These tiny fish, swan galaxias, can grow to a maximum length of about 5 inches. The introduction of brown trout to the island more than 160 years ago is a major culprit. A tiny fish in Tasmania might be in trouble. The Threatened Species Scientific Committee , an advisory body to the Australian government, states that the primary threat to this fish is competition and predation from alien fish.
Settlers made early, scattered attempts to introduce trout and salmon to the territory starting around 1841, but the breakthrough came in 1864, when trout eggs brought across the ocean from England were successfully hatched at Plenty, Tasmania. So the 2016 advice called for further genetic studies. When the advice was written in 2016, the fish’s eggs had not been found in the wild, so its spawning sites were still a mystery.
Eventually, trout became widespread around the island’s rivers and lakes. But now there was a new danger for the tiny native fish of Tasmania, who found themselves sharing their streams with a new predator. Moving fish around might not be the perfect fix. The committee noted that the natural genetic variety of the moved groups was unknown. Genetic diversity enables a species to adapt to change. The natural populations are also isolated from one another.
