468 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1960 



settles to the bottom, loses its swimming organs, and digs into the 

 substratmn. It is still microscopic in size at this time and very sus- 

 ceptible to predations by the myriads of creatures that inhabit the 

 bottom. It takes more than a month before it grows big enough to 

 be visible to the naked eye. 



This facet of the clam's history immediately posed the problem of 

 how to stock the farm. The farmer could not simply keep a breedmg 

 stock on one corner of his grant and expect any result. For all he 

 knew, the offspring of this stock might wind up many miles away 

 after the 2-week free-swiimning period. On the other hand, there 

 was just as much chance that a parent stock in some distant cove 

 might provide the offspring to populate his grant. However, he 

 could not depend on such a fortuitous occurrence but had to find a 

 sure way of stocking his grant. This was the first problem that we 

 of the Institution undertook to solve, under contract with the Massa- 

 chusetts Division of Marine Fisheries. 



We knew from some of our plankton studies that clam larvae are 

 always abundant in the water during the summer, even when adults 

 were relatively scarce, because of the enormous numbers of eggs pro- 

 duced by each female. We then made the assumption that the sub- 

 stratum must have some property that either stimulates or discourages 

 settlement at the end of the larval period. This assumption was bol- 

 stered by the report of an old fisherman in Barnstable who claimed to 

 have brought about the settlement of large numbers of clams on his 

 grant by resurfacing the area with sediments excavated from a certain 

 marsh bank. We then collected sediments from a wide variety of 

 places and analyzed them for the assortment of grain sizes. 



Our preliminary findings indicated that the size assortment of sand 

 grains taken from all places where clams existed in abundance seemed 

 to follow a similar pattern which was measurably different from those 

 taken from places where clams were absent. The materials taken from 

 the marsh bank suggested by the old fisherman fell into this size pat- 

 tern. We then obtained a boat and a scow and transferred materials 

 from other marsh banks where the assortment of grain sizes did not 

 fall into the pattern. The entire operation was done by hand and we 

 became as adept wdth a pick and shovel as we were supposed to be 

 with a microscope. 



At the end of the summer we surveyed our resurfaced areas and 

 found that they contained clams in what we thought were appreciable 

 numbers, running as high as 300 per square foot, while the surround- 

 ing flats remained practically barren. Curiously enough this proved 

 to be the case in all the areas we had resurfaced including the controls. 

 However, the latter plots had become much reduced in size because the 

 strong tidal currents washed the transferred sediments away. The 



