How a fishing method harms marine life and the climate

So-called bottom trawling, in which heavy nets are dragged across the seabed, costs society in Europe up to 16 billion euros a year, writes a research team from the USA and Canada in the journal "Ocean & Coastal Management". The economic costs of this practice exceed the profits from this type of fishing by around 12 to 90 times.

The main reason for this is the massive impact on the climate caused by the release of carbon stored in the seabed. For the study, the scientists analyzed data from more than 4,900 such fishing vessels flying the European flag, which spent an average of 5.5 million hours a year in the waters of the EU, the UK, Norway and Iceland from 2016 to 2021.

While the net profits for the industry are estimated at around 180 million euros per year, the costs for the general public amount to around 2 to 16 billion euros annually, according to the study. The fluctuation range results from different assessments of the social costs of one tonne of carbon dioxide (CO2).

Fishing in marine protected areas too

According to the study, the stirring up of sediment released around 112 million tons of CO2 annually between 2016 and 2021. This is almost a third of the global emissions from the seabed caused by bottom trawling, which the team led by Katherine Millage from the environmental organization Pristine Seas estimates at up to 370 million tonnes per year.

The authors are particularly critical of the ecological consequences of the practice. According to the analysis, around 23 percent of bottom trawling in Europe took place in marine protected areas. In countries such as Germany, the Netherlands, Belgium, France and Spain, it was even more than 25 percent.

Ban on bottom trawls in European protected areas?

The heavy nets, some of which are as large as twelve Boeing 747 aircraft, plow up the seabed and destroy important habitats. The researchers emphasize that this has a massive impact on the ability of fish and other marine life to regenerate. Despite the high effort involved, the fishing method only contributes to two percent of the animal protein consumed in Europe, according to the researchers.

The authors of the study therefore call for a ban on bottom trawling in protected areas as a first step. In addition, a general halving of these activities could maximize the social benefits and revive the overfished seas. Greece and Sweden have already announced that they will ban the practice in their protected areas by 2030 - this is also in line with the European Commission's general action plan.

Estimate: 300,000 whales and dolphins die in nets worldwide

The research team also points out that up to 75 percent of the sea creatures caught in these nets are bycatch. This can also include dolphins and whales that chase fish in the nets.

The animal welfare organization Whale and Dolphin Conservation (WDC) estimates that more than 300,000 whales and dolphins worldwide suffocate in fishing nets every year - albeit in different types of nets. The humpback whale that stranded several times in the German Baltic Sea also reportedly became entangled in a net, presumably a gillnet.