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HomeLifeBottom Trawling Effects Destroying BILLIONS of Acres of Sea Bottom

Bottom Trawling Effects Destroying BILLIONS of Acres of Sea Bottom

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Last month’s chapter of our commercial fishing series highlighted long-line fisheries which set some 10 BILLION hooks per year in seas around the world.  But, long-line fishing is only one of the contributors to the 190 BILLION pounds of fish hauled aboard commercial fishing boats in a year’s time.

While long-line fishing has a horrid record of catching and snagging multiple millions of non-targeted species such as dolphin, whale, sea birds, shark, and sea turtles, it does not damage the sea bed in most circumstances.  What does destroy the sea bed and bottom habitats, life sustaining coral reefs included, is bottom trawling.

According to Dr. Les Watling at the University of Maine’s Darling Marine Center, 2.4 BILLION acres of sea bottom are destroyed each year by bottom trawling and dredging commercial fisheries operations.  On land this kind of wanton destruction can be likened to clear-cutting a forest, and we know there are massive amounts of research demonstrating the long-term effects of clear-cutting.  Unfortunately, much of the 2.4 BILLION acres of sea bottom destroyed each year has not been explored; nevertheless, scientists around the world have no doubt that species yet undiscovered are being lost while the full effect of this destruction is now only beginning to surface.

Bottom trawlers, either in pairs or singly, drag huge nets along the bottom of all our oceans and seas, sometimes as deep as 3,000 feet, at speeds up to four knots per hour that scoop, knock down, and dig up every living thing in their paths.  The bottoms of the nets are heavily weighted, with the weighted lines being several inches to feet in diameter so that they remain on the bottom while the upper sides of the nets carry floatation lines to maintain the opening.  Weighing several tons, the bottom weights not only mow down all in their paths but they also dig deep furrows in the ocean bottom.  Boards known as otter boards or doors are used to spread the opening of the net and these boards act as huge, tremendously-heavy plow blades.  From their wide mouths the nets taper back in a V-shape as they reach the “cod-end” where the fish and any by-catch are retained.

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As these trawl nets are dragged over the bottom, corals are cut down and crushed, as is any sea weed growing in the nets’ paths, bottom sediments are dug up and redistributed, creatures living in the sediments are scooped up, crushed, or set adrift, and any sea life suspended or swimming in front of the gaping trawl nets is captured with little chance of escape.  Dragging a trawl net across a sea bed is tantamount to setting a bull dozer blade so that it takes down anything and everything in its path both on the surface as well as many inches below.

While destructive at any depth, those nets dragging the bottom thousands of feet down are plying cold waters where life is even more delicate and slower growing than that at much lesser depths.  Although we know that warm water corals grow only fractions of an inch per year and that our modern coral reefs began growing some 10,000 years ago; cold water corals are only now being studied and it is generally accepted that cold water corals grow much slower than those species found in warmer water.  Some believe that they may be so delicate and so slow to reproduce that their recovery from one pass of a bottom trawl net may be impossible.

And, as we all know, whether warm water or cold water, coral reefs are the nurseries and protectors of multitudes of fish and other sea life.  Without corals to nurture and protect them, fish disappear and with them go food resources as well as the beauty that calls so many of us to the sea.

According to Ibrahim Thiaw, Director General of the World Conservation Union, 80% of the catch brought up in one haul of a bottom trawl net is by-catch and thrown dead or dying back into the sea.  Elias Chin, Vice-President of the Pacific island of Palau, a country that is considered to embody the diving experience of a lifetime, stated recently that bottom trawling is responsible for 95% of the destruction of underwater habitats.  The UN  Food and Agricultural Organization’s statistics compiled over many years demonstrates that a mere .5 percent, one half of one percent, of global fish catches is contributed by bottom trawling operations yet those operations are responsible for the devastation of 2.4 BILLION acres of sea bottom each year.

While calling for more study on the long term effects of such destruction and devastation, last September the Secretary General of the UN, Kofi Annan, called for the application of a “precautionary principle” and a ban on bottom trawling.  The nations of Palau, Norway, the United States, Japan, and Australia now ban bottom trawling in territorial waters; however, no such ban has been implemented in international waters although many are hopeful that a total moratorium will be issued soon.

One only needs to study the statistics:  2.4 BILLION acres of sea bottom lost each year; 4.4 MILLION pounds of often already endangered by-catch thrown dead or dying back into the sea in the Pacific alone… in order to provide .5%, one half of one percent, of the world’s consumable fish???  How can anyone object to a world-wide ban on bottom trawling for eternity?

Sustainability in Commercial Fishing Series

Becky Bauer takes an in depth look at today’s Commercial Fishing…

After many years of debate, the dogged determination of environmental groups, and scientific studies, the cause of many large-scale disasters—killing floods and landslides, starvation from lack of topsoil in which to grow food, air and water degradation—is now recognized as a threat to global security. This threat is the clear cutting of forests throughout the world.

I am certain you are wondering what clear cutting has to do with commercial fishing. A recent study conducted by Dr. Les Watling of the Darling Marine Center at the University of Maine states that commercial bottom trawling and dredging destroys 150 times more sea bottom than clear cutting destroys forests per year. 150 x 16m = 2400m acres of sea bottom per year; 2,400,000,000 acres, a number so large as to be almost incomprehensible.

Take a walk with us and begin to understand the repercussions of our actions…  AWARENESS and Understanding are the keys to sustainability.

After 30 years as a wild and domestic animal rescuer, rehabber, and educator in the states, Becky Dayhuff became a scuba instructor and journalist covering the marine environment in the Caribbean.

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Becky Bauer is a scuba instructor and award-winning journalist covering the marine environment in the Caribbean. She is a contributing photographer to NOAA.

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