170 
BULLETIN OF THE BUREAU OF FISHERIES 
As the salinity of Woods Hole is not noticeably different from the outer waters, 
it probably plays no part in the distribution of the larval fish of this region. The 
governing factors are, then, temperature and food, if we omit the effect of winds 
and currents, which at times may influence the distribution greatly. 
The abundance of food has a powerful efi^ect on the lives of the young fish. 
Given favorable temperatures, the larvae will develop rapidly and in great numbers 
if food is plentiful. If food is scanty, few larval fish will be found. During the 
winter and spring months copepods make up practically the entire food of the 
young forms. The most abimdant copepods during colder weather are usually 
Temora longicornis and Psevdocalanus elongatus. No doubt both of these species 
contribute equally to the food supply. As the spring of 1923 was exceptionally 
cold, Temora did not appear. Scattering forms were taken during the winter, but 
never more than three or four specimens on any one day. Out of 200 examinations 
of stomach contents of larval fish this spring not a single Temora was found. 
Psevdocalanus elongatus and Centropages hematus were very plentiful, particularly 
the former, and these constituted their food, the bright red color of the Pseudo- 
calanus showing clearly through the thin walls of all the young fish collected. 
The summer fishes have a much greater variety of food and for the most part 
do not limit their menu to Copepoda, although Acartia tonsa and Centropages typicus 
are eaten in great numbers. A young puffer (Spheroides maculatus), 3.5 mm. in 
length, examined on June 28, 1922, was found to contain 12 Littorina litorea, 9 
Venus mercenaria, and 2 Acartia tonsa. Often a young fish was taken with a large 
copepod or phyllopod protruding from its mouth. 
The relationship of the larval fish to its food supply is therefore very close, 
and one must determine it accurately in order to understand the distribution of 
a species. Such a study was attempted at the Plymouth laboratory by Doctor 
Lebour, who obtained some interesting results. More extended observations will 
be necessary before the relationship of the many factors can be clearly understood. 
The following forms were taken in surface collections of 1922-23: 
Tautogolabrus adspersus (Walbaum) Gunner. 
Tautoga onitis (Linnseus) Tautog. 
Prionotus carolinus (Linnseus) Sea Robin. 
Stenotomus chrysops (Linnaeus) Scup. 
Brevoortia tyrannus (Latrobe) Menhaden. 
Syngnathus fuscus Storer Pipefish. 
Spheroides maculatus (Bloch and Schneider) Pufifer. 
Hippoglossoides platessoides (Fabricius) Sand dab. 
Merluccius bilinearis (Mitchill) Whiting. 
Poronotus tricanthus (Peck) Butterfish. 
Menidia menidia notata (Mitchill) Silversides. 
Pholis gunnellus (Linnseus) Rock eel. 
Urophycis Hake. 
Gadus callarias Linnaeus Cod. 
Leptocephalus, Elops?. 
Microgadus tomcod (Walbaum) Tomcod. 
Myoxocephalus seneus (Mitchill)? Sculpin. 
Lophopsetta macula ta (Mitchill) Window-pane. 
Rhinonemus cimbrius (Linnseus) Rockling. 
Ammodytes americanus De Kay Sand launce. 
