Dictionary of Ichthyology  

Ruhle trawl = a net designed to catch haddock in preference to endangered cod. The mesh size is enlarged allowing cod to escape from the forward end of the net, and the net fishes to allow for frightened haddock tending to swim up, while cod dive for deeper water. Named for the designer, Phil Ruhle, lost at sea when his vessel sank off New Jersey.

Wikimedia Commons: http://www.nefsc.noaa.gov/press_release/2008/News/NR0824/ruhlelarge.jpg

Canadian Museum of Nature