UNDERWATER and out of sight, deep in the wild and remote Abercombie River system a battle is underway. A battle that has been played out for over 150 years in many other areas across the southern Murray Darling Basin. It’s the battle between redfin (English perch) and our native species, and unfortunately it’s a battle that in a lot of cases has been lost by our natives.
One species that has been hit particularly hard by this invader is the Macquarie perch. Macquarie perch were once the dominate species across much of the slopes and upland regions of inland southern NSW and Victoria. They were a highly prized angling target, and considered by many to be one of the finest freshwater table fish in Australia.
Sadly, this species has undergone significant declines across its range and is now listed nationally as an endangered species. Habitat degradation, erosion and sedimentation, river regulation, blockages to migration and the predation, competition and diseases spread by introduced species have combined to push the species to the brink of extinction. So today’s anglers currently do not have the pleasure of seeing these magnificent fish in the wild, feeling their mighty tug on the end of their line or tasting their soft butter flesh.
Redfin were introduced into Australia in the 1860s as a sport and table fish and have long been implicated in the declines of many native fish. Since the 1860s, redfin have moved and been transported far and wide where they have caused havoc to not only native fish but also trout fisheries as well. One place they had not reached until recently was the Upper Lachlan and Abercombie Rivers above Wyangala Dam. This is one of the reasons why these areas were home to one of NSW's most abundant and widespread remaining population of Macquarie perch - that was until 2005!
The first ever official record of a redfin being captured from the Upper Lachlan Catchment occurred in November 2005, when a single fish was captured from a tributary of the Upper Lachlan. In April/May of 2006 three fish were caught, then in December 2006, 254 were caught; they were the most dominate species captured and were caught from virtually every site sampled.
Unfortunately, this dramatic increase in spread and numbers of redfin has led to the demise of the remnant Macquarie perch population that existed within the Upper Lachlan until this recent invasion.
Redfin have now become established in Wyangala Dam and are currently making their way up the Abercombie River, where they will likely have a similar devastating impact on the Macquarie perch population there.
So what is being done about it?
With it virtually impossible to remove pest fish such as redfin from a catchment once they become established, other measures have been taken to try and secure the Macquarie perch within this catchment. Firstly, a captive population was taken from the wild and established at the Inland Fisheries Research Centre at Narrandera where - with funding from recreational anglers - novel new techniques have been used to breed Macquarie perch in captivity, including the recreation of the species’ natural breeding environment.
2010 proved to be the first time ever that Macquarie perch were successfully bred from captive fish in a hatchery environment. Since then several thousand Macquarie perch have been bred at Narrandera; but there is no point breeding them if you don’t have anywhere to put them. With their original habitat under immediate threat from redfin and most of the remainder of their former range either degraded or similarly impacted, the hunt was on to try and find a suitable location where a refuge population of Macquarie perch could be established.
A suitable location was needed somewhere that had suitable habitat and was free from redfin. Somewhere the pest species could not get to on its own. After an extensive search a suitable location was discovered deep in the Abercombie National Park, the Retreat River, a spectacular and remote tributary of the Abercombie, this was to become the Macquarie perch’s Noah’s Ark against the flood of redfin.
The Retreat River has fantastic Macquarie perch habitat, no redfin and a barrier in the form of a waterfall to prevent them gaining access. So with help and support from recreational anglers, particularly the Central Acclimatisation Society, the Retreat River has begun to be populated with captive bred Macquarie perch; so far a total of 19336 fish have been released in three consecutive years. Recent surveys have shown that fish from all three releases are thriving in their new home, with fish from the first stocking now approaching breeding age. Fingers will be crossed that next spring the first juveniles will be bred within the refuge site.
This work would not have been possible without funding from both the Lachlan Catchment Management Authority and the Recreational Fish Trust. Whilst the apparent establishment of Macquarie perch within the refuge site shows great promise, there is still a long way to go before securing this species and ultimately one day having it returned as a prized angling species. While there has been some limited success with captive breeding the techniques are not yet perfected, and this work needs to continue, as does work to protect the remaining remnant habitat and wild populations.
Equally as important, the spread of redfin into new areas has to be stopped. Recently there have been several new invasions of redfin into new areas including Oberon Dam, Lake Lyell, Wentworth Falls Dam and the Wollondilly River where they are having devastating effects on not just native fish species but the trout fisheries as well.
If we desire to again be able to target the brilliant Aussie Macquarie perch and afford our children the same unique experiences that our forefathers enjoyed, than we need to act! Captive breeding techniques need to be perfected, and a concerted targeted reintroduction program established, coupled with habitat restoration and rehabilitation and the management of pest fish species.
See related story here.
Redfin are listed as a Class 1 noxious fish and therefore it is illegal to be in possession of live redfin within NSW, to use them as bait and to transfer them between any waterways.