A much-anticipated field trial for a biological control agent to cull the ecosystem destroying European carp has been pushed back to at least mid-2027, according to Department of Agriculture, Fisheries and Forestry projections.
The major introduced pest has caused havoc in Australian freshwater by disturbing sediment and adversely affecting water quality and plant growth and decimating native fish populations in many areas since the 1960s.
A battle plan to curb the proliferation of the invasive species through the introduction of a herpes virus was announced by then-Agriculture Minister Barnaby Joyce in 2016.
The $15-million National Carp Control Plan was then expected to be finished by the end of 2019 but that deadline was instead extended out to 2021.
However, following Covid-era disruptions and several other issues, Commonwealth and state and territory Agriculture Ministers pressed pause on the plan, ordering further research in October last year, in addition to the plan, to address "carp virus safety and feasibility knowledge gaps" that must be completed before the program could proceed.
A DAFF spokesperson said the additional research will likely take up to two years and be used to support the formal registration of the carp virus under Commonwealth legislation.
A controlled trial can then only commence if the virus has been approved for use in Australia by all regulatory agencies involved, a process "expected to take another two years."
"A field trial could not commence till at least mid-2027 when knowledge gaps have been addressed, regulatory approvals are in place and agreement sought from Agriculture Ministers," the spokesperson said.
Carp populations have exploded in Australia despite various methods to reduce numbers over decades and were also given a significant boost through recent flooding events.
Lead NCCP research agency, the Fisheries Research and Development Corporation, is currently waiting for the results of several pieces of CSIRO research to fold into the plan.
The research is attempting to answer many questions, but key are whether the cyprinid herpesvirus-3 viral disease, or koi herpesvirus, is effective at controlling carp populations long-term, if it could "jump species" and what the side effects of releasing the virus would be on water quality.
The NCCP currently includes nine other technical reports on the carp herpes virus, including a FRDC study showing decomposing carp could suck the oxygen out of river systems and kill native species if not quickly removed.
Meanwhile, CSIRO has also previously "identified that CyHV-3 does kill Australian pest carps, and it kills them quickly" and that the virus kills up to 95 per cent of infected fish under optimal conditions.
The virus first appeared in Germany in 1997 and, although spreading rapidly throughout the world, has yet to reach Australia or New Zealand.
It would not totally obliterate carp itself if introduced, but it would be expected to significantly thin numbers at a localised level where other carp-busting methods would then be employed to further reduce populations.
Experts also predict an unwelcome consequence of the government's current Murray-Darling Basin water buyback scheme could be an increase in carp populations.
A six-kilogram European carp can spawn 1.5 million eggs.
