Australian Grayling, Prototroctes maraena

The Australian Grayling (Prototroctes maraena) is a freshwater fish found in coastal rivers in Tasmania and southeastern Australia. This fish has often been called the Cucumber Mullet or Cucumber Herring due to its cucumber-like odor.

This fish is streamlined with a vaguely trout-like shape. It is silver on the flanks and dusky olive on the back, overlain with a golden shine. It can live 2 to 3 years and reach a length of roughly 7.9 inches. It has rarely been recorded up to 5 years of age and 13 inches long.

The Australian Grayling spawns in the freshwater regions of coastal rivers. Spawning is believed to occur in late autumn or early winter. Some reports estimate that egg counts range from 25,000 to 67,000. The eggs settle among the gravel and cobble in the riverbed before hatching. Hatched larvae are washed out to sea. The juveniles return to the rivers after about 6 months at sea and spend the rest of their lives in river habitats.

The diet of this fish is mainly algae, shrimp and small insects.

This was once a popular fish for angling. But the introduction of exotic trout species placed significant strain on the conservation of many native fish species and fly-fishing for the Australian Grayling subsided. However, there has been a small comeback of anglers who are discovering the pleasure of fly-fishing for this magnificent native fish.

The Australian Grayling suffered massive declines in 1869 and 1870 due to a large surge of unexplained fish kills. Descriptions of grayling killed in this event of being covered in “cottony growths” suggests a fungal pathogen making its way into freshwater habitats due to reckless importation of salmonid species.

Today, these fish are threatened by dams and weirs that block their migration and also reduce base flows, a key element of their habitat maintenance. It also affects spawning and movement of larvae and juveniles to and from the sea. Forestry and farming has also degraded river environments through siltation and other effects. Exotic trout species also threaten the grayling through predation and competition.

Australian grayling are listed as a vulnerable species under Australia’s Environment Protection and Biodiversity Conservation Act 1999.

Image Caption: A relatively small Australian grayling, caught from a small coastal stream in south-west Victoria, on a small dry fly (visible in picture). The grayling was carefully released after the photo. Credit: Nathan Litjens/Wikipedia(CC BY-SA 3.0)