Pharmacodynamic of a single oral dose of tramadol in Brook trout (Salvelinus fontinalis)

Fish are among the most common animals used in research laboratories. Yet, at this time no oral analgesic treatment is available for use to treat pain in fish. While immersion and injectable analgesic drugs have previously been described for use in fish, the objective our study is to evaluate the analgesic and sedative effects of oral tramadol, an opioid, in brook trout, a common species used in research in Canada.

We will use a validated model called the shuttle box (Loligo), which has previously been used to evaluate the effects of opioids in goldfish. The ultimate goal of the present study is to evaluate the effects of oral tramadol in a variety of fish. If proven to be analgesic, this drug could be administered in the food of fish exposed to painful conditions in research and in zoological settings. In comparison to injectable analgesics, this treatment would decrease the stress of capture for fish. Compared to opioids administered by immersion, this treatment would decrease the drug residues in water effluents.

The welfare of more than 2.5 million fish used in European laboratory research would potentially be improved by this project. In addition, the welfare of fish housed in aquaria and other zoological institutions would be improved as many treatments are often extrapolated from one fish species to another in this context.

The study’s outcomes will contribute to the growing body of knowledge supporting fish sentience and welfare requirements. By providing evidence-based analgesic protocols, this research supports the ethical treatment of fish in human care while advancing our understanding of pain management across vertebrate species. The establishment of effective oral analgesia protocols could revolutionize fish medicine, providing veterinarians and researchers with practical tools for improving aquatic animal welfare.

Image: Jay Fleming, US National Park Service, Wikipedia