Sea Cage fish farm produce large volumes of wastes and pollution. Fish produce waste products through faeces and excreted ammonia. Excess feed not taken up by the animals also enters the environment.

The Sea Cage fish farm proposed for Darwin Harbour will pump almost as much pollution in the form of nitrogen into the Harbour as the Larrakeyah raw sewage outfall!

The proposed Sea Cage farm in Bynoe Harbour , soon to be a Marine Park , will pump more pollution in the form of nitrogen into the marine environment than the Larrkeyah raw sewage outfall.

One of the key pollution problems in our marine environments comes from Nitrogen inputs.

- Larrakeyah raw sewage outfall - Nitrogen 100 tonnes per year
- Ludmilla sewage outfall - Nitrogen 90 tonnes per year
- Darwin Harbour Sea Cage fish farm proposal - Nitrogen 90 tonne per year
- Bynoe Harbour Sea Cage fish farm proposal - Nitrogen 135 tonne per year

Potential impacts of pollution include:

• accumulation of fish feed pellets and fish faeces on seafloor
• smothering of seafloor fauna
• degraded water quality
• eutrophication of water column
• growth of algae and epiphyte plants
• effects on animal habitats such as seagrass and coral communities
• alteration of algal and seagrass community structure – feed sources for turtle, dugong and other marine wildlife

“Aquaculture’s feed demands are pressuring wild fish populations” one page article from CSIRO’s magazine (PDF 952KB) click here

Seventy-five per cent of the world’s fish populations are currently fully exploited, over-exploited or depleted by the global fishing industry. Farming of marine species in aquaculture production isn’t expected to compensate for these impacts, and may well exacerbate them, particularly as aquaculture’s demand for wild fish species for feed continues to rise. According to CSIRO researchers, fishmeal production is an unsustainable use of wild fisheries resources.

Potential impacts include:

• transfer of diseases, parasites and other to wild barramundi populations. This may cause illness and death of native barramundi and other fish species.
• effects from the introduction of chemicals to the water column from the treatment of farmed fish.

5. Hazardous materials and chemicals

At each of the proposed sites, Darwin Harbour , Bynoe Harbour and Snake bay, there is a large number of chemicals and fuels to be stored in floating barges on the marine environment.

The Bynoe Harbour site for example will hold:

• Up to 10,000 litres of diesel fuel
• Up to 1,500 litres of petroleum fuel
• 250 tonnes of feed
• 1000 kg of potassium hydroxide
• 200kg of antibiotic
• 47 other chemicals

This large volume and wide range of chemicals would likely have a major impact on the Bynoe Harbour should the barge be sunk, unturned or ruptured in the course of a climatic or other event, such as a cyclone. We are expecting more severe and potentially more frequent cyclones in the NT. However the EIS does not discuss remedial actions in the event of a major or minor spill of contaminants. Nor does the EIS outline its contingency plan in the event of a cyclone.

For the Bynoe Harbour proposed site there are 13 rare and threatened species and 31 migratory species listed.
For the Darwin Harbour proposed site there are 13 rare and threatened species and 33 migratory species listed.
For the Snake Bay farm there are 11 rare and threatened and 19 migratory species listed.

In the Bynoe Harbour region internationally significant populations of green and hawksbill turtles forage in the region of the proposed sea cages and in adjacent areas. Flatback and Olive Ridley sea turtles nest in the region at Bare Sand and Quail islands and also at Indian Island (immediately adjacent to the proposed sea cage location). Dugongs occur in the proposed area, particularly around Turtle, Indian and Bare Sand Islands .

There are many and varied potential impacts on rare, threatened and migratory species:

• Sea cages attract predators to the area. This may result in an increase in predation of turtles and other species.
• Lighting associated with the operation is likely to attract hatchlings in the area. Survival chances would then be close to nil, either from predation or from using up their energy reserves before they reach open water.
• Disturbance is an issue for sea turtles and dugongs and increased disturbance may impact turtle and dugong in the area. Dugongs are shy animals and continuous disturbance will cause dugongs to move away from an area on a permanent basis.
• Increased nutrients may affect the algal and seagrass balance and the species composition within these groups and therefore affect (possibly decrease) food availability for turtles and dugongs
• Boat strike: Increased boats in the area could increase injuries and deaths from collisions with dugongs and turtles
  (Above information - Dr Scott Whiting pers. Comm)

7. Other Impacts

- Creation of noise and odour nuisance
- Loss of remoteness, naturalness and aesthetic values and associated tourism values
- Impacts on other users of the marine environment including Indigenous communities
- Wild fish aggregation and flow on impacts
- Impacts on Indigenous sites of significance
- Possible impacts of sourcing broodstock from wild populations, and selectively breeding fish with a very narrow genetic variation, which may in turn escape into the wild.