This photograph shows deep erosion of the tail of a hatchery-reared rainbow trout. Ranked on a severity scale of 0-5 the erosion on the caudal peduncle (narrowest part of the body before the tail) ranks a 5 (severe). The erosion penetrates through the dermis and muscle to expose vertebral bones. Moderate erosion continues along the margins of the caudal fin. There is also loss of pigmentation on the lower portion of the tail. This lesion was initially due to abrasion, followed by secondary bacterial infection. It is unlikely that this fish could have recovered from this lesion.

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UNIVERSITY OF MARYLAND College of Ag & Natural Resources Department of Veterinary Medicine Aquatic Pathobiology Center