To distinguish between pure marble trout and hybrid marble and brown trout, the difference in coloration (phenotype) described below is what should be considered to comply with the regulations. A trout specimen is considered a hybrid if its coloration exhibits, in addition to the characteristic marbled pattern, small red spots on the body or flanks, and a dark, black, or bluish spot located between the eye and the gill cover. The presence of both conditions (red spots and dark spot on the gill cover) determines the hybrid status. It is important to note that these coloration characteristics should be considered in adult specimens, as even young marble trout may have small red spots that disappear as they mature. Therefore, we invite all anglers who have doubts or uncertainties in recognizing whether a catch is a hybrid to consider it as a "marble trout" and release it with all due care to protect the species. (Below are some photos provided as a simple reference for possible hybrid colorations.)