Australia's Desert Fish Have Flourished for Millennia in a Changeable Environment TEXT by ROBERT LEHANE and BARRY SKIPSEY
Total Page：16
File Type：pdf, Size：1020Kb
Australia's desert fish have flourished for millennia in a changeable environment TEXT BY ROBERT LEHANE AND BARRY SKIPSEY Afloat in the Red Centre, pioneering freshwater fish researcher Hamar Midgley, assisted by his wife Mary at the oars, plies his science on one of the Finke River's permanent waterholes - refuges during dry times I for Australia's remarkable desert fish. About 10 species are found widely throughout Central Australia. The Midgleys found five at this NT waterhole, with bony bream, foreground, the most common. APRIL - JUNE 1996 105 • CHORUS OF BIRDS had shat- are literally the gene pools of Aus- tered the icy calm of the tralia's desert fish. Like the outback's A. winter sunriseI tanhrd woken other ephemeral watercourses, the peered Finke has only a few permanent holes, flap of my swag as a warming yellow but it's in them that fish survive dry gjow rose over the Finke River water- times, dodging predators and endur- hole. With each passing minute, the ing scorching summer days and bit- red dunes bordering the opposite bank terly cold winter nights. Then, like ripened to a richer hue. desert flowers, these remnant popula- Alerted by splashing, I shifted my tions explode into life when rains gaze back to the waterhole, where I come, multiplying and dispersing with saw — to my astonishment — a pair of long-awaited floodwaters to repopu- pelicans. I'd never seen these grand late the rivers and ephemeral lakes. birds so deep in Central Australia — To learn about these tenacious ani- I was only 110 kilometres south of mals, Fa joined an expedition led by Alice Springs. As one of the pelicans Hamar Midgley, one of the pioneers opened its bill and tipped back its head of Australian freshwater fish research. to swallow its prey I saw a flash of sil- Hamar's campsite was about 200 m ver-grey. My surprise turned to a smile distant and screened by river red gums, of recognition. The birds and I were but I could hear him chattering as he after the same thing — fish. dislodged ice from his water bucket. Permanent waterholes like the 400- His gravelly baritone voice had been metre-long beauty I'd camped beside stamped on my memory the moment PHOTOS: BARRY SKI PSEY "I've a fierce love of warm places," said Hamar Midgley — pictured with Mary, rugged up for a desert winter night. Married 54 years, the couple — based in Bli Bli, in south- eastern Queensland — have collaborated on freshwater fish studies at more than 500 sites since the 1960s. Hamar is a self-taught scientist, and his work has been widely lauded. In 1994, the University of Queensland awarded him an Honorary Doctorate of Science — a rare tribute. 106 AUSTRALIAN GEOGRAPHIC Two skilled fish catchers cruise the we'd met in Alice Springs the day rounding vegetation. Three of their Finke waterhole in a serene search before. "Glad you could make it, discoveries now bear their name - the for breakfast. The pelicans have Barry," he'd said, pumping my hand. shovel-nosed catfish or silver cobbler come to the right place. In spite of Hamar's friendly bushie welcome (Arius midgleyi), Midgley's carp gud- a range of clever adaptations, some disguised his studious calling. For 30 geon and Midgley's grunter. fish - usually weaker individuals of years, he and his wife Mary have After meeting in Alice, I'd followed a particular size - succumb to cold amassed an incredible body of infor- Hamar, Mary and a handful of their temperatures. When the Midgleys mation on the freshwater fish of north- friends and family to the Finke, where arrived at the Finke, pelicans, ern and Central Australia. At about we set up camp and deployed a string cormorants and even grey teal - not 500 sites they've searched for fish and of fishing nets across the waterhole. normally fish eaters - were feasting other aquatic life and recorded water Next morning, the sight of the feast- on 3-10 cm long bony bream. The temperature and chemistry, the phys- ing pelicans dispelled any doubts I'd 13°C water temperatures had the ical make-up of riverbeds, and sur- had about finding fish out here. fish in a torpor. APRIL - JUNE 1996 107 The extremes of desert life rarely faze the bony bream, also known as hairback herring (right), which can survive in water that's nearly as salty as the ocean and temperatures from 9-38°C. Found throughout Australia except the south-east, south-west and Tasmania, this distant relative of marine herrings and sardines is abundant, but seldom seen as it's not a popular target for anglers. It may grow to 40 cm, but is usually 12-25 cm. The spangled perch (below) is another widely