LOUGH: LARVAL DYNAMICS OF DUNGENESS CRAB 



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1969 1970 1971 

 CRNCER MRGISTER RT NH05 



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 CANCER MRGISTER RT NHIO 



March was 18% (Wyatt et al. 1972). High percen- 

 tages of returns near 3(f/c were observed only 

 during February and March 1961, 1962, 1963, 

 and 1967. 



April 1970 showed a high positive index value 

 (4-25) indicative of upwelling processes, whereas 

 downwelling was still in process during the same 

 month in 1971 (-2). However, by May 1971 the 

 upwelling intensity was twice the magnitude of 

 that in 1970 ( + 66 and +33, respectively). In all 

 regards the year 1971 can be considered the most 

 anomalous whereas 1970 can be considered the 

 least anomalous of the sampling period and the 

 most typical over a 20-yr span. Kukla and Kukla 

 (1974) reported large-scale global anomalies in 

 weather patterns developing early in 1971. Snow 

 cover in the northern hemisphere increased 

 dramatically for the months of February, March, 

 April, and September 1971. 



Larval Population Analyses 

 Between 1970 and 1971 



Despite the rather restricted data set, a rigor- 

 ous statistical analysis is attempted at this point 

 to explore the relative importance of some envi- 

 ronmental variables associated with the C. ma- 

 gister larval populations. An attempt is made to 

 examine potential causative factors underlying 

 the difference in larval abundance between 1970 

 and 1971 seasons. A basic assumption in the 

 analysis is that the larval data collected in a 

 single sampling transect are representative of a 

 much larger homogeneous area. Patches of larvae 

 may be quite localized so that differences in lar- 

 val abundance from year to year may be due to 

 dispersal and not mortality caused by an en- 

 vironmental variable per se. However, the dis- 

 tribution of adult breeding populations are 



359 



