GROWTH OF OYSTERS, O. VIRGINICA, DURING DIFFERENT MONTHS

¹ Milford Laboratory, U. S. Fish and Wildlife Service, Milford, Connecticut

1. The oysters grown in Milford Harbor did not increase in size, volume or weight during the hibernation period. However, if by some artificial means the temperature of the water is kept above the hibernation point, the oysters will continue to grow in the laboratory even in the middle of winter.

2. The maximum period during which oysters may grow in Milford Harbor is approximately of eight months' duration extending from April to November, both months inclusive. Only a small minority comprising approximately 3 to 4 per cent grew during all the eight months, while the majority grew only for five, six, or seven months. Some oysters did not start growing in length until June, and in volume until July.

3. The increase in length was most rapid during May, June, and July, representing 22.57, 19.03 and 22.12 per cent respectively of the total annual increment. The growth in width was especially rapid in June, giving 40 per cent of the total annual increase. The increase in the greatest depth was not appreciable until July.

4. The increase in volume continued from April through November; the greatest monthly increases were recorded during August and September; these two months combined gave approximately 55 per cent of the annual increase in volume.

5. The increase in size was most common during July and August, when almost all the oysters showed it, and least noticeable in April and November.

6. The process of gametogenesis did not interfere with the growth of the shell, at least as far as the increase in length and width was concerned.

7. The spawning activities did not adversely affect the rate of increase in length and in volume.

8. The chief increase in length and width of the oysters occurred during the first half of the growing period, while the increase in depth and volume was most pronounced during the second half.

9. Changes in the rate of growth in length and width showed only partial relationship with changes in the water temperature. However, a rather definite relationship was found between the changes in the rate of increase in volume and changes in the water temperature.

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