The New Nature Read online

  Africa’s Lake Victoria, although less than a million years old, has served as a remarkable laboratory for fish evolution. More than 300 cichlids in all shapes and colours evolved quickly from one unknown ancestor. Many species kept to rocky stretches of lake edge, where their numbers may not have exceeded a few hundred. But during the 1950s the British slipped Nile perch (Lates niloticus) into the lake as a food fish. The perch occurred naturally only a short way away. In their new home these big predators found a smorgasbord of gaudy cichlids awaiting them, and by the late 1980s more than half of the cichlid species had vanished. Their passing stands as one of the great extinction events of modern times.

  In 1968 the Queensland government set its sights on Nile perch. These fish are closely related to barramundi (Lates calcarifer), but unlike barra they will breed in dams. At a research station at Walkamin on the Atherton Tablelands ponds were installed to test the new fish after the federal government demanded a proper risk assessment. But Australia’s flirtation with Nile perch ended in 1985 when news of the Lake Victoria tragedy filtered through. Australia was castigated by Ugandan biologist Richard Ogutu-Ohwayo for risking the extinction of local fish.

  Queensland still had a research station raring to go, and what ensued was the Freshwater Fishing Enhancement Program, an ambitious plan to breed up millions of barramundi and other fish for ongoing release into dams. The idea was to replenish depleted waters, improve life in the bush, and draw tourists to fading country towns. Because so few Australian fish breed in dams, stocking would go on indefinitely, using new techniques to induce spawning. Stocking groups were formed to foster local ownership of fisheries and shoulder the work, and by 1995 there were fifty-eight of these in the southern half of Queensland alone, stocking seventy-odd dams. Big impoundments were the first to get fish, then smaller weirs, and finally rivers. More than 17 million fingerlings were freed.

  In less than a decade new fish went into almost every river along the east coast south of Cairns. Ten or more species now swim where they don’t belong. Some, including Outback Murray cod (Maccullochella peelii), yellowbelly (golden perch Macquaria ambigua) and silver perch (Bidyanus bidyanus), were translocated over vast distances. Others went into the right rivers but above ancient insurmountable barriers, such as waterfalls. The Burnett River in southern Queensland today boasts six new fish species (Murray cod, yellowbelly, bass, silver perch, saratoga, sooty grunter), and the Mary River three. These rivers are the native home of the lungfish, a famous living fossil, and the Mary also carries endangered Mary River cod (Maccullochella mariensis) and very rare turtles (Elusor macrurus), neither of which occurs naturally anywhere else.

  Alf Hogan of the Walkamin Fisheries and Aquaculture Centre speaks proudly of the role played by his centre in this work. At a 1995 symposium he explained the need to ‘create systems that contain as much diversity as possible’. The Barron River, which passes right by Walkamin, he described as:

  probably the most stocked waterway in Australia. Its original inhabitants were prawns, eels, rainbowfish, spangled perch and purple-spotted gudgeons. Introduced species include rainbow trout, brown trout, bony bream, hardyheads, archer fish, blue eyes, mouth almighty, banded grunter, sleepy cod, three species of eel-tailed catfish, fork-tailed catfish, fire-tailed gudgeons, saratoga, sooty grunter, khaki bream, silver perch, golden perch, jungle perch, three strains plus one crossbreed of barramundi, redclaw, guppies and tilapia – a total of 24 species plus exotic aquarium fish. One could say without fear of contradiction that the Barron is a highly modified system!

  Years later I asked Alf about all these fish. The trout and catfish (which died out) were freed by acclimatisers, and the guppies by hobbyists, but virtually all the rest came from Walkamin. ‘There’s been a lot of stuff go down the drain here, I suppose,’ Alf mused, but he said that most of what went in was deliberate. I find it ironic that a river coursing through World Heritage rainforests (a famed ‘wilderness’ area) might be ‘the most stocked waterway in Australia’.

