Few on-the-spot observations of lthe effects of cold winter water conditions on such marine fishes as the black drum, Pogonias cromis (Linnaeus), and striped burrfish, Chilotycterus schoepfi (Walbaurm), have been reported in the literature. Deaths of various species of marine fishes have usually been attributed to geologic, seismic (Taylor 1917) or planktonic (Gyrnnodinium) (Gunter, Williams, Davis, and Smith 1948) causes. The bulk of these observations have dealt with the death or the effects of lowering of water temperatures (Fries 1952) following sudden cold periods in southern waters (Miller 1940; Gunter 1938, 1941, 1947, 1948; Gunter and Hildebrand 1951; Gunter, Smith, and Williams 1947a, 1947b; Storey 1937; Storey and Gudger 1936; and Taylor 1917a, 1917b). It is, therefore, the purpose of this paper1 to call attention to the natural effects of cold water temperatures on the black drum and striped burrfish as held in a freely flowing salt-water aquarium. Bean (1903) noted the singular observation that aquarium-held black drum died February 10, 1897, when water temperatures were 3.3YC (38?F). Gunter (1941) observed one Pogonias cromis in a stunted, practically moribund condition in 4?C Compano Bay, Texas. He likewise found dead Chilomycterus schoepfi at Mustang Island in January 1940, when the water temperature was 4.7?C. In contrast, no black drum deaths occurred at Fort Myers, Florida (Gunter 1947) when water conditions were: temperatures 24.1?C, pH 8.2, and salinity 21.437.0 ppt. One striped burrfish was killed during this period. Gunter and Hildebrand (1951) found dead black drum but no dead striped burrfish at Mustang Island, Texas, after the air temperatures had dropped from 65 to 25?F in 4 hours. Hildebrand and Cable (1930) did not find deaths among numb and drifting black drum, in January 1927, which were field tolerant of 5?C water temperatures. Pearse (1929) contradicts Hildebrand and Cable (1930) who say that young black drum can withstand cold better than adults. He believes that drum are often 'found in bays but that they are unaffected by cold water temperatures. Storey (1937) found that the striped burrfish was always killed at Sanibel Island, but she did not note the temperatures at which deaths occurred. Frisbie (1961) has commented on the presence of Pogonias cromnis in the Chesapeake Bay and adjacent waters. Sampling yielded 3 specimens (160275 mm total length) of this species, which occurred abundantly in autumn (October 5-9, 1961) in the Patuxent River between Boat House 1 of the Patuxent Naval Air Station and Mears Creek. Environmental conditions in the river at this time were: salinity 14.1 ppt, and water temperature 20.5?C (Table I). These specimens were transferred to a large 4 ft2 aquarium in the main research laboratory of the Chesapeake Biological Laboratory, Solomons, Maryland. Here, these specimens fed voraciously on the soft clam, Mya arenaria. They stopped feeding December 26, 1961, when the salinity was 17.4 ppt, water temperature 4.6?C, and the oxygen content 7 ppm. Swimming and feeding activities before November 20, 1961, were normal in all appearances. After this date, the water temperature dropped below 100C (50?F), the