The Native Americans celebrated with oysters & # 39; colossals & # 39; more than seven inches long
About 2,000 years ago, Native Americans living in the Gulf of Mexico delighted with oysters & # 39; colossals & # 39 ;, some of which were more than seven inches long.
The finding is based on shells collected from former & # 39; garbage dumps & # 39 ;, or mounds, in Crystal River, Florida, USA. UU., Where the natives threw fish remains from the year 50 to 1050 AD. C.
American researchers say that the average body size of today's oysters is only two-thirds the size of these huge ancient ancestors.
While today's oyster shells reach heights of around 4.7 inches, "colossal" oysters that reached average heights of 7.4 inches no longer remain.
The reason for the decrease in size is unknown, but researchers warn that a decrease in size in other fisheries has previously been a warning sign of population collapse.
Modern oyster shells (left) compared to smaller and larger prehistoric shells (right) and a quarter of US. UU.
Crystal River feeds the Gulf of Mexico, which is home to the world's largest wild oyster fisheries.
Most of the oyster reefs in the world have been lost in the last 200 years and almost a third of those that remain are functionally extinct, they no longer play a role in their ecosystem.
The larger the oysters, the more likely they are to overcome the destructive processes caused by humans, such as sea level rise.
Oysters also benefit the wider ecosystem by filtering water and stabilizing the coasts, preventing them from collapsing in storms.
"Oysters in the Gulf of Mexico are getting smaller, even in areas that are considered relatively" virgin, "said lead study author Stephen Hesterberg, a PhD student in anthropology at the University of South Florida.
‘Size is one of the most important attributes of an oyster, which affects the amount of water it filters per day.
"They also affect the ability of oyster reefs to protect the coasts of storm surge and create habitat for other commercially important fisheries."
A comparison between the prehistoric oyster (left) and the modern oyster shell. The largest prehistoric shells ranged from impressive 3.5 to 7.5 years, while today's larger oysters had an age range of 2.5 to 4.5 years.
The team studied the prehistoric oysters of two seven-mile-long archeological sites on the Crystal River where indigenous peoples occupied sites more than 2,000 years ago.
The team used the analysis of oxygen isotopes in five of the old oyster shells recovered from the dumps and five modern oysters from the larger classes, to estimate growth patterns and maximum ages.
While both sets showed similar growth patterns in the first year, modern oysters had grown 35% and 38% less in their second and third years, respectively.
Excavation efforts take place near Crystal River Florida. the researchers took their garbage samples: archaeological mounds composed of shellfish shells and other ancient waste
The largest prehistoric shells ranged from impressive 3.5 to 7.5 years, while today's largest oysters had an age range of 2.5 to 4.5 years.
Its maximum lifespan of 3.5 years was also 12 months shorter than colossal oysters, says the team.
"Colossal individuals can never be restored in Big Bend and the wider Gulf of Mexico region due to irreversible changes in adjacent watersheds and climate," said Hesterburg, whose team published its research in Biology letters.
"Truncated size has also been observed in oyster reefs in other parts of the region, confirming what can be a general phenomenon throughout the north and east of the Gulf of Mexico."
An oyster reef along the Crystal River off the Gulf of Mexico, in Florida, United States.
Previous studies have claimed that future climate change and sea level rise could have a great impact on commercial oysters worldwide.
A study by the University of Stirling in Scotland in 2018 found that Sydney's famous rock oyster from New South Wales is shrinking, caused by ocean acidification.
Ocean acidification, called the "evil twin" of global warming, occurs when the world's oceans absorb atmospheric carbon dioxide, which reduces the pH levels of the oceans.
"Acidic water is damaging the ability of oysters to grow their shells," said Dr. Susan Fitzer, an independent NERC researcher at the Stirling Aquaculture Institute, at the time.
"We see a lot of mess in the calcite layers, because there isn't enough carbonate in the water so that the oysters can take advantage of the optimal formation and growth of the shells."
Oysters used to be an abundant and cheap snack for the British working classes of the 18th century.
Garbage dumps in Australia, Japan and the United Kingdom have provided evidence of oyster consumption for thousands of years.
As recently as in the 18th and 19th centuries, they used to be a cheap and hearty snack for pub visitors and often drank a beer mug.
Its popularity has raised market prices over the years, giving them the reputation of being an expensive delicacy.
The reduction in oyster size is part of a worldwide trend, and seafood, including mussels and scallops, also gets smaller.
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