Til. RESULTS 
1. Bioassays Using Mineral Solids. 
Eleven of the 14 species used in this study were exposed to suspen- 
sions of kaolinite (Hydrite-10). All fish exposed to kaolinite survived 
24-hour exposure in concentrations as high as 140 g 1-1. Several species 
(white perch, spot, toadfish, mummichog, hogchoker, and menhaden) were 
exposed to 140 g 17! kaolinite for 48 hours with the same result; no 
deaths were directly attributable to the mineral. Usually, the fish 
became highly active for a short time when placed in kaolinite suspensions. 
Activity returned to normal after 0.5 to 2 hours. Three species (bluefish, 
cusk eel, and bay anchovy) were not exposed to kaolinite because too few 
individuals were collected. 
Survival of the 14 species was assessed in suspensions of fuller's 
earth. Three species (toadfish, cusk eel, and hogchoker) showed no 
mortality attributable to the effects of fuller's earth after 24-hour 
exposure to concentrations of 96 to 140 g 171. 
The response of 5 of the 11 species killed in the fuller's earth 
suspension (striped bass, croaker, weakfish, bluefish, and menhaden) was 
not consistent enough to calculate accurate LC values. The tolerance of 
these fish, as the lowest concentration at which 100-percent mortality 
occurred, is presented in Table 2. 
Exposure of the remaining six species (Atlantic silverside, striped 
killifish, white perch, bay anchovy, spot, and mummichog) to fuller's 
earth resulted in consistent concentration mortality responses. From 
these responses, calculations of lethal concentrations for 10-, 50-, and 
90-percent mortality in 24-hour bioassays were made. Consistent concen- 
tration mortality responses of white perch were observed for 12-, 18-, 
and 24-hour exposures. Spot showed consistent responses for the 12-, 20-, 
and 48-hour exposures. 
The six species varied widely in sensitivity to suspensions of fuller's 
earth, as indicated by 24-hour lethal concentration (Table 3) and 
concentration-dependent response curves (Fig. 1). The LCs5g response range 
was 36.60 g 1~! and varied from 2.40 g 17! (Atlantic silverside) to 
39.00 g 17! (mummichog). LCgg values for 24-hour assays had a range of 
56.57 g 1-1, from 9.60 g 17! (bay anchovy) to 62.17 g 17! (mummichog). 
The total range of LCj9 values was 23.90 g 1-1, from 0.57 g 17! (Atlantic 
silverside) to 24.47 g 171 (mummichog). 
The concentration range from LCjg to LCgg within each species varied 
widely. The species with the highest LC5q value (mummichog) showed a 
range of 37.70 g 17! between LCj9 and LCgq (Table 3). The species with 
the lowest LCs5g value (Atlantic silverside) showed a range of 9.43 g yo 
between LCjg and LCog. Species with intermediate 24-hour LCsa values 
(white perch and spot) showed ranges of 28.76 and 18.54 g 1™°, respectively, 
10 