distributed species, found in eastern and northern coastal areas as well as the inland. Rarely surpassing 25 cm in length, it preys on small aquatic insects, crustaceans and molluscs, and will tolerate saltier water and greater temperature extremes than bony bream. CRAMMED INTO a 2.4 m tinnie, the Environmental Studies at the Aus- When I told Hamar that I'd never Midgleys' friends, Professor Henry Nix, tralian National University and a reg- heard of bony bream, he reminded me Mike Tyre11 and his son Kendrick, ular associate on Hamar's field trips. that only a few fish that ply desert rowed in from the centre of the water- "Although they're full of bones and waters, generally the favourites among hole after clearing the nets. I'd waited regarded as inedible by humans, anglers, are well known. Most of the 10 ashore with Hamar, whose 75-year- they're the major food fish of our fresh- species distributed widely throughout old fingers stiffen in cold water. Three water systems. They support the larger Central Australia are small and mys- silvery fish, the largest about 30 cen- predator fish, like yellowbelly, that we terious, and scientists have only timetres long, lay in the bottom of the do like to eat." recently begun unlocking their secrets. cluttered boat. "You'd expect bony bream to be Among the most common are bony "These are all bony bream, some abundant here," added Hamar. "They bream, desert goby, Lake Eyre hardy- of the largest I've seen," said Henry, eat algae, and there's plenty of that in head and spangled perch, which are director of the Centre for Resource and this waterhole." found in artesian springs and artificial GUNTHER SCHMIDA The yellowbelly, also known as callop or golden perch, is one of the largest and best known of our inland fish. Until recently, the Murray-Darling species (above) was thought to be the only yellowbelly, but the callop inhabiting the ephemeral watercourses of the Lake Eyre Basin is now classed separately. It has the ability to spawn within three days of rainfall — a handy trait in its temperamental environment. APRIL - JUNE 1996 109 bore drains as well as ephemeral water- entire drainages in a remarkably short ways. All have evolved remarkable time. But this underlines how abso- adaptations to suit their changeable lutely vital permanent waterholes like environment. this are. If they get degraded or fished For example, yellowbelly - also out, you've effectively blown the known as golden perch or callop - can whole system." survive in water that's almost as salty As an environmental scientist, as the ocean, and water temperatures Henry lauds Hamar and Mary's work. ranging from 4-37°C. When females "It's probably the single best biological spawn - triggered by rising water lev- record of any kind in the country," he els and temperatures - they'll produce told me. "Its big advantage is that up to 500,000 eggs. they've returned to sites to get a pic- Later that morning, Hamar and ture of what changes have taken place Mary rowed out to measure the water's over the years. This is vital because oxygen content and temperature. As freshwater fish are a very good indica- Hamar's navigational instructions tor of the health of the environment. resounded around the waterhole, Generally, the number of fish species Henry told me that several factors drops off as water quality declines." influence the survival of desert fish, The Midgleys have built this record but none match the impact of the out- with remarkable dedication. Although back's natural cycles. businesses and governments have "The distribution and abundance often paid them to undertake research, of inland fish is more a result of rain- they've funded many expeditions from fall than anything else," Henry said as their own pockets. "I only started the we drank tea and watched his artist work because I was a keen fisherman, wife Katharine paint a bony bream. and I wanted to catch more fish," "During a flood, they can repopulate Hamar told me later that evening, as PHOTOS: BARRY SKIPSEY The Midgleys fund many of their own expeditions, with family and friends often lending a hand. One regular helper is environmental scientist Professor Henry Nix (above, at right), pictured returning to shore after checking nets with Mike Tyre11 and Mike's son Kendrick. Hamar, left, secures the boat. To catch a wide cross-section of the waterhole's fish, Hamar (left) deploys gill nets of several mesh sizes. One species that didn't get away was the inland rainbow fish (right), a natural predator of mosquito larvae and a popular choice for home aquariums. Its remarkable ability to disperse in floodwaters has seen it establish populations in bore drains. 110 AUSTRALIAN GEOGRAPHIC 111 we sipped port by the campfire.