“We’ve already talked about the damage acidification inflicts upon reefs. Also of consequence is the destruction inflicted by the weaponry of the industrial fisheries, particularly the bottom trawlers. Some people refer to those heavily weighted nets with their rollers and rockhoppers as ‘ocean bulldozers’.
The image is apt.
[T]hose rollers have the power to push aside twenty-five-ton boulders. They pulverize everything in their path, crushing deep coral, grinding boulders to rubble, wiping out populations of old fish and other creatures, which will take generations to recover, and leave behind a flat, lifeless moonscape of gravel and sand.
This destruction is often compared to clear-cutting a forest. But it’s actually far worse. Calculations show that the total area of seabed trawled by the world’s fishing fleet each year is 150 times the area of forests cut. Studies have estimated that each year, trawl nets disturb a seabed area twice the size of the contiguous United States.
And it’s not just the sea bottom that suffers. Those silt clouds–the blooms of fine-grained sand churned up by the trawl nets, some as much as seventeen miles in diameter–are incredibly destructive as well. They can change the chemistry of the water itself, releasing pollutants trapped in the seafloor mud. And those suspended near-microscopic grains of silt can enter and clog the breathing and feeding systems of all kinds of marine life, from coral polyps to sea turtles.
It can take decades, even centuries for a seabed to recover from a single pass of a bottom trawl net. The before-and-after images of a bottom-trawled reef forest are heartbreaking.
But to the fishing industry, this kind of destruction is nothing more than collateral damage, as are the millions of tons of unwanted fish and other forms of marine life that are accidentally caught in their nets or snagged by the hooks of long-liners every year. No one knows the true amount of the dead and dying sea life that is discarded by fishermen–after all, on the vast majority of fishing boats, there’s no one there to watch. Some scientists believe bycatch worldwide could be as much as a third of the landed catch–with the most destructive fisheries discarding 80 to 90 percent of their catch. Some 20 million tons per year counts only the creatures that are actually hauled up from the sea and thrown back. There’s no telling how many creatures are maimed or killed by those nets and hooks but never get hauled up. One thing we do know for sure–the reported totals of discarded fish are grossly inaccurate.
We also know that sharks make up huge numbers of bycatch victims–some 50 million a year are accidentally snagged by trawlers, longlines, and gill nets. That’s half of the world’s total shark catch.
And those cod that are trying to make a comeback in the Georges Bank region off New England? As much as 70 percent of the remaining cod population in those waters in recent years has been lost to bycatch…
Another grim, haunting image is what the industry calls ‘ghost nets’–drift nets, gill nets, and purse seine nets that accidentally get detached from boats. Written off as lost, these floating death traps drift eerily beneath the surface of the high seas, entangling and killing whatever creatures are unlucky enough to cross their paths. Again, there is no way of knowing exactly how many fish and other animals die in these nets, or, indeed, how many such nets are out there, but guesses are that the number is in the millions.”