346 American Fisheries Society 



(a) What do the young fishes eat? It is already well 

 known that copepods form a large part of the food of young 

 fishes and it was found that by far the greater number of those 

 examined ate crustaceans, chiefly Entomostraca, even at the 

 very early stages. Copepods and Cladocera are most generally 

 taken, and copepods certainly form the most important food. 

 Remains of green algse were found in some of the young clu- 

 peoids, especially the sprat, also in the sand launce, Ammo- 

 dytes, and a few others, showing a vegetable diet at the 

 earliest stage, but as a rule there is little sign of this and vege- 

 table food occurs very sparingly in the young fishes. A strik- 

 ing exception, however, occurs in the flounder (Pleuronectes 

 flesus), which was several times found to be eating the flagel- 

 late Ph?socystis. 



Diatoms are occasionally recognized among the food 

 remains. An Ammodytes of 10 mm. contained many Rhizo- 

 solenia (one of the needle-like diatoms), and fishes that were 

 hatched in the acquarium and fed on very fine plankton also ate 

 diatoms sparingly. Young gobies only a few days old in these 

 aquaria took Asterionella, Thalassiosira, and Chaetoceros, but as 

 they all died this apparently is not a suitable diet. A young 

 sculpin (Cottus) of 4.5 mm. from the tow-nets had inside it 

 Bidulphia, Coscinodiscus, and Thalassiosira. All these are dia- 

 toms commonly occurring in the plankton, but it is only very 

 seldom that any of these are found even in the youngest fishes. 



Of other unicellular organisms coccospheres, peridinians, 

 radiolarians and infusorians occasionally occur, chiefly in the 

 smaller specimens. 



Besides Crustacea, larval mollusks are almost the only rec- 

 ognizable metazoa eaten by the young fishes. These occur 

 occasionally in many species with Crustacea. In the her- 

 ring they often occur in the newly hatched young, and the brill 

 (Rhombus Icevis) and turbot {Rhombus maximus) up to about 

 20 mm. often contain them, but the only young fish examined 

 that seems to feed habitually on larval mollusks is the garfish 

 (Rhamphistoma belone), which up to at least 36 mm. usually 



