44 
BULLETIN OE THE BUREAU OP FISHERIES 
on April 5; the cyprid stage in abundance on the 9th, with only a few nauplii; 
while by the 19th cyprids alone were taken. These dominated the surface plankton 
during the last week of April, after which their numbers diminished, though some 
persisted in that region until mid-May. 
The reproduction of barnacles is at its height at about the same season along the 
eastern shores of the gulf, for their nauplii occurred at all our stations over the 
shallows from Yarmouth to Browns Bank on April 13 to 15, 1920 — abundantly in 
the North Channel (station 20105; fig. 24). At St. Andrews, in the Bay of Fundy, 
where because of the violent tides the surface waters warm slowly in spring, barnacle 
larvae (either nauplii, cyprids, or both) are recorded by Doctor McMurrich in his 
plankton lists as early as the last week of January, regularly after mid-February, 
reaching their maximum abundance during April, occurring in diminishing numbers 
until June 8, and occasionally still later in that month. In 1917, according to Willey 
(1921), barnacle nauplii dominated the plankton at St. Andrews on April 7; nauplii 
and cyprids in subequal numbers formed nearly the entire catch on May 1 ; and 
cyprids alone on the 17th. The season is about the same for them in the Irish Sea. 
The spring season, likewise, sees striking additions to the plankton of the coast- 
wise and shoaler waters of the gulf generally, in the shape of buoyant fish eggs. 
Haddock eggs in particular are produced in such numbers locally during March and 
April (which is the height of the breeding season) that they may be a considerable 
element on the more prolific spawning grounds, such as the eastern part of Georges 
Bank, the neighborhood of the Boon Island ground, and locally in Massachusetts 
Bay. The extremely characteristic eggs of the plaice ( Hippoglossoides platessoides) 
appear early in March (that is, slightly later than those of the haddock) and are taken 
until mid-June, with the height of the spawning season during April and May. 
Rusty-flounder (Limanda) eggs are first seen in the tow toward the end of April, 
most numerously in June and July, and rarely as late as mid-September. The 
spawning season of the witch flounder (Glyptocephalus) likewise follows hard on 
that of the haddock. Spring is the season most prolific in fish eggs in the Gulf of 
Maine, but they are seldom numerous except in the immediate vicinity of the spawn- 
ing grounds, or anywhere over the central deeps of the gulf, outside the 100-meter 
contour. 22 
The most obvious effect of the very active reproduction of copepods just 
described, coupled with the scarcity of most other planktonic animals in the offshore 
waters of the gulf at the time, is that soon after its inception the zooplankton in 
the more productive centers of propagation becomes almost pure copepod; and, 
whether by local breeding or by drifting out from the coastal belt, as seems more 
likely, their numbers so multiply offshore as the water warms with the advance of the 
season that they overwhelmingly dominate the pelagic community of the whole 
gulf north of a line from Cape Cod to Browns Bank in May and during the first half 
of June. Since, furthermore, the other planktonic groups of animals that assume 
faunal importance later on in the year (e. g., Sagittae, amphipods, eupliausiids) do 
not commence multiplying actively until later in the season, it is during late spring 
and the first weeks of summer that the zooplankton of the upper 100 meters (empha- 
22 For the chief spawning grounds and breeding seasons of Gulf of Maine fishes see Bigelow and Welsh (1925). 
