Conserving the unknown

Since the mid-20th century, our ability to exploit the world's oceans has increased tremendously, largely using technology originally designed for sea warfare. Fishing boats now reach the furthest oceans, schools of fish are tracked underwater with pinpoint precision, and huge nets and lines harvest many fish rapidly.

Despite this vastly increased efficiency, the total world harvest of fish has hardly changed in the last 30 years. Most of the world's important fisheries, including Australia's, are either fully exploited or overexploited; many have collapsed completely, with no fish left to catch. It is not just the targeted fish species that have suffered. Overfishing is often compounded by collateral damage to the marine environment and other inhabitants of the ocean.

In a CSIRO study of damage caused by trawling off deepwater sea mounts south of Tasmania, video cameras revealed that chains and nets dragged by boats fishing for orange roughy removed dense communities of benthic organisms. The tragedy is not only the number of species lost from these communities, but also that the number could not be estimated because we know little about the inhabitants of the ocean floor. Most of the diversity found in marine ecosystems consists of invertebrates living in or on bottom sediments, with estimates of the number of marine benthic species varying from 0.5 to 5 million.