chloramphenicol) at a density of 25 larvae/liter. 

 Larvae were fed rotifers, Brachionis plicatilis, be- 

 ginning two days after hatching; on the seventh 

 day after hatching, brine shrimp Artemia sp. 

 were added to the diet. 



Early larval development from spawning to 

 first feeding was determined for larvae from three 

 separate spawnings. Newly hatched larvae (6-15 

 hours old) were pipetted into an aquarium and 

 10-15 removed immediately and preserved in 

 70% ethanol. Additional larvae were sacrificed 

 daily for nine days. These samples were examined 

 to relate early development and age. 



Results and Discussion 



Three adult fish died of undermined causes dur- 

 ing the period of winter conditions in 1984-85. 

 Four additional fish died after jumping from the 

 tanks. The initial spawning by the remaining 

 population of four fish occurred five weeks after 

 spring conditions were achieved. This was fol- 

 lowed the next day by another spawning. Spawn- 

 ing continued for nine weeks at 10-14 d intervals. 

 Spawning episodes usually consisted of produc- 

 tion of fertilized eggs over 2 successive days. 

 While actual spawning was never observed, it al- 

 ways occurred between sunset and 08:00 the fol- 

 lowing day. 



After cessation of spawning, the four fish were 

 removed from the tanks and their sex deter- 

 mined. Two of the fish drummed when handled 

 and were clearly males. At least one (and proba- 

 bly both) of the two remaining fish were females. 

 The fish were returned to the system after exam- 

 ination. 



The temporal sequence of the spawning events 

 (two successive days at 10-14 d intervals) sug- 

 gests that each female may have spawned as 

 many as four times during the 9-wk period. This 

 is in contrast to reports for natural populations of 

 C. regalis (e.g., Merriner 1976), but has been 

 reported for laboratory populations of other 

 sciaenid fishes. For example, Arnold (1984) ob- 

 served 82 spawning events in a laboratory popu- 

 lation of 12 C. nebulosus over a 27-mo period and 

 52 spawning events in a similar population of six 

 S. ocellatus over a 3-mo period. It is not clear why 

 the C. regalis in our investigation ceased spawn- 

 ing after several months of long days and high 

 temperatures while the C. nebulosus in Arnold's 

 system continued to spawn over a much longer 

 period. Perhaps this is related to the smaller an- 

 nual variation in photophase and temperature 



typical of C. nebulosus habitats. However, go- 

 nadal resorption has been reported for at least 

 one other sciaenid species iB. icistia) held in the 

 laboratory for extended periods of long day-length 

 (May 1974). 



Spawning from the 1985-86 conditioning pe- 

 riod first occurred four weeks after spring 

 conditions were reached with a second spawning 

 nine days later. Further spawning in the 1985- 

 86 population did not occur because of an 

 unidentified infection resulting in the death of all 

 10 fish in the system over a period of a few weeks. 

 Autopsies revealed that all fish had highly 

 developed ovaries or testes at the time of 

 death. 



Newly hatched larvae (6-15 hours old) had a 

 yolk sac, no mouth, and little development of the 

 eyes. By 24-36 hours after hatching, the yolk sac 

 had been virtually absorbed, the mouth was just 

 beginning to form, and the eyes were not yet pig- 

 mented. By 48-60 hours, larvae had a completely 

 formed mouth and digestive system, and the eyes 

 were pigmented. Larvae were capable of feeding 

 at this stage. 



Chloramphenicol improved larval survival, 

 which was as high as 24% over 11 days. This 

 survival is comparable to that reported for other 

 sciaenid larvae (Holt et al. 1981; Houde and 

 Taniguchi 1981; Holt and Arnold 1983). However, 

 growth was less than the maximum seen in the 

 laboratory for C. nebulosus. After 11 days C. re- 

 galis larvae in the present experiments had 

 grown from a mean, posthatching size of 2.7 mm 

 (36 fxg dry weight) to 4.5 mm (235 \i.g dry weight). 

 In contrast Houde and Taniguchi (1981) found 

 that one group of C. nebulosus larvae reached a 

 size of 13.6 mm (7,082 fxg dry weight) in 12 days 

 when reared on a concentrated ration of natural 

 zooplankton at very low stocking density and 

 high temperature (32°C). However, when fed a 

 rotifer diet at comparable temperatures and 

 stocking densities, growth of C. nebulosus larvae 

 was somewhat less than that of C. regalis larvae 

 in the present experiments. 



Our results show that the spawning cycle of 

 weakfish can be manipulated to produce repeated 

 spawnings without the aid of hormone injections. 

 While the fish appear to resorb their gonadal tis- 

 sue after several months of exposure to long day 

 length and high temperature, the differential ma- 

 nipulation of several groups of fish could allow 

 year-round production of fertilized eggs. Further- 

 more, survival and growth of larvae produced in 

 this manner appear comparable to survival and 



170 



