FACTORS DETERMINING THE DISTRIBUTION OF POPULATIONS OF CHAETOGNATHS IN THE GULF OF MAINE

¹ From the Biological Laboratories, Harvard University, and the Woods Hole Oceanographic Institution, Woods Hole, Mass.

1. Data are presented concerning the distribution and numerical abundance of five species of chaetognaths taken in the Gulf of Maine during the year 1933-34 and the hydrographic features controlling their abundance is discussed.

2. It is concluded that Eukrohnia hamata, Sagitta maxima and S. lyra, which are carried into the Gulf by deep currents and do not breed there, occur in numbers which depend not only on their relative abundance in various offshore waters which mingle in the Gulf, but on their longevity after entering the Gulf.

3. Sagitta serratodentata is a terminal immigrant from the superficial waters of the Atlantic which fluctuates in its abundance as the result of periodic changes in the circulation of water entering the Gulf from the east.

4. Sagitta elegans is the only chaetognath truly endemic to the region. The permanence of its occurrence appears to depend on the presence of a relatively stable eddy on Georges Bank. Its occurrence in other regions varies with the season to a degree which may be explained by local conditions of circulation.

5. Sagitta enflata is recorded for the first time from the margins of the Gulf of Maine.