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By Root 2060 0

that same unproductive land, and because Australian coastal waters lack nutrient-rich upwellings comparable to the Humboldt current off the west coast of South America. Australia’s marine populations tend to have low growth rates, so that they are easily overfished. For example, within the last two decades there has been a worldwide boom in a fish called Orange Roughy, caught in Australian and New Zealand waters and providing the basis of a fishery that has been profitable in the short term. Unfortunately, closer studies showed that Orange Roughy are very slow-growing, they do not start to breed until they are about 40 years old, and the fish caught and eaten are often 100 years old. Hence Orange Roughy populations cannot possibly breed fast enough to replace the adults being removed by fishermen, and that fishery is now in decline.

Australia has exhibited a history of marine overfishing: mining one stock until it is depleted to uneconomically low levels, then discovering a new fishery and switching to it until it too collapses within a short time, like a gold rush. After a new fishery opens, a scientific study by marine biologists may be initiated to determine the maximal sustainable harvesting rates, but the fishery is at risk of collapsing before recommendations from the study become available. Australian victims of such overfishing, besides Orange Roughy, include Coral Trout, Eastern Gemfish, Exmouth Gulf Tiger Prawns, School Sharks, Southern Bluefin Tuna, and Tiger Flathead. The only Australian marine fishery for which there are well-supported claims of sustainable harvesting involves the Western Australian rock lobster population, which is currently Australia’s most valuable seafood export and whose healthy status has been evaluated independently by the Marine Stewardship Council (to be discussed in Chapter 15).

Like its marine fisheries, Australia’s freshwater fisheries as well are limited by low productivity because of low nutrient runoff from the unproductive land. Also like the marine fisheries, the freshwater fisheries have deceptively large standing crops but low production. For example, Australia’s largest freshwater fish species is the Murray Cod, up to three feet long and confined to the Murray/Darling river system. It is good eating, highly valued, and formerly so abundant that it used to be caught and shipped to markets by the truckload. Now, the Murray Cod fishery has been closed because of the decline and collapse of the catch. Among the causes of that collapse are the overharvesting of a slow-growing fish species, as in the case of Orange Roughy; effects of introduced carp, which increase water turbidity; and several consequences of dams built on the Murray River in the 1930s, which interrupted fish spawning movements, decreased river water temperature (because dam managers released cold bottom water too cold for the fish’s reproduction, rather than warmer surface water), and converted a river formerly receiving periodic nutrient inputs from floods into permanent bodies of water with little nutrient renewal.

Today, the financial yield from Australia’s freshwater fisheries is trivial. For instance, all freshwater fisheries in the state of South Australia generate only $450,000 per year, divided among 30 people who fish only as a part-time occupation. A properly managed sustainable fishery for Murray Cod and Golden Perch, the Murray/Darling’s other economically valuable fish species, could surely yield far more money than that, but it is unknown whether damage to Murray/Darling fisheries is now irreversible.

As for freshwater itself, Australia is the continent with the least of it. Most of that little freshwater that is readily accessible to populated areas is already utilized for drinking or agriculture. Even the country’s largest river, the Murray/Darling, has two-thirds of its total water flow drawn off by humans in an average year, and in some years virtually all of its water. Australia’s freshwater sources that remain unutilized consist mainly of rivers in remote northern areas, far from human