The Disappearing of Fale

Forest and Bird, Issue 312, 1 May 2004, Page 20

The Disappearing of Fale

BERNIE NAPP

New Zealand's native long-finned eels are disappearing from Our rivers, and new research suggests that commercial fishing is ‘significantly’ to blame, reports

ew Zealand’s eels are one of nature’s mysteries. Born in tropical waters off Fiji and Tonga, the larvae of long-finned and short-finned eels drift to New Zealand, entering rivers as glassy juveniles, where they transform into elvers, and spend decades reaching maturity. The adults then migrate out to sea, swimming thousands of kilometres back to the tropics to spawn and die. That’s if they don’t die of natural causes or get caught first. Long-finned eels, the rarest of New Zealand’s three freshwater eel species, must avoid spears, lines and nets for decades if they are to reach breeding age, says Don Jellyman, scientist with the National Institute of Water and Atmospheric Research (NIWA). In many New Zealand rivers, the chances of that happening are practically zero. On current trends, long-finned eels are expected to decline in numbers by five to 30 percent in the next decade, earning the species a chronically-threatened ranking in the Department of Conservation’s threatened species classification. In many rivers the larger eels have gone.

Overfishing is ‘a significant contributing factor’ in the decline of long-finned eels, as Dr Don Jellyman reported in November last year to the American Fisheries Societies’ International Symposium on Freshwater Eels. It is a global problem for the world’s 15 species of freshwater eel (Anguilla spp). Dr Jellyman was also among scientists from 18 countries attending an international freshwater eel symposium in Quebec, Canada, in August last year who agreed ‘to raise an urgent alarm’ to protect eels. ‘Precautionary action — curtailing exploitation, safeguarding migration routes and wetlands, improving access to lost habitats — must be taken immediately, the symposium’s communiqué said. This call for action may come as a surprise to many New Zealanders, for whom eels are slippery fish best not met at a swimming hole, or yanked onto a riverbank out of curiosity. Peter Todd, a stock-assessment manager with the Ministry of Fisheries, concedes that eels do not rate highly on the public radar screen. ‘They are rather slimy things that look like snakes, he says. The Nelson-based eel scientist got hooked on eels for their fascinating life history and the special problems they present for fisheries management. While he does not believe that long-finned eels are in dire straits, he agrees with his colleagues at DoC and NIWA that more action, such as native-habitat restoration, is needed to protect New Zealand eels. Intense discussions are underway among Officials, scientists and eel fishers about further directions in eel management. Glass eel runs are estimated at only onequarter the size of runs of 30 years ago, a concern of those drafting advice on the inclusion of North Island eels into the commercial harvest system this year. Total adult stock numbers of any species are currently unknown, as are total harvest levels, and quotas needed to ensure adequate protection. The true effect of human impact may take decades to measure, because of eels’ long life cycles, according to a report by the Ministry of Fisheries. ‘Overfishing of the resource may only become apparent immediately prior to the fishery’s collapse. South Island eels have been under the commercial harvesting regime of the Quota Management System since October 1, 2000. No one knows whether regulations governing commercial, customary and recreational harvest will adequately protect long-finned and short-finned eels, Dr

Jellyman of NIWA says. ‘All we can do is to be very conservative. The most effective thing we can do is to have reserve areas.’ A NIWA report commissioned by DoC last year found that in Southland and Westland only six percent of rivers and 20 percent of lakes are protected from fishing, and then except for customary harvest by Maori — the lucky eels live within national parks. A further 14 percent of rivers and 29 percent of lakes in inland DoC reserves are protected but fishing near the sea would affect the migration success of eels from these areas. The Ministry of Fisheries is now extending the survey to the rest of the country.

