Science: What Settles Spats

When an oyster egg hatches it produces a larva. The larva eventually “settles” and cements itself as a “spat” to a clean submerged stone or old shell, where it grows until big enough to eat. Just what makes the spats settle has always been an ostreiculture problem. Last week Herbert F. Prytherch of the U. S. Bureau of Fisheries gave an answer, in Science.

At the oyster beds of Milford Harbor, Conn., where the Indian River empties into Long Island Sound, he found the spats settling only at low tide. That is when the salt sound water is most diluted by the fresh river water. Something in the river water evidently makes the very young oysters want to nestle to a stone or shell. By tedious eliminations, Mr. Prytherch determined that this settling factor is a trace of dissolved copper. Injurious to plant and animal life when administered in large quantities, copper sulphate may now become one of the tools of oyster farming. And copper (also iron, magnesium) makes oysters a fine blood-builder in the human diet.