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In static tests with juvenile mullet, the acute incipient lethal level for zinc was 9 mg/l, the 168-h LC50 value for cadmium was 16 mg/l, and the 96-h LC50 values for tri- and hexavalent chromium were 53 and 24 mg/l respectively; in similar tests with pre-adult hardyhead, the acute incipient lethal level for zinc was 33 mg/l and the 168-h LC50 value for cadmium was 21 mg/l. In continuous-flow tests with mullet the acute incipient lethal level for zinc was 12 mg/l, but incipient lethal levels were not attained for cadmium or chromium; however, the 120-h LC50 value for cadmium and the 96-h LC50 value for hexavalent chromium were 14 and 31 mg/l respectively. In similar tests with hardyhead, incipient lethal levels for zinc and chromium were 37 and 36 mg/l respectively. An acute incipient lethal level for cadmium was not attained, but the 168-h LC50 value was 15 mg/l. Generally, mullet and hardyhead were more sensitive to the acute effects of cadmium, chromium and zinc than other marine and estuarine fishes for which toxicological information is available. Increased temperature also appeared to increase the sensitivity of mullet to the lethal effects of zinc.

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