Physiological changes in fish in response to stress are generally interpreted as an indication of the severity of a stressor as well as a reflection of the capacity of a species of fish to manage a particular level of stress. In farmed fish, an increased level of continuous stress culminates into eventual decrease in disease resistance as well as reduced growth rate. Biologists are well familiar with these physiological responses of fish to stress various investigations on using nutraceuticals in modulating physiological stress responses are ongoing. In this study, we tried to observe the effects of tryptophan, an essential amino acid, in modulating physiological processes in Channel catfish , Ictalurus punctatus, raised in stressed and a diseased conditions with virulent Aeromonas hydrophila (vAh). In particular, we have checked levels of blood glucose and hematocrit , before and after the disease challenge with virulent Aeromonas hydrophila (vAh; ML09-119). We had 4 different experimental groups : (1) control fish fed with control feed, (2) control fish fed with tryptophan-treated feed; (3) stressed fish fed with control feed; and (4) stressed fish fed with tryptophan- treated feed. After five weeks of feeding, we challenged the catfish with vAh and kept the fish in the challenged condition for 72 hours. Our preliminary results showed that catfish fed with tryptophan-fed feed had considerably improved levels of blood glucose and hemtocrit , both in the stressed and diseased conditions. Further research is being conducted to optimize the concentration of Tryptophan in the feed in order to ascertain the potential immunomodulating properties of this essential amino acid.