What is the disadvantages of mariculture?

It depends on what form of aquaculture. species such as salmon and those that are carnivorous and actually require feed derived from wild fish. The amount of captured fish to raise farmed fish is massive (something like a ratio of 4:1) this then is a huge issue for the sustainability of wild fish stocks.

Beyond this many of the farms can be environmentally degrading affecting local fish with disease, escapment etc. additionally the seabed can become a wasteland. It should be noted that the extent of effects are limited by the location and size of farms.