The following is a summary of the article referenced.

The cyanobacteria spirulina is commercially produced for human consumption as well as agricultural feed ingredients. Recently, whole spirulina and cell extracts were found to enhance immunity in animals by increasing phagocytic activity. The purpose of this study was to determine the effect of spirulina enhanced diet on the nonspecific immune response of channel catfish, ictaluras punctatus. The sample population consisted of "young of the year" channel catfish obtained from Fish Producers, Niland, CA. Fish (50/tank) were maintained in glass aquaria equiped with undergravel filters. All fish were fed a diet of Trout Starter Diet (Rangen, Inc) for a month until they were large enough to ingest adult brine shrimp (artemia franciscana). The control diet consisted of adult brine shrimp. The test diet consisted of adult brine shrimp biencapsulated with spirulina. Adult brine shrimp were allowed to feed on dried spirulina powder for 3-4 hours to maximize bioencapsulation. Preliminary studies indicated that channel catfish fed spirulina had an increase in the number of splenic macrophages determined by esterase staining compared to controls. Not only were more macrophages present in the spleen, but also the macrophages appeared activated. Activation determined by morphology on scanning electron microscopy, was characterized by the presence of numerous folds and ruffles. This research was performed on a single population of catfish over a period of months. While data suggests nonspecific immunostimulation elicited by spirulina in the diet, further study on different populations of fish is underway to confirm the preliminary data.