Gadomski and Caddell: Effect of temperature on egg development and 



45 



2 6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 66 70 74 



Hours after fertilization 



Figure 4 



Development of eggs of California halibut, Paralichthys 

 califormcus, at three temperatures. Eggs died at 8"C during stage 

 I and at 24°C during stage II. Descriptions of egg stages are pre- 

 sented in Table 2. 



incubation temperature were best fit by exponential 

 functions (Table 4). 



Discussion 



Many egg-staging systems have been developed for 

 fishes (Ahlstrom, 1943; Colby and Brooke, 1973; 



Riley, 1974; Laurence and Rogers, 1976; 

 Ferraro, 1980; Thompson and Riley, 1981; 

 Haynes and Ignell, 1983; Walsh et al., 1991). 

 We found it difficult to devise a system that 

 could be used for all four species because the 

 embryonic development of barred sand bass and 

 fantail sole was faster in relation to germ-ring 

 migration than that of white croaker and Cali- 

 fornia halibut. Species-specific rates of embry- 

 onic organogenesis relative to blastopore closure 

 were also noted by Ahlstrom and Moser (1980). 

 Although not commonly considered, these de- 

 velopmental differences could be useful traits 

 in identifying field-collected fish eggs. 



Absolute temperature ranges tolerated by 

 eggs of the four species reflect temperatures 

 encountered owing to seasonal spawning pat- 

 terns off southern California (Love et al., 1984; 

 Lavenberg et al., 1986; Walker et al., 1987; 

 Moser and Watson, 1990; McGowen, 1993). 

 High temperatures successfully tolerated by 

 barred sand bass ( 16— 28°C ) and fantail sole ( 16- 

 24°C) eggs coincide with their summer and late 

 summer-fall spawning seasons. Surface tem- 

 peratures in the nearshore zone of southern Califor- 

 nia are generally highest in August, reaching peaks 

 of 20-22°C, and lowest in January or February with 

 temperatures of 13-15°C (Petersen et al., 1986), al- 

 though unseasonably low temperatures, caused by 

 upwelling, can occur during spring or summer. Both 

 white croaker and California halibut eggs survived 

 only at lower temperatures (12-20°C); peak spawn- 



Table 3 



Rates of development for eggs of four California fishes 

 reared at five temperatures in the laboratory. Rates are 

 expressed as the slopes (/3) of age regressed on stage (Age=/J 

 stage). Age is time (hours) from fertilization to the nine 

 egg developmental stages (I-DC); embryonic developmen- 

 tal stages E, O, and S were not considered in this analysis. 

 Dashed lines are temperatures where eggs of that species 

 did not survive. For all regression equations, r 2 >0.95. Su- 

 perscripts indicate means that were significantly differ- 

 ent from each other in using the Tukey multiple-range test 

 (P<0.05). 



Temperature (°C) 



Species 



L2 



Hi 



'JO 



24 



28 



Barred sand bass 9.53 4.95 3.12 2.46 2.04 



White croaker 7.54 4.73 3.25 



California halibut 7.14 4.98 3.42 



Fantail sole — 5.78 3.38 2.51 



Mean/} 8.07 1 5. II 2 3.29 :i 2.49 3 



:.' oi 



12 



11 



CO 



24 



28 



Temperature (°C) 

 Bass » Croaker D Halibut 



Sole 



Figure 5 



Relationship between egg age at hatching (hours from fer- 

 tilization to hatching) and temperature (T) for barred sand 

 bass, Paralabrax nebulifer, white croaker, Genyonemus 

 Imeatus, California halibut, Paralichthys californicus, and 

 fantail sole, Xystreurys liolepis. 