  Stocked fish meet two criteria: they are predators (they take bait) and they are big. Saratoga (Scleropages leichhardti) grow a metre long. Previously confined to one system, the Fitzroy, they now lurk in waters much further north and all the way down to the Gold Coast, becoming the biggest freshwater fish in most rivers where they swim. Murray cod grow to 1.8 metres (though not often). Big predators like these exact a toll on crayfish, frogs, molluscs, and other fish. Murray cod will take yellowbelly, snakes, turtles, even ducks. They influence the ecology wherever they go. Stockers say their work is safe because their fish go into artificial waters, not rivers, but most dams sit on rivers, and fish swim upstream or ride spillways during floods. At Lake Tinaroo, a dam near Cairns, a huge net had to be installed because half the fish were washing out after every big wet (Queensland Fisheries admitted this).

  Exactly what damage these big fish are causing is difficult to say, because they hide behind veils of water. ‘There’s no resources and no real research into what the impacts might be,’ admitted Peter Jackson of Queensland Fisheries. Lake Eacham is held up as one example, but that little crater was special, and mouth almighties are small – I’ve never encountered one more than 12 centimetres long. Trout in the south are devastating, but what about all these relocated ‘native’ fish? Alan Webb of James Cook University studied Townsville’s Ross River above the weirs, both before and after barramundi stocking. Barra are native here but they can’t surmount the dams on their own. Alan recorded ‘an absolutely massive drop in the number of native fish’, because local stockers went too far. ‘They were just adding more and more predators to the system.’ He dissected some barramundi. ‘They were eating small juvenile fish, which was indicating that they’d eaten their way through the larger and subadult populations and were heading down the scale.’ Overstocking may be commonplace. According to biologist Damien Burrows, ‘the unwritten rule is that you stock as many fingerlings as you can buy’.

  Another revealing study was done by Brad Pusey of Griffith University. Sleepy cod (Oxyeleotris lineolatus) possibly belong in the lower reaches of the Burdekin River, but weren’t found above Burdekin Falls until some from Walkamin were put in during the 1980s. A decade later their numbers exploded. Brad chronicled a wave of sleepy cod working their way downstream from the headwaters. ‘They’ve now colonised every piece of available habitat in that upper river,’ he wrote. ‘I can track the loss of other species, particularly other gudgeons, as the colonising front came through.’ He suspects drought influenced his survey results, but blames sleepy cod – sluggish fish that lie still at night and lunge at passing prey – for much of the change.

  We need more studies like these. Without them we can only speculate about stocking, as Geoff Johnson of the Queensland Museum points out. ‘Well, it can’t be good news,’ he told me, ‘but whether it’s disastrous or only moderately bad news, only time will tell.’ He suspects that spangled perch (Leiopotherapon unicolor), which was spread about very early on, helped exterminate Brisbane’s very own cod, a huge fish that vanished before any museum could nab a specimen. Coalminers were dropping gelignite into cod holes, netting was rife, and the big fish were doing badly. ‘Then this new voracious predator turns up in huge numbers,’ said Geoff. ‘It absolutely explodes, as feral species often do when they first arrive. It comes up against a species that’s not terribly fecund, and under pressure.’ The last cod were caught in the 1930s.

  A new fish discovered by Brad Pusey in the upper Bloomfield River may now be in danger. A runty cousin of the Murray cod, it’s an ancient relic that held out against bigger fish by living above a north Queensland waterfall. But someone recently put sooty grunters (Hephaestus fuliginosus) into its domain, illegally. This new cod (Guyu wujalwujalensis) may now be in grave trouble. Sooty grunters have also been placed, legally, into streams carrying Lake Eacham rainbowfish.

  Rare frogs and crayfish are also at risk. Lake Morris, near Cairns, now carries barramundi, archer fish, bony bream, c
atfish, sleepy cod and sooty grunters, some of which belong in the system and some of which don’t. Koombooloomba Dam on the Tully River also has new fish. Both of these dams have feeder systems arising in Wet Tropics rainforests. Predatory fish may be swimming upstream in these places and devouring rare tadpoles and crays. ‘There are two rainforest frogs that could be threatened by fish,’ said Jean-Marc Hero, ‘the waterfall frog (Litoria nannotis) and the common mist-frog (Litoria rheocola). The World Conservation Union lists them as critically endangered.’ They hang on within a narrow altitudinal band, with chytrid fungus striking them at high altitudes and fish taking their tadpoles down below. In California native trout stocked in montane lakes have pushed the mountain yellow-legged frog (Rana muscosa) to extinction’s door.

