The Tasmanian salmon industry used more than 2,400 underwater explosives against seals in the last quarter, with Huon Aquaculture reporting the death of two seals on its leases.

Department of Natural Resources and Environment data disclosed under Right to Information laws show Huon Aquaculture used 1,887 explosives in the three months to the end of June, a rate of more than 20 a day. The company has used more than 10,600 since January 2021.

Huon accounts for 20 of the 25 seal deaths reported by the salmon industry since January 2021, although it produced just over one-third of the salmon grown in the state in the second half of last year. The company has been owned by the Brazilian meat corporation JBS since November.

The company said it used more explosives than its competitors because about two-thirds of its salmon is produced at offshore sites where seals are more prevalent. They include Storm Bay, off Bruny Island.

Huon claimed in 2016 that its move into offshore waters was made possible by the development of double-walled “fortress pens” designed “to keep seals out and our fish in”.

Pene Snashall, a spokesperson for Huon, said seals often used the entry platform to its pens as a resting spot but “structural changes” to the pen walkways and netting in the past few months had “reduced interactions”.

“We want to minimise any breaches of the nets to protect the seals, our fish and our staff. No one likes trying to cajole a 450kg male bull seal into leaving a treasure trove of food,” she said.

Fur seals are protected in Tasmania after being hunted to near extinction last century. The department said it permitted salmon companies to use various devices “to deter fur seals”, including underwater explosives, called “seal crackers” in the industry, which produce a loud noise and a flash of light. The industry has used more than 134,000 explosive devices in Tasmanian waters since 2016.

The explosives are intended to scare seals away from salmon pens, but they can be deadly. A Tassal report on the death of a seal in August 2018, made public after an RTI request by the conservation group Environment Tasmania, described a cracker being thrown outside a pen five metres from a seal.

“After the cracker went off, the seal surfaced. The seal was showing lots of blood and blowing a lot of bubbles before sinking and [was] not sighted again,” the report said.

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Tassal, the state’s largest salmon producer, almost halved the number of underwater explosives used in the last quarter compared with the preceding 15 months. However, the company remains the only salmon producer to continue to use “bean bag rounds” – fabric-coated plastic shells containing lead shot – against seals. The company fired 70 bean bag rounds at seals in the last quarter.

Tassal did not respond to a request for comment.

Jessica Coughlan, from Neighbours of Fish Farming, said the use of bean bag rounds should be banned.

“In Tasmania, two out of three companies don’t use bean bag rounds, so there is no reason we shouldn’t outlaw the practice here.

“With the recent acquisition of Tassal, Cooke Aquaculture is on notice that the public will not accept increases in animal cruelty in Tasmanian waters.”

Petuna, the smallest of the three salmon companies, reduced its use of underwater explosives by more than 10% in the last quarter.

Rebecca Howarth, a marine campaigner with Environment Tasmania, welcomed Tassal and Petuna “responding to community pressure” by reducing their use of underwater explosives.

“But seals are still being harmed with Huon Aquaculture increasing their use of ‘crackers’ and Tassal increasing their use of lead projectile beanbags,” she said.

A recently released upper house report recommended a review of the department’s seal management framework, “including the efficacy and safety of all seal management devices”. The government responded by saying it planned a new aquaculture standard for wildlife interactions to replace the framework.

Howarth supported the recommendation.

“There is a need for a full investigation into all seal deterrents and the harm they cause,” she said.

A discussion paper on the government’s proposed 10-year salmon plan says the industry needed to “effectively avoid and manage interactions with seals and other wildlife”, but provides no analysis of current trends or proposals for change.

Source: The Guardian