FISHERY BULLETIN: VOL. 73. NO. 1 



hours before each experiment to stabilize oxygen 

 tension and pH. Potassium penicillin G (50 lU/ml) 

 and streptomycin sulfate (0.05 mg/ml) were added 

 to the water just before it was placed in the in- 

 cubators. Salinities were calculated by multiply- 

 ing chlorinity values (Schales and Schales 1941) 

 by 1.80655 (Johnston 1964) and remained within 

 ±0.5%o of the original salinity during an experi- 

 ment. Temperatures were maintained within 

 ±0.2°C of the desired value by immersing petri 

 dishes and incubators in water baths equipped 

 with cooling coils and thermostatically controlled 

 heaters. The incubators were illuminated con- 

 tinuously from fluorescent room lamps which gave 

 an intensity of from 320 to 480 Ix at the water 

 surface. Dissolved oxygen concentration in the in- 

 cubators decreased with increasing temperature 

 and salinity, and measured concentrations were 

 wathin 2 or 3% of the saturation values given by 

 Kinne and Kinne ( 1962). The highest oxygen con- 

 tent (at 18°C and 15%o) was 6.24 ml/liter, and the 

 lowest (at 30°C and 55%o) was 4.05 ml/liter. The 

 pH in the incubators increased with increasing 

 salinity and decreasing temperature, varying be- 

 tween 8.08 and 8.27. 



The percentage hatching and the condition of 

 the larvae at hatching were recorded for each in- 

 cubator. Supplementary containers (20-ml petri 

 dishes) with 30 fertilized eggs each, were provided 

 at each treatment to allow examination of eggs 

 during development vdthout disturbing the eggs 

 in the incubators. Hatched larvae were not fed; 

 some were kept in 400-ml beakers (without the 

 polypropylene inserts used prior to hatching) and 

 the pattern of mortality of the starved larvae re- 

 corded, and some were used in experiments on the 

 temperature and salinity tolerance of yolk-sac 

 larvae (May 1972). 



During an early experiment, histological prep- 

 arations were made of newly hatched larvae from 

 different salinities at 25°C. Larvae were fixed in 

 Bouin's solution, dehydrated in ethanol-normal 

 butyl alcohol, embedded in paraffin, and sectioned 

 transversely at 8 idm. Sections were stained with 

 Mayer's hemalum and eosin. 



Experimental Series 



Two series of experiments on fertilization suc- 

 cess, embryonic development, and hatching 

 success were conducted, each series involving 

 observations at 25 different combinations of tem- 

 perature and salinity. Each series included two 



separate hormone-induced spawnings offish held 

 under identical conditions. The two spawnings in 

 each series constituted a composite factorial array 

 of treatments (a 3 x 5 plus a 2 x 5 factorial); this 

 design, similar to those employed by Alderdice 

 and his colleagues (Alderdice and Forrester 1967, 

 1971a, b; Alderdice and Velsen 1971), allowed 

 coverage of a large factor space without utilizing 

 all possible combinations of treatments. The 

 ranges of temperature and salinity employed cov- 

 ered the viable ranges for bairdiella eggs, as de- 

 termined in preliminary experiments. Table 1 in- 

 dicates the temperatures and salinities in which 

 eggs were fertilized and incubated in the two 

 spawmings of each series. 



The fish utilized for Series A were captured to- 

 ward the end of the spawning season in the Salton 

 Sea on 7 June 1971 and maintained on a 16L:8D 

 photoperiod in 22°C water until the first 

 hormone-induced spawning of the series on 23 

 August 1971 and the second on 1 September 1971. 

 Ovarian biopsies indicated that the eggs were 

 ready for spawning at this time, but only max- 

 imum oocyte diameters were measured and no 

 oocyte size-frequency distributions were obtained. 

 The tests were repeated in a second series of exper- 

 iments. Series B. A group offish captured in the 

 Salton Sea on 20 May 1970 was shifted gradually 



Table 1. — Dates and temperature-salinity conditions for exper- 

 iments in Series A and B, 1971. There were two spawnings, 

 performed at different dates, in each series; each spawning 

 utilized eggs and sperm from different fish. 



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