THE BIOLOGY OF CALANUS FINMARCHICUS IN THE GULF OF MAINE AND BAY OF FUNDY

¹ From the Woods Hole Oceanographic Institution, Woods hole, Mass.

1. Calanus finmarchicus is the most abundant pelagic animal in the Gulf of Maine, averaging 39.9 per cent of the total zoöplankton population during the period April to September, 1932, with a peak of 60.4 per cent in May. In the Bay of Fundy there was a mean of 35.5 per cent for the year 1931-32.

2. The adult stock varies markedly in abundance in different areas, the smallest numbers occurring in the Bay of Fundy and westward along the coast of Maine to Penobscot Bay. The population is everywhere at a minimum in late February and early March.

3. Calanus passes the winter largely in copepodite stage V, the final moult taking place in February and early March shortly before vernal augmentation.

4. An average difference of approximately one month in the time of spawning in the eastern and western parts of the region is reflected in succeeding generations after dispersal. Two breeding stocks can thus be distinguished.

5. In the western stock there are two well-defined breeding periods, March-April, and June-July, with a possible third in September, and two periods, April-May, and July-August in the eastern stock.

6. A developmental period of two and one-half months is indicated in both stocks, one month from nauplius I to copepodite I, one-half month from copepodite I to copepodite V, and one month for the final moult, maturation, and incubation of eggs.

7. Mortality is highest among maturing adults.

8. The total length of life in spring and summer does not exceed four months. The winter stock has a maximum existence of 10-11 months.

9. After reaching maturity the males die off before the females.

10. The western Gulf forms the principal source of supply of Calanus for the entire region. Propagation east of Mt. Desert in the inner Gulf is largely if not entirely, unsuccessful.