Report | September 1, 2022
Exploring alternatives to Europe’s bottom trawl fishing gears
The effects of bottom trawling are wide-spread in the European Union (EU), seriously affecting the seabed, its associated ecosystems, and its carbonstoring capacity, as well as fuelling the overexploitation of fish stocks. Phasing out bottom trawling might at first seem unimaginable given it landed 7.3 million tonnes of marine life between 2015-2019, which represent 32% of the EU’s total landings and a great variety of species. There exist, however, alternative gears to partly replace bottom trawling. These alternative gears each have their own associated impacts that need to be considered, especially with regard to bycatch of sensitive species. In order to match bottom trawling’s current landings, these alternative gears would need to be scaled up.
To avoid scaling up their associated environmental impacts, a reduction of fishing effort should be considered. The species most landed by bottom trawlers are sandeel and cod, both overfished stocks that could benefit from reduced fishing effort. Sandeel and other species landed in high quantities by bottom trawlers are used for fish feed in aquaculture; reducing fishing efforts as a result of the transition to alternative gears would therefore not necessarily have consequences for current human food supply. It would, however, be of great benefit to the environment and associated dependent coastal communities. In the transition away from bottom trawling, the socio-economic wellbeing of the people employed by the trawl fleet needs to be ensured by designing and implementing effective just transition programmes
Bottom trawlers destroy habitats by incidentally killing bottom-living organism and by causing physical disturbance to bottom sediments, thereby ruining seafloor integrity. They also hinders the capacity of the ocean to mitigate climate change by altering or triggering geochemical processes such as the release of nutrients and chemical substances, including blue carbon stored in coastal areas, thereby affecting the functioning of the entire ecosystem (Olsgard et al. 2008; van de Velde et al. 2018; Luisetti et al. 2019). If these ecosystems are degraded or lost, they may release part of their carbon back into the atmosphere (Hilmi et al. 2021, Epstein et al. 2022, Sala et al. 2021). The recovery time for seabed communities affected after a single pass of a beam trawl has been estimated at between 7.5 and 15 years (Pedersen et al. 2009). Bottom-trawling vessels also emit three times more CO2 than non-trawlers, resulting in one of the highest carbon footprints for seafood – and indeed for any protein source – thereby contributing directly to climate change (Clark and Tilman 2017). Switching to alternative gears and practices to avoid bottom trawling presents an opportunity to conserve fisheries resources and protect marine ecosystems and the climate; these are central to the European Union’s Biodiversity Strategy for 2030 (European Commission 2020) but also to the European Green Deal’s objectives to make Europe climateneutral and protect our natural habitat in order to deliver the wellbeing of people. In this report, we quantitatively describe the impacts of bottom trawling and potential alternatives that exist in the EU.
We used the EU’s Scientific, Technical and Economic Committee for Fisheries (STECF) 2015–2019 catch-composition dataset (STECF 2020) to describe bottom trawling in the EU and identify potential alternatives to bottom trawling, if it were phased out. It is important to note that given the methods (see end of document) used to identify potential alternatives to bottom trawling, the alternative gears identified imitate the catch composition of bottom-trawling gears. Such alternatives are not necessarily the lowest environmental impact gears (which usually are hand line, pots and traps, creels), but instead non-trawl gears that can catch species similar to trawls; they therefore might have some negative environmental impacts, such as bycatch (purse seines, gillnets, longlines) (Zhou et al. 2010).
Herein we use “bottom trawling” to refer to all mobile bottom-contact towed gears, including beam trawl, bottom otter trawl, bottom pair trawl, otter twin trawl, boat dredges, and mechanised dredges, all of which involve beam trawling, demersal trawling and/or seining, and dredging techniques.
