Rainbow Trout

Latin name: Oncorhynchus mykiss

Common names: Ocean Trout, Trout

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Note: Choose rainbow trout farmed in tanks and ponds on land if available. If you can’t be sure, or only “ocean trout” or trout farmed in sea cages is available then choose a sustainable alternative below.

Key Facts

  • Rainbow trout is a non-native species that is farmed mainly on land in small-scale tanks, ponds and raceways in southern Australia. Rainbow trout are also farmed in seacages in Tasmania’s Macquarie harbour. Rainbow trout farmed in seacages are typically marketed as ‘Ocean Trout’.
  • Rainbow trout have been released into waterways for recreational anglers. It is a carnivorous predator that has been responsible for declines in populations of native species of freshwater fish.
  • Rainbow trout are a carnivorous salmonid fish that is dependent on wild caught fish that is manufactured into fish feed. Although the amount of wild caught fish in feed has been reduced over recent years, the amount of wild-caught fish used in feed is currently more than the weight of trout produced.
  • Serious negative environmental impacts of salmonid farming have been recorded in Macquarie Harbour (from both Atlantic salmon and rainbow trout farming, which occur together), which is a unique and sensitive waterway adjacent to a World Heritage Area.

More information

  • VIC (<989t in 2020/21), SA (<295t), TAS (not disclosed), WA (9t in 2021), NSW (228t in 2021/22)

Rainbow trout is an introduced  salmonid species that has been stocked in many fresh waterways in cooler regions of Australia for recreational anglers. It is a carnivorous predator that has been responsible for declines in freshwater native fish populations.

Rainbow trout is a carnivorous species, and the fish require moderate amounts of fish protein in formulated fish feed. Feed manufacturers use fish caught in the wild as a part of the feed used in rainbow trout farms. The amount of wild-caught fish used in feed is currently more than the weight of fish produced, although feed manufacturers are working to produce feeds with lower quantities of wild caught fish.

Rainbow trout is farmed mainly on land in tanks, ponds and raceways. These fish require cool flowing water to survive, which limits the areas in which they can be farmed. Wastewater from farms must be treated before being released on land or into natural waterways. The scale of rainbow trout farms on land are usually small and generally have a low impact on natural habitats.

In outdoor pond farming, physical barriers such as fences and mesh netting is used to exclude wildlife (principally birds including cormorants) from impacting trout production. These control measures are unlikely to have lethal effects on wildlife.

There is not a serious risk posed by rainbow trout escapes from farms on land or in seacages, as introduced populations are generally well established and actively propagated in the regions where farming occurs.

Rainbow trout is also farmed in seacages in Tasmania’s Macquarie Harbour. Rainbow trout farmed in this manner is typically marketed as ‘Ocean Trout’ .

Management actions taken to reduce the impact of salmonid (rainbow trout and Atlantic salmon are farmed together in Macquarie Harbour, using similar approaches) farming on Macquarie Harbour have included reducing the amount of salmon that can be farmed in the area significantly from a period in the mid-late 2010s when salmonid  farming companies were allowed to grow far more salmon in the Harbour than that unique and vulnerable environment could tolerate. The Harbour is additionally impacted by climate change, historical mining in catchments and hydro power generation.  The increase in salmon farming, in addition to these other stressors, resulted in pollution that drove severe depletion of oxygen in deeper Harbour waters. This created ‘dead zones’ throughout the Harbour, including in a World Heritage Area, and caused over a million farmed fish to die from environmental stress and related disease outbreaks. Though a cap on the amount of fish able to be farmed in the Harbour has been reduced since this time, in recent years companies were able to modify their production in a way that slightly increased the level of fish farming and resultant nutrient pollution. To address this, a new form of production limit is being introduced in 2023. Oxygen levels in Macquarie Harbour have shown some signs of recovery since the permitted production was reduced, but remain problematic despite favourable environmental conditions in recent years, and potentially dangerous deoxygenation events have continued to occur.

These impacts from salmonid farming in Macquarie Harbour pose a serious threat to a marine species which is likely the world’s rarest skate. The Maugean skate is categorised as ‘Endangered’ under Australia’s national environment law. It is unique to Tasmania, and is now only found in Macquarie Harbour. Scientists consider that the species is at serious risk of imminent extinction; and while the skate’s population is poorly understood and very difficult to study, there is evidence that serious impacts to the population have occurred. Significant and welcome conservation efforts are underway, and restoring the health of Macquarie Harbour as soon and as much as possible must be an urgent priority to avert extinction of the Maugean skate. GoodFish is aware of no other Australian aquaculture industry contributing this degree of conservation risk to an endangered species. For these reasons seacage farmed rainbow trout ala ‘Ocean Trout’ is a significantly less sustainable option than pond and tank-farmed rainbow trout, and should be avoided.