642 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



OCT 



NOV 



Fioube 32. — Distribution of leptocephali (X's) from plankton samples; and early nietarnorphic larvae (small dots), 

 mid-metamorphic larvae (large dots), and late metainorphie larvae and juveniles (circles) from seine samples; 

 by size frequencies and dates of capture for the period from March 1953 to October 1956. 



pieces of both fish. The live fishes were swallowed 

 head first, the Elops usually swimming alongside 

 its prey for some time before darting ahead, turn- 

 ing abruptly, and seizing it. A fish grabbed cross- 

 ways would be released and recaptured head-on. 

 Bits of fish lying on the bottom of the aquaria were 

 often snatched from forceps and eaten as an at- 

 tempt was made to remove them. A 35-mm. late 

 metarnorphic larva (E. saurus) was eaten by a 

 73-mm. juvenile/?, saurus within a half hour after 

 being placed in the aquarium with the larger fish. 



Treatment of water. — On several occasions the 

 fins of some fish were attacked by fungus or bac- 

 teria. Treatment of the water in the infected 

 tanks with several drops of Mercurochrome us- 

 ually cleared up the infection, and fins later re- 

 generated. Other than this treatment, and 

 removal of bacteria covered sand mentioned pre- 

 viously, no special attention was given the aquaria. 



Measurement of specimens. — About once a week 



the fish were removed from their aquaria and meas- 

 ured with dividers and a millimeter ride. Care 

 was exercised to minimize injury to specimens 

 during handling. By separating specimens by 

 date of capture and size (a few to each aquarium) , 

 it was possible to determine growth rates for in- 

 dividual fish. 



Table 12 shows periodic measurements for indi- 

 vidual specimens, and figure 32 is a graphic pre- 

 sentation of their growth. One early metarnorphic 

 larva (No. 1) was reared from 35 mm. through 

 metamorphosis and up to a juvenile of 96 mm. 

 standard length before death occurred. Several 

 additional larvae lived through early and mid- 

 metamorphosis and died. One juvenile, No. 6, 

 lived 4 months, growing from 60 mm. to 135 mm. 

 The mandible, and sometimes the upper jaw, of 

 the larger specimens became blunt from pressing 

 against the sides of the aquarium. 



Metamorphosis. — Tables 12 and 13 and figure 31 



