The Fishy Physician

While Japanese Koi may be the stars of national competitions and command six-figure sums for champion specimens, there is another fascinating pond fish that's closer to home.

At first the humble Tench (Tinca tinca) might not seem like much, but this unique and hardy fish is actually an unsung master of adaptability and survival. Native to almost all of Europe as well as large parts of Western Asia, there is actually only one species of Tench with no subspecies currently accepted. In fact the Tench is so unique that it is regarded as the only member of its own subfamily, the Tincinae.

Not only can it hibernate in the winter but it can also “aestivate” in the summer, meaning that when temperatures get too high and arid conditions threaten, it can enter a period of metabolic dormancy to avoid drying out. Coupled with its ability to tolerate very low oxygen levels and even brackish water, this means that in hotter summer months, the Tench is often the only inhabitant of smaller pools.

The Tench has been part of European culture for so long that, unbeknownst to many modern-day fish-keepers, a wealth of fable has grown up around this deceptively familiar fish. While the Romans weren’t very partial to its taste, calling it a food fit only for the poor, it became valued in other ways. The extraordinarily thick layer of mucus on its body gave rise to superstitions about its abilities as a “fish doctor”, with other injured fish rubbing against the mucus to heal themselves.

The myth even goes so far as to say that predatory Pike and Perch will not feed on Tench out of “gratitude” for their healing services, but this is unfortunately as much of a baseless superstition as the belief that strapping a Tench to various bits of your body will drive away everything from jaundice to headaches to plague and fever.