Bottom Trawling

PHOTO BY SAVE OUR SEA FOUNDATION

Bottom trawling is a industrial fishing method whereby huge nets with heavy weights are drag across the seabed, scooping up everything in its path. This method is usually used in catching fishes that live on the seafloor, such as shrimp, cod, sole and flounder (Marine Conservation Institute, 2014).

One consequence of bottom trawling is that it rakes up large amount of sediments on the seabed, which adsorbs contaminants in the ocean. Frequent trawling causes plume of sediment floating above the seabed and can be seen from pictures captured from the sky. Research has shown that marine life (such as mussels, benthic, prawns and flatfish) living on the seabed are particularly at risk as they end up adsorbing the contaminants ( European Commission, 2012). 

Landsat image showing pervasive sediment plumes

PHOTO BY SKYTRUTH

Another impact of bottom trawling is its destruction to the seabed habitat. The method is unselective and besides the targeted species, many other species are caught and thrown away as by-catch. Corals, which serves as a habitat for many other marine life, dominate the by-catch, leaving the ocean floor bare. Since coral reefs are estimated to only grow by millimeters per year (Tracey et al, 2007), recovery of coral ecosystem will be very slow. This leaves the marine ecosystem permanently damaged. 

PHOTO BY NOAA

 References:

Marine Conservation Institute. (2014). Destructive Fishing. [ONLINE] Available at: https://www.marine-conservation.org/what-we-do/program-areas/how-we-fish/destructive-fishing/. [Accessed 29 September 14].

European Commission. (2012). Pollutants released by seafloor trawling affect marine life . Science for environment policy, [Online]. 309 (12). Available at:http://ec.europa.eu/environment/integration/research/newsalert/pdf/309na3_en.pdf [Accessed 29 September 2014].

Tracey D.M. et al. (2007) Deep-sea scleractinian coral age and depth distributions in the northwest Atlantic for the last 225,000 years. Bull Mar Sci 81:371–391