The gulper exclusion proof-of-concept trial has been successful. Read on to learn more and see trawl footage taken at 500m depth.
Harrisson’s dogfish and southern dogfish are part of a group of sharks called Upper-Slope Dogfish or Gulper Sharks. To rebuild populations of gulpers AFMA has put a series of closures in place. These closures are equivalent in area to about 25% of total dogfish habitat available in the fishery. Many of these closures overlap with grounds where royal red prawns are caught in the South East Trawl Fishery off Sydney.
In early 2014 SETFIA announced that it would trial a grid that aimed to catch royal red prawns but exclude gulpers. The project team commissioned something they named a Gulper Exclusion Device or GED. These are widely used in other Australian prawn fisheries.
A GED is an angled aluminium grid in the net that will deflect gulpers and other large fishes up and out of the net unharmed, while the smaller royal red prawns pass through to be caught (see image below). Underwater cameras were used to understand how gulper sharks and other larger fishes are ejected from the trawl net (see video above taken at 500m).
The footage clearly shows that the device works in that it ejects skates, small sharks and other fishes such as pink ling while allowing most prawns to pass through and be retained in the trawl’s codend. Only four shots were completed and these were not in gulper habitat so none were encountered.
The Association and AFMA will now consider further research which aims to allow trawl fishing with a GED inside the Sydney gulper closure.
SETFIA thanked AFMA for funding the work, net-maker David Guillot who installed the GED, Wallace Hill the net maker and the Bagnato brothers who operate the survey vessel Francesca.
Final report on the project: