60 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Pollock ( PollacMus virens). 
Tlie spawning season for pollock at Gloucester, Mass., includes October, Novem- 
ber, and a part of December. 
The first eggs were taken October 30, 1888, and the last December 17, 1888. 
The period of incubation varied from seven to twelve days. 
During November 50 females furnished 20,256,300 eggs, an average of 405,125 
each. From December 3 to 17, 39 females furnished 11,623,500 eggs, an average of 
nearly 300,000 each. 
On October 30, when the first eggs were taken, the temperature of the water at 
noon was 48°, and its density 25. The temperature of the air at noon on the same 
date was 48°. During November the temperature of the water at noon ranged from 
41° to 49° ; the lowest temperature being observed from the 23d to the 26th, both 
inclusive. 
The density of the water during this month was from 25 to 26. 
The air temperature at noon during November varied from 24° to 59°, the lowest 
temperature having been reached on November 23. From December 3 to 17 the water 
temperature at noon ranged from 38° to 45°, and its density from 25 to 26°. 
The eggs of the pollock are small and tender — much more so than those of the cod. 
They are adhesive after three days’ time, and require very pure clear water, and no 
motion whatever. The eggs measure 22 to the lineal inch, and a quart contains 614,172. 
Some eggs were tried by liquid measure and numbered 19,216 to the ounce. 
Pollock when hatched are transparent, and almost of the same color as the sac; 
they will burst from the shell in seven or eight days ; they are weak and lifeless for a 
time, then they begin to dart from place to place like the cod, and stop quite sud- 
denly as if entirely exhausted. The eye is not very distinct, and the fish appears 
blind unless closely observed. The spawning season is short compared with that of 
the cod. 
The eggs of this species were circulated at Gloucester, Mass., without difficulty 
by means of the automatic jet. The first eggs were received October 18, 1889, and 
collections continued until December 20. The largest number obtained in one day was 
upward of 5,000,000, on November 7 ; about 40,000,000 were taken in all. The number 
of females furnishing these eggs was 181, and the average yield of each was nearly 
222,000. Nearly 15,000,000 fry were developed, all of which were liberated at Glouces- 
ter; the first on October 27, obtained from eggs collected October 18, and the last on 
December 29, from eggs obtained December 20, 1889. 
Flatfish ( Pseudopleuronectes americanus). 
At Woods Holl, from February 3 to April 24, 1890, the number of females han 
died was 87, which yielded 5,848,000 eggs. Over 4,000,000 fry were produced, which 
were liberated from 2 to 5 days after hatching. The average number of eggs to the 
female was 67,220. The period of incubation is about 20 days. The adults were caught 
in a fyke net. In severe cold spells the fish leave the harbor and go into the deep 
water of Vineyard Sound and Buzzards Bay, but return when the temperature rises 
so that the anchor frost disappears. 
