Ml I 2 ' 3 ' 3 I 5 ' 



Morfolity levels 

 » 



Fouling levels 



> 



Figure 4. — Histograms representing the percent of Dungeness 

 crab samples from each region found in the mortality and fouling 

 categories. The arrows represent increasing mortalities and in- 

 creasing fouling. Sample sizes from each region are shown. 



that 99% and 98%, respectively, of the adult 

 female population had been inseminated, indicat- 

 ing that the fishing industry (which only legally 

 catches males greater than 6^^ inches across the 

 carapace) is not significantly reducing the repro- 

 ductive capabilities of the crab population. Also, 

 tagging studies have shown that an estimated 90 

 to 100% of the legal-size males in fishing areas of 

 the California coast have been caught each year 

 since 1929 (Pacific Marine Fisheries Commission 

 1965). Cleaver (1949) and Peterson (1973) stated 

 that the fishing pressure has been similar in 

 Washington and Oregon. It therefore appears that 

 fisheries along the coast are capable of maintain- 

 ing production despite the virtually maximum 

 fishing pressures. Poole and Gotshall ( 1965) con- 

 cluded that the fishing regulations at that time 

 were sufficient to protect the crab from depletion 

 through overfishing. 



Physical factors may be responsible for periodic 

 fluctuations in crab abundance. The Pacific 

 Marine Fisheries Commission (1965) suggested 

 that shifting currents played a role in these fluc- 



FlGURE 5. — A single Dungeness crab egg showing an intact 

 membrane, an atrophied and nonviable embryo (168 x). 



- Eureka- Ft Bragg 

 -Oregon 

 San Frartciico 



Crab 5«oson Ycori (1948-19/21 



Figure 6. — A graph comparing the Dungeness crab catches 

 reported from 1948 to 1972 in three areas. Note that the San 

 Francisco crab catch did not increase from the 1961-62 level. 



tuations by disturbing larval settlement. Lough 

 (1974) found a correlation between rainfall during 

 salinity-sensitive larval stages and crab catch 4 yr 

 later when those larvae were to enter the fishery. 

 Peterson (1973) and Botsford and Wickham (1975) 

 have found a positive correlation between upwel- 

 ling intensity and crab catch. 



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