The European Otter: A Living Indicator of Clean Rivers in Greece

The European otter (Lutra lutra) serves as one of nature's most reliable indicators of environmental health, particularly regarding water quality in Greek rivers and streams. This semi-aquatic mammal, once widespread throughout Europe, has become an important bioindicator species whose presence or absence tells a compelling story about ecosystem integrity. In Greece, the otter inhabits various freshwater habitats including rivers, lakes, marshes, and coastal areas. Its requirements for survival are stringent: clean water, abundant fish populations, undisturbed riparian vegetation, and minimal human interference. When otters thrive in a waterway, it signals that the entire aquatic ecosystem is functioning well. The otter's role as a pollution indicator stems from its position at the top of the aquatic food chain. As apex predators, otters accumulate contaminants present in their prey, making them particularly sensitive to water pollution. Heavy metals, pesticides, and other toxic substances concentrate in their tissues, affecting reproduction and survival rates. Greek rivers hosting otter populations include the Evros, Nestos, Axios, and Aliakmonas in the north, as well as various waterways in western Greece. Conservation efforts focus on protecting riparian corridors, reducing pollution, and maintaining connectivity between habitats. The presence of otters also indicates healthy fish populations, adequate prey diversity, and suitable breeding sites. Their dens, called holts, require undisturbed riverbanks with dense vegetation cover. The species serves as an umbrella indicator—protecting otter habitat automatically preserves countless other species sharing the same ecosystem. Monitoring otter populations through sprainting surveys and camera traps provides valuable data about water quality trends over time. Recovery of otter populations in previously degraded rivers demonstrates successful environmental restoration efforts.