Any mayo requires good olive oil, salt and some acid--lemon, vinegar, lime. It also requires eggs. The usual ones are hen eggs, All the ingredients need to be at room temperature and good. They don't need to be overwhelming; it depends what the mayo will be served with.
Just returned from St Barth--wonderful, thank you--where I came upon a can of sea urchin roes. Once opened the roe did not turn out to be something that I would want to eat or serve on its own; but it reminded me of other eggs and other mayos.
My first experiment--very good too--was in Aspen when at the house of a fabulous fisher. She had returned from a high-mountain trip where it was legal to keep your trout catch. I volunteered to be the cook. First, I had to clean the the fish. As I cleaned, I noted that some of the fish were ladies with egg sacks. What to do? I made a sauce--warm--with the eggs. It was sensational. Since then, I have gone on to using other fish roes when available. I wouldn't use beluga or other glamorous roes; but there are many that are good and that work.
When buying fish, ask the monger to save the roe for you and not discard it. Incidentally, striped bass roe can be poached and served as you would the mos elegant of quenelles.
Today, I am using shad roe as it is in season and I have half of a very small pair (three ounces) extra. I used a half cup of mild but good olive oil, a quarter teaspoon of salt and the juice of half a lemon--excellent. I would serve it with cod or chicken. I'll let you know tomorrow.
I made it in the blender; but in St Barth i had to prove i could stil whisk.
Think of all the roes that are out theree in jars and bottles as well as fresh. Experiment; have fun