The objective of this study was to determine the refractive index of vitreous humor in fish from artisanal fisheries in Puerto Salaverry and Playa Las Delicias, Trujillo province, Peru._x000D_ The species Sciaena deliciosa "Lorna" and Galeichthys peruvianus "Bagre" were caught with a hook at Las Delicias beach; the species Mugil cephalus "Lisa" and Paralonchurus peruanus "Suco", were captured in the Salaverry Harbor. 10 specimens of each species were captured, adding a total of 40 per week, during May to September 2017._x000D_ 5 specimens of each species were exposed to the environment and another 5 specimens were refrigerated (ice culer), the vitreous was extracted and placed in vials of penicillin for environmental evaluation and ziplock bags for evaluation in refrigerated. The readings were then made in the ABBE Refractometer, refractive index and temperature, whose data were subjecte...