The Director of the Environment Protection Authority (EPA) has completed his review of the Spring 2016 salmonid monitoring data for Macquarie Harbour.
This is the most recent round of benthic monitoring undertaken by the three salmon companies operating in Macquarie Harbour and the first assessment by the Director since the Tasmanian Government transferred the environmental regulation of salmon farming to the EPA on 1 July 2016. A summary of this information will be made available on the EPA Tasmania website at the end of November.
The EPA Director, Mr Wes Ford said that marine farming licence conditions require the licence holders to undertake regular visual monitoring of the benthic habitat in and around all salmonid marine farming lease sites in the State. He explained that the survey work is undertaken by the companies using remotely operated underwater vehicles mounted with cameras, and that a range of controls apply to the management of lease areas and compliance points situated 35 meters outside the lease boundary.
"The recent surveys indicate that four lease sites have significant visible impacts, as defined in the licence conditions, at some of the compliance points adjacent to the lease areas," Mr Ford said.
"Following the reporting of these visible effects and as a consequence of the licence conditions, I have written to the respective lease holders advising them that management actions are required to reduce the impact of particulate waste on the benthic environment in proximity to the affected compliance sites."
"This will require targeted fallowing of the affected lease areas, site management plans to be submitted and sediment condition to be re-assessed prior to any proposed restocking," he said.
Mr Ford explained that the fallowing strategies used by the companies vary across lease areas, and typically, only about 50 to 70 per cent of the available pen bays across lease sites operated by each company are stocked with salmon pens. Outputs of the benthic monitoring undertaken by the companies are assessed relative to marine licence conditions and will be validated against independent research conducted by the Institute of Marine and Antarctic Studies (IMAS), and against research commissioned by the companies themselves.
As part of the review of the monitoring data the Director was briefed on the research being undertaken by IMAS and CSIRO.
"Water quality monitoring data, collected by the EPA, industry, IMAS, and the CSIRO through separate monitoring programs, shows that the low level of dissolved oxygen in the deeper parts of the harbour has continued for much of the year, and in some areas the dissolved oxygen has dropped to very low levels," Mr Ford said.
"As a result, the industry and the EPA are monitoring the situation in the harbour very carefully and I will determine whether further management action is required, beyond that of my current directions to the companies." he said. The data collected over the next few months will be critical in informing management decisions taken by the companies, and the Director, that will determine stocking levels for 2017.
"All three companies have reduced their stock of salmon, such that the total biomass will be significantly less than the approved biomass cap for the harbour for the 2016/17 period," said Mr Ford.
Mr Ford said "The appropriate management of the impacts of nutrient inputs into the benthic system is essential for the ongoing sustainability of the Harbour, the ecosystems it supports and the ability to grow salmon in a sustainable manner."