To understand the marwhale you first must understand jade
. The planet does not have a solid core, it is instead composed entirely of a substance similar to water. On the surface of this substance there are a number of drifting atolls, none of which are very large. The majority of the "human" population of jade live on boats. Since storms and even bad weather do not manifest in jade this is an ideal form of habitation.
Inhabiting the "water" of jade there are momentous mammalian fish hybrids known as marwhales, they are so large that they literally grow to be thousands of kilometers long.
Every year these monumental creatures surface to breathe, typically it takes almost a week for them to fill their lungs with air before they resubmerge.
During this week long period most of the inhabitants of jade form fishing parties, where they take small swift skiffs and board the backs of several marwhales. Using specialized tools they "harvest" long strips of flesh from the marwhales.
The creatures are so vast that while this irritates them, it does not actually harm them, in fact it is so relatively painless that while the fisherpeople harvest tons and tons of flesh, the marwhales tolerate the abuse and do not submerge. Less than a month later the marwhales will be completely healed.
The fishing season is very brief and precious, this is the only time during the year that the fisherpeople have to gather the marwhale meat that is crucial for their survival. Since it is essentially their only significant source of protein aside from trace quantities absorbed through the various seaweeds and lichens that constitute the remainder of the jade diet.
The meat that is harvested is later cut into much smaller strips and either stored in salt or dried in kilns to make a very nutritious jerky that will last for several seasons.
Marwhales themselves feed on a type of jellyfish called a lampfish
that utilizes nuclear energy to animate. Incidentally the marwhales are photosynthetic beings, they consume the jellyfish only to absorb the radiation that they emit. The jellyfish in turn live out their entire lives comfortably inside the marwhale's stomach. Typically a marwhale will consume billions of jellyfish during its exceptionally long life.