Otters breed for second consecutive year in the Tordera basin

Llúdrigues / Nutrias

Otters have bred in the Tordera basis for the second year in a row, according to researchers of the “Otter monitoring and research project in the Besòs and Tordera basins” of the Rivus Observatory, coordinated by the ICTA-UAB and the Rivus Foundation.


This is a remarkable fact, since the reproduction of this mammal is one of the best indicators of the good state of the fluvial systems and of their correct ecological operation. In total, five family groups have been identified in the Tordera basin and one in the Besòs basin.

The monitoring, carried out by biogeographer Arnau Tolrà under the supervision of Dr. Jordi Ruiz Olmo, began during the autumn of 2018. During this period, they have confirmed the reproduction of the otter for two consecutive years in the Tordera basin (2019 and 2020), and in the Besòs basin during 2020, as well as quantified a total population of around thirty specimens. The current population is approximately 10 otters in the Besòs basin and at least 20 in the Tordera.

The Rivus Observatory, coordinated by Dr. Sonia Sánchez-Mateo, researcher at the ICTA-UAB and technician at the Rivus Foundation, is an interdisciplinary research project whose main objectives are to define biological, hydromorphological, hydrological and physicochemical indicators of the state of river ecosystems; carry out medium and long-term monitoring, and make them widely known to society through the Environmental Education, Communication and Training Program (Proeco). The project has been developed in collaboration with the Barcelona Zoo Foundation and the Besòs Tordera Consortium.

Therefore, the reproduction of the otter in the two basins after its local extinction at the end of the past century represents one of the best indicators of the good state of the river systems and of their correct ecological functioning. The breeding areas of the otter coincide with the river sectors that enjoy the most natural river dynamics, a greater availability of shelters on the shores and heterogeneity of environments, with the presence of elements such as dead wood inside the channel. This environment guarantees greater tranquility and a greater abundance of and accessibility to food.

The reproduction of the otter is a large step towards the recovery of the species in Catalonia and the best evidence of the restoration of the ecological functions for these rivers in particular, for which it is necessary to continue promoting measures of conservation of these habitats, especially in the middle and lower courses.