Tuna fish die from Silica / Silt
poisoning – overload
Page Published 20th January 2025
When Clevor Trevor was living up the road from Port Lincoln South Australia where they filmed the JAWS movie in the late 1970’s and living near the Whyalla South Australia King fish farm, there were storms and knowing fish float when they die he wondered why would the fish farms need divers to retrieve dead fish from the bottom of the net after a storm.
Friends said that it was just the muck stirred up by the fish that dived down trying to get away from the turbulent waters like they would in the ocean but in the ocean they just swim in a storm and not go in circles stirring up the muck.
Yes but why would they sink CT wondered and never got the answer until he read about the newlywed woman who drunk silica and died 15 minutes later and was stone in 45 minutes. It made sense the silica the fish stirred up turned them to stone once they breathed enough in during a 24hr or 48 hour storm. They had a stiff look to them on the TV news videos. They had turned from floating due to buoyancy like a dead whale to a stone heavier than water.
No videos could be found of the news articles at the time of the report below.
News Article from May 2nd 1998
Story by Nigel Hopkins May 2, 1998 – 10.00am
When a violent storm hit Port Lincoln’s Boston Bay in April two years ago, it nearly blew Australia’s fledgling tuna farming industry out of the water. By the time the waters calmed, 70,000 caged tuna – more than half the industry’s total – were dead or dying from silt swept into their gills. It was a $60 million blow from which an industry run by lesser mortals than Port Lincoln fishermen might never have recovered.
Instead, they are moving forward with new, aggressive plans for value-adding, stronger research programs and an acute awareness of the difficulties of building an environmentally sustainable industry. And despite weaker demand from their sole export market, Japan, the tuna farmers are still increasing quality sufficiently for higher prices to maintain the value of their catch (which last year totalled $83 million).
The 1996 storm was not the first to be weathered and overcome. By the end of the ’80s Australia’s tuna fishing industry, centred on the Great Australian Bight, was on the point of collapse. The 1989-90 blue fin tuna quota was cut by 67 per cent on the previous year in a bid to restore stocks.
The industry was taken aback by the severity. The Australian quota had been progressively slashed from 14,500 tonnes in 1984-85 to 5,265 tonnes in 1989-90 – which is still the current figure. It led to an industry decision to allocate some of this much smaller quota to tuna farming rather than to immediate sale and to pursue a high value-added strategy.
Farming enables tuna to more than double their weight (from 15-20kg to around 35kg) in four months or less, in a controlled situation over a longer period of the year. Once a seasonal industry, tuna farming has become a year-round business.
The farmed tuna flesh, as with any farmed fish, was different – in this case more marbled and fatty, which fortunately was adored by the Japanese.
About two-thirds of the total domestic catch now goes to Port Lincoln’s 13 major tuna farm operators. Licensing conditions are strict and stocking rates are closely monitored. For the tuna fishermen, it has required a major culture shift from hunter- gatherers to sustainable animal husbandry.
“A huge mental leap” is how Brian Jeffries, president of the Tuna Boat Owners Association of Australia, describes it: “I don’t know of any other aquaculture system in the world based on fishermen.”
The sharp learning curve was no doubt driven by the increased value of the product. The farmed southern blue fin tuna regularly fetches twice the price of the wild, pole-fished product, averaging about $33/kg at the daily Tokyo fish market and sometimes reaching $50-60/kg. This is still well short of the top prices for farmed tuna from Japan, Turkey or Italy, which can fetch up to $150/kg – and is worth perhaps $3,000/kg by the time it is served at some exclusive little sashimi bar in the Ginza.
“In retrospect, [the tuna fishermen] were not making the best use of the resource,” Jeffries says. “But you only tend to go into high value-added business when you’re in trouble. We don’t expect to see an increase in the quota, so we have to make more out of each tonne.”
Japanese demand is sagging along with the economy, but Australian tuna is maintaining market share and the fishermen have taken out “plenty” of forward cover on the value of the yen.
“We don’t have any disease yet, but we will,” Jeffries says phlegmatically. In a week when Hong Kong aquaculture fisheries were struck by poisonous algal blooms, he conceded that not enough is known about the life cycle of the southern blue fin tuna.
“There is a major dispute within the scientific community over the target date for recovery of stock levels,” he says. The target – to be achieved by the quota cuts – has been for a return to the 1980 spawning level by 2020. International scientists say it will be achieved easily; the CSIRO claims there is only a 50 per cent chance of it.
And research on tuna recovery levels in seas no longer fished for tuna has been stalled by a standoff with the Japanese who want an additional quota for this, rather than allow research catches in these areas to be included in existing quotas.
Carl Young, general manager of aqua-culture for Primary Industries and Resources SA, says the main growth limiter for the industry – the size of quotas – may be overcome by the development of tuna hatcheries, for which a federally funded feasibility study is to be conducted in WA, near the tuna’s natural spawning grounds in the Java Sea. “I think it’s do-able,” he says. “But it could take 10 years.”
Young is also keenly aware of the tourism industry’s potential hostility to aquaculture, with recent public objection to proposals for trial tuna farms off Kangaroo Island.
Ten years ago, when he was helping set up fish aquaculture in Greece, Young was stoned by hostile villagers who feared deadly algal blooms which could repel tourists. Greece now has a 50,000-tonne-a-year aquaculture industry (compared to the present
4,000 tonnes in SA), much of it happily co-existing in tourist areas.
But perhaps the strongest factor on the side of farmed tuna is the huge spin-off benefits to local communities, which now see year-round rather than seasonal activity, the development of stronger communities as a result and the growth of a large range of skills and services demanded by the industry, from marine scientists to spotter plane pilots and divers.
A report in February this year, prepared for Young’s aquaculture division, estimated that direct business income generated locally by tuna farms at Port Lincoln was $83 million in 1996-97, with a further $99 million in flow-ons to other sectors. And each job directly generated by tuna farming adds a further 3.2 jobs elsewhere – a sashimi-bar bounty that rivals (and could ultimately contribute to) that created by Japanese tourists.
End of Article