ARTHUR: FOOD AND FEEDING OF LARVAL FISHES 



Table 4.-Crustaceans as percentage of total number of iden- 

 tifiable food particles. Size groups of larvae-small = end of 

 yolk-sac stage to 4.5 mm, middle = 5.0 to 6.5 mm, and large = 7.0 

 to 9.0 mm. 



Size of Food 



Figure 6 compares the size ranges of food 

 particles ingested by the three larvae. Because of 

 their larger mouth, jack mackerel larvae can 

 ingest particles about 3 times larger in diameter 

 than can sardine larvae of the same length. This 

 represents a difference in bulk of about 27 times 

 between maximal ingestible sizes for the two 

 larvae. The small anchovy can ingest particles 

 about 40 to 50 jum larger than the maximum-sized 

 particles of the sardine but does not appear to feed 

 as frequently on organisms near to the maximum 

 ingestible size as the sardine does. 



Feeding Incidence and 

 Its Relation to Type of Intestine 



Feeding incidence increases with length in the 

 jack mackerel but decreases with length in the 

 anchovy and sardine (Figure 7). The high percent- 

 age of jack mackerel larvae containing food may 

 indicate that either they are more voracious 

 feeders, or their digestive rate is slower, or per- 

 haps they are less apt to void their guts while 

 being caught and preserved. Feeding incidence of 

 larval fish appears to be associated with the 

 morphology of the gut. The intestine of the sar- 

 dine and anchovy remains long and straight with 

 little observable differentiation until the larva is 

 about 20 to 25 mm long. On the other hand, when 

 the jack mackerel has attained a length of about 

 4.25 mm, a portion of its gut forms a loop. This loop 

 divides the larval gut into definite functional 

 parts. Based on a long-range study of feeding 

 habits of fish in the Black Sea, Duka (1967) clas- 

 sified the larval gut into three types: long straight, 

 short straight, and looped. Duka noted also that 

 larvae with looped guts usually contained much 

 more food than larvae with straight guts. Cie- 

 chomski and Weiss (1974) noted that the feeding 

 incidence of E. anchoita larvae (0-28.0%) was much 

 lower than of hake larvae (63.3-94.5%) taken in the 



A A---A Jock Mackerel 



^ • • Sardine 



o o Anchovy 



34 56 7 8 910 II 12 

 LENGTH OF LARVAE (mm) 



Figure 6.-Size range of food particles ingested by larvae of 

 Pacific sardine, northern anchovy, and jack mackerel. 



100 r 



7 9 II 



LENGTH OF LARVAE (mm) 



13 



Figure 7.-Comparison of feeding incidence of Pacific sardine, 

 northern anchovy, and jack mackerel larvae. Values for sardine 

 and anchovy larvae are averages of day and night feeding 

 incidences. Values for jack mackerel larvae are for all samples 

 combined. 



same plankton samples and that intestines of hake 

 larvae are not straight but have several folds. 



523 



