8-24 



individuals) (Table 8-3) . Such yearly variations may be attributed to 

 natural fluctuations in growth, mortality and recruitment as well as 

 variations in catch success of the otter trawl. Similar fluctuations in 

 the annual abundance of Cancer have been observed in other New England 

 waters (Turner, 1954) . 



Populations of Cancer in the harbor showed a well-defined 

 seasonal pattern of abundance (Figure 8-5). Although the pattern 

 exhibited some variability from year to year and station to station, 

 highest numbers were typically encountered during the winter, spring and 

 fall. A siibstantial decline was coincident with periods of high water 

 temperatures and low dissolved oxygen during July, August and September. 

 Seasonal distribution of Cancer in New Haven Harbor, by year, is shown 

 in Figure 8-6. Cancer was generally most abundant in the outer harbor 

 during fall and winter with abundances increasing in the inner harbor 

 during spring. During summer Cancer was collected in low abundances at 

 all stations sampled. Abundances again increased in the outer harbor 

 with the return of fall. This pattern occurred during each year with 

 only minor exceptions. 



Although extensive migratory behavior is not characteristic of 

 Cancer, local inshore-offshore movements have been documented for popula- 

 tions located near their southern geographic limit (Saila and Pratt, 



1973) where Cancer is abundant in shallow waters during the colder 

 months only; during summer it migrates to deeper waters. In New Haven 

 Harbor migration generally begins around April or May, and immigration 

 from the Sound to the harbor occurs in October. This is similar to 

 observations by Winget et al. (1974) for Cancer irroratus in Delaware 

 Bay, where crabs began migration from the bay in April and returned in 

 November. Similar patterns of abundance were observed at Stamford 

 Harbor during the 1971-1973 Stamford Harbor Ecological Studies (NAI, 



1974) and at Port Jefferson during the 1976 pot survey of commercially 

 important invertebrate species (EEHI, 1977). 



