Table Illa-Spawning Data, Pertaining to Oyster Propagation, Edge Cove, 1914. June 28. July 2... Ezra. July 2... July 6... Lab.. July 7.. Lab.. July 7... E.. July 18.. July 18.. July 21... Mull. July 21.. July 23... Lab.. July 27... Tank. July 27.. July 27.. July 27.. July 27.. July 27... July 30... Tank. July 30. July 30... July 30... Lab.. July 30.. $5 SPATTING DATA. Explanatory of Tables IV and IVa. In Tables IV and IVa there is exhibited the record of the observations on spatting for the season of 1914, respectively at Barnegat and at Tuckerton. The first column gives the dates when cultch was placed, the second, gives the dates when the same cultch was taken at the close of the experiment. The third column contains the designation of the stations at which these experimental exposures of cultch were made. At Station B, which is the same as B in Table II, the cultch was, with few exceptions, put in a floating crate, while at C, which corresponds to C of Table, II, the cultch was put on the bottom, that is, its position was "fixed." In the fourth column, the kind of a cultch is indicated whether "shells" (mainly oyster shells) or tiles, "T," (mainly flat tiles); curved tiles are called "cave" "T." In the column headed "Conditions," the position and exposure of the cultch are described whether exposed all the time or only by daylight, or only during the night. The inner side of oyster shells being concave corresponds to the "cave" side of tiles. The outer side corresponds to the convex ("vex") side of tiles. Sometimes the concave side, sometimes the convex side was uppermost. In the column headed "Distribution, Nos. and Sizes," the number of spat caught is given with their position, whether on the upper or lower side, the outer or inner, etc. The size is given in millimeters, "mm." (A millimeter is the twenty-fifth part of an inch.) In the Miscellaneous Column, the principal information given is the probable date of the "setting." Spatting Phenomena of, 1914. A glance at the tables, particularly that of Barnegat, shows that numerous experimental exposures of cultch were made. Experiments of this sort have given marked results in previous years; but during this past season, most of them proved negative. Even in the positive cases the number caught on each piece of cultch was so small that it became necessary to leave the cultch for one or even two months before the spat were easily discoverable. During this period there occurred from two to four special dates of spatting, so that we secured spat of corresponding sizes. The spatting periods were not determined directly from the cultch experiments as in previous years, but rather were calculated from the plankton data. Under these circumstances it remains possible that the differences in size found do not, all of them, represent different spatting periods, but are due to differences in the rate of growth. The plankton data fixed the spatting dates at June 25th to the 29th, July 8th to the 27th, August 3rd to the 10th, and August 20th to the 28th. The largest proportion set in the second half of July. At Barnegat no spatting was observed after that period, nor at Tuckerton, earlier than that period. It is somewhat difficult to explain this, as the water was slightly warmer at Tuckerton. Judging from reports published early in Au gust, most places on the North Atlantic Coast followed the Tuckerton time in that the oyster propagation occurred unusually late. Relative to Canada, the writer discovered by microscopic examination August 29th, the earliest spat set in Richmond Bay, Prince Edward Island, and placed the commencement of the spatting at August 27th. This was two or three weeks later than on previous years as reported by Dr. Stafford. Thus there was a general delay in propagation for the North Atlantic border, most marked the farthest north; and such a general result could only be due to conditions that were general. It is both interesting and important to trace these influences of the weather on oyster propagation. It seems likely that the matter is complicated to such an extent that the exact determination of the relations cannot quickly or easily be made. This is why the writer has supported the plan of the observation service, established for the Bureau of Shell Fisheries. For himself he prefers to take up some of the many other problems connected with oyster culture, among which may be mentioned the "pollution" problem, the "freshening" problem, the "food value" problem, growth and fattening, artificial breeding, etc. Then too every little while comes up the problem of excessive death rate among oysters of all ages from spat to adult stage, calling for special and urgent investigation. It was the unusual death rate of oysters in certain beds in Mobile Bay that called our chief assistant, T. C. Nelson, to the South. His report will appear in the Bulletin of the U. S. States Bureau of Fisheries. |