132 THE SCALLOP FISHERY 



formulate Table D. Afterwards only one measurement, the height, 

 was taken, as the gain in volume for any locality could be determined 

 from the table. The growth line proved of great assistance, as the 

 increase from May 1 at any date could be determined by making two 

 measurements, (1) the height, and (2) the growth Une. 



Tagged Scallops. — A method of recording the growth of individual 

 scallops as well as obtainiug data upon their migratory habits was 

 obtained by " tagging " each specimen. A small hole was punched 

 through the " ear " close to the hinge line, and a numbered copper 

 tag was attached by a fine wire, as in Fig. 66. The. scallops were 

 then liberated in the Powder Hole, after their measurements -vyere taken. 

 Whenever found, the number and size were recorded, thus obtaining 

 the exact growth of the individual specimens. The tag apparently did 

 not interfere with the growth or movements of the animals. 



Another method of identification was used in the pens. The scallops 

 were notched with a file across one valve, the number of notches giving 

 the class of the scallop, when more than one size were confined in the 

 pen. 



The Pens. — Most of the growth experiments were conducted in 

 pens (Pig. 80), as the activity of the scallop rendered confinement 

 necessary. In this way, under what might be termed artificial con- 

 ditions, the rate of growth of Pecten irradians was obtained in several 

 localities. The pens were of two kinds: (1) of 1%-inch wire chicken 

 netting; (2) of old seines. They were constructed by driving in the 

 soil posts of 2 by 3 inch joist, at sufficient intervals, to hold the netting 

 firmly in position. When wire netting was used little difficulty was 

 experienced in making the bottoms of the pens tight to prevent the 

 escape of the scallops, as the netting set firmly on the soil,_which had 

 previously been leveled. When seines were used the bottom was se- 

 cured either by baseboards or by fastening the netting by long wooden 

 pegs, an uncertain method at best. The pens were made either of a 

 sufficient height to rise above the average tide, which was possible 

 at Chatham and Monomoy Point, where there is a comparatively small 

 rise and fall of the tide, or were fitted with netting tops when the tide 

 proved high, as at Marion and Monument Beach. The pens, which 

 ranged from 40 to 400 square feet in size, were situated in water from 

 1 to 2% feet in depth at low tide, and under a variety of conditions 

 as regards current, soil, eel grass and tide. 



Wire Cages. ■ — Scallops were suspended in wire cages (Fig. 71) from 

 a raft in the Powder Hole, Monomoy Point, in order to obtain the rate 

 of growth, especially of the young " seed," too small to confine in pens. 

 The baskets consisted of a wooden framework, 2% feet long, 1^2 feet 

 wide, 1 foot deep, covered by netting with % to 1% inch mesh. 

 Smaller cages were used for the young scallop with galvanized mos- 

 quito netting. The objection to the use of a small mesh is due to the 



