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Huon Estuary/D'Entrecasteaux Channel nutrient enrichment assessment: Establishing the potential effects of Huon Aquaculture Company P/L nitrogen inputs

posted on 2023-05-25, 04:39 authored by Bell, J, Donald RossDonald Ross, Mardones, J, Wild-Allen, K, Catriona MacLeodCatriona MacLeod
Aquaculture, like most farming practices, has the potential to impact the environment through the introduction of nutrients; nitrogen (N) in particular can have an impact as it generally limits primary productivity of coastal marine systems. N enters the environment as overfeed, faeces and urine. Approximately 85% of the N released is dissolved (urine) and immediately available to primary producers in the water column. The remainder is released as particulate material (faeces and feed), which settles onto the seabed where sedimentation processes break down the particulates, consuming oxygen in the process, and releasing various forms of N back into the water column, providing an additional nutrient source to feed primary productivity. This, along with naturally occurring forms of N, can lead to nutrient enhancement and potentially eutrophication and algal blooms.

Nutrient inputs from the salmonid aquaculture industry in the D’Entrecasteaux Channel and Huon region are regulated through a feed cap, to help ensure levels remain environmentally sustainable. In the Huon River and Port Esperance Marine Farming Development Plan (MFDP) area and the D’Entrecasteaux Channel MFDP area each salmonid company has been allocated a Total Permissible Dissolved Nitrogen Output (TPDNO) limit. This limit and the period over which it applies has been determined in accordance with the provisions of Management Controls contained in each of the MFPDs. Dissolved nitrogen outputs that can be discharged within the MFDP area must not exceed the prescribed limit during any 12-month period. In July 2015, Huon Aquaculture Company (HAC) reported to government that it had exceeded its TPDNO limit in the Huon/Port Esperance MFDP area. Further, it was also clear that they would continue to exceed this limit for some time.

As a result the present study was commissioned to 1) document the nature, timing and location of HACs N exceedance, 2) assess the extent of any adverse ecological effects using available monitoring data, and 3) evaluate the potential risk of adverse effects using modelling. The findings of the resultant report would then be used to help determine what (if any) management response might be needed to reverse any observed negative impacts in the Huon Estuary/Port Esperance MFDP area.

The primary resource available for this assessment is data collected for the Broadscale Environmental Monitoring Program (BEMP). The BEMP is a comprehensive environmental monitoring program that was designed to track broadscale changes in the system; both natural and in response to changes in salmon aquaculture inputs and other sources of nutrients. It is a legislative requirement of finfish aquaculture license holders in the D'Entrecasteaux Channel and Huon/Esperance MFDP areas. As a result, a range of nutrient, water chemistry and algal composition data are gathered monthly throughout the year and fortnightly during summer.


Commissioning body

Institute for Marine and Antarctic Studies, University of Tasmania






Institute for Marine and Antarctic Studies


Institute for Marine and Antarctic Studies, University of Tasmania

Place of publication

Hobart, Tasmania

Repository Status

  • Restricted

Socio-economic Objectives

Aquaculture fin fish (excl. tuna)

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