A comparison of the external microbial assemblages between native southern strain and wild northern brook trout, Salvelinus fontinalis, of hatchery ancestry

Hatchery reared, northern strain brook trout have been stocked in streams within the home range of southern strain brook trout in an effort to restore or enhance native trout populations since the late 1800s. But, brook trout native to the southern Appalachians are genetically distinct; raising ecological and ethical concerns regarding the impact of the past stockings. In this study, the external microbial assemblages on native southern and wild fish of hatchery ancestry were compared by characterizing colony morphologies and estimating densities of colony forming units. The hatchery-ancestry fish had significantly higher densities, and assemblages were more similar to that of the surrounding water than those of the southern strain fish. These results suggest that the native southern strain fish exhibit a greater ability to inhibit microbial growth in their epidermal mucus than do the fish with hatchery ancestry.