Accidental Petroleum Hydrocarbon Exposure in Farmed Rainbow Trout (Oncorhynchus mykiss): Effects on Tissues, Water Quality, and Fish Muscle

Accidental petroleum contamination can affect fish health and food safety in aquaculture, yet evidence from commercial production systems remains limited. This study evaluated the effects of an accidental diesel spill on a rainbow trout (Oncorhynchus mykiss) farm operating under a continuous flow-through system in Santander, Colombia. Water and fish muscle were analyzed for petroleum hydrocarbons, and exposed fish were examined by histopathology and immunohistochemistry. Following the rollover of a diesel tanker truck, the producer reported a diesel-like odor, an oily surface film, and reduced feed intake, although no spill-related mortality was observed and water quality remained within acceptable ranges for trout culture. Polycyclic aromatic hydrocarbons were detected in production water, with 2-methylnaphthalene quantified at 21.2 μg/L. Fluorene, 2-methylnaphthalene, phenanthrene, and acenaphthene were quantified in muscle. Histopathology revealed lesions in the kidney, liver, gills, skeletal muscle, and intestine, including interstitial nephritis, hepatocellular lipidosis, branchial degeneration, myonecrosis, and villous atrophy. Melan-A immunoreactivity and negative Perls’ Prussian blue staining supported melanin-associated renal pigmentation. These findings indicate that accidental diesel exposure in a commercial flow-through rainbow trout farm can cause detectable PAH contamination and multisystemic tissue injury without acute mortality. Integrated chemical and histopathological monitoring is therefore advisable for aquaculture toxicology and food safety surveillance.