The results are likely to show that the percentage of fully protected rivers and lakes nationwide is small, says Richard Allibone, a freshwater scientist with DoC. "Many fisheries issues need to be resolved, he says. "The Quota Management System in the South Island is flawed because it does not differentiate between species. Longfinned eels are four times more likely than short-finned eels to be caught because they live longer and reach a larger size. Females, which grow larger than males in both species, are more likely to be caught’

It gets worse, Dr Jellyman of NIWA says. Removing the bigger eels allows more smaller eels to survive, increasing overall eel numbers. While that may appear to be a good thing, it seems that the majority of young eels in such conditions turn into males. In one river surveyed, 95 percent of eels were males. He is extending this research elsewhere to confirm this hypothesis. Proposals to farm eels, based on captured glass eels, will not immediately solve the overfishing problem, Dr Jellyman says. Eel farming from captured glass eels is a practice popular in Japan, Taiwan and China, but is in its infancy in Australia and, closer to home, in the Wairarapa and in Northland. Eels spawn only once in their lives. Glass eel harvests would need to be sustainable, and the current sustainable level in New Zealand may be zero till species recover. Eels face many other serious problems, says Dr Todd of the Ministry of Fisheries. More than 90 percent of wetlands — key habitat for short-finned eels — have been removed from New Zealand in the last 150 years. Hydro dams block eel passage on the way upstream. Even if they do get around dams, migrating eels get chopped up in power turbines on the way down. Huge areas of South Island river habitat are consequently shut off to eels, in particular, long-finned eels. In the Waikato River system with its several hydro dams, eel fishers are transferring around a million elvers each year from below the last dam, Karapiro, and introducing them to upstream hydro lakes for later harvest. Long-finned eels are a taonga species for Maori. One tradition has it that eels (tuna) were descendants of the ocean people,

Scientists worldwide, New Zealanders among them, want urgent action to protect all freshwater eels from extinction.

Eel life cycle:

Adult female eels lay millions of eggs each in deep water off Tonga and Fiji, during spawning in September-December. + Leaf-shaped larvae, leptocephali, drift for 9-10 months in ocean currents and change into glass eels. * Glass eels enter estuaries and river mouths in September-November; earlier in the North Island, and later on the east coast of the South Island. * Glass eels turn into dark-coloured elvers on entering fresh water and begin moving upstream in January and February. * Adult eels spend decades living in estuaries, rivers, lakes and swamps, without breeding. Short-finned eels migrate at 9-41 years, and rarely, up to 60 years. Long-finned eels migrate at 49-56 years, and up to 100 years or more. * During periods of heavy rain in autumn (March-May), migration-ready eels, having narrowed heads and enlarged eyes, move downstream and out to sea. * Migrating eels swim thousands of kilometres to the tropics, without feeding for up to five months, to spawn.

Hine-moana and Kiwa. In another, the eel came down from the sky and seduced Maui’s wife. Maui dug a trench, and as the eel swam along it, chopped it into bits in revenge. From these pieces sprang other life forms, including the conger eel, vines, rata and other plants. Maori knew when to catch eels: ‘the silverbelly eels are caught on the flood waters of the first heavy rains after summer’. They were observing eels of breeding age — having narrower heads, enlarged eyes, and a silvery sheen — leaving freshwater haunts

for the sea, Dr Jellyman says. He recently tagged 10 migrating females to determine where they went. The eels were to get to their destination, spawn and die, upon which the tags would detach, float to the surface and emit satellite signals. Information was received from only four of the tags. One started signalling near New Caledonia but only after several weeks had elapsed since it rose to the surface. For now, Fiji and Tonga are his best guess for spawning sites. Eels may originally have been tropical

species, Dr Jellyman says, which invaded temperate waters over the aeons, yet never lost their spawning habits. Continental drift would have gradually shifted eel rivers far from the tropics. Will New Zealand eels survive? Dr Allibone says: Long-finned eels won't become extinct in the short term but at this rate will become rare. If not enough fish are spawning, they will reach a point of no return. — BERNIE NAPP is a media adviser to the Department of Conservation.

Long-finned or short-finned

Here’s how to distinguish the long-finned eel from its short-finned cousin. Both species range in colour from grey to black, and both may get called yellow-bellies or silver-bellies. A third species, the Australian longfin eel was first confirmed in northern New Zealand in 1997.

