may include other species possibly useful as 

 indicators. 



SUMMARY 



1. Data on zooplankton and hydrography were 

 obtained at lat. 21° 10.3' N., long. 158° 19.0' W. 

 from June 1957 to December 1958. The station was 

 visited once a month, and samples were taken once 

 at highest tide and once at lowest tide. In June 

 1957, the station was occupied for 48 hours to 

 obtain samples for studies of diel variation. 



2. Volume of zooplaniiton from the 4:8-hour 

 series conformed to the characteristic sinusoidal 

 variation for the first, day, but not for the second. 

 A diatom that prevented drainage of moisture dur- 

 ing determination of the volumes probably caused 

 the high volumes during the morning of the second 

 day. Variations in abundance were distinctly sinu- 

 soidal for Ostracoda, Euphausiac«a, Pteropoda, 

 and fish larvae. Variations in surface temperature 

 were attributed to heating during the day and cool- 

 ing during the night. Variations in the depth to 

 the top of the thermocline were attributed to inter- 

 nal waves. 



3. Correlations were significant and positive be- 

 tween day volumes of zooplankton and salinities 

 at the surface and at to 60 ni., and for night vol- 

 umes of zooplankton and salinities at 200 to 300 

 m. Positive correlations for night volumes of zoo- 

 plankton and salinities at to 60 m. and for day 

 volumes and salinities at 200 to 300 m. were vei"y 

 close to the 5-percent probability. Correlations 

 were significant and negative between both day 

 and night volumes of zooplankton and depths to 

 the top of the thermocline. 



4. The 19 months were divided into nine periods, 

 each period having a temperature-salinity curve 

 different from the preceding and the following 

 periods. 



5. Salinities and depths to the top of the thermo- 

 cline were dissimilar for the same months in 1957 

 and 1958. Night volumes of zooplankton were high- 

 est in the fall of 1957. 



6. Variations in the night volumes of zooplank- 

 ton coincided with variations in salinities > S5.0%c. 

 As the salinity increased, zooplankton increased; 

 as salinity decreased, zooplankton decreased. The 

 abundance of Siphonophora, Chaetognatha, Eu- 

 phausiacea, decapod Crustacea, and Pteropoda 



fluctuated coincidentally with the night volumes 

 of zooplankton and with salinity. 



ACKNOWLEDGMENT 



Paul E. Smith, William H. Lenarz, and George 

 D. Grice reviewed our manuscript. 



LITERATURE CITED 



Beinton, Edwabd. 



1967. Vertical migration and avoidance cai)ability of 

 euphausiids in the California Current. Limnol. 

 Oeeanogr. 12: 451^83. 

 Flemingeb, Abraham, and Robert I. Clutter. 



1965. Avoidance of towed nets by zooplankton. Lim- 

 nol. Oeeanogr. 10 : 96-lOi. 

 King, Joseph E., and Joan Demond. 



1953. Zooplankton abundance in the central Pacific. 

 [U.S.] Fish Wild]. Serv., Pish. BuU. 54: 111-144. 



King, Joseph E., and Thomas S. Hida. 



1954. Variations in zooplankton abundance in 

 Hawaiian waters, 1950-52. [U.S.] Fish Wildl. 

 Serv., Spec. Sci. Rep. Fish. 118, vi -f 66 pp. 



1957a. Zooplankton abundance in the central Pacific. 



Part II. U.S. Fish Wildl. Serv., Fish. Bull. 57 : 365- 



395. 

 1957b. Zooplankton abundance in Hawaiian waters, 



1953-54. U.S. Fish Wildl. Serv., Spec. Sci. Rep. 



Fish. 221, iv + 23 pp. 

 Legand, Michel. 



19.58. Etude .sommaire des variations quantitatives 



diurnes du zooplancton autour de la Nouvelle-Cale- 



donie. Rapp. Sci. Inst. Franc. Oc6an. (6), 42 pp. 

 McGart, James W. 



1955. Mid-Pacific oceanography, Part VI, Hawaiian 

 ofiPshore waters, December 1949-November 1951. 

 [U.S.] Fish Wildl. Serv., Spec. Sci. Rep. Fish. 152, 

 iii -1- 138 pp. 



Nakamura, Eugene L. 



1967. Abundance and distribution of zooplankton in 

 Hawaiian waters, 1955-56. U.S. Fish Wildl. Serv., 

 Spec. Sci. Rep. Fish. 544, vi -f- 37 pp. 

 ScRipps Institution of Oceanography of the Univebsity 

 OF Galifoknia. 

 1965. Oceanic observations of the Pacific: 1957. 

 Berkeley and Los Angeles, University of California 

 Press, 707 pp. 

 Seckel, Gunter R. 



1955. Mid-Pacific oceanography, Part VII, Hawaiian 

 offshore waters, September 1952-August 1953. 

 [U.S.] Fish Wildl. Serv., Spec. Sci. Rep. Fish. 164, 

 vi 4- 250 pp. 



1962. Atlas of the oceanographic climate of the 

 Hawaiian Islands region. U.S. Fish Wildl. Serv., 

 Fish. Bull. 61 : 371^27. 



SHEatMAN, Kenneth. 



1963. Pontellid copepod distribution in relation to 



VARIATIONS IN MARINE ZOOPLANKfTON IN HAWAIIAN WATERS 



99 



