Seabirds are virtually always drawn to the offal around trawlers.
A simple, cheap intervention has enabled South Africa’s commercial deep-water hake trawl fishery to reduce by-catch seabird fatalities by up to 99%. Seabirds have a slow breeding rate and are one of the most threatened groups of birds in the world, and because of this, commercial fisheries are a major cause of decline in global populations.
In the 1990s, longline fishing was identified as the main threat to seabirds, but since then significant mortalities caused by demersal (close to the sea floor) trawl fisheries have been documented. During trawling operations the birds are injured and accidentally killed by collisions with cables and net entanglements. In 2004 the deep-water hake trawl fishery, the most commercially valuable fishery in South Africa, achieved Marine Stewardship Council certification.
This meant the industry had to assess its environmental impacts and reduce associated risks. The most effective way to avoid bird by-catch would have been better management of the discarding of fish offal by trawlers, but this involved retrofitting the vessels and was regarded as too expensive. Instead bird-scaring lines were attached to trawlers, on the advice of BirdLife South Africa’s Albatross Task Force.
The lines cost less than R2000 each and consist of long streamers attached to a vessel at 2m intervals, providing a visual deterrent to keep the birds away from the trawler and cables. Research released by BirdLife last week shows the bird-scaring lines helped to reduce all seabird mortalities caused by hake trawlers by 90% between 2006 and 2010 —from about 9 300 seabirds killed in 2004 to 2005 to 990 in 2010. The reduction in fatalities among albatrosses, of high conservation concern because of their low numbers, was 99% — from an estimated 7 200 annual deaths in 2004 to 2005 to less than 100 annual deaths since 2009.
“Bird-scaring lines are a trivial expense for a measure that reduces fatal interactions with threatened seabirds so effectively,” said BirdLife’s Ross Wanless.
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