There are a number of impacts that fishing has on the environment. These impacts range from habitat damage, through fishing techniques and pollution, to disruption of the food web through overfishing and ghost fishing.
One of the ways that fishing affects aquatic habitats is by trawling when aiming to catch demersal fish. This is because heavy nets are dragged across the sea bed; churning it up and destroying any of the natural habitats there. DEGREE is a research project funded by the European Union. They have redesigned, and successfully trailed, fishing gear that can reduce the impact of trawling on the environment.
As fish stocks are reducing, ships have to be out at sea for longer to catch the same quantities as before. The factory ship is an example of a vessel which has been designed for such a purpose. These ships are very large and use up a lot of fuel which causes the emission of exhaust fumes that lead to the formation of nitrogen oxides which can cause acid rain and damage habitats. They also emit CO2 which can lead to increased global warming, land ice melting and flooding of habitats. Additionally, the effluent from processing the fish is discharged into the sea where it is broken down and can cause deoxygenation (a problem in waters where the waste can’t disperse easily). This can affect marine habitats and sea organisms.
Also, fishing vessels may have toxic antifouling paints which can cause water pollution. A solution to this problem is to use non-toxic paints.
Overfishing means that the populations of bycatch species are reduced as well as the populations of catch species. This can affect food webs. For example, competitor species may become more common as there may be a greater amount of their food species available and a reduction in the numbers of their predators. Various methods have been implemented to reduce bycatch: reflective metal discs are used on drift nets to help dolphins detect their presence and the weighting