The rivers of Spain and Europe have undergone numerous changes over time, mainly due to the construction of dams, weirs and other infrastructures that, although they have contributed to human development, have meant serious obstacles to aquatic lifeOne of the main victims are migratory fish, such as salmon, trout, and eel, which depend on free movement through rivers to complete their life cycles.
Restore river connectivity has become a priority for environmental management agencies and biodiversity experts. In this context, fish passes, also known as ladders, ramps, or crossing devices, play a crucial role in restoring river habitats and recovering declining species.
Why are fish passes necessary? River fragmentation due to artificial barriers prevents many species from reaching spawning or breeding grounds. This can result in drastic decline in populations, as has happened with salmon, which need to swim upriver to reproduce in clean, well-oxygenated waters.
How fish passes work
Un fish passage It consists of a system of channels, ramps, stairs or tunnels designed with gentle slopes and moderate currents so that fish can move around barriers. The structure It must be adapted to the morphology of the river and the target species, taking into account their needs and swimming capacity.
The most common models are the stairs de peces (with a succession of small jumps or pools), ramps with controlled currents, and lateral bypasses, which allow the barrier to be circumvented. Mechanical lifts are sometimes even used on large dams. The right design It is essential, since poorly adapted solutions can be ineffective or even dangerous for wildlife.
Positive impacts of fish passages
The installation and improvement of fish passages contributes directly to the stability of populations de peces migratory. It has been proven that the removal of obstacles and the creation of safe routes They promote reproductive success, access to key habitats, and the recovery of endangered species.
On an ecological level, restore the natural flow of rivers It improves water quality, increases biological diversity, and helps restore essential ecological functions, such as nutrient transport and invasive species control. It also reduces mortality associated with failed dam removal attempts, benefiting both species and river ecosystems as a whole.
Challenges and future in river management
The correct implementation of fish passes It requires detailed planning and collaboration between administrations, scientists, engineers, and water users. Much work remains: it is estimated that thousands of barriers exist on the peninsula that hinder fish migration, many of them obsolete or no longer in use.
The challenge is Integrate river restoration into water management plans, investing in solutions that truly allow us to recover the mobility of species and the natural processes of rivers. It is also important to raise awareness about the importance of keeping rivers alive and connected, as the environmental benefits impact the quality of rural and urban communities.
Recent experiences show that when you bet on remove obstacles and create effective steps, not only is biodiversity protected but also opportunities for sustainable tourism, recreational fishing, and environmental education are opened.
The use of fish passes It is essential to halt the loss of biodiversity and restore the health of our rivers, ensuring the survival of such iconic species as salmon and promoting more resilient and balanced aquatic ecosystems.
