Early in the summer, usually during the months of June and July in these waters, the Massachusetts oyster spawns. Both sperm from the adult male and the eggs from the adult female oysters are extruded in considerable quantities into the water, and there the eggs are fertilized. As fertilization is somewhat a matter of accident, undoubtedly the great majority of eggs never develop. The fertilized eggs pass rapidly through various changes in the course of a few hours, and emerge as microscopic embryos, with thin, transparent coverings. At this period these forms are free swimming, and are found in great numbers in the water. They are extremely delicate, and great quantities are destroyed by natural agencies, such as cold storms, sudden changes in temperature, etc. They likewise are subject to the depredations of all sorts of marine creatures, and comparatively few in proportion survive. The survivors, after leading this free-swimming existence for several days, settle to the bottom, where they attach themselves by a calcareous fixative to stones, shells, pieces of wood, etc. Here, unless buried by silt and soft mud or killed by exposure, poisonous pollution, etc., the young oyster rapidly becomes of a size suitable for planting.
The economic utilization of this scientific knowledge is as follows: shells offer a very good surface for the attachment of the young oyster, and many thousand bushels are annually strewn over the bottom previous to the spawning season. Considerable judgment is needed in choosing the right time to plant these shells, which after a few weeks in the water become so coated with slime that fixation of the "spat" becomes impossible. In Massachusetts the area between high and low water mark has been found by experiment to be the most valuable territory for this purpose, as shells planted here collect the heaviest set and can be handled with the least expense. A projecting sand bar or point with a current is also well adapted for catching oyster spat.
The scallop shell is the most serviceable in spat collecting, because it is more brittle, and the clusters of oysters when attached are readily broken apart. After the oysterman has obtained a successful set, he allows the young oysters to obtain a suitable growth before he makes a final planting, either in the spring or fall.
III. Size of the "Seed" used for Planting.—While many oysters are raised from native spat in the Buzzards Bay district, the greater part of the seed is purchased in Connecticut and Long Island, and is carried in schooners or steamers to Massachusetts waters. The usual price ranges from 35 cents to $1 per bushel, according to size and quality. The oystermen cannot always choose the size of "seed" they desire for planting, as the set of any one year is very uncertain, and several seasons may pass before a large quantity of "seed" can be obtained. Thus the oyster planters are forced to take whatever size they can obtain, whether it be two, three or four year old "seed." As a rule, the small "seed" is most in demand, as it means relatively faster growth and less money invested. Often, when the ground is most favorable for fattening, large oysters are preferred for planting, and certain oystermen make this line of work a specialty. Certain localities where there is plenty of lime in the water are well adapted for growth, and yet produce poor-"meated" oysters, while in other grounds the reverse is true. The oystermen occasionally by a double transfer utilize both grounds, planting oyster "seed" for the first few years in the rapid-growing localities, and then transplanting the large oysters to the "fattening" ground six months before marketing.
IV. Preparing the Grant.—The first step in preparing the grant is to remove all débris. In the deep water, this is usually done by dredging; in the shallow water, by whatever means is the easiest. If the bottom is of firm soil, the grant is then ready for planting; however, if the soil is soft mud, it is necessary to shell the bottom in order to give it greater firmness. The oysterman continually has to keep a sharp lookout in order to protect his grant from enemies such as the starfish and the oyster drill, and to keep it clear of seaweed and other matter which would interfere with the growth of the oyster.
V. Sowing the "Seed."—The "seed" oysters are planted on the prepared bed by scattering them with shovels or scoops from the boats and scows. The oysterman, knowing the maximum amount of "seed" the bed will grow to the best advantage, plants the required number, taking care that the oysters are properly scattered, as for the best growth oysters should lie separate and not in crowded masses. The amount of "seed" that can be planted on a given area depends upon the natural conditions of the locality.
VI. Enemies.—The oyster, having passed through the countless dangers of his embryonic career, is still harassed by several enemies. Of these, the most destructive is the starfish. This animal, commonly known as the "five-finger," occurs along the entire Massachusetts coast, and is especially abundant in Buzzards Bay. Occasionally whole oyster beds are wiped out by this pest, which sweeps over the ground in vast armies. The method of attack of the starfish is unique. By exerting with its tube feet a steady pull in opposite directions on both valves of the shell of the victim, the starfish tires the contracted muscle of the oyster, and the shells open. The starfish then extrudes its stomach so as to enwrap the prey, and in this curious manner devours the oyster.
A close second to the starfish in amount of damage is the oyster "drill" or "borer" (Urosalpinx cinerea). This little mollusk with its rasping tongue drills a small hole through the shell of the oyster, and then sucks out the contents.
A third enemy, according to the oyster planters, is the "winkle" (Fulgur carica and F. caniculatus). The method of attack is somewhat obscure.
Besides this dangerous trio of living enemies, the oyster is subject to constant peril from inanimate agencies. Probably the greatest of these is shifting bottom. Where oysters are grown on sandy soil, the violent waves of winter storms frequently tear up the bottom, or else the force of currents is such as to kill the oysters by completely burying them in the sand. Again, if the oysters are growing in very muddy bottom they are constantly liable to be smothered in the slimy ooze. Ice in winter frequently tears oysters from their beds and bears them to some unfavorable environment, where they soon die.