Lebour. — Food of Larval and Post-Larval Fishes 347 



contains them, even after the long bill is formed. Oyster spat 

 and the pteropod Limacina were often offered to young fishes 

 in the aquaria and nearly always refused. 



Certainly the most important food of the young fishes is 

 small Crustacea, especially the Cladocera, Podon and Evadne, 

 cirripede nauplii, and, most important of all, copepods, both 

 nauplii and adult. Decapod larvae only rarely occur until the 

 fishes reach a much larger size. 



In Plymouth Sound and outside, Podon and Evadne are 

 only available in large quantities in the summer months, cirri- 

 pede larvae in late winter and early spring, and again in July 

 and August. When these are in season many fishes eat them, 

 often together with the copepods which form their food at other 

 times. Very young fishes can eat them and they are often to be 

 found in the newly hatched specimens. Copepods, however, 

 undoubtedly form the chief food of larval and post-larval 

 fishes, and those most often eaten are the species that are com- 

 monest, but each fish appears to prefer some special species 

 and usually keeps to it or to two or three species, not feeding 

 indiscriminately. 



The copepods most frequently eaten are Temora longicor- 

 nis, Pseudocalanus elongatus, Acartia clausi, and Calanus fin- 

 marchicus. These occur practically all the year round, now 

 and then with short periods of disappearance of one or the 

 other, but they are most abundant and commonly breed in the 

 spring and summer when the young fishes are at their maxima. 

 Many very young fishes eat the nauplioid and small copepod 

 stages; those with large mouths eat the fully developed cope- 

 pods almost at once and the slightly older forms eat them 

 habitually. 



Other copepods fairly often eaten are Metridia lucens, 

 Euterpina acutifrons, Paracalanus parvus, and several others. 



(b) Do the young fishes select their food or take it indis- 

 criminately? Most of the young fishes prefer a certain kind of 

 food and keep to it. Thus a fish may usually eat a species of 

 copepod and only take others when this is not available, or it 



