Hungry shoppers are tipped to buy up to 700 tonnes of seafood – including 130 tonnes of prawns – in a 36-hour pre-Christmas fish market frenzy in Sydney.

The bumper buy-up comes amid a warning that the ongoing drought means shoppers will have to pay more for prawns this festive season.

The Sydney Fish Market opened at 5am on Monday and will not close again until 5pm on Tuesday.

Spokeswoman Stephanie Margrain said about 100,000 people were expected to shop at the market in that time. They will buy 700 tonnes of seafood, including 130 tonnes of prawns and nearly a million oysters.

“Prawns and oysters are always favourites at Christmas time and people will be glad to know that supply is plentiful for both of those items and prices are comparable to last year,” she said.

The Sydney Fish Market expects 100,000 shoppers on Monday and Tuesday. Photo: Sydney Fish Market

Elsewhere, however, the Professional Fishermen’s Association has warned prawn lovers that prices are higher than normal this Christmas, as the drought continues to affect supply.

Chief executive Tricia Beatty said the continued hot, dry weather was taking a toll.

“It’s a well-established fact that when you have drought on land, you have drought in water,” Ms Beatty told the ABC.

“No one has closed, but it’s been a really hard time for us as an industry.”

At the Wallis Lake Fishermen’s Co-Op, on the NSW mid-north coast, operations manager Suzie McEnallay said the lack of rain had resulted in lower catches.

“The drought definitely has had a huge impact on us,” she said.

“This season has started off a lot later, and we definitely need some rain to stir things up a little bit.”

School prawns had been selling for about $30 a kilogram – compared to $10-$12 in previous years, she said.

Back in Sydney, fish market spokesman Alex Stollznow said shoppers should plan their trip during the market’s busiest two days of the year.

“It’s a very motivated crowd – people come in and out and the queues move very quickly. There’s not a lot of lingering [and] there’s not a lot of loitering, so it’s an efficient way to shop,” he said.

“We recommend that you take a minute to plan out exactly what you’re going to need over Christmas period.”

He said prawn prices generally jumped about 10 per cent at Christmas.

“What this means is that the vast majority of prawns sold are still going to be around that $30-$35-a-kilogram mark,” Mr Stollznow said.

“If you’re not averse to trying the medium-sized prawns, you should find these for $30-$35 a kilogram and they are absolutely stunning.”

Whole fish could be a more economic alternative for the Christmas dining table, he said. And scallops are also a surprise bargain buy this year.

“Supply is strong and there is plenty of seafood to go around,” he said.

“This year we’ve had a great commercial scallop harvest from the Bass Strait. They’re going to be harvesting them right up until December 31 and you’re going to see them retail for less than $1 each, which is outrageously good.”

-with agencies