ABSTRACT 



During the years 1952, 1953, and 1954 a total of 1,780 horseshoe 

 crabs ( Limulus polyphemus) were tagged and released in or near Plum Island 

 Sound, Mass . Recovery of tagged crabs indicated an onshore migration that 

 began early in March and reached a peak in June. The largest numbers of 

 crabs were present in the Sound during June, July, and August, after which 

 an offshore migration resulted in a reduction of their numbers on the flats. 

 Low recoveries of crabs during the year they were tagged indicated that in- 

 dividual crabs may spend a fairly short time in the Sound each summer . A 

 population of horseshoe crabs that is probably local for Plum Island Sound 

 and nearby estuaries was indicated by the tag recoveries . Five tagged crabs 

 were recovered almost 4 years after tagging. 



