Blockading Taiwan's Ports
Susceptibility to Blockade
Taiwan's two key ports (Kaohsiung and Keelung) are located on the west and north coasts, making them easy targets for a Chinese blockade. If it wasn't clear enough, China pointed it out in 1996 by launching one missile each into the waters at the entrance to both ports.
The ROC Navy's key bases also fall victim to unfortunate locations. Kaohsiung (including Tsoying, which is just north of Kaohsiung port) and Keelung are the ROCN's largest bases. A blockade of Kaohsiung and Keelung would also be a blockade of both Taiwan's largest bases. I am not familiar enough with the breaking of blockades to know whether having the ROCN inside the port being blockaded would be an advanatage or disadvantage. Is it either to break in or break out? My guess is that it would be better for the ROCN to be at sea when the PLAN takes its position. That would allow the ROCN more freedom of movement, whereas being trapped inside the port would make them sitting ducks to be disposed of at a time of the PLAN/PLANAF's chosing.
Could Taiwan Survive a Blockade?
Whether or not the people of Taiwan would capitulate in the face of a blockade depends on countless factors (and thus I will only highlight a couple of the numerous variables). Assuming the blockade was unprovoked by Taiwan and that China was just imposing a blockade (not attempting an invasion or launching missiles at the island), I feel the key factors would be the overall economy and the availability of both fuel and food.
The stock market in Taiwan responded to the 1996 Strait Crisis by dropping 21% that day alone (source: David Shambaugh's Modernizing China's Military, 320). If two missiles carrying a message caused that drastic of a drop, one can expect that a real war (after all, blockades are an act of war) would bring a much greater reaction. (Unlike 1996, a war between China and Taiwan would likely cause a similar financial exodus from the mainland, but unlike Taiwan, China tends not to concern itself the well-being of its people, thus the economic drop should be relied on to provide much in the way of deterrence.) It has been argued that Taiwan's people are more concerned about economic performance than the location of their capital and some people could be convinced to surrender simply by threatening the economy of the island. Such ideas remain unverifiable in peace time and hopefully we will never know the truth, but I doubt this generalization applies to a significant section of the population.
Taiwan's strategic petroleum reserve (SPR) is estimated by the American Department of Energy (DOE) to stand at about 60 days (at the current level of consumption). Although David Shambaugh cites a 1999 article in the International Herald Tribune as saying that Taiwan's SPR had dropped to 18 days (MCM, 321), I'm going to side with the DOE data as it is likely more recent and/or authoritative. With rationing, the reserve could obviously be stretched much longer than 60 days.
I am unsure about Taiwan's ability to sustain itself on domestically produced food, but I suspect that Taiwan would experience hardship but not starvation were it deprived of food imports. Taiwan's food imports top $7 million a year (2002 data). Taiwan imports a large share of its meat and wheat, but the people of Taiwan could shift their diet temporarily to foods that are more readily available domestically.
Breaking the Blockade
Taiwan could survive a lengthy blockade, but I suspect the greatest factor in determining the willingness/ability of the people to stand strong such an embargo would be the amount of hope that there would be a favorable outcome. The people of Taiwan would likely look to the ROCN and (to a greater extent) the US Navy (USN) and Japanese Maritime Self-Defense Force (JMSDF) to end their crisis.
ROC - The ROCN and ROCAF together could wreak havoc on a small Chinese naval force off Taiwan's coast, but to do so would risk elevating the crisis. Taiwan would likely do whatever it could to avoid firing the first shots of the conflict. One would expect the ROC military would begin mobilizing its reserves to defend the island against a possible invasion and look to the US and Japan for intelligence and support.
America - I have no doubt about the USN's ability to break a Chinese blockade if it decided to do so. It would not be easy for the USN to get around to Taiwan's west coast and escort ships in and out of Kaohsiung port if there was a standing blockade. America would be reluctant to bring its carriers too close for fear of China's anti-carrier rhetoric/capabilities. America's nuclear submarines don't perform quite as well in shallow water (like the Taiwan Strait) as in the deep ocean and thus China's diesel submarine force, the largest submarine fleet in the world, would have the home field advantage in more ways than one. It is likely that the US would seek to amass overwhelming concentration of force before it would cruise into that shallow water, and that takes time.
Japan - The JMSDF recently acquired a new mission (implicity if not explicitly), when the government of Japan signed on as a defender of Taiwan. The JMSDF is a more potent blue water navy than it is given credit for. Japanese forces likely would not be used unilaterally, only in support of an American mission. Japan role would be to help America get as much power to the strait as quickly as possible as a show of support for Republic of China.
The Belmont Club offers another idea on how to break a blockade, which could be implemented by the ROC or America: a counter-blockade.
I feel that the outcome of a Chinese blockade of Kaohsiung (and/or Keelung) would have more to do with America's willingness to intervene than the willingness of the people of Taiwan to accept the resulting hardships. As long as the people of Taiwan have hope of being rescued by the navies of the ROC, Japan, and America, they could stand the privation. If America and Japan show no willingness to intervene, one day would likely be too long to wait for a conclusion to the crisis, in the eyes of Taiwan's people.
Food For Thought
Would it be in Taiwan's best interest to expand one of its ports on the east coast (Hualien or Taidong) and/or expand its primary naval base on the east coast (Suao)? Both ports are quite small and I suspect neither are able to accept a very large crude carrier (VLCC) or ultra-large crude carrier (ULCC). Expanding one or both of those ports would seriously reduce China's ability to embargo the island. Expanding its only sizable naval base on the east coast would allow the ROCN a greater reach and give it more choices in the event of a crisis in the strait. Both propositions would undoubtedly be expensive. The stretch of land on which these facilities could be built is quite narrow because the central mountain range is so close to the coast. Reclaimed land might be the only way. Is the added strategic flexibility and defense against a blockade worth it?