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Bycatch the real concern as super trawler heads for Australia

Concerns about licensing a foreign super trawler to fish our southern seas have centred on the negative effect on fish stocks. These fears are largely unfounded. The real concern is for Australian mammals…

It’s not the fish we should worry about, but the other creatures the “super trawler” will catch. Charles Van den Broek

Concerns about licensing a foreign super trawler to fish our southern seas have centred on the negative effect on fish stocks. These fears are largely unfounded. The real concern is for Australian mammals which will inevitably meet their demise in some numbers because of the mid-water trawl method of fishing.

Catch likely to be sustainable

There is little doubt that the quota of 18,000 tonnes of small pelagics, issued by the Commonwealth to the MV Margiris to be taken off Australia’s south coast, will not lead to depletion of fish stocks. This quota is only half of the total allowable catch (TAC) currently set for the fishery.

The catch of jack mackerel in the Commonwealth managed Small Pelagic Fishery (SPF) has been very small because fishing has been unprofitable. Only 156 tonnes of jack mackerel was taken in 2009-2010. The total catch of the several species in the SPF was only 2,482 tonnes. The low catches will have enabled the recovery of stocks after very heavy fishing in the 1980s and 1990s.

Commonwealth of Australia

Having said that, the fishery is due for an update to its harvest strategy based on a biomass assessment, something that has not been done for five years. It is important to review stocks so that TACs can be confidently declared for the longer term. A biomass assessment will be particularly useful for the slow growing, long-lived and slow to breed jack mackerel (east), whose TAC has been recently raised from 4,600 to 10,000 tonnes – and of redbait (west), listed as “uncertain” in status and with a TAC of 5,000 tonnes.

Problems with the mid-water trawl

The small fish are the regular diet of the Australian fur seal (Arctocephalus pusillus doriferus). The fish in the net being trawled behind the MV Margiris will be very enticing for the seals; but for many it will be their last dive.

Monitoring has shown that seals enter the body of a trawl in half of all shots; and that about one in every five interacting seals will drown. Trawlers provide a seal exclusion device (SED) in their nets. But many seals fail to find the mouth of the net or the hole provided by the SED.

Underwater cameras have shown that more seals meet their demise in mid-water trawl nets than was previously thought. This is because the dead ones roll out of the net unseen during hauling. The seven independent scientists who recently gave the SPF a clean bill of health, augmented their conclusions as follows: “… measures … will be required to manage the ongoing risk of marine mammal interactions and capture”.

Seals get inside trawler nets to eat fish. Some can’t get out. Lyle and Wilcox

Research recommends the top-opening SED, yet the main vessel that has been fishing uses a bottom-opening device. There is considerable scope to further refine the orientation, size and scope of SEDs. But crucial trials to find optimum devices have not taken place, due to lack of funding and very low activity in the mid-water trawl fishery.

MV Margiris will continually encounter seals. Several dolphin and whale species might also invade trawl nets. And there are two bird species listed as “vulnerable” under Commonwealth legislation (shy albatross and black-browed albatross) that may suffer mortality but at low rates.

Who cares about seals?

The NSW Government lists the Australian fur seal as “vulnerable”. It says that the seal is directly threatened by fishing operations and that fishing may limit the availability of prey. And it says the species is also threatened by entanglement or ingestion of plastic debris increasingly discarded from boats or washed out to sea.

The depleted population of Australian fur-seals resulting from commercial sealing has increased the species' vulnerability to other threats. For example small colonies on islands are susceptible to stochastic events such as oil spills.

The range of the Australian fur seal overlaps the Commonwealth’s SPF, but the Commonwealth does not share the concerns of the NSW government and has not listed the Australian fur seal as endangered under the Environment Protection and Biodiversity Conservation Act 1999. It is an offence to kill, injure, take, trade, keep, or move Australian fur-seals in Commonwealth waters. But it can be done with a permit, and presumably a permit will be issued.

Environment Minister Burke is thus toothless when it comes to stopping fishing by the MV Margiris on the grounds of threats to listed species unless he invokes the threat to listed albatross, which is very unlikely.

The Commonwealth may have had some authority in demanding that the MV Margiris deploys nets configured to minimise seal mortality. But such action cannot be taken because effective SEDs don’t exist. Monitoring and observing the super trawler is all very well, but the Commonwealth won’t be able to stop the drowning of Australian fur-seals.

Instead of feeding small fish to tuna then eating the tuna, why not eat the small fish? norobodo/Flickr

Culinary switch recommended

Most of the catch of small pelagics and sardines in Australian waters goes to fatten juvenile southern bluefin tuna (SBT) caught and penned in South Australian waters. Under the Commonwealth’s own assessment, the tuna is overfished and subject to overfishing. Moreover, the species is listed as “threatened” under the Victorian Flora and Fauna Guarantee Act 1988, and “endangered” under the New South Wales Fisheries Management Act 1994. The World Conservation Union lists this tuna as “critically endangered”. Though it lists the SBT as “conservation dependent”, the Commonwealth continues to issue SBT quota because of the business is so lucrative.

Using small pelagics to fatten tuna is inefficient: the conversion ratio is very low. Every tonne of farmed tuna requires between 10 and 20 tonnes of feed. The feed is Australian-caught small pelagics, Australian sardines or imports.

This inefficiency is grounds to suggest we stop eating tuna, and start eating small pelagics and sardines ourselves. These highly nutritious fish – delicious when grilled Portuguese style – would make an important contribution to healthy diets and at the same time could relieve pressure on overfished shark and snapper. Before we make such a culinary switch, however, we should prove that trawling is not killing animals and birds.

Meanwhile, it looks as though we will have to grit our teeth knowing that Australian fur-seals will likely be drowning in numbers while the MV Margiris is trawling our waters.

bJORk(D)mAN/Flickr