Among professionals, it is generally agreed that the most difficult branch of taxidermy is fish mounting. Creating a technically accurate fish mount can be a real challenge. The top award-winning fish taxidermists are almost all outstanding flat artists as well. The ability to draw, paint, mix colors, and sculpt are shared among most of the world's best fish taxidermists.

Mounting fish not only requires the ability to accurately recreate the anatomy of the subject, but to restore all of the colorations as well. When a fish skin dries, most of the color goes away, leaving only brownish patterns on the skin and scales. Fish taxidermy is the one area of wildlife art where the artist must totally recreate the colors of the skin all over the animal. In bird taxidermy, the taxidermist must paint the legs, feet, and bill, but the feathers retain their natural colors. In mammal taxidermy, the taxidermist must paint the nose and eyes, but the fur requires no color correction. In fish taxidermy, however, the taxidermist has to paint every square inch of the specimen, and make it appear natural.

There are a lot of different ways to produce a fish mount, and fish taxidermists usually are required to choose different mounting methods to match their particular subjects.

Warm water fish with tough skins and large scales (such as bass, crappie, and bream) are good candidates for skin mounts. A skin mount means that the fish is skinned, the skin is preserved, and the skin is either mounted over a mannikin, or the fish's body cavity is packed with a filler material which is shaped and then allowed to harden. These types of fish are not particularly greasy, so they are usually mounted with the natural skull still attached to the skin. The fins and tail are also the real thing.

Cold water fish such as trout, salmon, and char have thin, smooth skins with fine scales. Their skins and bones are also more greasy than their warm water cousins. Mounting these fish is a bit more difficult because any lump of mache or hide paste under the skin can be visible. The preferred method for mounting these specimens is over a smooth foam mannikin. The natural skulls are sometimes used, but due to increased problems with shrinkage, spoiling, and grease bleed-through, many taxidermists use artificial heads (cast in polyester resin) attached to a natural skin-mounted body.

Most saltwater fish (as well as many cold water fish) are entirely recreated from man-made materials. Without question, these synthetic mounts are the most long-lasting taxidermy renderings. While the fish is fresh, a carefully constructed mold of the fish is made. Then, the body and fins of the fish are cast in fiberglass reinforced polyester resin. The mold of the fish is called a fiberglass "blank" at this point, because it has no markings or color. The taxidermist must entirely create the coloration on the mount to make it appear like a live fish.

Due to the restrictive costs of molding and reproducing fiberglass gamefish, it is not commercially feasible to make a special mold for every sportsman's catch, nor is it necessary. Taxidermists found out years ago that one 84" sailfish was shaped pretty much like any other 84" sailfish. A new industry was born as taxidermists with a good selection of fish molds started constructing multiple reproduction fish from their molds. These fiberglass fish blanks are sold to other taxidermists throughout the country who only have to prepare the fish and paint it to convincing coloration.

Fiberglass reproductions are gaining in popularity. They are ideal for use on difficult species to mount: large fish, greasy fish, or fish which are difficult to skin, such as catfish. They are also great for catch and release programs or other conservation methods. Another advantage is the longevity of the mount. A fiberglass reproduction could conceivably last for thousands of years. They are practically indestructible.