You need a good old fashioned two sided carborundum stone, wet (one side quite smooth) and a proper butcher's steel, with, for meat etc German or Swiss made butcher's knives.I have had this set up for about 25 years!! Trouble is if you leave the very sharp knives in a normal drawer the house 'elf and saftey think the results are too dangerous.
My steel is oval but with quie acute angles at the narrow bit. - it says "JSLEUR Rustless", and was made in Switzerland. My knives are Victorinox and Fairfax - but as they are even more than 25 years old, I do not know if the brands are still extant. I used to run a large meat processing plant and most butchers would sharpen their knives with a stone once or twice a day only, but use the steel quite frequently. With a high throughput a knife could wear out in a couple of months.Fish filleting knives are thinner and may need to be even sharper to neatly skin or fillet a fish.If you have a local old fashioned butcher he may be able to obtain such stuff for you via his supplier.
Working in the butcher trade for 15 years in days gone bye we always used Victorinox knives ,We also had some German Knifes that never kept there edge,i still have my knives and a good steel ,if your not used to useing a steel i think its best that you put the tip of your knife on a bread board and run the steel in small circles up and down the knife, this will save you having a thumb like mine that has more short cuts than a Tom Tom