts and Richard Nelson for his 

 technical assistance. 



Literature Cited 



COUCH, J. N. 



1942. A new fungus on crab eggs. J. Elisha Mitchell Sci. 

 Soc. 58(2):158-162. 

 FISHER, W. S. 



In press. Laboratory studies on the relationships of 

 epibiotic fouling and mortalities of the eggs of the 

 Dungeness crab {Cancer magister). J. Fish. Res. Board 

 Can. 

 FISHER, W. S., AND D. E. WICKHAM. 



1976. Mortalities and epibiotic fouling of eggs from wild 

 populations of the Dungeness crab, Cancer magis- 

 ter. Fish. Bull., U.S. 74:201-207. 



Orcutt, H. G., R. N. Tasto, and p. w. wild. 



1975. Dungeness crab research program. Calif. Dep. 

 Fish Game Mar. Resour. Adm. Rep. 75-8, 35 p. 



Rogers-Talbert, r. 



1948. The fungus Lagenidium callinectes Couch ( 1942) on 

 eggs of the blue crab in Chesapeake Bay. Biol. Bull. 

 (Woods Hole) 95:214-228. 



Sandoz, M. D., R. Rogers, and C. L. Newcombe. 



1944. Fungus infection of eggs of the blue crab Callinectes 

 sapidus Rathbun. Science (Wash., D.C.) 99:124-125. 



3 Fisher, W. S., and R. T. Nelson. Therapeutic treatment for 

 epibiotic fouling on Dungeness crab {Cancer magister) larvae 

 reared in the laboratory. Submitted for publication. 



william s. fisher 

 Daniel e. wickham 



University of California 

 Bodega Marine Laboratory 

 Bodega Bay, CA 94923 



237 



