You can preserve a dead fish using several methods depending on your goal: a wet specimen in a jar, a dry-mounted taxidermy piece, or a resin-encased display. Each approach requires different chemicals, tools, and timelines, but all share one principle: you need to stop tissue decay quickly, ideally within hours of the fish dying.
Wet Specimen Preservation
Wet preservation keeps a fish suspended in liquid inside a sealed jar, maintaining its three-dimensional shape and soft tissue indefinitely. This is the method museums and research collections use, and it works well for fish of almost any size. The process has two stages: fixation and long-term storage.
Fixation
Fixation is the chemical step that halts decomposition by hardening the fish’s tissues in place. The standard fixative is a 10-percent buffered formalin solution, made by mixing one part formalin with nine parts water. Adding about three grams of borax per liter of this solution neutralizes its acidity, which prevents the fish’s bones from softening and reduces tissue shrinkage over time.
For fish longer than about six inches (150 mm), you’ll need to make a small incision, roughly an inch long, along the right side of the belly. This lets the fixative penetrate the body cavity instead of only preserving the outer layers while the organs rot inside. Place the fish in the solution and arrange it in the position you want before the tissues stiffen. Leave it submerged for two days to one week, depending on the fish’s size. Larger or thicker fish need longer.
Transfer to Alcohol Storage
Formalin is excellent for initial fixation but not ideal for decades-long display. Most collections transfer fixed specimens into ethanol for permanent storage. The standard ratio is three parts 95% ethanol to one part water, creating roughly a 70% alcohol solution. If you’re using ethanol instead of formalin from the start (which avoids the safety concerns of formaldehyde), the fish needs to soak for at least a full week before it’s adequately fixed.
For long-term storage, the jar matters. You need a glass container with a tight-sealing lid, since alcohol evaporates readily through loose seals or plastic. Check the fluid level every few months and top off with the same ethanol-water mixture as needed. A well-sealed specimen jar in a stable, cool environment can last for decades with minimal maintenance.
Safety When Using Formalin
Formalin contains formaldehyde, a known irritant and carcinogen. If you choose to work with it, wear chemical-resistant gloves, safety goggles, and an apron. Work in a well-ventilated area or outdoors. OSHA recommends a respirator if you can’t keep airborne exposure low through ventilation alone. Have an eyewash station or at minimum a clean water source nearby in case of splashes. Many hobbyists skip formalin entirely and use 95% ethanol for both fixation and storage, which is safer, though it requires a longer initial soak and may not preserve internal tissues quite as thoroughly on larger specimens.
Fish Taxidermy (Skin Mounting)
Taxidermy produces a dry, wall-mountable fish and is the most popular choice for anglers preserving a trophy catch. Unlike wet preservation, you’re keeping only the skin and discarding the flesh entirely, then stretching that skin over a sculpted form.
Skinning and Curing
Start by soaking the whole fish in a mixture of borax powder and salt for about 24 hours. This draws moisture from the skin and slows decay while you work. For a smaller fish, two cups of borax and one cup of salt is a reasonable starting ratio. Scale up proportionally for larger fish.
Once cured, make a single incision along the belly from the vent to the lower jaw using a scalpel or sharp craft knife. Work carefully to avoid puncturing through the outer skin. Peel the skin away from the flesh starting at the tail, using a spoon or fleshing tool to scrape off any remaining meat and fat from the inside of the skin. Fat left behind will eventually rot and ruin the mount, so be thorough.
Mounting and Finishing
You’ll need a fish form, which is a pre-shaped foam or urethane body that matches your fish’s species and measurements. These are available from taxidermy suppliers in a wide range of sizes. Fit the cleaned skin over the form, gluing it in place with epoxy or polyester resin. Pin the fins in a natural, spread position and let everything dry completely.
Once dry, the fish gets painted. Even well-preserved skin loses most of its color during the curing process, so taxidermists repaint the fish using reference photos. A final coat of clear lacquer or varnish seals the paint and gives the mount a lifelike wet sheen. The entire process from skinning to finished mount typically takes several weeks, with most of that time spent drying and painting.
Resin Casting
Encasing a fish in clear epoxy resin creates a permanent, fully enclosed display piece. It looks dramatic, but the preparation is more involved than simply pouring resin over a raw fish. Moisture trapped inside the casting will eventually cause the specimen to decay, cloud, or crack the resin from within.
The fish must first be fixed in a 10-percent neutral formalin solution, just as with wet preservation. After fixation, the key step is thorough dehydration. Researchers working with resin-embedded specimens run the fish through a series of acetone baths at decreasing concentrations: 90%, then 70%, then 30%. Each bath pulls more water from the tissues. After the final acetone soak, the fish is partially dried on blotting paper before being placed in the resin mold.
Pour the resin in layers, allowing each to partially cure before adding the next. This prevents the fish from floating to the surface and helps avoid large air bubbles. Epoxy resins designed for deep pours generate less heat during curing, which reduces the risk of yellowing or cracking. The finished piece is essentially permanent, though it should be kept out of direct sunlight to prevent the resin from discoloring over time.
Quick Freezing as a Short-Term Option
If you’ve caught or found a fish and aren’t ready to start a full preservation project, freezing buys you time. Wrap the fish tightly in plastic wrap, press the fins flat against the body, and place it in a freezer. This halts decomposition but doesn’t preserve the specimen permanently. Frozen fish can be held for weeks to months before thawing and beginning one of the methods above. Position the fish in the shape you want before freezing, since it will be much easier to work with if it thaws into a natural pose rather than a rigid curve from being crammed into a freezer shelf.
Choosing the Right Method
- Wet specimen in a jar: Best for scientific study, small display pieces, or preserving the whole fish including internal anatomy. Requires ongoing fluid checks but maintains soft tissue indefinitely.
- Taxidermy mount: Best for wall display and trophy fish. Produces the most lifelike result when painted well, but only the skin is preserved.
- Resin encasement: Best for a sealed, maintenance-free display. Requires the most preparation steps and gives you no access to the specimen afterward.
For any method, start as soon as possible after the fish dies. Decomposition begins within hours, especially in warm conditions, and once it’s underway, no preservation technique can reverse the damage to the tissues. If you can’t begin immediately, get the fish cold or frozen right away.