numbered white disk was placed on a nickel 

 pin and diis pushed through the hole so that 

 this disk was under the prosoma. The red 

 disk with a notice of reward and address for 

 mailing was placed on the upper side. The 

 width of the crab was measured at its widest 

 point and the sex noted. This information was 

 recorded with the serial number of the tag. 



Usually a day's catch could be tagged, 

 measured and released the same day it was 

 caught, but some large collections were held 

 overnight in the boat or laboratory. This ap- 

 parently did the crabs no harm as they were 

 lively when released and some of the highest 

 returns came from crabs so held. A case in 

 point is a collection of 38 made on June 26, 1952, 

 which was brought to the laboratory, kept out 

 of water overnight, tagged and released the 

 next day. Seven have been recovered; 4 in 1953, 

 1 in 1954, and 2 in 1955. Also, 92 collected on 

 August 14, 1952 and released the next day, have 

 yielded 14 recoveries; 4 in 1952, 2 in 1953, 5 

 in 1954, and 3 in 1955 . 



The recovery of tags may be roughly 

 divided into three groups, according to who 

 found them: (1) recoveries made throughout 

 the year by our staff while collecting crabs for' 

 tagging and other data; (2) recoveries by "alerted" 

 persons who knew of our tagging program and 

 were deliberately searching for tagged crabs 

 within Plum Island Sound, either for the reward 

 or to help us; and (3) purely accidental recover- 

 ies by visitors to the seashore. This last group 

 includes many people from inland towns and the 

 general surprise and curiosity is quite evident 

 from the letters. These may be considered 

 chance or random recoveries, which might be 

 expected from any popular beach or shoreside 

 area. The first two- groups, those found by the 

 staff and "alerted" persons, are not random in 

 geographical distribution because most of the 

 searching was done within Plum Island Sound. 



RESULTS 



Results are tabulated in tables 1 to 7 

 and shown in figures 1 to 3 . 



Table 1. --Summary of intertidal collections of horseshoe crabs in upper and lower 

 parts of Plum Island Sound, Mass., 1951 through 1954 



Total 



52 



28 



1,364 



2,816 



26.2 



100.6 