  In the 1990s concern grew within Queensland Fisheries that stocking was running amok; that it clashed with the new policy of ecologically sustainable development. Peter Jackson drafted a new policy. Most stockings would continue – to appease anglers – but some would stop. Phil Cadwallader was lured up from Victoria to sell the changes, but he rejected some requests to stock saratoga into the wrong waters, and the Freshwater Fishing and Stocking Association of Queensland objected loudly. There were demands for ‘a more common sense and consensus based approach’. ‘People said I was a ratbag,’ Phil told me.

  Peter and Phil lobbied the stockers, and their cause was helped by a new fiasco. A hatchery had its broodstock infiltrated by barred grunters (Amniataba percoides), pugnacious fish that belong further north. They ended up in many a dam in southern Queensland and even in the Clarence River, New South Wales, where endangered freshwater cod (Maccullochella ikei) survive precariously. Too small to be worth eating, they grab baits before bigger fish can strike, and exact a heavy toll on native shrimps.

  Queensland now has a stocking policy that points in the right direction. All the western and Gulf rivers are permanently off limits, but meeting expectations in the east remains difficult. ‘We’re definitely trying to wind back the clock,’ said Peter. ‘It’s not easy.’ Yellowbelly and silver perch still go into the Mary River, despite government policy forbidding translocations into waters with threatened species. Some past wrongs can be righted because some Outback fish, including yellowbelly and silver perch, don’t breed in coastal waters. But getting yellowbelly out of the Mary remains politically impossible. Stockers want more fish, not less. Often they apply to stock species that aren’t even available. The core problem, one biologist said, is that ‘every recreational fisher thinks he has a God-given right to catch a catchable fish in every body of water in Australia – and that’s just fundamentally ludicrous.’

  Queensland Fisheries could do more if only conservationists would back them. ‘In the conservation movement there was no real concern about aquatic systems,’ Peter Jackson said. ‘That’s changing a fair bit.’ Still, all the political pressure has come from anglers. They flexed their muscles in 1994, and a government plan to ban fishing from national parks was dropped like hot coals. ‘Anglers slam plan for national parks ban’, one newspaper proclaimed. Fishermen now know they wield more clout than conservationists.

  Queensland, like other states, now has laws that restrain fish going into farm dams. Many thousands of fingerlings bred by private hatcheries are bought by landholders. But dams overflow during floods or after torrential rains, sending fish into distant rivers. You only need to see footage of flooded farmland to guess how far fish can go. Spangled perch often escape from dams, swimming on their sides when water flows over ground. I have one in the tank in my lounge room that I scooped out of my local creek – where it does not belong – when the water was low. ‘They do well in dams,’ Geoff Johnson told me. ‘Lots of people on acreage have these little dams that don’t serve any purpose. The people think, We’ve got a dam, let’s put fish in it. We won’t put exotics in, let’s put in a large native fish that the kids can catch. The spangled perch fits. They wash out of the dams, or people have them in tanks and release them. After wet weather I’ve had several enquiries from people saying they’ve seen big fish in their creek they’ve never seen before. The first thing I say is, “Are there any dams upstream?” Nine times out of ten the fish turn out to be spangled perch.’

  My perch is 13 centimetres long and bold as brass. After ten days he was snatching insects from my hand. Sometimes he strikes my finger. His gape is enormous. Kitchen cockroaches vanish in one gulp. Small fish are chased and swallowed whole. They leap from the water in fear. My perch eats anything that moves, right down to tiny mosquito wrigglers. He is handsome, but I wonder about all his mates patrolling waters where they don’t belong. And spangled perch are quite small. What are all the big fish doing?

