There have been several fishermen "strikes" over the past few months. It started out with an squid fishermen's strike, and has now broadened.
As with many things in Japan, a direct translation does not always convey what is going on. First, strikes in Japan are rarely the long grueling processes that you see in other countries. I remember when I first came to Japan, there was a strike on the private railway that many people used each day to get to work. When people said that there would be a strike starting the next day, I started wondering how to prepare for the coming weeks or months. But the strike ended up being just several hours long, just long enough to make a small point. The issues were settled not long after.
In this case fishermen are "striking" against the consumer, and it is not clear to me what they hope to gain. The first squid strike caused a temporary jump of 32% in the wholesale price of squid. The purpose was call attention to high fuel prices which make fishing unprofitable.
In this more general strike, the aim is the same - calling attention to the effect of high fuel prices. Eventually, they appear to want fuel subsidies from the government, but have not made specific demands yet.