A new study has found populations of the endangered Maugean skate have remained relatively stable but vulnerable, as NGOs continue to push against salmon farming near its habitat.
The study, performed by the University of Tasmania and the Institute for Marine and Antarctic Studies, investigated the populations of the species in Macquarie Harbour, located in Tasmania, Australia. The Maugean skate currently only lives in Macquarie Harbour, and is considered a “micro-endemic” species.
The species recently retained its endangered status, after advocates for the skate pushed for it to be shifted from endangered to critically endangered. Environmental advocates have heavily criticized companies that farm salmon in Macquarie Harbour and have pushed for retailers to stop carrying salmon from companies that farm in the harbor via shareholder resolutions.
The new report from the University of Tasmania and the Institute for Marine and Antarctic Studies found the population has remained relatively stable, and also determined that a recruitment event in 2020 has had several individuals survive to maturity.
“New information presented in this report provides an updated understanding of recent demographic trends in the population, including evidence of recent recruitment pulses and continued stabilization of relative abundance,” the report said. “However, the population remains highly vulnerable due to its restricted distribution, suspected pulse-driven recruitment dynamics, potential sensitivity to adverse environmental events, and recruitment levels lower than those inferred during 2006-2008.”
The report also found that the population has shifted into the Tasmania Wilderness World Heritage Area (TWWHA) in the harbor, as an increase in catch inside the region during the study “cannot be explained solely through population growth,” the study said.
NGO Environment Tasmania is attributing the shift to the area to salmon farming, and said it shows the population is still “on a cliff’s edge.”
“It appears from this report that the skate is in decline and seeking habitat away from salmon farms,” Environment Tasmania Senior Skate Campaigner Jess Coughlan said. “Skate populations are relocating to the TWWHA but this doesn't necessarily mean safety for the species – dangerously low oxygen levels persist in the Heritage Area.”
NGOs have long attributed the low oxygen levels to salmon farms located in the harbor, and have protested in a push to get the government to ban all aquaculture in Macquarie Harbour.
Environment Tasmania said that without rehabilitation of the region and improved oxygen levels, the skate is in danger of extinction.
“As the population of the endangered Maugean skate edges closer to the cliff, we can’t know for sure that its survival is protected for even the next decade – or has the resilience to withstand the upcoming El Niño event,” Coughlan said. “Without annual and thriving recruitment, each year that passes, the species is on a knife-edge.”
The salmon industry in Tasmania has consistently defended the presence of salmon farms in the harbor, and has also pointed to its work to contribute to the Macquarie Harbour Oxygenation Program, which has been adding dissolved oxygen back to the harbor.
