Hoppers separate bycatch, ease effects of trawling

ISHERMEN in the east coast trawl fishery will have the opportunity to assess hoppers which separate prawns from bycatch and return the unwanted species to the sea alive, with the potential to mitigate the effects of trawling.

The use of hoppers on the rear deck of trawlers has been gathering momentum in recent years and is now extensive in the northern prawn fishery in the Gulf of Carpentaria, South Australia and Shark Bay in Western Australia.

The hoppers were originally developed by companies in Queensland and South Australia to increase the value of the prawn catch, but they have also proved to be ecologically friendly.

Up to 10 tonnes of mostly dead bycatch is thrown back into the sea for every tonne of prawns caught in the East Coast trawl fishery. However, where hoppers are used up to 70 per cent of the bycatch is returned alive and swimming.

The device enables prawns and other desired species to be sorted from bycatch quite naturally — the hopper is full of sea water and prawns sink to the bottom while other marine animals swim above them. A conveyor belt then gathers the prawns and delivers them to deck hands to be classed and packaged.

Throughout the process, the prawns are sprayed with sea water and are therefore still alive and in premium condition when packaged and snap frozen.

In the meantime the bycatch, which also remains in water throughout the procedure, is funnelled over the side or stern of the trawler and mostly escapes to swim another day.

The hoppers have caught the attention of prawn fishery fleets because of the premium prices that prime-condition prawns can demand, but the Great Barrier Reef Marine Park Authority says it is impressed by the technology because of the environ-mental advantages of returning the bycatch live to the ocean.

The director of the GBRMPA’s Fisheries group, Phil Cadwallader, said hoppers were reported as reducing mortality of bycatch by 40–70 per cent depending on the grounds being fished and the unwanted species being caught.

"Industry and fisheries managers have come a long way with the introduction of bycatch reduction devices. However, we would like to see the managers of the Queensland fishery pursue the feasibility of using hoppers in the trawl fleet to reduce the mortality of fish and other organisms taken on board, so they can be returned to the sea alive," he said.

"The current generation of BRDs is estimated to reduce bycatch by an average 20 per cent, so if the survival of bycatch taken on board can be increased, then the overall impact of trawlers on fish and other similar animals can be decreased quite substantially.

"Hoppers were originally developed primarily as a way of enhancing commercial returns to fishers by producing high value product because it is alive as it’s being snap frozen, but the effects on the survival of bycatch have also been quite remarkable.

"When the bycatch species are returned to the water alive they stand a much better chance of not being eaten by sea birds, sharks, dolphins and other predators that follow the boat feeding on discarded animals.

"If it’s alive it has a much better chance of survival and the overall result of that is to reduce the impact of the industry on the biodiversity of an area. That matters to us because we have an obligation to protect the natural ecological values of a World Heritage Area and to mitigate the impacts of trawling."

Deck hands sort prawns with one of the hoppers

The GBRMPA’s enthusiasm for the environmental advantages of the hoppers is supported by Seanet, a service to the seafood industry delivered by the Fisheries Extension Network Australia funded by the Natural Heritage Trust.

Extension officer Denis Ballam said he had first noticed the advantages of hoppers when he spotted three trawlers in the Gulf of Carpentaria last year. Two of them were being followed by flocks of seabirds feeding on the dead trail of bycatch but there was a notable absence of scavengers behind the third boat which, he later discovered, had been fitted with a hopper.

Mr Ballam emphasised that he was not a lobbyist for the hopper manufacturing industry but said he was confident he would be able to organise demonstration trawls at major ports along the Queensland coast to point out their advantages despite the initial cost.

"Trawler operators are looking at paying out $50,000–$60,000 for a hopper, and that is what has put off the east coast trawl fishery so far; however, it may be possible to develop a smaller, cheaper product," he said.

"They may well be worth the initial outlay anyway, because of the increased value of the catch and the fact that the boats require one less deck hand. The industry may also consider petitioning the government for a 150 per cent tax reduction over, say, a couple of years.

"The value to the ecology of the sea bed far outweighs the relatively small cost of implementation, so it’s a win-win situation for everyone concerned."

Mr Ballam stressed that the prawns harvested by trawlers with hoppers were of the highest quality because they were not crushed by tonnes of bycatch and were still alive when snap frozen in boxes ready for the market.

He estimated that the premium product commanded prices as much as 30 per cent higher than prawns trawled without the use of hoppers.