A New Zealand-based Tongan man who lost friends in the Princess Ashika ferry tragedy in Tonga says the sentences handed to three of the men found guilty over the incident are a joke.

New Zealander John Jonesse, the former head of the Shipping Corporation of Polynesia (SCP), was jailed for five years for manslaughter, sending an unseaworthy ship to sea, forgery and dealing with a forged document.

Three other men and the shipping corporation were also sentenced today on charges related to the sinking of the ferry in August 2009, in which 74 people died.

The ship's captain Maka Tuputupu was handed a four-year jail term but will serve only six months after being convicted of manslaughter by negligence in relation to the death of Vaefetu'u Mahe, 22, the only Tongan whose body was recovered after the sinking, and of sending an unseaworthy ship to sea.

Viliami Tu'ipulotu, a former director of Tonga's Ministry of Transport, was handed a three-year suspended sentence after also being convicted of manslaughter and sending an unseaworthy ship to sea.

The ship's first mate Semisi Pomale was jailed for five years but will serve 18 months in jail on a manslaughter conviction.

The Government-owned Shipping Corporation of Polynesia was ordered to pay $1.4 million in fines.

Auckland-based Alani Taione, who said he lost family and friends in the tragedy, was unhappy at the sentences for the three Tongan men.

"Those sentences are like a joke. To me the families will be very unhappy with that," he said.

"They should serve at least for five years."

Mr Taione, who organised a protest march in Auckland in 2009 criticising the Government's slowness in recovering bodies from the wreckage, said he had not been confident of getting stronger sentences as he had little confidence in the Tongan justice system.

However, he thought the Government had learned a lesson from the tragedy.

"They will no longer do any stupid things like this with the life of the people, I'm pretty sure."

Supreme Court Judge Robert Shuster said Jonesse had shown no remorse over the loss of the Princess Ashika ferry in August 2009.

"I accept you have no shipping experience, I accept you are a management person but, frankly, you led a shambles of an organisation," Judge Shuster told Jonesse during sentencing, Agence France Presse reported.

"You are the one person here who showed no remorse nor [offered] any explanation."

The Princess Ashika was on a voyage from Nuku'alofa to an outlying island when it sank, trapping passengers, mostly women and children, below deck in the country's worst maritime disaster.

The six-week trial heard evidence that the ship, built in the early 1970s, was riddled with rust holes and poorly maintained.

The SCP bought the Princess Ashika three months before the sinking and it was on its fifth voyage when it went down.

Survivors at the time recalled water building up in the cargo hold before the ferry lurched violently and sank with little warning.

Judge Shuster said passengers on the ferry were not told where life jackets were located or where they should gather if there was an emergency.

"It is utterly disgraceful," he said.

- NZPA