EFFECTS OF TEMPERATURE AND SALINITY ON 



FERTILIZATION, EMBRYONIC DEVELOPMENT, AND HATCHING 



IN BAIRDIELLA ICISTIA (PISCES: SCIAENIDAE), AND 



THE EFFECT OF PARENTAL SALINITY ACCLIMATION ON 



EMBRYONIC AND LARVAL SALINITY TOLERANCE^ 



Robert C. May^ 



ABSTRACT 



Eggs and larvae of the sciaenid fish bairdiella, Bairdiella icistia, were obtained from fish matured in 

 the laboratory by photoperiod manipulation and induced to spawn by hormone injections. The effects of 

 temperature and salinity on fertilization, embryonic development, hatching, and early larval survival 

 were studied with the material thus obtained, and the effects on gametes of parental salinity acclima- 

 tion were also investigated. Fertilization took place over a wide range of temperatures and salinities, 

 but was completely blocked at salinities of 10%o and below. A low level of spermatozoan activity may 

 have accounted for the lack of fertilization at low salinities. Successful embryonic development 

 occurred between temperatures of approximately 20° and 30°C, and salinities of 15 and 40%o. The 

 production of viable larvae was estimated to be optimal at a temperature of 24.5°C and a salinity of 

 26.6''/oo. An interaction of the two factors was apparent, development at high salinities being most 

 successful at low temperatures and development at high temperatures being most successful at low 

 salinities. The stage of maturity of the spawning female had a great influence on the overall viability of 

 the eggs produced, as well as on their response to temperature and salinity. Adult bairdiella matured 

 sexually in dilute seawater with a salinity of 15%o, and the salinity tolerance of the eggs produced by 

 these fish was unaltered. 



The bairdiella, Bairdiella icistia (Jordan and Gil- 

 bert), is a sciaenid fish native to the Gulf of 

 California. In 1950 the species was successfully 

 introduced into the Salton Sea, a large saline lake 

 in southern California (Whitney 1961). Salton Sea 

 water has an ionic composition different from that 

 of ocean water (Carpelan 1961; Young 1970), and 

 its overall salinity, now approximately 38%o,^ is 

 rising at a rate of about l%o every 3 yr (U.S. 

 Department of the Interior and the Resources 

 Agency of California 1969). This rising salinity 

 has caused concern that the present sport fishery 

 in the Salton Sea (based on several fish species, 

 including bairdiella) will fail when the upper sa- 

 linity tolerances of the fishes are exceeded 



'Based on a portion of a dissertation submitted in partial 

 satisfaction of the requirements for the Ph.D. degree at the 

 University of California at San Diego, Scripps Institution of 

 Oceanography. 



^Hawaii Institute of Marine Biology, P.O. Box 1346, Kaneohe, 

 HI 96744. 



^This value varies somewhat with season and location in the 

 Salton Sea. 



(Walker et al. 1961). Lasker et al. (1972) found 

 that the survival of bairdiella eggs and early lar- 

 vae was severely inhibited by Salton Sea water at 

 a salinity of 40%o; thus, at the present rate of 

 salinity increase, the bairdiella population may 

 suffer a loss in recruitment within the next 10 yr. 



The work reported in this paper was undertaken 

 to provide more information on the salinity toler- 

 ance of bairdiella during early development, espe- 

 cially as influenced by temperature and by the 

 acclimation of spawning parents to different 

 salinities. Because of poor embryonic and larval 

 survival in Salton Sea water (May 1972), these 

 experiments were all conducted in seawater of 

 ordinary ionic composition. The effects of Salton 

 Sea water per se and their implications for the 

 population of bairdiella in the Salton Sea will be 

 discussed elsewhere (May in preparation). 



Bairdiella normally spawn during April and 

 May in the Salton Sea (Whitney 1961; Haydock 

 1971). However, thanks to the work of Haydock 

 (1971), bairdiella can be induced to mature and 

 spawn in the laboratory at any time of the year, 



Manuscript accepted March 1974. 



FISHERY BULLETIN: VOL. 73, NO, 1, 1975. 



