SOME EMBRYONIC AND LARVAL STAGES OF THE WINTER 



FLOUNDER. 



By C. M. BREDER, Jr. 

 Formerly Fishery Expert, U. S. Bureau of Fisheries. 



The height of the spawning season of the winter flounder, Pseudopleuronectes 

 americanus (Walb.), in the vicinity of Woods Hole, Mass., is reached at what is usually 

 the coldest time of the year, most frequently during February. The material on which 

 this paper is based was acquired during the period extending from January 28 to Feb- 

 ruary 23, 192 1, the spawn being gathered from Bowen's pond, Poket, and Waquoit. 

 These are small arms of the sea superficially quite lacustrine in appearance and of rather 

 low salinity, due to a considerable influx of fresh water. The fish were taken in small 

 fyke nets set at a depth of about 8 feet through breaks in the ice. The temperatures 

 and salinities of these spawning grounds during the period of observation, which proba- 

 bly give a fair indication of the average variation, were as follows: 



Locality. 



Tempera- 

 ture ° F. 



Specific 

 gravity 

 at 60° F. 



Bowen's pond. 



Poket 



Waquoit 



33-37 



32-37 



35 



1.011-1.020 

 1. oio-i.oii 

 I.OIO-I.022 



Possibly the temperatures dropped a little lower at times when no records were 

 taken. 



On February 23 the entire catch of one fyke net (85 specimens) was examined in 

 detail and 24 per cent was found to be ripe, 37 per cent spent, 33 per cent partly spent, 

 and 6 per cent immature. These data would seem to indicate that the season was 

 well under way and about to wane, which was substantiated by statements of the 

 men and subsequent observations. A few examples of the younger fish were always 

 found along with the mature fish, apparently following them to the spawning grounds, 

 although sexually immature and unable to partake of the activity. 



These fish had fed sparingly if at all. Seven were completely empty, and of the 

 remainder very few contained more than mere traces of a yellowish white paste destined 

 only to become offal. The volumetric percentages of the various items of the stomach 

 contents were as follows: Gastropods (Haminea solitaria-}) , 1+ per cent; amphipods 

 (sand fleas), 8— per cent; prawns (small), trace; mud, 11— per cent; yellowish white 

 paste, 80 per cent. The yellowish paste might well have been the remains of food 

 taken before migration to the spawning grounds, as the peristalsis of fishes in winter is 

 usually extremely slow. 



93575°— 22 311 



