of histopathological abnormalities. Results of these 
studies are reported in the following sections of this 
technical report. 
METHODS AND MATERIALS 
Collection and Conditioning 
Cunners were collected in modified eel pots, a 
cylinder of 2-inch-mesh hardware cloth with a funnel 
in one end and a hinged door at the other end. Pots 
were baited with cracked hard clams, Mercenaria 
mercenaria, and fished in 10-25 feet of water in the 
Stratford to New Haven, Conn., area of Long Island 
Sound. Fish were transported to the laboratory in 15- 
liter polyethylene buckets and placed in tanks of flow- 
ing seawater at ambient temperature. Before being 
exposed to cadmium, the fish were transferred to 
tanks of recirculating artificial seawater (Zaroogian, 
Pesch, and Morrison, 1969), adjusted to 25 ppt salini- 
ty, and maintained at room temperature for at least 1 
wk for acclimation. The fish were fed Purina Trout 
Chow? during this time, but were unfed for 2 days 
prior to and during the experiment. 
Exposure 
For exposure to cadmium, the fish were placed in 
glass aquaria filled to 60 liters, with artificial seawater 
(Instant Ocean), which was aerated throughout the 
entire exposure period. Cadmium, as cadmium chlo- 
ride (CdCl,*2’2 H,O), was added to test aquaria at 
concentrations of 0, 3, 6, 12, 24, and 48 ppm of Cd**. 
Stock solution for all tests was made up with reagent 
grade cadmium chloride dissolved in water at 50 g 
Cd?+ per liter and acidified to a pH of 2.5 to maintain 
stability. Proper aliquots of the cadmium stock solu- 
tion were added immediately prior to the addition of 
the artificial seawater to obtain desired cadmium con- 
centrations, and aeration was begun a few minutes 
prior to the introduction of test fish. Temperatures 
ranged from 21° to 25°C and pH levels remained 
between 7.3 and 7.6 during the entire study. The 
above five concentrations of cadmium were tested in 
duplicate, with two aquaria serving as controls, in 
each of a series of seven tests. Four cunners were plac- 
ed in each aquarium and were observed daily 
throughout the 96-hr exposure period, and dead fish 
were removed each day. At the termination of each 
test the fish were made available to resident scientists 
at the Milford laboratory; in addition, specimen 
samples were prepared for histopathological examina- 
tion by scientists at the Oxford laboratory, Oxford, 
Md. Supplementary tests of the same design were 
subsequently performed for those research projects 
needing further samples. 
> Reference to trade names does not imply endorsement by the 
National Marine Fisheries Service, NOAA. 
bho 
Of a total of 500 fish tested, 126 were sampled for 
weight and length, averaging 45.2 g in weight and 
146.3 mm in length, with a range in length from 115 to 
170 mm. 
RESULTS AND DISCUSSION 
Although the intent of this study was to determine 
the physiological response of cunners exposed to sub- 
lethal levels of cadmium, rather than to determine 
TL,,, some mortality data were nevertheless obtained. 
Concentrations of cadmium (in ppm water) tested 
and percent mortality (in parentheses) follow: con- 
trols 0 (1.8%), 3 (3.5%), 6 (5.4%), 12 (1.8%), 24 
(10.7%), and 48 (26.8%). It is obvious from these data 
that cunners can tolerate high concentrations of cad- 
mium for at least 96 hr. It was also noted in other 
phases of this study, however, that those fish exposed 
to 48 ppm of cadmium for 96 hr and then placed in 
clean seawater all died within a few days. Hisler 
(1971) reported that the tautog, Tauwtoga onitis, a fish 
in the same family as the cunner, can also tolerate 
high levels of cadmium for a short duration. He also 
reported that the sheepshead minnow, Cyprinodon 
variegatus, and the mummichog, Fundulus 
heteroclitus, had TLso values of 50 and 55 ppm, 
respectively, for a 96-hr exposure to cadmium. 
Although it appears that marine teleosts are relatively 
resistant to cadmium, it will be apparent from the 
sections that follow that cadmium does, in fact, cause 
physiological stress at sublethal concentrations. 
LITERATURE CITED 
CALABRESE, A., R.S. COLLIER, D. A. NELSON, and J. R. 
MacINNES. 
1973. The toxicity of heavy metals to embryos of the 
American oyster Crassostrea virginica. Mar. Biol. (Berl.) 
18:162-166. 
EISLER, R. 
1971. Cadmium poisoning in Fundulus heteroclitus (Pisces: 
Cyprinodontidae) and other marine organisms. J. Fish. 
Res. Board Can. 28:1225-1234. 
EISLER, R., G. E. ZAROOGIAN, and R. J. HENNEKEY. 
1972. Cadmium uptake by marine organisms. J. Fish. Res. 
Board Can. 29:1367-1369. 
GARDNER, G.R., and P. P. YEVICH. 
1969. Toxicological effects of cadmium on Fundulus hetero- 
clitus under various oxygen, pH, salinity and temperature 
regimes. Am. Zool. 9:1096. 
1970. Histological and hematological responses of an estuarine 
teleost tocadmium. J. Fish. Res. Board Can. 27:2185-2196. 
JACKIM, E., J. M. HAMLIN, and S. SONIS. 
1970. Effects of metal poisoning on five liver enzymes in the 
killifish (Fundulus heteroclitus). J. Fish. Res. Board Can. 
27:383-390. 
McKEE, J. E., and H. W. WOLF. 
1971. Water quality criteria. 2nd ed. Calif. State Water 
Qual. Control Board, Publ. 3-A, 548 p. 
