FISHERY BULLETIN: VOL. 71, NO. I 



distilled water, and temperature control baths 

 were modified from Reed (1969). Each bath 

 was equipped with a thermostat, two 125-w 

 heaters, a maximum-minimum thermometer, and 

 an air stone to circulate the water. A grate sus- 

 pended in each bath supported the culture ves- 

 sels. The baths were placed inside a cold room 

 maintained at 11°C, where a 60-w bulb controlled 

 by a timer provided 14 hr of light every 24 hr, 

 approximately coincident with times of natural 

 daylight. Although the temperature regimes 

 are referred to above and throughout the paper 

 as 20°, 25°, and 30°C, the observed temperatures 

 (mean ± one standard deviation) were 20.3°C ±: 

 0.7°C (range, 18.3° to 21.1°C), 25.4°C + 1.0°C 

 (range, 22.8° to 26.7°C), and 30.6°C ± 0.5°C 

 (range, 29.4° to 31.7°C), respectively. 



An ovigerous female was collected near Wach- 

 apreague, Va., on 12 June 1970. Salinity at the 

 collection site was approximately 30^f. The 

 shrimp was maintained in a glass bowl at 30^f 

 salinity and 25°C in the laboratory, and larvae 

 were obtained on the day following collection. 

 Active larvae were first placed in mass cultures 

 at room temperature and fed newly hatched Ar- 

 temia nauplii (California Brine Shrimp, Inc., 

 Menlo Park, Calif.). Zoeae to be reared in 5, 

 10, and 15%fi salinity were acclimated in 15/^f 

 for 4 hr, and those to be reared in higher salin- 

 ities were maintained in 30/^f for 4 hr. Larvae 

 were then transferred with a large-bore medi- 

 cine dropper to test media in compartmented 

 plastic boxes. Each box contained 18 compart- 

 ments in rows of six, and one zoea in 50 ml of 

 media was placed in every compartment. Three 

 salinities were tested per box (i.e., each row 

 of six compartments was a replicate of a par- 

 ticular temperature-salinity combination), and 

 there were six boxes in each of the three water 

 baths. Thus, there were three replicates (one 

 in each of three boxes) of each temperature- 

 salinity combination, and a total of 18 larvae 

 was reared at each condition. 



Larvae were transferred to clean boxes with 

 fresh media and fed an abundance of newly 

 hatched Artemia nauplii once daily. Molts, 

 deaths, and maximum and minimum tempera- 

 tures were recorded at this time. Mean temper- 

 atures and standard deviations were calculated 



from the maximum and minimum temperatures. 

 The experiment was terminated after 40 days, 

 when all survivors were in postlarval stages. 



RESULTS 



A detailed presentation of survival and devel- 

 opmental history of each larva reared in the pre- 

 sent study is given in Appendix Table 1. 



SURVIVAL 



In general, survival was similar (>60%) at 

 20° and 25°C but was lower at 30°C in nearly 

 all salinities. Survival in 5/^r salinity occurred 

 only at 25°C, where 13 zoeae successfully com- 

 pleted the first molt, and two survived through 

 metamorphosis; in contrast, at 20° and 30°C 

 only two zoeae molted once, and none survived 

 to molt again. 



An analysis of variance on arcsin transfor- 

 mations (Steel and Torrie, 1960) of the per- 

 centage survival data showed difi["erences in sur- 

 vival between temperatures and between salin- 

 ities at the 1% level, and the temperature-sa- 

 linity interaction was significant at the 5 /f level 

 (Table 1). Student-Newman-Keuls' multiple 

 range tests (Steel and Torrie, 1960) were used 

 to explain the significant differences (Table 2). 

 Perhaps the simplest way of looking at these 

 differences in Table 2 is to compare survival in 

 each salinity under each of the different tem- 

 peratures, as is shown graphically in Figure 1. 

 Thus, between 20° and 25°C there were signifi- 

 cant differences in survival only in 5 and 30%c 

 salinity. Survival at 25°C, ^Vk was significantly 

 greater than that at 20°C, hVu, while at 20°C. 

 30%f survival was significantly greater than at 

 25°C, 30^/^r. Comparing 20° and 30°C, survival 

 at 20 °C was significantly greater than that at 

 30°C in 10, 15, and 257ff . Finally, comparing 25° 

 and 30°C, survival at 25°C was significantly 

 greater than that at 30°C in 5, 10, 15, and 25^^. 

 Highest overall percentage survival (88.99^) 

 occurred at the combination 20°C, 20^. (Table 2, 

 Figure 1). 



116 



