Table 2. — Samples of Atlantic menhaden larvae, pre- 

 juveniles, and juveniles for food studies collected in 

 haul seines within the Indian River estuary, Del., 

 April to June 1961 



in the pyloric stomach (gizzard) and intestine. 

 Identifiable contents were treated in the same 

 manner as the contents of the alimentary tracts 

 of the larvae. Diatoms were cleared by the 

 Van Der Werff (1955) method and mounted in 

 hyrax before examination. 



Concomitant plankton samples were usually 

 taken for each fish collection. Zooplankton was 

 collected with a high-speed sampler described 

 by Miller (1961) and monofilament nylon net 

 (mesh aperture 0.24 mm.). Most samples were 

 preserved in 5 percent buffered Formalin. 

 Phjrtoplankton was collected in a 140-ml. water 

 sampler and preserved with the chrom-osmic 

 mixture used for contents of alimentary tracts. 

 Some zooplankton and phytoplankton samples 

 were only chilled prior to examination. Orga- 



nisms in aliquots of preserved and fresh plank- 

 ton samples were identified, counted, and meas- 

 ured. Diatoms, when present, were cleared 

 (Van Der Werff, 1955) and mounted in hyrax. 



FOOD OF MENHADEN AND RELATIONS TO 

 ESTUARINE PLANKTON 



We took samples at the inlet and within the 

 estuary. 



Samples at the Inlet 



The contents of the alimentary tracts of lar- 

 vae consisted of zooplankton. Of 592 tracts 

 examined, 349 (59 percent) were empty. Of 

 the 243 that contained food, 52 percent were 

 less than one-quarter full, 28 percent were 

 about half full, and 20 percent were over half 

 full. The contents were 99 percent copepods, of 

 which Centropages was the most common of 

 those identified (table 3). The number of food 

 organisms averaged 3 per alimentary tract, 

 but varied between 1 and 12. Composition of 

 tract contents showed no apparent changes 

 during the sampling period. 



The size of copepods ingested varied widely 

 (0.65-2.00 by 0.16-0.65 mm.) but generally in- 

 creased with fish length (fig. 1). Pseudodiap- 

 tomus was the only copepod found in larvae 

 under 23 mm. long. Centropages occurred in 

 larvae 23 mm. and longer, whereas Acartia and 

 Temora were found in specimens from 24 to 

 30 mm. long. 



Table 3. — Alimentary tract contents of 2US Atlantic menhaden larvae collected at Indian River Inlet, Del., 



November 1960 to May 1961 



FOOD OF YOUNG ATLANTIC MENHADEN IN RELATION TO METAMORPHOSIS 



495 



