Commercial fishing to blame for Antarctic toothfish decline?

by Rebecca Priestley / 18 August, 2012
A fall in antarctic toothfish numbers would seem to have an obvious cause.
Antarctic toothfish decline - Clive Evans thinks commercial fishing is to blame


The antarctic toothfish (Dissostichus mawsoni) is not a pretty creature. These large ancient looking fish have enormous heads and a mouth full of teeth – useful when you’re the top fish predator in the Southern Ocean. Toothfish feed on many smaller species of fish and squid. Above them in the food chain are colossal squid and marine mammals like weddell seals and sperm whales. And now humans, too. For almost two decades, trawlers have been catching antarctic toothfish in the Southern Ocean, including in the Ross Sea directly south of New Zealand. Headless, gutted slabs of fish are frozen and shipped around the world, where they are served up to markets and restaurants as “Chilean sea bass”, a name invented to appeal to the palate. The Antarctic tooth fishery is now worth about $20 million a year to New Zealand – not a lot for a $1.5-billion-a-year fishing industry. The Government says the fishery is sustainable and has given permission for the toothfish stock to be reduced to half the original levels. But the development of the fishery has coincided with a precipitous decline in toothfish in the McMurdo Sound, according to a team of scientists who have been studying the species for more than five decades. 

Clive Evans from the University of Auckland and Art Devise and Chris Cheng from the University of Illinois have been working, with other colleagues, on a series of toothfish projects, including weighing and tagging fish as part of a long-term monitoring project, dissecting fish to study the antifreeze protein that allows them to survive in waters that hover around minus 1.9°C, and gathering DNA samples to sequence the fish genome. But where they used to hook up to 500 fish weighing up to 70kg or more each, this season they hooked just one 5kg fish. They first noticed the decline in the summer of 2002 and they think it’s because of the fishery. “It is difficult to attribute this decline to any factor other than the fishery, which on modelling estimates has already removed 20% of the Ross Sea stock,” says Evans. “It might be argued that it is a sustainable fishery, but if you’re going to take out 50% of the top fish predator, you’re going to upset the ecosystem somewhere. If our data are meaningful, there’s been a reduction in the toothfish in the southern limits of their range, in McMurdo Sound.” 

There’s a lot we don’t know about the antarctic toothfish. From Devise’s long-term tagging project, we do know the fish have a growth rate of about 2.5cm a year and become sexually mature somewhere between nine and 16 years of age. But we don’t know exactly where they spawn. “This is a migratory species about which we know little. We don’t even know if the eggs float; we’ve got no idea where the larvae go,” said Devise at Scott Base last year. If toothfish disappeared from McMurdo Sound, what would this mean for the rest of the toothfish population, and for the complex marine ecosystem that ranges from single-celled organisms through sponges and fish to migrating whales? “We simply don’t know,” says Evans. “Should we continue fishing in the Ross Sea in the light of these uncertainties? The sensible approach would be to urge [the introduction of] a moratorium while gathering more data on the consequences to local ecosystems of removing half the population of the top piscine predator.” ­

Upcoming Antarctic Events



  • The Last Ocean, a documentary about the race to stop commercial fishing in the Ross Sea, plays at the New Zealand International Film Festival, nationwide, August, www.lastocean.org

  • The Christchurch Writer’s Festival has several events with an Antarctic theme. Christchurch, August 30-September 2, chchwritersfest.co.nz

  • This year’s Antarctic season is launched with the first New Zealand IceFest, a celebration of
    New Zealand’s relationship with Antarctica. Christchurch, September 14-October 14, nzicefest.co.nz

MostReadArticlesCollectionWidget - Most Read - Used in articles
AdvertModule - Advert - M-Rec / Halfpage

Latest

Best red and white wines for winter
75447 2017-06-24 00:00:00Z Wine

Best red and white wines for winter

by Michael Cooper

The winter chill has us instinctively reaching for bold reds and sturdy whites.

Read more
What to do and see in Auckland
74332 2017-06-24 00:00:00Z Sport

What to do and see in Auckland

by Noted

The shopping! The beaches! The cafés! The volcanoes! Auckland is New Zealand’s biggest and busiest city and has everything on offer all the time.

Read more
How the All Blacks inaugural World Cup triumph revived the game of rugby
75187 2017-06-24 00:00:00Z Sport

How the All Blacks inaugural World Cup triumph rev…

by Paul Thomas

The sport was bruised by the fallout from the 1981 Springbok tour, the rebel Cavaliers’ visit to South Africa and a rampant rival football code.

Read more
Grenfell Tower fallout: Two Auckland high-rises found with combustible cladding
75398 2017-06-23 10:10:32Z Property

Grenfell Tower fallout: Two Auckland high-rises fo…

by Phil Pennington

Two Auckland high-rises have the same cladding as that of Grenfell Tower, but the Council won't say which ones.

Read more
Pauline Hanson is wrong, children with disabilities should be in the classroom
75392 2017-06-23 09:17:07Z World

Pauline Hanson is wrong, children with disabilitie…

by The Conversation

Pauline Hanson claims kids with disabilities should learn in special classrooms. Is she right? Two experts examine the evidence.

Read more
National aims to put Todd Barclay affair behind it
75388 2017-06-23 08:18:46Z Politics

National aims to put Todd Barclay affair behind it…

by Demelza Leslie

Senior members of the National Party are confident this weekend's annual conference won't be overshadowed by the controversy around Todd Barclay.

Read more
Labour intern scheme: Awataha Marae rejects 'substandard' housing claim
75385 2017-06-23 06:47:58Z Politics

Labour intern scheme: Awataha Marae rejects 'subst…

by Mihingarangi Forbes

The marae housing Labour's interns isn't substandard, Trust bosses say, while local Māori say they've been fighting to access it for years.

Read more
The demise of Todd Barclay and all the Gor-r-rey details
75338 2017-06-23 00:00:00Z Politics

The demise of Todd Barclay and all the Gor-r-rey d…

by Jane Clifton

The Todd Barclay debacle says more about PM Bill English than the tyro MP.

Read more