|
Les mammifères marins jouent divers rôles dans les écosystèmes marins, que l'on connaît mal toutefois dans la plupart des cas. Les mammifères marins peuvent être des prédateurs d'un niveau trophique supérieur s'alimentant d'autres mammifères marins (morse, orque) et de poissons (orque, phoque du Groenland, phoque à capuchon) ou être d'un niveau beaucoup plus bas, par exemple ceux qui s'alimentent d'organismes benthiques (loutre de mer, morse, baleine grise) et d'invertébrés pélagiques (phoque du Groenland).
|
|
Marine mammals play a varied role in marine ecosystems, which in most cases is poorly understood. Marine mammals may act as top level predators feeding on other marine mammals (walrus, killer whale), on fish (killer whale, harp seal, hooded seal) or they may feed at much lower levels on benthic (sea otter, walrus, grey whale), and pelagic (harp seal) invertebrates. In some cases marine mammals play a very clear role in structuring marine ecosystems. For example sea otter predation on sea urchins reduces grazing pressure, which allows the proliferation of kelp bed forests. This leads to the development of new ecosystems and an increase in marine fauna density and diversity. As top level predators, marine mammals are also accused of having a negative impact on commercial fisheries through damage to fishing gear such as nets and traps, transmission of parasites, that must be removed before fish can be sold, and finally consumption of fish limiting their availability to fishermen.
|