17 November 2010

Macquarie perch are a medium sized freshwater fish native to the Murray-Darling Basin. They were historically found throughout the slopes and upland areas of the southern Murray Darling Basin and where a popular target for fishermen. However, populations began to crash by the mid 1900s because of river regulation, fish passage barriers, introduced species, sedimentation and pesticide use. By the 1970s, Macquarie perch were considered to be seriously threatened with extinction. Since then, the species has continued to decline, with populations considered viable as recently as 2005 having declined or disappeared.

Only a small number of self-sustaining populations remain and the species is now endangered at a state and national level.

One remnant population in the upper Lachlan catchment was threatened by the recent introduction of redfin perch into their habitat. Because of the serious threat redfin are believed to pose to Macquarie perch, I&I NSW used funds supplied by recreational fishers in NSW (via the Recreational Freshwater Fishing Trust) for an emergency rescue mission and captured 122 Macquarie perch from the population in case of catastrophic collapse of the population in the wild. These fish are being held in captivity at the Narrandera Fisheries Centre until a safe haven can be established and they can be reintroduced back into the wild.

While at the Fisheries Centre, I&I NSW researchers and hatchery staff have been supported by the Recreational Freshwater Fishing Trust to trial methods to breed the species in captivity. Past attempts to breed captive Macquarie perch have failed, as mature fish have never been able to reach breeding condition in captivity. Past hatchery programs for the species have relied on capturing spawning run fish from the wild - something that would best be avoided for an endangered species such as Macquarie perch.

Using the novel approach of constructing an ‘artificial stream’ at the Narrandera Fish Hatchery, I&I NSW have been able to coax the captive perch into thinking they were in a natural environment and as a result, both male and female Macquarie perch have reached breeding condition for the first time in captivity. This has happened after only two years of preparation and research by the committed team involved with the project.

With advice from the Department of Primary Industries in Victoria (who have successfully artificially bred spawning-run Macquarie perch in the past), I&I NSW where able to obtain viable eggs and sperm from the captive fish and fertilise them in the hatchery. The first of the eggs began to hatch today (12 November 2010) and I&I NSW anticipates having several hundred baby Macquarie perch to release into the wild in early 2011.

Having developed the capacity to establish a captive breeding and reintroduction program for the species (without putting pressure on precious remnant populations), I&I NSW has just opened the door to a large-scale recovery of this important endangered species in those parts of the Murray-Darling Basin where they are extinct.

 

By Dr Dean Gilligan
Industry & Investment NSW
Aquatic Ecosystems Research unit