Just six months after moving into the White House, US President Donald Trump declared the launches “reckless and dangerous”, and called on China and the United Nations to apply tougher sanctions on North Korea to curb its nuclear programme.

In February, China announced it would ban coal imports from North Korea, in line with an earlier UN resolution.

On August 15, nine days after the UN Security Council approved tough new sanctions against North Korea, China extended its ban on imports from its reclusive neighbour to include iron, iron ore and seafood.

It was the worst possible news for Feng.

“I used to sell 1,500kg of North Korean shellfish a day,” he said. “Now, almost nothing is coming over the border. Today, we only had 250kg.”

Chinese consumers started getting a taste for North Korean seafood about two years ago, Feng said, and the market boomed.

“North Korean shellfish is much cleaner, with hardly any sand on it, so the restaurants love it,” he said, adding that he buys most of his stock through suppliers in northeastern China, close to the border with North Korea.

“But now, when the chefs and buyers come to the market looking for North Korean clams, we have to tell them we’ve hardly got any.”

So how does a ban on seafood stop Kim Jong-un from launching missiles?

The idea behind the UN sanctions and China’s blockade on selected imports is that by starving North Korea of money, its leader will be unable to continue with his nuclear weapons programme.

In 2016, Pyongyang generated US$190 million from sales of seafood to China. In the second quarter of this year, sales totaled US$68 million.

The thinking seems to be that while some Chinese businesses, including Feng’s, might suffer as a result of the sanctions, by starving Kim Jong-un of export revenue he will be unable to fund his missile programme.

And all the experts agree that will work?

Clearly, lots of people do. The US, China and most of the rest of the world have given their support for the UN sanctions, but whether they will work remains a moot point. The problem is that people like Kim Jong-un do not like being told what to do.

Sun Xingjie, a Korean affairs expert from Jilin University, said a large proportion of North Korea’s earnings from exports was allocated to its military programmes.

“China’s ban this time will make Kim feel the pressure ... but it might also spur him on,” he said.

As Kim feels the growing threat from the international community he might be moved to hasten his nuclear programmes, as “that will be the only means he has to ensure his regime’s survival”, he said.

“The sense of euphoria in the Kim [Jong-un] regime is pretty high in the sense that they are on the cusp of making history,” the Asian security analyst said on a recent visit to Hong Kong.

“Never has a country that is not a great power possessed a nuclear ICBM [intercontinental ballistic missile].”

Seafood vendor Feng said he had never been across the border to North Korea, but knew a little about its people.

“North Koreans are brave, and don’t hide what they are thinking,” he said. “They won’t allow themselves to be bullied.”

So is that what countries want? For China to bully North Korea?

“Beijing’s quick response to ban North Korean coal, iron ore and seafood is not aimed at hurting Pyongyang’s economy at all,” said Hwang Jae-ho, a regional security analyst at Hankuk University of Foreign Studies in Seoul.

“[It was] merely a gesture to Washington, showing Beijing is not happy with North Korea.”

Justin Hastings, an international relations specialist at the University of Sydney, agreed. Although Beijing said the ban on coal, seafood and iron ore would remain in place indefinitely, he questioned what long-term impact it would have on the North Korean economy.

“China will probably enforce the ban on coal, iron, and seafood in the short term, but given the prevalence of smuggling and the likelihood of China easing off on very strict enforcement after a while, my guess is that the effect on North Korea’s economy will not be 100 per cent,” he said.

“North Korea will probably be hurt in the short term, but in the long term, unless China completely changes its approach, North Korea will likely be able to adapt.”

So Trump is going about it all the wrong way?

“I’m not supportive of putting so-called pressure on China,” he said. “Economic and trade relations should not be commingled with national security issues related to North Korea.”

But China does have a special economic relationship with North Korea?

Yes it does, but things have been changing over the years.

Experts said the declines might be due in part to Pyongyang becoming more self-sufficient in producing energy rather than the impact of sanctions aimed at getting it to rein in its nuclear weapons programme.

Satellite pictures released by Nasa three years ago showed that North Korea was almost completely dark at night, compared with the bright lights over South Korea, sparking concerns about the lack of electricity in the reclusive state. However, in the second quarter of this year it actually exported more than 71.5 million kilowatt-hours of electricity to China, earning US$2.3 million.

How about trade in other commodities, like food?

Chinese customs data showed a surge in exports of nearly 30 items, with corn increasing 32-fold from 400 tonnes to nearly 12,724 tonnes, bananas from just over 63.4 tonnes to 1,156 tonnes and wheat powder from less than 0.6 tonnes to 7.6 tonnes.

Exports of spirits also more than quadrupled, rising from 2.1 million litres to 9.5 million litres in the second quarter, while exports of other items such as beer, confectionery, chocolate, bread and biscuits also increased.

Although the international community agreed to punish North Korea over its nuclear programme, food exports were excluded from the UN sanctions in the hope of ensuring a minimum living standard for its citizens.

Are they getting it?

That’s hard to say. North Korea’s food production – including staples such as cereals, soybeans and potatoes – in 2016 was estimated at 5.4 million tonnes, a fall of 9 per cent from 5.9 million tonnes in 2014, according to the Rome-based Food and Agriculture Organisation.

The country has had an ongoing food crisis since a serious famine in the 1990s, and according to the UN, two in five of its citizens are undernourished and more than 70 per cent of them rely on food aid.

A UN report published in March said an estimated 18 million people across North Korea continued to suffer from food insecurity and malnutrition, as well as a lack of basic services.

So what is the state of North Korea’s economy?

Despite its poor relationship with many of the world’s biggest markets, the North Korean economy grew at its fastest pace in 17 years in 2016, according to figures from South Korea’s central bank. The expansion was driven by growth in the mining and energy sectors, it said.

Also, Russia boosted its trade with Pyongyang by 73 per cent in the first two months of 2017, USA Today reported in June, citing Russian media sources.

Analysts said the rise in Chinese food exports might be a sign that North Korea’s economy was slowly developing.

“The surge could be a result of greater demand from North Korea, as its economy is gradually reviving and the black market is booming, ” said Cai Jian, an expert on Sino-North Korean relations at Fudan University in Shanghai.

“It also shows the increasing dependence of Pyongyang on Beijing, as it can’t import anything freely from other countries.

“The different types of food are going to the military and the elites in Pyongyang ... but people in the hinterlands are still going hungry. A wide variety of food being imported is thus not a sign that there is no food crisis,” he said.