74 BULLETIN OF THE BUREAU OP FISHEBIES 



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 this 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 larvae 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 



» 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. 



