42 



Fishery Bulletin 94(1). 1996 



ing from 1.8 to 7.6 m diameter and supplied with 

 flow-through coastal seawater at a salinity of 34- 

 35%c. Temperature and photoperiod were maintained 

 at ambient levels simulating natural conditions in 

 nearshore southern California waters (Caddell et al., 

 1990). Experiments generally began during the 

 spawning season and at a temperature at which 

 spawning would naturally occur for each species 

 (Table 1). The hormones gonadotropin and carp pi- 

 tuitary were used to induce ovarian development of 

 white croaker and fantail sole, respectively, follow- 

 ing the methods of Caddell et al. (1990). California 

 halibut brood stock ripened naturally. For each of 

 these three species, eggs were stripped from one fe- 

 male and sperm from 2 or 3 males and these were 

 combined to obtain a single batch of newly fertilized 

 eggs. Barred sand bass spawned naturally in captiv- 

 ity, and newly fertilized eggs floating at the water's 

 surface were collected. The number of individual sand 

 bass participating in a spawning event was unknown. 

 Egg development was initially monitored for each 

 species at five temperatures: 8°, 12°, 16°, 20°, and 

 24°C. Barred sand bass eggs were also exposed to 

 28°C water because of their warmer (summer) spawn- 

 ing season. Since fantail sole eggs exhibited high sur- 

 vival at 24°C during the initial experiment, an addi- 

 tional trial was conducted at 28°C in order to establish 

 the upper temperature tolerance limit of sole eggs. This 

 trial was conducted approximately one year later, with 

 incoming water heated to a typical summer-fall tem- 

 perature ( 18.5°C) to facilitate gonad maturation. 



For each species, an experiment began immedi- 

 ately after egg fertilization. Eggs were stocked in 

 3-L glass jars at a density of about 100 per liter. The 



jars contained filtered, UV-light-sterilized seawater 

 at the ambient spawning temperature (Table 1). Jars 

 were placed in temperature-controlled water baths, 

 and jar temperatures were raised or lowered 1"C 

 every 15 minutes until the desired treatment tem- 

 peratures (see above paragraph) were reached. In 

 order to incubate adequate numbers of eggs, two jars 

 were maintained at each treatment temperature 

 (±0.5"C) for the duration of the experiment. Each jar 

 was mildly aerated to avoid the formation of tem- 

 perature gradients. Light cycles were maintained at 

 12L:12D. Every 2 hours until hatching, at least five 

 buoyant eggs per jar were sampled and preserved in 

 4% formalin. Water in the jars was not exchanged 

 with fresh seawater during the experiments other 

 than as necessary to siphon out dead eggs that accu- 

 mulated on the bottom. 



Eggs were examined with a dissecting microscope 

 to characterize development. We did not illustrate 

 stages of development; eggs of California halibut and 

 fantail sole are illustrated in Oda ( 1991), and white 

 croaker eggs are illustrated in Watson (1982). We 

 devised a staging classification system based on 

 Ahlstrom (1943) and Walsh et al. (1991) (Table 2). 

 Because the rate of embryonic development in rela- 

 tion to germ-ring migration and blastopore closure 

 varied by species, we could not develop a sequential 

 staging system incorporating all developmental events 

 that could be used for all species. We formulated, there- 

 fore, a staging system where some events of embryonic 

 development (stages E, O, and S) were separate from 

 general egg developmental stages I-LX (Table 2). 



For each temperature-by-species treatment, a 

 sample size of at least ten eggs per 2-hour time pe- 



