Lebour. — Food of Larval and Post-Larval Fishes 351 



eggs (probably copepod) and copepod nauplii. It therefore 

 appears to be quite usual for solid food to be taken although 

 the yolk sac is present. At 7 mm., the usual length at hatching, 

 food consisting of green remains, larval mollusks or eggs was 

 found inside the young herring. Copepod nauplii are taken a 

 little later, thus agreeing with the observations of H. A. 

 Meyer* with artificially reared herring which first contained 

 greenish matter, later on larval mollusks, copepods and cope- 

 pod nauplii, the copepod diet increasing as the fishes grew. 



Brill from 4 mm. which still retained the yolk sac were 

 found to contain many Temora nauplii. Gobius minutus hatched 

 in the aquarium were found to have eaten diatoms when still 

 retaining the yolk sac. A plaice {Pleiironectes platessa) of 

 four days old, hatched in an aquarium, ate diatoms from the 

 bottom of the glass when still retaining the yolk sac. These 

 diatoms ( Navicula sp. ) grew in a dense layer at the bottom of 

 the glass jar. 



It is thus certain, as already shown by those investigators 

 who have experimented in rearing fish, that food is taken 

 before the disappearance of the yolk sac, or at any rate in 

 many species. 



(d) Do the food fishes eat the same food as those which 

 are unimportant economically? Although this question is 

 barely touched on, many fishes unimportant as food have also 

 been examined. These, especially young Callionymus lyra, 

 Trachiniis viper a, several species of Gobius and Cottus and 

 many others, occur abundantly with the young of the food fishes 

 and eat much the same sort of food, especially the copepods, 

 Pseudocalanus, Temora and Acartia, with Podon. Calliony- 

 mus ate all these apparently indiscriminately, Pseudocalanus 

 was a favorite with the gobies, and Cottus ate many larval mol- 

 lusks with copepods and other small planktonic organisms. 



It is to be remembered, however, that although these young 

 fishes are extremely abundant and eat the same food as the 



*i88o, Biological Observations made during the Artificial Rearing of Herrings in 

 the Western Baltic. Report of the U. S. Fish Commission for 1878. 



