Where is fat and what is this gel in refrigerated fish soup? I simmered some mackerel and added some kale.

I wanted to remove the fat so refrigerated overnight.

I didnt see any fat layer existing as you would see with refrigerated chicken or fatty meat but I did see eat some while still hot the before refrigeration.

After refrigeration I didn't see any fat and instead saw the whole liquid had become like a thick gel.


Why wasn't there\should there be a layer of fat like i see with chicken or red meat?
What is this gel?  Is it the collagen from fish bones, the problem is that it was on the stove for 30 minutes and mackerel has little bones so how come there was so much?
i was wondering where all the water had been replaced by gel?  if its collagen does it absorb all the water which is why i cant see a separation of gel and water?
Q1. Chicken and red meat is much more fatty than most fish, so you get a more noticeably thick layer of fat on top of say, chicken soup. Perhaps your fish was lacking in fat. 

Q2. Gelatin is contained in other parts of animal flesh besides just the bones. [Sometimes vegetable matter as well e.g. tomatoes...unless vegetable "gelatin" has another name; if so, people will let me know I'm sure]

Q3. I wouldn't say the water had been "replaced" by gel. The water is taken up into the gel and becomes part of it. Think of Jello: You start out with a lot of water, then you mix the gelatin powder into it and cool it, and you wind up with a gel. The water didn't disappear or get replaced by a gel, it is simply a component of the resulting gel.