Bottom trawling is good

02:56, Nov 30 2010

In a study sure to enrage extreme greenies everywhere, scientists in California have discovered that bottom trawling may not be systematic environmental pillage.

In fact, it may even be good for the seabed.

As reported in the latest issue of New Scientist, a five-year study by The Nature Conservancy is looking at the impact of bottom trawling on a strip of seabed 23km off Morro Bay, between Los Angeles and Monterey.

The scientists marked out eight plots, each 1km by 330m, that had not been trawled for a decade or more. Four would remain untouched and four would be trawled.

Last year the trawling zones were hit twice and  photographs of the seabed taken after each trawl. More photographs were taken six and 12 months later.

"Early signs indicate that marine life survived, even thrived, after last year's trawls," the New Scientist wrote. "Donna Kline, a fish ecologist at California State University in Monterey Bay, thinks that far from destroying a habitat, the trawl may have created a new one by etching grooves into the flat bottom."

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This would be a remarkable conclusion, but it is way too early to be sure. A more intensive series of five trawls in each zone took place last month and time must pass before the impact can be assessed. Any conclusions may also be inapplicable to New Zealand seas.

Still, it is an interesting study.

In New Zealand's exclusive economic zone bottom trawling is banned in 17 deep sea areas totalling 1.2 million sq km, as well as around several underwater features such as seamounts.

This is a wise precaution, but it's also clear we know woefully little about our marine ecology.

Part of the deal with the fishing industry to close those areas involved industry paying a third share of costs to research deepwater seabed environments - ie, a maximum of $330,000 a year.

That's not a lot, frankly. Given the industry's strong financial interest in understanding the sea, I would have thought one third of research costs was woefully inadequate.

However, let's keep things in perspective. Many people think of farming as a clean green countryside activity, whereas farming has obliterated the natural environment almost completely. A farm is not countryside, it is a factory without a roof.

Is this a bad thing? No. We need farms to feed us. With farms we can sustain ourselves using less land than we'd need if we were all hunter gatherers.  

There's a lesson there for the fishing industry. If it's not prepared to invest in researching wild fisheries, aquaculture should be a priority.

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