The analysis was aimed at identifying the characteristics of hybrids of Atlantic salmon, Salmo salar L., and sea trout, Salmo trutta L. Nineteen metric characters and 11 meristic characters of reciprocal hybrids of these species aged 0+ and 1+ which were released into and grew in natural watercourses were analyzed. At ages 0+ and 1+, both of the hybrids were similar to trout in head length, minimum body depth, and dorsal fin height. Both hybrids were similar to salmon at the age of 0+ in the length of the caudal fin indentation (fork length as the % of total length) and at age 1+ in upper jaw length (% of head length). Hybrid metric characters were also either intermediate or exceeded the parental species (length of pectoral fins at age 1+). Analysis indicates that metric characters are difficult to use to identify hybrids. Among the meristic characters, low gill raker and pyloric caeca counts can be used to identify hybrids.
