Trawling
Trawl Net © Sarah Lelong, Marine Photobank.

This fishing method consists of using bottom otter trawl equipment. It consists of a body, usually composed of 2-4 panels of mesh, closed by one or two cod-ends and with lateral wings extending forward from the opening. The Otter trawl is kept open horizontally by two otter boards. A boat can be rigged to tow a single or two parallel trawls.

Deepwater fishing occurs between 200-1650m in depth, and catches a number of deep sea sharks, including the Leafscale Gulper Shark (Centrophorus squamosus) and Portuguese Dogfish (Centrophorus coelolepis). However many other elasmobranchs are also caught, such as rays and chimaeras. Both of the above species are taken in the several mixed trawl fisheries, and as bycatch in other fisheries like those within the angler gillnet fishery in the Northeast Atlantic. Abundance indices from Scottish survey from 2000-2010 indicate a decline since 2000, with estimated landings in 2009 for the Portuguese Dogfish and Leafscale Gulper Shark were 140 tons. In addition historical commercial CPUE (catch per unit effort) in the Northeast Atlantic suggests this species was severely depleted. There is now a zero TAC (Total Allowable Catch) for these species in the Northeast Atlantic; however sharks are still caught as bycatch. In Australia Centrophorus spp catch rates from 126 to 0.4kg/h from 1976-1997.

Very little is known about the biology of deep water shark species. However the low productivity of many deep water fish and the apparent sensitivity of deep water sharks to exploitation suggest that they may be even more at threat than pelagic species.