Old McDonetsk Had a Farm
Being situated inland, the Chernobyl Nuclear Power Plant depended upon local rivers and a 22 sq/km (8.5 sq/mi) man-made cooling pond. The pond built adjacent to and connecting with the Pripyat River and the Kiev Reservoir was 18m (59 ft) deep and, due to its prime use, warmer than any natural lake in the region. Obviously such a resource should not have been wasted and thus, a commercial fish farm was established.
(image via: Maxim Nikitka-Mirovich)
Things were going swimmingly (unless you knew the source of your fresh, farm-raised fish) until April 26th, 1986, when Reactor #4 exploded during the course of an ill-advised test. Radioactive fallout spread over significant portions of Europe and the cooling pond, just 1.5 km (just under a mile) from the reactor complex, was showered in radionuclides. This probably wasn't good for business at the fish farm, and to their credit Soviet authorities shut it down… but it wasn't abandoned.
Almost immediately after the initial cleanup from the disaster was completed, a long-term radiological study of the local environment – specifically the fish and other organisms in the cooling pond – commenced. The study ran until 1996, outliving the USSR itself, and provided useful information on how vertebrates are affected by radiation in their environment over time.