FISHERY BULLETIN: VOL. 71, NO. 3 



operating as individuals 2 to 4 m apart. Some 

 occur as far as 2 km off the beach. 



4. The prey of the silverside are zooplankton, 

 mostly crustaceans between 0.5 and 3 mm in 

 greatest dimension, that occur right at the 

 water's surface after dark. Generally they are 

 species that rise to the surface at night, and des- 

 cend to deeper waters during the day, and are 

 selected by the silverside from among other 

 organisms of similar size that are not taken. 



5. Major prey include a hyperiid amphipod, 

 myodocopid ostracods, the tretomphalus stage 

 of foraminiferans, caridean shrimp larvae, and 

 calanoid copepods. 



6. At first morning light, about 1 h and 15 

 min before sunrise, the silverside begin to 

 concentrate in the shoreward part of their feed- 

 ing ground. The school continues to develop for 

 about 45 min, then having attained daytime 

 proportions, it moves inshore over the same 

 route it had taken when moving outward the 

 night before. About 20 min before sunrise it 

 arrives at its diurnal schooling site, and the day- 

 time period of inactivity begins. 



7. The behavior of silverside less than 30 mm 

 long is in contrast to that of large individuals. 

 Limited evidence indicates that these small fish 

 feed by day and not at night. 



ACKNOWLEDGMENTS 



We are grateful to Frank Hester and his staff 

 at the Southwest Fisheries Center, Honolulu 

 Laboratory, National Marine Fisheries Service, 

 NOAA — especially Thomas S. Hida and Everett 

 C. Jones — for the cooperation and logistic sup- 



port. We also thank Gary J. Brusca, Humboldt 

 State College, and Abraham Fleminger, 

 Scripps Institution of Oceanography, for help 

 in identifying the planktonic organisms. Fin- 

 ally, we thank Carl L. Hubbs and Richard H. 

 Rosenblatt, Scripps Institution of Oceano- 

 graphy, as well as Abraham Fleminger, for 

 helpful comments on a draft of the manuscript. 

 Kenneth Raymond, Southwest Fisheries Cen- 

 ter, La Jolla Laboratory, National Marine 

 Fisheries Service, NOAA, drew the figures. 



LITERATURE CITED 



Hida, T. S. 



1971. Baitfish scouting in the Trust Territory. 

 Commer. Fish. Rev. 33(1 1-12):3 1-33. 

 HOBSON, E. S. 



1965. Diurnal-nocturnal activity of some inshore 

 fishes in the Gulf of California. Copeia 1965: 

 291-302. 



1968. Predatory behavior of some shore fishes in the 



Gulf of California. U.S. Fish Wildl. Serv., Res. 



Rep. 73, 92 p. 

 Johnson, M. W. 



1949. Zooplankton as an index of water exchange 



between Bikini lagoon and the open ocean. Trans. 



Am. Geophys. Union 30:238-244. 

 Myers, E. H. 



1943. Biology, ecology and morphogenesis of a 



pelagic foraminifer. Stanford Univ. Publ., Univ. 



Ser., Biol. Sci. 9, 30 p. 



SCHULTZ, L. P. 



1953. Family Atherinidae: Silversides. In L. P. 

 Schultz, E. S. Herald, E. A. Lachner, A. D. 

 Welander, and L. P. Woods. Fishes of the Marshall 

 and Marianas Islands, Vol. 1, p. 309-310. Bull. 

 U.S.Natl. Mus. 202. 

 Starck, W. A.. II, AND W. p. Davis. 



1966. Night habits of fishes of Alligator Reef, 

 Florida. Ichthyol. Aquarium J. 38:31 3-356. 



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