the source (27 aquaria per circle) to give the 

 two dose rates used in the experiment. Radia- 

 tion dose rates were measured in the center 

 of the aquaria with glass rod dosimeters cali- 

 brated to read directly in rads. This reading 

 was used to calculate the dose to the fish on the 

 assumption that the fish moved randomly 

 throughout the aquaria. 



Postlarval pinfish were caught during mid- 

 morning on late flood tide in a plankton tow 

 from the bridge connecting Pivers Island with 

 the Beaufort causeway, about 1,6 km. from 

 Beaufort Inlet. A fixed channel net was used 

 for the collection. All fish used in this study 

 were collected in 30 minutes and are assumed 

 to be of the same age. 



The fish were separated into three groups 

 to reduce crowding and put into 30 p.p.t. sea 

 water at 15 C, the same conditions that 

 existed in nature at the time of the collec- 

 tion. Fish were kept under these conditions for 

 3 days to elinninate the weak and diseased. 

 They were then acclimated for 4 days in 20 

 p.p.t. and 20° C. water--the median salinity 

 and temperature used in the experiment. Three 

 groups of fish were brought to the test tenn- 

 peratures of 15 , 20 , and 25 C. in 2 days, 

 after which 30 fish withdrawn at random were 

 placed into each aquarium. At the end of 3 days, 

 irradiation was begun. Another sample of 

 50 fish was then taken at random from the 

 remaining stock at the three temperatures and 

 measured to establish the meanbody measure- 

 ments at the beginning of the experiment. 



Measurements of 1,215 fish (405 fish for each 

 sample day) were made to the nearest 0.01 mm. 

 with a calibrated micrometer in a binocular 

 microscope. These measurements included: 

 SL (standard length), H (head length), S- V (snout 



to vent length), D (greatest body depth), E (eye 

 diameter), DS (last dorsal spine length), DR 

 (first dorsal ray length), and AS (second anal 

 spine length). After all excess moisture was 

 blotted off, WT (wet weights) were determined 

 to the nearest milligram on a single-pan bal- 

 ance. All measurennents other than standard 

 length and wet weight are presented as ratios 

 of standard length to establish a base for com- 

 parison. Standard lengths are presented in 

 millimeters and weights in milligrams wet 

 weight per millimeter standard length. The 

 mean measurements +1 standard error of 50 

 fish at the beginning of irradiation were: 



SL 11.98 + 0.08 mm. 



SL/H 3.77 + 0.02 



SL/S-V 1.99 + 0.01 



SL/D 4,77 + 0.03 



SL/E 10.04+ 0.06 



SL/DS 17.74 + 0.28 



SL/DR 11,57 + 0,21 



SL/AS 14.23+ 0,18 



WT/SL 1.32+ 0.03 mg. /mm. 



Environmental Factors and Interactions 

 Affecting Growth 



An analysis of variance was done for each 

 of the nine measured characteristics after the 

 fish had grown for 45 days under the described 

 conditions. The 45-day sample was the only 

 sample analyzed in this manner, since the 

 main interest of this study was in the end 

 result. Of the nine body characteristics meas- 

 ured, nine were significantly changed by tem- 

 perature, five by salinity, and only two by 

 radiation (table 6), 



Table 6. — Composite results from the analyses of variance 



Source of variation 



Measured characteristics^ 



SL SI/H Sl/S-V Sl/D SL/E SL/D6 SL/DR SL/AS WT/SL 



Replications 



Treatments : 



Fiadiation 



Salinity 



Temperature 



Radiation x salinity.... 

 Radiation x temperature. 

 Salinity x temperature,. 

 Radiation x salinity x 

 temperature 











■X-K 



See above for explanation of abbreviations. 

 - Not significant. 

 * Significant at 5-percent level. 

 ■»<*Signif leant at 1-percent level. 



42 



