Peptic activity has been shown in a number of cultures and commercial species including Anguilla japonica, Tilapia mossambica, Pleuronecthys, both Salmo and Oncorhynchus species, Ictalurus, Micropterus, Lepomis and Perca. The presence of pepsin is so universal in vertebrates having stomachs that its presence can be presumed in fish for which no data is available.