During the first week under these conditions, red hemorrhages appear on the snout and fins. In the next week, hemorrhages appear under the skin, and on the internal organs, followed by tissue necrosis, and eventually, death. In the laboratory, young mullet were able to endure brief cooling to temperatures of 1 - 1.5 C for up to 1 day. There were no adverse effects on mullet when they were gradually warmed to their original acclimation temperature. Changes in red blood cells also occur in thermally stressed mullet.
Low temperatures decrease the functionality of blood hemoglobin and lead to asphyxia.
Rather, mullet that are cold stressed increase the catabolism of bodily proteins. This results in the alteration of blood chemistry with respect to increased ammonia nitrogen excretion. Adult M. cephalus are highly euryhaline , and survive in a range of salinities from 0 ppt. At 11 ppt., the majority of fertilized eggs died, and those that did develop further, ultimately died in the gastrula stage. Hatching in this study occurred at salinities between 10 - 55 ppt., but no larvae survived at either 10 or 55 ppt.