"We have record biomass in the water and are confident that the completion of our second major efficiency and expansion program will deliver a sustainable reduction in costs beyond financial year 2020," the Tasmanian-based fish farmer said on Friday.

"There is good reason to be optimistic that both operating and statutory earnings will recover strongly this year on those reported in financial year 2019."

Huon reported net profit after tax of $22 million for the six months to December 31, which was down from $26.4 million in the corresponding period a year earlier.

It said the latest results reflected lower selling prices in the international market.

"Following two consecutive years of challenging operating conditions, the investment in rebuilding the biomass has resulted in the harvest increasing 48 per cent to 13,300 tonnes, consistent with our forecast of at least 25,000 tonnes for the year," it said.

"There is a significant increase of biomass in the water which will underpin increased production in financial year 2021 and financial year 2022."

Huon was buoyed by the growth of a class of fish known as the 19 year class, saying its performance was the company's best ever.

It said that was mostly due to structural improvements and an investment program which included construction of the Whale Point Nursery, which allowed Huon to grow smolt to a larger size before putting them to sea.

"Fish are the biggest they have ever been at this time of year, survival rates the highest and with improved feed conversion rates (into fish weight)," it said.

"The benefits of the improved 19 year class won't be realised until financial year 2021 and the increase in working capital it has driven has resulted in high debt levels being maintained," the company said.

"While we remain focused on driving operating efficiencies through the business, the residual impact of the fish losses and poor growth from the 2018 year class have slowed the rate at which the cost of production can come down."

Summer conditions in 2018-19 and salmon deaths and gill necrosis caused by moon jellyfish affected harvest weights and fish growth early in the financial year.

Huon said growth rates were slow to pick up, but there was a noticeable improvement in spring and early summer.

It said global demand for salmon was growing at about 7 per cent a year.

However, coronavirus and its impact on Chinese demand were creating uncertainty.

Half-year revenue increased by 31 per cent to $178.1 million.