This extract below is from a article in "The New Yorker" magazine. It is a must read in understanding some of the issues and I would really like to see this idea used in a few locations around the world. The article is lengthy and and touches on commercial fishing and longline fishing for shark fins.

Read all of the article here PAUL WATSON ARTICLE

The Farley, he decided, would cross the Pacific. It would stop in the Galápagos, where Sea Shepherd has an office that helps Ecuador’s police fight marine poaching, and then continue to the Grand Banks, off the coast of Newfoundland,
where the crew would dump into the ocean twenty tons of steel I-beams welded together to form large spikes. Watson called the spikes “net rippers,” because they would be designed to destroy bottom-trawling nets. He planned to scatter them across the Grand Banks seabed, and announce that they were there but not say where. The tactic—much like tree spiking, a nineteenth-century method of sabotaging logging equipment, which Watson helped revive in the eighties—would mix propaganda with action, so that fishermen would have to assume the worst.