Trawls are designed and rigged to work near the bottom. According to the type used, one may distinguish: low opening trawls, especially adapted to the capture of demersal species, such as beam trawls and shrimp, sole or nephrops trawls; and high-opening trawls, suitable mainly for the capture of semi-demersal or pelagic species. In bottom trawls, the lower edge of the net opening is normally protected by a thick groundrope ballasted with chain sinkers and often covered with rubber discs, bobbins, etc. Nedelec and Prado (1990).
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