Anti-trawling devices are a specific kind of artificial reef. Trawling is a controversial fishing practice which has attracted environmental, legal, and political objections. Anti-trawling devices have been invented, manufactured, and deployed to damage trawlers' nets and thus slow them down, force them to stop operating, or force them elsewhere. They are usually large concrete blocks with metal hooks or blades embedded in their tops. Anti-trawling devices are being used by environmental groups, fishermen, and sometimes even by governments.[1][2][3][4][5][6][7][8][9][10][11][12]
As with artificial reefs in general,[13][14][15] the actual effectiveness of anti-trawling reefs is understudied.[14][15] An Australian Government analysis anticipates very high costs and difficulty if they are removed.[16] If they are removed, however, they expect:[16]
They recommend changing permitting processes to account for the cost, and for whether removal is even feasible.[16]