Source: OceanWatch Australia
"Oysters are filter feeders, so fine ash could compromise their ability to feed. If they can't feed, they will stress and then they will die."
The rains have also increased the likelihood of algal blooms, which can be harmful to oysters, and has also meant the NSW Food Authority has temporarily curbed the selling of the product.
"Worst case scenario is we could actually have a lot of oyster farmers have a lot less oysters to sell," Ms Henry said.
Rod Terry is one of the many farmers who have been affected.
A significant amount of ash and debris has washed into the Clyde River where Mr Terry works.
"I've seen the 1974 flood and this is only a baby compared to that ... But as far as the other damage goes it's a lot worse than I have ever seen," he told SBS News.
"This is a very unusual event for us. With the bushfires, it's a double whammy."
Mr Terry, who also lost crucial farming infrastructure in the recent bushfires, said the subsequent flooding has proven an immediate setback.
"I actually do farmers' markets in Canberra, and that has been very good to me," he said.
"I won't be back there, fingers crossed, until March - hopefully, I'll have some nice fat oysters by then."
This NSW town survived bushfires, only to face floods
According to OceanWatch Australia, the NSW oyster industry produces about 60 million oysters every year worth $35 million.
There are 300 oyster farming businesses in NSW, spread across 32 coastal estuaries.
Over the course of the bushfire season, 33 people have died, thousands of homes have been destroyed and more than one billion animals have been killed.