  Queensland is not, of course, the only place where fish are moved about. Other states violate their waters with trout and salmon. In the south there are fewer native fish to choose from, and fewer dams to put them in, but ample attempts have been made over the years. A push was made to stock Victoria’s isolated Wimmera system, and in went Murray cod, yellowbelly, catfish, silver perch, and – by accident – western carp gudgeon (Hypseleotris klunzingeri). Macquarie perch (Macquaria australasica), now rare, went all over Victoria. Trout cod (Maccullochella macquariensis), now endangered, exists only in two sizeable populations, one of which (Seven Creeks, Victoria) was translocated. River blackfish (Gadopsis marmoratus) were moved about in Tasmania, and inland catfish (Tandanus tandanus) now frequent the Hawkesbury and Hunter Rivers.

  And then there are crayfish to consider. Yabbies (Cherax destructor) from the Outback have been stocked widely into dams, and they now occupy rivers and nature reserves in Western Australia and ponds in Sydney and southern Queensland. They walk from farm dams to nearby streams. Marron (Cherax tenuimanus), originally found south of Perth, have ended up in streams well to the north and east, and even on Kangaroo Island in a national park. Plans to farm them in the eastern states raise eyebrows. In recent years redclaw (Cherax quadricarinatus) from northern Australia have been moved around Queensland with unbridled enthusiasm. They’re now in new streams in the Wet Tropics and in reservoirs right down to Brisbane. People stock them and come back later with traps. ‘There was an absolute explosion of them in the North Pine Dam [near Brisbane],’ Geoff Johnson told me. ‘On weekends it’s quite a tent city. People were catching bucketfuls of the things. Big ones. People were driving hundreds of kilometres purely to catch them.’ Western Australian Fisheries won’t allow redclaw farms anywhere near pristine rivers, yet Queensland Fisheries have strived to create feral populations, dumping redclaw in the Burdekin and Tully and who knows where else.

  There are also worrying by-products of translocation. One is disease. This is a real fear where fish and crays are crowded together in warm, faeces-fouled ponds before release into the wild. Streptococcus iniae was brought recently to Adelaide on barramundi from northern Australia, killing silver perch at a farm. A native nodavirus, also very lethal to silver perch, came south in much the same way. Microsporidiosus has recently killed many yabbies at farms in Western Australia, raising suspicions that someone smuggled in infected yabbies from further east. Disease expert Lee Owen bewails our ignorance. ‘People don’t want to hear this story so it’s very hard to get funding.’

  Another concern is genetic pollution, the result of isolated stocks being brought together accidentally, or deliberately. Bernadette Kerby of Queensland Fisheries worries that Queensland will end up with no pure stocks of some fish. A third concern is genetic impoverishment, whereby huge numbers of fish are bred from a few spawnings, resulting in hundreds of thousands of near-identical fingerlings that flood the wild, greatly reducing genetic diversity. A further concern is loss of information, with experts not knowing if certain fish belong in rivers or not.

  But stocking is here to stay. Several of our Outback fish no longer breed well in the wild because the summer floods that induce spawning no longer come (blame irrigators for that). Murray cod, silver perch and yellowbelly are now se
mi-domesticated species, most wild stock originating in hatcheries. Stocking has also helped save endangered Mary River cod and freshwater cod from extinction.

  I wonder about the future. The catalogue of fish available to stockers can only grow. Any new rules will prove impossible to police. As Geoff Johnson said about illegal stocking, ‘If you were caught you’d be the most unlucky person alive.’ In the future there will be many more strange fish and crays, both Australian and foreign, lurking in our waters. Will any rivers remain inviolate? Australia has a National Policy for the Translocation of Live Aquatic Organisms, but it’s no real help. It declares that ‘for a stocking program the establishment of a feral population may be the desired outcome’. Stockers have done to the water what native gardening and pet owners have done on land: reshuffle the ecological pack, throwing species together in unpredictable new combinations.

  1  Freshwater fish stocking, research and monitoring have been the responsibility of various sections within the Queensland government, usually answerable to the Minister for Primary Industries. Department names and structures have changed over the years, but for simplicity I just say Queensland Fisheries.

  ‘When is a native not a native?’

  National Parks leaflet on golden wreath wattle