I am so sorry about your fish. The same thing happened to us. The raccoons ate our favorite goldfish who would come to us & they left quite a mess.
I don't know if they would want to snack on a yorkie but I would be careful so that your babies don't get into any fights with a raccoon. They can be quite vicious when cornered.
If you decide to get more fish this may help. A farmer I used to get hay from had his chickens getting eaten by raccoons. Once I stopped by there at dark. He had spotlight set up with a radio on. All of his chickens, pheasants and ducks were together in his yard sleeping under the spotlight. He said they all came up at dusk to sleep there by themselves. Evidently the raccoons were kept at bay from the light & voice from the radio. No more missing chickens.
Also, you may want to try a net over the pond. Hope this helps.