FISHERY BULLETIN: VOL. 74, NO. 3 



procedure proved to be difficult, unnecessary, and, 

 at times, actually misleading. It was unnecessary 

 because no food was ever found in the thin walled 

 anterior intestine which forms about half of the 

 total length of the digestive tract. Also, to view the 

 anterior intestine, the liver which surrounds most 

 of it must be carefully teased away resulting in the 

 production of many fragments which may be 

 confused with possible food particles. Schumann 

 (1965) observed that food particles pass through 

 this portion of the gut in about 25 s in labora- 

 tory-reared sardine larvae. The intestines of jack 

 mackerel larvae are not as readily observable as in 

 sardine or anchovy larvae because they are 

 covered by well-developed pelvic fins and because 

 of the earlier development of substantial body 

 walls. 



The presence of a single food particle in larval 

 sardines or anchovies can usually be detected by a 

 localized swelling of the surrounding gut wall. 

 When several food particles are present, the 

 posterior intestine may be highly expanded over 

 its entire length. Food particles were dissected out 

 of the gut by means of an instrument consisting of 

 a pig's eyelash, bevelled cut to form a chisel point, 

 and mounted in beeswax in one end of a glass tube. 

 Food particles were identified to taxa as far as 

 their condition allowed. 



Each organism found in the intestine was mea- 

 sured as to the maximum cross section that the 

 larva would have to encompass for ingestion. 

 Herring larvae have been shown to ingest crus- 

 tacean food particles "head on" by Hardy (1924), 

 Bowers and Williamson (1951), and Blaxter (1965). 

 This maximizes the ingestible size of the organism 

 and positions appendages, spines, and setae to the 

 rear of the food organism during its transit 

 through the intestines. 



To facilitate a consideration of changes in food 

 with respect to growth, the size ranges of larvae of 

 each of the three species of fishes being considered 

 here have been subdivided into three length 

 groups. The length intervals used in these sub- 

 divisions are based on the distribution of sizes in 

 the collections rather than on any definite changes 

 in the larvae with respect to age. 



FOOD OF SARDINE LARVAE 



Table L-Food of sardine larvae. 



are presented in Table 1. Length of sardine larvae 

 at the end of the yolk-sac stage is variable. One as 

 small as 3.4 mm contained food, others as long as 

 5.5 mm still had yolk, but no larva was observed 

 containing both yolk and ingested food organisms. 

 Eggs, nauplii, and juvenile stages of copepods 

 composed almost all of the identifiable food. 

 Copepodid stages in the diet increased in percent- 

 age by a factor of 100 through the successive size 

 groups of the larvae. This is undoubtedly due to 

 the severe size restrictions placed on the young 

 larva by the small size of its mouth. As the larva 

 increased in size, its mouth likewise increased in 

 gape, and consequently a larger range of the size 

 spectrum of plankton became available. 



Size of Food 



Although they are not always of the largest 

 ingestible size, the food particles increased in size 

 isometrically with the increased length of sardine 

 larvae (Figure 1). A larva in doubling its length 

 from 4 to 8 mm likewise doubled its maximum 

 ingestible food size from 80 to 160 /xm. 



Type of Food 



The qualitative results of the examination of 

 food material from intestines of larval sardines 



Feeding Incidence 



The percentage of fish containing at least one 

 food particle is termed the "feeding incidence" for 



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