Around twenty fish species have travelled from the waterways that feed into the canal and now call the canal home. You will find carp, bream and many carnivirous fish such as pike-perch, perch, pike and black bass, and even silurid fish in some canal pounds (the section of canal between two locks). The canal is heaven-on-earth for fans of fishing! There are also shellfish here such as swan mussels (freshwater mussels) and corbicula (freshwater clams). Amphibians and reptiles can also be added to the list, including the viperine water snake which is an excellent swimmer in wetlands.
Biodiversity is taken into account when any work is done on the canal and on its banks.
Since 2008, Voies Navigables de France has established a 'zero phyto' approach and does not use any chemicals along the waterway. Alternative techniques are sometimes tested. Whenever it is possible, mowing is delayed along the banks (after spring or even at the end of the summer), to protect the areas used as refuges for small animals and pollinating insects.
The use of plant-based engineering techniques is encouraged thanks to planting aquatic plants whose roots prevent the banks from eroding.
Waste from human activities is the main cause of deterioration in the quality of water. Hydrocarbons from navigation or from the roads (via run-off water), nitrates and pesticides from farming activities, unwelcome discharges and direct disposal from boats of grey waters from cleaning or black water from toilets all impact the quality of the water.
Regular monitoring of the quality of water was set up in 2017. Water is regularly sampled and analysed at the 16 stations dotted along the Canal du Midi.
Biodegradable oils and grease are used on all the canal engineering structures. VNF also works to prevent any accidental pollution, especially due to hydracarbons (from boat discharges or damage) by relying on assistance from the fire service or by using their own equipment (barriers, devices to absorb hydrocarbons, etc.).
VNF and the local authorities work together to clean the canal all year round. VNF takes care of removing any heavy waste and shipwrecks. Together with the management teams from the ports, local authorities and water boards, VNF has rolled out a project to create around thirty decantation stations along the canal (one every 20-30 km), to collect wastewater from boats.