88 



BULLETIN OF THE BUREAU OF FISHERIES 

 Zooplankton volumes, mouth of Massachusetts Bay 



Evidence that a similar augmentation spread generally throughout the coastal 

 waters west of Penobscot Bay in 1915 is afforded by volumes as great as 100 to 150 

 cubic centimeters per square meter off Penobscot Bay, off Cape Elizabeth, and near 

 the Isles of Shoals during that October. However, we have yet to learn whether 

 this increase is an annual event, nor does our experience suggest that it extends east 

 of Penobscot Bay, because vertical hauls yielded only 30 cubic centimeters per square 

 meter off Mount Desert Island and 20 cubic centimeters off Machias on October 9 

 (stations 10328 and 10327). 



We have made no quantitative hauls in the gulf during the period between Octo- 

 ber and late February, but the comparative scantiness of the yields of the horizontal 

 nets in Massachusetts Bay during the cold months of 1913 (Bigelow, 1914a) and at 

 all our inshore stations from Cape Cod to Yarmouth, Nova Scotia, in December, 

 1920, and January, 1921, points to an ebbing zooplankton as characteristic of the 

 coastal belt in late autumn and early winter, leading progressively to the extremely 

 barren state of the water typical of the first weeks of spring (p. 82). Hauls made 

 near Mount Desert Island and in the northeast corner of the gulf from January 1 

 to 5, 1921 (stations 10497, 10500, and 10502) were equaUy unproductive, 42 but I 

 hesitate to conclude from this that the water was actually so barren there, because 

 horizontal hauls were hardly more productive in that general region in March, 1920, 

 although the vertical nets yielded large catches, a fact suggesting that the former 

 missed the level at which the plankton was most concentrated. However this 

 may be, it seems that in winter and early spring the zooplankton is far more plentiful 

 in the western side of the basin than near shore, because we made a rich horizontal 

 catch there on December 29, 1920 (station 10490), a rich vertical haul (though a 

 rather scanty horizontal) on February 23, 1920 (station 20049), and a rich horizontal 

 and a comparatively rich vertical on March 24 of that year (station 20087). 



The results of both vertical and horizontal hauls point to the Massachusetts 

 Bay region and the neighboring part of the basin, on the one hand, and to the deeps 

 off Lurcher Shoal and the eastern part of Georges Bank, on the other, as the parts of 

 the gulf uniformly most productive of zooplankton; wbile the deep water in the 



» Yield of half an hour's haul with a M-meter net was only about 100 to 150 cubic centimeters in each case at 50-0, 75-0, and 

 150-0 meters. 



