The containership and bulker boom continues to boost Tufton Oceanic Assets' net asset value (NAV).

But the London-listed shipping fund has also seen its negative charter value rise to reflect how older term deals for its vessels are lagging the hot market as rates continue to rise.

The owner of 21 ships said NAV stood at $371.1m, or $1.32 per share, on 31 August.

At the end of June, this figure was $322m, based on a NAV of $1.15 for 280.57m outstanding shares. On 31 March, the NAV was $284.44m.

Tufton noted strongly rising containership and bulker markets during August, in an update on Monday.

"Because of the rising benchmark time charter rates in containerships and bulkers, the portfolio negative charter value increased to minus $121.7m during the month," the fund added.

The negative value was $44.6m in April.

Heading to zero?

Tufton maintains the negative figure will rise towards zero in the medium term, however, as ships are fixed on new charters at higher rates.

"In targeting cash flow stability from a diverse portfolio to pay consistent strong dividends, this will mean our NAV will be much more stable too than the shipping markets overall," Paulo Almeida, chief investment officer at affiliated investment manager Tufton Investment Management, told TradeWinds in April.

The value of the company's fleet if it were charter-free would be $470.6m, while the value with charters attached is $348.9m.

Tufton Oceanic said the group continues to identify "attractive" opportunities to buy more vessels.

The company added that prospective investments include product tankers, handysize bulkers and one or more larger containerships with four- to seven-year charters already in place.

In its annual report earlier this month, the shipowner said it was confident of better tanker markets next year.

The company logged net earnings of $79.5m in the year to 30 June, against a loss of $1.2m a year ago, as it recorded a gain of $60.7m in the value of its financial assets.