FISHERY BULLETIN: VOL. 73, NO. 1 



ASONDJ FMAMJ J ASONDJ FN. AMJ J 

 1954 1955 1956 



MONTH a YEAR 



Figure 15. — Maximum surface temperatures in the Salton Sea. 

 Open circles: measurements made at Sandy Beach, Salton Sea, 

 from August 1954 to July 1956 (after Carpelan 1961). Closed 

 circles: measurements made at various stations on the Salton 

 Sea during 1967 (after Young 1970). The shaded areas indicate 

 the major spawning period oi Bairdiella icistia, and the vertical 

 dotted lines indicate the latest records of bairdiella eggs in the 

 plankton in 1955 and 1956, according to Whitney (1961). 



35°C. Such late spawning by bairdiella seems un- 

 likely, however, and Whitney may have collected 

 eggs of the orangemouth corvina, Cynoscion 

 xanthulus, which spawns during the summer and 

 probably produces similar eggs, rather than bair- 

 diella. In any event, it seems possible that late 

 spawning bairdiella in the Salton Sea could re- 

 lease their eggs in water with a temperature high 

 enough to reduce embryonic and larval survival 

 severely. In view of the temperature-salinity in- 

 teraction which occurs in the case of both em- 

 bryonic and larval tolerance, bairdiella which 

 spawn at relatively low temperatures early in the 

 season will probably have a selective advantage as 

 the salinity of the Salton Sea rises. 



In the absence of detailed information on the 

 distribution of bairdiella and the physical condi- 

 tions obtaining in its native habitat, the Gulf of 

 California, it is difficult to apply the present 

 findings to the ecology of this species in that area. 

 However, the utilization of Colorado River water 

 for irrigation has caused an increase in the river's 

 salinity (Wolman 1971); if this, and the accom- 

 panying reduced flow of fresh water into the upper 

 Gulf of California, results in a significant rise in 

 salinity in areas where bairdiella spawn, the com- 

 bined action of salinity stress and heat in this arid 

 region could adversely affect early survival in 



the local bairdiella population. The warm brine 

 effluent from a proposed desalination plant in this 

 area (Thomson et al. 1969) could aggravate the 

 situation considerably if dispersal of the effluent is 

 not adequate. 



ACKNOWLEDGMENTS 



I take great pleasure in thanking Reuben 

 Lasker, Southwest Fisheries Center La Jolla 

 Laboratory, National Marine Fisheries Service, 

 NOAA, for advice and encouragement throughout 

 this study and for providing equipment and 

 laboratory space and making available the excel- 

 lent aquarium facilities, without which this work 

 would have been impossible. Irwin Haydock and 

 David Crear introduced me to techniques for 

 maturing and spawning bairdiella in captivity, 

 and Robert G. Hulquist of the California Depart- 

 ment of Fish and Game facilitated collecting ef- 

 forts at the Salton Sea. James R. Zweifel, South- 

 west Fisheries Center La Jolla Laboratory, 

 National Marine Fisheries Service, NOAA, 

 helped in the statistical treatment of some of the 

 data, and Dale Mann drafted the figures. Finan- 

 cial support was provided by the University of 

 California Institute of Marine Resources. 



LITERATURE CITED 



Ahlstrom, E. H. 



1943. Studies on the Pacific pilchard or sardine, 

 (Sardinops caerulea). 4. Influence of temperature on the 

 rate of development of pilchard eggs in nature. U.S. Fish 

 Wildl. Serv., Spec. Sci. Rep. 23, 26 p. 



AXDERDICE, D. F., AND C. R. FORRESTER. 



1967. Some effects of saUnity and temperature on early 

 development and survival of the English sole (Parophrys 

 vetulus). J. Fish. Res. Board Can. 25:495-521. 



1971a. Effects of salinity and temperature on embryonic 

 development of the petrale sole (Eopsettajordani). J. Fish. 

 Res. Board Can. 28:727-744. 



1971b. Effects of salinity, temperature, and dissolved ox- 

 ygen on early development of the Pacific cod {Gadus 

 macrocephalus). J. Fish. Res. Board Can. 28:883-902. 

 Alderdice, D. F., and F. P. J. Velsen. 



1971. Some effects of salinity and temperature on early 

 development of Pacific herring (Clupea pallasi). J. Fish. 

 Res. Board Can. 28:1545-1562. 

 Battle, H. L 



1929. Effects of extreme temperatures and salinities on 

 the development of Enchelyopus cimbrius (L.). Contrib. 

 Can. Biol. Fish., New Ser., 5:109-192. 

 BisHAi, H. M. 



1960. Upper lethal temperatures for larval salmonids. J. 

 Cons. 25:129-133. 

 Box, G. E. P. 



1956. The determination of optimum conditions. In O. L. 



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