Fish bones are far more useful than most people realize. Whether you’ve just filleted a whole fish or have a pile of scraps from dinner, you can turn those bones into rich homemade stock, nutrient-dense fertilizer for your garden, or even a crispy snack. Here’s how to get the most out of them.
Make Fish Stock
The single best use for fish bones is homemade stock. It’s faster than chicken or beef stock and produces a deeply flavored base for soups, chowders, risottos, and sauces. You want bones from white, lean fish like cod, halibut, snapper, or bass. Oily fish like salmon, mackerel, or tuna produce a heavy, strongly flavored stock that overpowers most dishes. If you do use salmon bones, plan to use that stock specifically for salmon chowder or a similar recipe where the bold flavor works.
Place the bones, heads, and any skin or trimmings in a pot with a splash of white wine, an onion, celery, and a few herbs. Add enough cold water to cover everything by an inch or two. Bring it to a gentle simmer and let it go for 45 minutes to one hour, no longer. A long-simmered fish stock turns cloudy, bitter, and unpleasantly fishy. Strain it, let it cool, and you’ll have a stock that’s leagues beyond anything sold in a carton. It freezes well for months.
Fry Them Into Crispy Snacks
In Japan, leftover fish bones are deep-fried into crackers called hone senbei. This works best with bones from small fish like sardines, where the bones are thin enough to become completely crunchy. Heat oil to about 180°C (355°F), drop the bones in, and fry until golden brown and crisp. Sprinkled with a little salt, they’re surprisingly addictive, with a texture similar to a chip. It’s a great way to use every part of a fish you’ve filleted at home, and it pairs well with beer or as a garnish on salads.
Use Them as Garden Fertilizer
Fish bones are packed with phosphorus and calcium, two nutrients that plants need for root development and cell structure. Commercially processed fish bone meal contains roughly 10% phosphorus by weight and around 28 to 30% nitrogen, making it a potent organic fertilizer. You don’t need to buy the commercial version if you have bones at home.
The simplest approach is to dry your fish bones thoroughly (in the oven at a low temperature or in the sun), then crush or grind them into a coarse powder. Work this into the soil around tomatoes, peppers, roses, or any flowering plants that benefit from extra phosphorus. The calcium content, which can reach 7 to 9% of the bone’s weight, also helps prevent blossom end rot in tomatoes.
Compost Them the Right Way
Fish bones can go into compost, but standard backyard compost bins struggle to break them down. The bones are dense, decompose slowly, and can attract animals if your pile isn’t managed carefully. A traditional hot compost pile that’s actively turned and maintained will eventually break them down over several months, but it requires consistent effort to keep temperatures high enough.
Bokashi composting handles fish bones much more effectively. This anaerobic fermentation method uses inoculated bran to break down meat, bones, dairy, and other scraps that traditional composting can’t process well. The fermentation takes as little as two weeks to produce a nutrient-rich material you can bury in your garden soil, where it continues decomposing. Because the bucket stays sealed, it also contains odors, which is a real advantage when composting fish scraps indoors.
Eat the Bones for Calcium
Fish bones are edible when softened properly, and they’re a significant source of calcium. Per 100 grams of fish bone meal, the calcium content reaches about 735 mg, which is comparable to drinking nearly three glasses of milk. Phosphorus comes in at around 345 mg per 100 grams, along with meaningful amounts of iron and protein.
The easiest way to eat fish bones is to cook them until they’re soft enough to chew. Canned sardines and canned salmon already have fully softened bones that you can eat without noticing. At home, pressure cooking whole fish or fish frames for 30 to 40 minutes softens bones to the point where they crumble between your fingers. You can also simmer small fish bones in vinegar-based sauces, which dissolves the hard mineral structure over time.
Keep Them Away From Pets
Cooked fish bones are dangerous for dogs and cats. Cooking makes the bones brittle, causing them to splinter into sharp fragments that can puncture the mouth, throat, esophagus, stomach lining, or intestines. Internal punctures can lead to bleeding, infection, or peritonitis, a life-threatening abdominal infection. Raw fish bones carry the same puncture risks, though they’re slightly less likely to splinter. The safest policy is to keep all fish bones out of reach of pets entirely.
Disposing of Fish Bones Safely
If you’re a recreational fisher cleaning your catch near the water, you can generally return fish carcasses and bones to the ocean without a permit. The EPA only requires permits for ocean dumping of fish waste when it happens in harbors, enclosed coastal waters, or locations where it could endanger health or ecosystems. In open water, tossing scraps back is typically fine and provides food for marine life.
At home, wrap fish bones tightly in a bag before putting them in the trash to prevent odors. Avoid putting them down the garbage disposal, as the bones can dull or jam the blades. If you’re not ready to use them right away for stock or fertilizer, freeze the bones in a zip-top bag. They’ll keep for two to three months in the freezer, and you can accumulate scraps from multiple meals before making one large batch of stock.