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Friday 17 February 2012

Trawl tracks on the seabed.

Image courtesy of Koen aboard the Cefas Endeavour.

Both blogs aboard the Cefas Endeavour are continuing to give an insight into the work of the research teams, especially the use of multi beam sonar. The image above is taken from a grey-scale rendering of the seabed showing clearly the tracks from a trawler working in the same area as the survey vessel.


This post immediately attracted a comment: This image actually goes to show just how little of the seabed is touched by the trawlers. We simply do not have enough trawlers left in the EU fleet to cause the widespread impacts alleged by eNGOs!


It would be useful to have an indication of scale on the image - given the stability of the track scribed on the sea bed these tracks are those of a beam trawler - nicknamed a chain-harrow gang by some - but then why does a farmer use a chain harrow over his fields?


From the web site Master Farm Services:
Reasons for harrowing? Several reasons for harrowing are listed below: 
- Pasture renovation; breaking up & levelling heavy soil. 
- Root aeration; for better water infiltration & growth. 
- Works in fertiliser to both spread & maximise effectiveness. 
- Surface levelling in equestrian centres, race tracks & running tracks. 
- Stimulates growth by aerating & loosening thatch.

Not often we turn to our land-based welly-booteed cousins for help!