BURROVJING ABILITli: OF JUVENILE CLAIMS 



An experiment was conducted in Feburary 1953? at the United States 

 Fishery Laboratory in Boothbay Harbor, Maine, to study the burrowing 

 ability of juvenile clams, Mya arenaria, (2-22rnmo long), while exposed 

 to various current velocities, and to study the effect of currents on the 

 dispersal of the clams. The work was prompted by the fact that clams of 

 this size are often exposed to tidal currents and wave action for varying 

 periods, and their resulting dispersal may be an important factor in the 

 distribution of adults ^ The juvenile clams become exposed either by being 

 washed out of their burrows by storms or by voluntarily leaving their bur- 

 rows to null themselves along the surface of the flat a few inches at a 

 time by alternately'- extending and contracting the foot. It is while the 

 clams are thus wandering about that they maj"" be "caught unawares" by an 

 increase in vjave action or current velocity, and the clams' subsequent 

 movements become dependent upon physical forces. 



The ability of young clams to move short distances about the surface 

 of the flat by use of the foot is well known (Kellogg 1899). The fact that 

 a continuous large-scale redistribution of juvenile clams occurs during 

 normal weather conditions was demonstrated by Smith (1952) . After more than 

 a year of field experiments, in which he recessed square-foot trays of clam- 

 less mud in the tidal flats for short periods in Newburyport, Mass., Smith 

 reported that "both the numbers and sizes of clams coming into a square 

 foot area in a period of two weeks follows very closely the numbers and 

 sizes in the open flats where they have had all season to collect." 



The assistance of the following biologists of the U. S= Fish and 

 Wildlife Service Clam Investigations is gratefully acknowledged: John B. 

 Glude, and Ifilliam J„ Brown for construction of the flume, Alden P, 

 Stickney for sediment analyses, and Osgood R, Smith for giving invaluable 

 advice and criticism. 



Materials and Methods 



A wooden flume was constructed 8 feet long, l~'i/h inches wide, and 6 

 inches deep (figure 1), A 2-foot section of the bottom at the upstream 

 end and a 1-foot section at the downstream end were built up 3 inches. 

 This provided a recess in the center, h feet long and 3 inches deep, to 

 contain a miniature mud "flat" and a similar recess 1 foot long at the 

 downstream end as a sediment trap. On the upstream end a stilling-basin 

 was constructed 2I1 inches deep and lit inches square. Thirteen inches from 

 the bottom of this basin was a baffle with a circular opening 9 inches in 

 diameter through which a 2-inch pipe delivered sea xrater about 1; inches 

 from the bottom, the volume of flow being controlled by a gate valve. To 

 help reduce turbulence, a piece of llixl6 mesh plastic screen was lashed 



