The Australian grayling (Prototroctes maraena) is a primarily freshwater fish found in coastal rivers in south-eastern mainland Australia and Tasmania. In past decades it has also been known as the cucumber mullet or cucumber herring, for its cucumber-like odour. Description and diet The Australian grayling is a streamlined fish with a long and slender body and small conical head. Colouration is usually silver on the flanks and dusky olive on the back, overlain with a gold sheen. Australian grayling commonly live for 2–3 years and reach around in length, although rare individuals have been recorded up to at least 5 years in age and in length. The fish has an omnivorous diet, feeding upon algae, shrimp, and small insects. They have specially adapted teeth and a long gut to help with the digestion of algae. Reproduction Australian grayling spawn in the freshwater reaches of coastal rivers. Spawning is thought to occur in late autumn or early winter. McDowall (1996) reports that egg counts range from 25,000 to 67,000 in females 170–200 mm long, and that the small (~1 mm) demersal eggs probably settle among gravel and cobble in the river bed before hatching. Hatched larvae are washed out to sea. Australian grayling juveniles return to the freshwater reaches of rivers after roughly 6 months at sea and spend the rest of their lives in river habitats. Angling Before the introduction of exotic fish species including the Eastern mosquitofish and trout to Australian waterways the Australian grayling and spotted galaxias were keenly fished by recreational anglers using fly-fishing gear. The species was appreciated for its willingness to take wet and dry flies, its excellent fighting ability on very light tackle, and its relatively large size. However, due to declining numbers the fish is now protected under the Environment Protection and Biodiversity Conservation Act 1999. Heavy penalties apply for taking any of the fish. Historical declines and current threats Australian grayling suffered massive initial declines in 1868–70 through very large, unexplained fish kills (Saville-Kent, 1888). Australian grayling killed in these events are described as being covered in "cottony growths", a characteristic hallmark of the exotic fungus-like oomycete Saprolegnia; these kills likely mark the arrival of this exotic pathogen in Australian freshwater habitats via the importation, culturing and stocking of exotic salmonid species. Saville-Kent then went on to consider the apparent epidemic some 17–18 years previously which had caused the demise of the