Despite the high quality of Tasmania’s marine natural values, they are under threat. Fishing isn’t as good as it used to be and many ecosystems are in decline. Impacts such as the expanding salmon industry, invasive species, depleting fish stocks and agricultural run-off are compounded by climate change and management issues. Many of Tasmania’s endemic species are only found in the sheltered waters where human impacts are highest.
Depleting Fish Stocks
Tasmania’s seafood is world class and our island State has become a top destination for “foodies” keen to sample the bounty of our exceptional marine environment.
Tassie also has the highest level of boat ownership in the country, and up to one in five Tasmanians engage in recreational fishing.
Unfortunately, Tasmania’s fish stocks are under pressure, with the 2021 Government assessment of scalefish species noting that six Tasmanian species are depleted or depleting including sand flathead, calamari and striped trumpeter.
The Tasmanian government is currently reviewing the state’s Harvest Strategy Policy and the Scalefish Fishing Rules. The government has also made the tough interim decision to reduce bag limits for the depleted Sand flathead.
Fishing is a Tasmanian way of life. Environment Tasmania supports sustainable fishing practices that will ensure that future generations can continue to enjoy fishing.
Tasmania is on the frontline of global, marine climate change impacts with Tasmania’s east coast recognised as a climate change hotspot. The warm, nutrient-poor waters of the East Australian Current are flowing further south causing Tassie’s east coast to warm up at four times the global rate. This warming has been linked to the devastating loss of 95% of Tasmania’s iconic giant kelp forests.
Tassie is also experiencing an influx of new species travelling south to find cooler waters, some of which are extremely problematic, causing devastation to marine ecosystems. For example, the long-spined sea urchin leaves nothing but desolate “urchin barrens” in their path. The RedMAP project, a citizen science project spearheaded by scientists at Tasmania’s Institute of Marine and Antarctic Studies (IMAS) has found that 50% of inter-tidal species and dozens of fish species have extended their range further southwards in the last 50 years. The gloomy octopus has now expanded its range south to Tasmania in high enough numbers to be commercially fished.
Climate change also exacerbates existing stressors on the marine environment, of which there are many.
Since the 1990s, Tasmania’s salmon farming industry has rapidly expanded to the detriment of the marine environment and local communities.
Salmon farming releases high loads of waste – poo and uneaten feed – into our public waterways that can cause algae blooms, reduced water quality and sea-floor degradation.
Wild fish can be impacted by farm-derived diseases and antibiotics. Numerous fish escape events have left community members fearful of predation on wild fish species.
The industry has been exposed for alarming accounts of seals being trapped, shot, injured and killed at salmon farming sites. Other animal welfare concerns include large numbers of salmon that have died at farms on several occasions, the worst of which occurred over six months in 2016/17 when 1.35 million fish died in Macquarie Harbour due to low oxygen. Concerningly, the environmental damage caused by the reckless expansion in Macquarie Harbour has also pushed the harbour’s Maugean skate near the brink of extinction.
Coastal communities complain of noise and light pollution adjacent to fish farms. Meanwhile, plastic debris falling off farms and ending up on beaches or sometimes even perilously striking boats are common.
Yet, despite a lack of social licence, the Tasmanian Government continues to support the industry’s expansion. In 2021, a Parliamentary Inquiry Report into the salmon industry made strong recommendations such as the ceasing of operations in sheltered, sensitive and biodiverse waters. Government has failed to act on these.
"At least 14 million tons of plastic end up in the ocean every year, and plastic makes up 80% of all marine debris found from surface waters to deep-sea sediments. Marine species ingest or are entangled by plastic debris, which causes severe injuries and death" - International Union for Conservation of Nature
Three hundred million tonnes of plastics are produced every year and increasingly this plastic is reaching the ocean. Marine animals either try to eat it or become entangled in the plastics which can result in death. Plastics are found on the shorelines of every continent and the main sources of ocean plastics are land based. Microplastics are plastics that have broken down from UV radiation, wind, currents or other natural factors, to under 5 mm across. Micro-plastics are now found in human blood, human breast milk and in Antarctic ice.
Numerous studies have focused on the impacts that the ingestion of physical plastics have on the health of seabirds, but a recent study from Tasmania’s Institute of Marine and Antarctic Studies (IMAS) has discovered for the first time a plastic-induced sickness present in flesh-footed shearwaters that otherwise appear healthy. This is the first time this has been detected in animals. Flesh-footed shearwaters have been in decline across the south-west Pacific Ocean and WA’s south coast. More information about this research can be found here.
Currently Tasmania is the last State in Australia that has not banned Problematic Single-Use Plastics (PSUPS).
The health of Tasmania’s coastal marine environment is impacted by land-based activities including agriculture run-off, ageing septic systems, sewage outfalls, heavy industry, boatyards, cruise ships and other pollution from coastal industry and development.
Hobart’s waste water from both the city and heavy industry went largely untreated until the 1980’s, and often contained pathogens, nutrients, arsenic, PCB’s (polychlorinated biphenyls), heavy metals, acids and other compounds. Heavy metals still persist in the sediment of the Derwent Estuary and PCB’s in the flesh of both filter feeders and fish. The Derwent Estuary Program has made tremendous progress in improving the health of the waterway. Unfortunately, the expansion of salmon farming within Storm Bay comes with the risk of remobilising these heavy metals.
Boat slipways, boatyards and marinas are a source of hazardous liquid and solid waste, oils and paint chips which often contain toxic heavy metals.
In early 2023, Rights to Information documents showed that the ageing Macquarie Point sewage treatment plant had been in regular breach of its EPA commitments and leaking chemicals into the Derwent Estuary, creating a “high risk” of toxicity. The debate over whether this plant will be moved further up-river to a newer facility at Self’s Point has not been resolved.