Before being appointed Indonesia's Maritime Affairs and Fisheries Minister, Ms Susi Pudjiastuti was running a successful seafood export business as well as Susi Air, an aircraft charter company.

Not known to mince her words, the 51-year-old has brought her strong personality to President Joko Widodo's government, adding bite and much-needed focus to his maritime masterplan.

She was in the spotlight leading Indonesia's assertion that it will not relinquish its sovereign rights to its exclusive economic zone (EEZ) in the South China Sea.

This after a Chinese coast guard vessel intervened in a poaching incident involving a fishing boat from China in the Natunas last month.

Since taking office in 2014 , Ms Susi has ordered the sinking of 153 vessels caught poaching in Indonesian waters - with 31 more expected to go down this week. She has demanded that Beijing return the fishing boat Kway Fey so that it too can be blown up and sunk.

"I believe they will honour me by handing over the vessel... I think as a big country, you cannot bully smaller countries," said Ms Susi, when asked about the latest incident in the waters off the Natuna Islands.

Her tough stance on illegal fishing has propelled her popularity, with a public opinion poll last year rating her as the country's top-performing minister.

She has also stood firm in banning the transshipment of seafood, which leads to illegal fishing, as well as the use of second-hand imported fishing boats in Indonesia's waters.

Critics accuse her of over-regulating and hurting the industry, but she told The Straits Times that those are mainly the voices of people with vested interests. "The more you regulate, the more productive your ocean will be."

Ms Susi is reportedly a close ally of Mr Joko and remains one of the few ministers who survived last year's Cabinet reshuffle.

The President and the First Lady Iriana were among the first to attend the wake of Ms Susi's eldest son Panji Hilmansyah, who died in January at age 31, due to heart failure. Ms Susi, a single mother, has a younger son and daughter from another marriage.

Mr Joko, a former furniture businessman, and Ms Susi share a common history - both had built successful businesses before entering politics.

She began her entrepreneurial journey in 1983 as a seafood distributor at a fish auction facility in her native Pangandaran, West Java.

By 1996, the business evolved and grew into a major seafood processing enterprise, specialising in high- quality lobsters packaged under the "Susi" brand and exported regionally and to the United States.

Growing demand for her fresh seafood led her to venture into the aviation business, primarily to facilitate the fast distribution of her products beyond Indonesia. In 2004, she set up an aviation company and acquired a plane to distribute her catch to places such as Singapore, Hong Kong and Japan.

When the Indian Ocean earthquake and tsunami struck Aceh and the west coast of Sumatra on Dec 26 the same year, Susi Air - with only two Cessna planes flying out of Medan at the time - was one of the first to help distribute aid to victims in isolated areas.

Susi Air now operates a fleet of 50 aircraft, including helicopters, making more than 225 flights a day across Indonesia and the region.

In 2014, Ms Susi received a call from the newly elected President Joko to join his Cabinet.

Although she has relinquished her positions as president director of her companies - at least, until she leaves government - Ms Susi did not abandon her business acumen. Some of her critics say she runs the Maritime Affairs and Fisheries Ministry like a corporation, often unilaterally discounting academic or scientific approaches to policy-making.

Ms Susi, who never went to university, dismissed those claims as baseless, adding that she appreciates the input from the 11,000-strong ministry, which is "full of academics".

"My aides are professors, PhD holders, former ministers. I am surrounded by very scientific, academic people... they are all university graduates. The only one who is not is the minister," she said.

To revive Indonesia's shipbuilding and fisheries industries, Ms Susi has been trying to maximise the potential of the sector through, among other things, modernisation of industry practices, abolishing transshipment activities, and going after poachers. She has also ramped up enforcement as well as enhance Indonesia's maritime surveillance capabilities, in a bid to stave off the US$20 billion (S$27 billion) to US$25 billion that Indonesia's fisheries sector loses annually to poaching, which explains her strong assertion of her country's rights in its EEZ.

China has yet to officially respond to Indonesia's protest over the incident in the Natunas, but Ms Susi does not believe it will hurt relations, adding that the two countries "will remain good friends".

"China is a giant that strongly enforces its own laws back home," she said. "China will let us do the same."

On whether she will continue with her tough action of blowing up fishing boats caught poaching in Indonesian waters, she said: "It is actually not fun blowing up ships, but we have to create a deterrent and uphold our Constitution."