8-19 



area. As a result, mean lengths and abundances decreased in Delaware Bay 

 from spring to late siimmer. Price was not certain whether this was due 

 to increased predation or migration, but he suggested that Crangon 

 undergoes a seasonal change in spawning grounds from inshore waters to 

 deeper offshore waters. Seasonal migrations are also documented for 

 Crangon septemspinosa in estuaries near Beaufort, North Carolina; here 

 shrimp move offshore beginning in July and August and return the follow- 

 ing v/inter and spring (Williams, 1965). 



Seasonal migrations of the European brown shrimp, Crangon 

 crangon, in European waters are well documented (Boddeke, 1975 and 

 1976) . Adult shrimp were observed to undergo local inshore-offshore 

 movements . Shoreward movement was observed during the spring with 

 gravid females the first to move in followed by adult males; emigration 

 of adults, including sexually ripe shrimp, occurred during the fall. 

 Juvenile shrimp did not migrate to the extent of adults and usually 

 remained in coastal waters year round (Boddeke, 1976) . 



i 



In New Haven Harbor, size-data for Crangon septemspinosa sug- 

 gest that adult shrimp migrate into the harbor during spring and peak in 

 abundance during May and June which would explain the gradual increase 

 in the modal size of shrimp during this period. During summer, increas- 

 ing temperatures and possibly decreasing dissolved oxygen levels may act 

 to stimulate emigration of adults from the harbor to deeper waters. 

 Since juveniles do not migrate to the extent of adults (Boddeke, 1976; 

 Price, 1962), modal size-distribution observed during the summer would 

 reflect a predominantly juvenile population. Also, since the number of 

 small shrimp collected during the summer tends to increase - possibly as 

 a result of growth to catchable size from the previous years' spawning - 

 migration of adult shrimp is not apparent in the abundance data. During 

 winter and spring, a gradual return of adult shrimp occurs with a 

 resulting increase in modal size. Observations by Richards and Riley 

 (1967) on the benthic epifauna of Long Island Sound further supports 

 this conclusion; they found that the standing crop of Crangon in Long 

 Island Sound increased during late sxommer. This may reflect movement 

 of adult sand shrimp from inshore waters to the deeper waters of Long 

 Island Sound during this period. 



