74 
BULLETIN OF THE BUREAU OF FISHERIES 
the general neighborhood of Mount Desert Island is the most easterly location 
along the northern shores of the gulf where we have found gadoid or flatfish eggs in 
any numbers. 
The rather uniform transition in the state of tidal mixing, with its consequent 
effect on salinity and temperature, which characterizes the coastal belt from the 
Bay of Fundy to Casco Bay, indicates an improvement from east to west in condi- 
tions for buoyant fish eggs and larvae; but outside the outer islands 33 salinities and 
temperatures vary so little from Penobscot Bay westward and southward to Massa- 
chusetts Bay, especially during winter and spring when most of the more important 
gadoid and flatfish species spawn, that there is nothing in the physical state of the 
water to suggest one part of this zone as notably more suitable for their successful 
reproduction than another. 
With the dominant set of the water tending to drift all fish eggs and larvae 
produced along the northern shores of the gulf toward the west and south, and with 
few or no accessions coming from the east to the coastal zone between Mount 
Desert and Cape Elizabeth because of the sterility of the Bay of Fundy in this 
respect, tows there might be expected to take eggs and very young larvae, but seldom 
older ones or the post-larval stages. Actually, most of our tow nettings there have 
yielded eggs alone (fig. 34) ; but the larvae hatched from buoyant fish eggs are so 
small and soft until two weeks or so old that they are apt to be mashed past recog- 
nition amongst the mass of other plankton, hence may very well have been over- 
looked, and by the time they are large and resistant enough to be noticed among 
the hard-shelled copepods, etc., they may have drifted for a considerable distance. 
Mavor’s (1920 and 1922) recent experiments with drift bottles give some 
idea of the actual speed with which the surface water, and consequently the fish 
eggs and larvae floating with it, may travel westward and southward around the 
gulf, indicating that a drift of about 4 nautical miles per day is not unusual in 
summer and autumn, although more or less intermittent. The rate is probably 
higher than this during the spring. 
On this basis, buoyant eggs spawned off Mount Desert Island and far enough 
out from the land to be caught up in the general peripheral eddy of the gulf (how 
far tins means is not yet known) might drift well beyond Cape Elizabeth during 
the two weeks interval that may be set as a fair average incubation period 
for gadoids and flatfishes in general in Gulf of Maine temperatures. Whether the 
eggs actually equal the drift bottles in the speed of their journey depends on whether 
they float at the same level — that is, in the upper two meters or so. Many of them, 
and perhaps most, taking the year as a whole, do so; but locally, and especially 
when the surface is at its lightest after the river freshets, many eggs float deeper 
down where the dominant drift probably is slower, notably those of the haddock, 
which is spawning actively at that season (Bigelow and Welsh, 1925). During 
the interval after hatching, when the larvse are so small that they are seldom 
recognized in ordinary tow nets, the small proportion of them that survives the 
vicissitudes of pelagic life very likely drifts another 50 miles or so, so that Mount 
33 Low surface temperature close in along the land between Penobscot Bay and Casco Bay in summer may be a bar to the local 
breeding of the cunner, though this would not apply up the many estuaries that indent this section of the coast. 