Long-finned eel Anguilla dieffenbachii * The dorsal fin extends much further forwards than the ventral fin, distinguishing this species from short-finned eels. * More likely to have a yellowish than a silvery belly, and more likely to be black in overall colour. + May grow to more than 20 kilograms in weight and nearly two metres long. * Live in estuaries, rivers and lakes from the coast to the mountains, preferring stony rivers and clear water. * Peculiar to New Zealand. Short-finned eel Anguilla australis * Dorsal fin is only slightly longer than the ventral fin. * More likely to have a silvery belly than a yellowish belly and have a greyish overall colour. * Typically grow to no more than a few kilograms in weight and one metre long. + Live in estuaries, rivers, lakes and swamps near the sea. * Native to New Zealand, eastern Australia and Tasmania, and South Pacific islands. Australian longfin eel Anguilla reinhardtii * Resembles the long-finned eel but has numerous black blotches on the back and sides. * Native to eastern Australia and Tasmania, and appears intermittently in the Waikato River, and other areas of the northern North Island.

Eel farming a sustainable option?

Worldwide, eel farming is a huge industry, dwarfing New Zealand catch levels. ¢ Japan alone eats up to 130,000 tonnes of eels a year, a market worth more than $US1.3 billion. In 1999 Japan farmed 23,211 tonnes (of A. japonica) and caught 817 tonnes in the wild. It imported the remainder of its requirements, mainly from China, Taiwan and Europe. Only 0.6 per cent of the total was wild-caught. ¢ A US study (by the National Oceanic and Atmospheric Administration) suggests that glass eel harvesting levels in Japan are not sustainable. ¢ Taiwan produces 26,000-56,000 tonnes of farmed eels every year, worth more than US$400 million, in exports and for domestic consumption. That’s based on a harvest of 30-150 million glass eels a

year, which may be 45-75 per cent of total glass eel runs. ¢ A NIWA study on the potential for eel aquaculture in Northland, for the Enterprise Northland Aquaculture Development Group, did not consider the environmental impacts of eel aquaculture. Nor did an Australian feasibility study for farming A. australis and A. reinhardtii in New South Wales. ¢ In 1999, the Australian State of Victoria was producing 300 tonnes of eels a year. Instead of taking 10 years to grow to adult size, they took around 18 months. Ten per cent of glass eels taken are put back into the wild fishery after three months to conserve wild populations. The impact of this is as yet unknown. ¢ New Zealand scientists agree that sustainable eel farming is feasible.

| Eel management tools

Despite threats to their survival, eels are classified as a commercial fishery to be governed by the Quota Management System. e Eels, as commercial species, are managed by the Ministry of Fisheries. e The Department of Conservation advocates for conservation of eels, as native species and, in the case of longfinned eels, as a chronically-threatened species. ¢ South Island eels entered the commercial harvesting regime of the Quota Management System in October 2000, with no differentiation between species. Long-finned eels in this fishery make up 80 percent of commercial catch. e Harvest under the Quota Management System is mainly on the basis of ‘maximum sustainable yield’ — that is, to allow fishers to remove as many eels as possible over time, without driving them toward extinction. Quotas, in theory, are set to ensure sustainable use of the resource. e In the North Island, the Ministry of Fisheries issues eel-harvesting licences, but fixes no quota. The North Island fishery will enter the Quota Management System on October 1 this year, with

separate quotas for long-finned eel, and short-finned/Australian longfin eels. ¢ North Island commercial catch distribution is estimated to be: longfinned (20 percent), short-finned (70 percent), Australian longfin (10 percent). Estimated commercial catch levels have dropped from 656.9 tonnes in 1990-91 to 534.1 tonnes in 1998-99, a fall of 19 percent in eight years. e Minimum commercial catch size in the South Island is presently 220 grams and the maximum four kilograms; except at Lake Ellesmere, and in the case of Maori customary or recreational harvest. It can take a female long-finned eel 35-50 years to reach four kilograms. ¢ Customary harvesting by Maori is approved ad hoc and is permissible in national parks, where all other forms of eeling are prohibited. Customary catch levels are unknown. ¢ Recreational fishing regulations introduced in 1994 fix a daily bag limit of six eels a day and one fyke net per person. e Eel experts agree that more action is needed to protect eels. More reserve areas where eeling is prohibited would be an effective first step.