Three billion people depend on fishery products as their main source of protein. Fishing is also the principal means of subsistence for nearly 900 million people on the planet. While this activity appears to be a pillar of the world economy, it also affects the marine environment, particularly marine mammals.
How fishing affects cetaceans ?
Attracted by the same prey, it is not uncommon for cetaceans and humans to find themselves around schools of fish. Thus, while hunting herring alongside tuna, dolphins, for example, can get caught in the nets of tuna seiners.
Driftnets and various fishing lines also generate bycatch. These catches are called "accidental" since these protected species are not targeted. They are not taken on board and their remains are thrown back into the water.
While dolphins can die of asphyxiation, unable to free themselves from fishing gear to come up to the surface to breathe, more robust animals such as whales may escape, but at the cost of deep scars.
It is estimated that each year, 300,000 cetaceans are captured accidentally throughout the world. This phenomenon is the greatest cause of mortality for cetaceans in the world.
More than 90% of fish stocks are fully exploited or overexploited. Some of these stocks are the main source of food for several cetacean species. The reduction in their food resources can lead to the displacement of populations to more food-rich areas, or even the local disappearance of certain populations.
Cohabitation between cetaceans and fishermen can be difficult...
Competition for resources has exacerbated tensions in many regions of the world. Indeed, cetaceans sometimes take fish directly from fishermen's nets or lines, causing a significant loss of income and deterioration of fishing equipment that is expensive to repair or renew. This is called depredation.
…but sometimes harmonious.
In several regions of the world, a voluntary collaboration has been established between dolphins, who bring the fish toward the shore as the artisanal fishers cast their nets. The fishers catch more fish, and the dolphins catch their disoriented and isolated prey more easily.