Why the Longfin Eel/Tuna Kuwharuwharu requires our help

The breeding habits of tuna kuwharewhare

To understand why commercial fishing of longfin eels- tuna kuwharewhare needs to stop, one needs to understand the lifecycle of the species.

Unlike many animals, eels only breed once, at the end of their lives.

Males don’t mature until they are 23 to 25 years old, and females till they are 34. They can be 80 years old before they migrate.

At the end of their lives longfin eels swim 6000 kilometres to deep warm trenches, possibly off the Tongan coast, where each eel lays or fertilizes eggs. A female longfin eel can have up to 20 million eggs. All the adults then die.

The eggs develop into tiny see through creatures called leptocephalus. These drift on currents back towards the New Zealand coast.

Leptocephalus develop into glass eels. Between July and November large numbers of the tiny glass eels enter waterways. A week later glass eels develop dark skin pigment and become elvers which move further inland.

What this means: You can’t just let longfin eels get down to their last 500, put them in an enclosure and try to build the population back up. You need masses of them meeting up together in the vast Pacific Ocean. Once you break the migrational cycle, it is broken forever.

High Levels of Historical Abuse

Abuse of eels has continued for most of the period since European colonization. One of the most notorious was the bounty placed on eels to try and exterminate them so that introduced trout could survive and thrive.

What this means: The longfin eel (and shortfin) have had 150 years of cultural abuse which has contributed to their present dire circumstances.

Habitat loss, land-use changes and pollution

A key issue is habitat loss due to land use changes and development, including wetland drainage, the construction of dams, irrigation schemes, river diversions and culverts.

Ninety percent of pre-European wetlands have now been drained, and around 70% of pre-European forest has been removed, all radically affecting the habitat of the eel.

The Wairarapa has historically experienced two examples of significant habitat loss- Lake Wairarapa wetlands being drained and Te Tapere Nui O Whatonga (The seventy-mile bush) being cleared except for Pukaha Mt Bruce.

But despite the destruction from the 1870s onwards, both still supported healthy eel populations – that is until commercial fishing started. Both Maori and pakeha elders agree upon this.

Eel populations are also impacted by pollution. Eutrophication from sewerage and effluent and fertilizer runoff from farms and industry can remove large quantities of oxygen from the water, meaning the eels will either die or move away.

Urban impacts on natural waterways have also added to the deterioration of water quality, these impacts include industrial pollution, road runoff, storm water, herbicides, domestic cleaners and fertilizers^.

What this means: There are many things contributing to the present situation of tuna but these will take decades to turn-around. In the meantime, commercial fishing is having an immediate impact that gives them no chance of recovery. Ending commercial fishing will take some of the pressure off and give us time to improve the long-term outlook.

Alarming Evidence of declines

Trap and transfer operations at some hydro dam sites in recent years have revealed that the number of longfin elvers moving up our rivers nowadays is very low – at least a 75% reduction – in stark contrast to the huge elver runs that were witnessed prior to the 1960s.

Commercial catch records reveal a trend of decreasing size of all eels caught, 50 percent nationwide, and 96 percent in the Waikato River now being within the lowest size category (220–500g). Very few large longfin eels are now seen anywhere.

Regularly fished rivers now show longfin eel ratios of up to 100 males to 1 or 2 females.

A predicted further decline of 5-30% in the total population is predicted in the next 10 years and that decline is predicted to continue beyond the 10-year timeframe.

What this means: Longfin eel are well below the stage where, like all fish species, they are supposed to be at around 20 percent of original numbers which is the international standard the Ministry of Primary Industries (MPI) is supposed to be abiding by.

Not only have numbers and sizes dropped dramatically but the situation is almost 100 times worse for females.

The small number of females has obvious implications for future spawning populations. There is now concern is that very few mature eels are now making it to reproductive maturity with the result that there are now fewer elver recruits.

Commercial Fishing

The commercial fishing of eels commenced in 1960s, with harvesting peaking in the mid-1970s, with about 2500 tonnes caught.

Since the early 1990s the commercial harvest of eels has halved due to a rapidly declining population.

In 2016 suspension of commercial fishing of longfins took place in four of the six management areas in the South Island.

In 2018 MPI decreased the total allowable catch for commercial fishing for all North Island longfin eel stocks from 167 tonnes to 141 tonnes for the 2018/19 fishing year.

Despite the constant reduction in quotas, commercial fishers are not able to fill their quotas.

What this means: Commercial harvesting is a sunset industry. Every year more of the existing stock will be fished out without being replenished. Eventually commercial fishing of longfin eel will stop but by then it will be too late to save the species.

A cruel live export trade

More than half of all caught eels are exported live around the world, with around 700 to 1000 eels being caught PER DAY.

These eels are exported to various countries around the world. Eels exported alive are stunned and then encased in ice and flown overseas, at least some of them ending up in Asian restaurants where they are skinned, and sometimes cooked alive. You can buy 12kg of live eels for about $120.

What this means: A 30 year-old longfin eel could end up with a stake through its head, skinned alive, and possibly then cooked alive for $NZ12 or thereabouts

Calls for a moratorium on commercial harvesting

Tuna kuwharewhare have absolutely NO protection whatsoever under law.

Tuna are very easily caught, with 90% or more of tuna population at most riverine sites able to be caught in baited traps in a single night.

In 2013 Parliamentary Commissioner for the Environment, Dr Jan Wright, released the report On a pathway to extinction? An investigation into the status and management of the longfin eel, calling or for a moratorium on the commercial harvesting and for DOC to step up its protection of the species.

The Department of Conservation gives out permits to harvest on the conservation estate, despite its classification of the longfin eel as“chronically threatened in gradual decline.”

What this means: You could spend the next ten years improving the habitat for eels and overnight a commercial fisher can come along and take nearly every eel in the area and THIS HAPPENS.

What does this ALL mean?

What it means is that the longfin eel - tuna kuwharewhare is on the edge of “functional extinction” which means you may still find the creatures in the Wairarapa’s streams, rivers and lakes for many years but the reproductive cycle will be broken forever.

What can you do?

Learn as much as you can about tuna kuwharewhare and share your knowledge with your friends. But don't forget to mention the situation as regards commercial harvesting of tuna.

Be the eyes and ears for tuna tuwharewhare. If you know of anything going on with commercial fishing in the Wairarapa let me know and I will pass this information to other like-minded souls.

Join the "Eel Activists Wairarapa" facebook group or the "Manaaki Tuna - Save the Longfin Eel from Commercial Fishing" facebook page.

Sources for this presentation and useful links

Submission on the Long-Finned Eel (Anguilla dieffenbachia) – North Island – Sustainable Wairarapa

Potangaroa, Joseph. 2010. ‘Tuna Kuwharuwharu-The Longfin Eel: Facts, Threats and How to Help. ISBN 978-0-473-16583-3.

http://www.longfineel.co.nz/wp-content/uploads/2011/06/Tuna-Kuwharuwharu-Longfin-Eel.pdf

4. Don Jellyman, Forty Years On’ the Impact of Commercial Fishing on Stocks of New Zealand Freshwater Eels” in “Eels on the edge” Published by the American Fisheries Society May 2009.

file:///C:/Users/Jim/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/Full-evidence-text%20(1).pdf

Manaaki Tuna – lifeline for longfins.

http://www.longfineel.co.nz/extinction-crisis/#footnotes

Eel export catches - https://seafoodnewzealand.org.nz/