8-17 



abundance data can be used with some degree of quantitative validity, 

 particularly in evaluating relative spatial and temporal trends in 

 abundance . 



Although catch-abundances of Crangon were variable, size 

 distribution of Crangon populations in New Haven Harbor exhibited a 

 measurable degree of seasonality with modal size increasing from fall 

 through spring and decreasing during summer (Figure 8-3) . From July 

 through October 1976, 60% of the Crangon measured in trawl samples 

 ranged in length from 21 to 30 mm with the 26-30 size-category con- 

 taining the largest proportion of the catch. Modal size of Crangon 

 increased from November 1976 through February 1977 when 60% of the 

 individuals measured ranged in length from 26 to 40 mm and the 31 - 35 

 mm size-category contained the largest portion of the catch. During 

 spring (March through June 1977) the modal size of Crangon continued to 

 increase. During this period 60% of the individuals measured ranged in 

 length from 31 to 45 mm and the 41 to 45 size-category contained the 

 largest portion of the catch. During summer and early fall (July- 

 October 1977) the modal length of Crangon decreased. As in 1976, 60% of 

 the individuals measured ranged in length from 21 to 30mm and the 26-30 

 size-category contained the largest portion of the catch. This decrease 

 in population size was attributable to both a large decrease in the 

 number of shrimp in the larger size-categories as well as an increase in 

 the number of shrimp in the smaller size-categories. 



In New Haven Harbor, it is not certain whether adult shrimp 

 migrate from the harbor during summer or whether they are simply exposed 

 to an elevated level of predation once having reached a certain size 

 (maximum size of C. septemspinosa is approximately 70mm; Price, 1962; 

 NAI, 1978a) . Price (1962) observed a similar seasonality of size- 

 distribution of Crangon in Delaware Bay; highest abundance of sand 

 shrimp was observed during spring with largest individuals also collect- 

 ed during this period. Three year-classes of females and two year- 

 classes of males inhabit the waters of Delaware Bay during spring; 

 during summer, the oldest year-classes of both sexes disappear from the 



