Bycatch and release of pelagic megafauna in industrial trawler fisheries off Northwest Africa | Consortium for Wildlife Bycatch Reduction

Zeeberg, J., Corten, A., Graff, E.

The addition of a filter grid (inclined at ca. 20 degrees) that leads to an escape tunnel in trawl nets allowed 100% of rays and turtles to escape, 75% of manta rays, 40% of billfish and between 20-75% of sharks to escape.

http://www.xs4all.nl/~jzeebe1/Mauritanie_Zeeberg.pdf