Fish decay in freshwater, saltwater, and occasionally even in the air. When you get your first glimpse of a rotting fish carcass on the shore, you’ll know exactly what to attribute it to. The saltwater is most often the culprit in these situations, but sometimes it can be a combination of both!
The question is, how long does it take for a fish to completely decompose? The general rule is about three weeks for most fresh and frozen fish, and up to a month for a few select species. Let’s take a closer look at how long it takes for a fish to decompose and the main factors that determine how quickly or slowly it will go. (And to be clear, this article is not meant to replace professional advice. Always speak to a biologist or a fish specialist if you have any questions about the safety of consuming raw fish.)
Table of Contents
Temperature
The first and most obvious rule of fish decay is that it takes place at room temperature. Fish that are frozen will not decompose at all, and those that are freshly caught and placed on ice will keep their freshness for only a very short time. The rule of thumb is that every three to four hours that a fish is out of water, its metabolism will slow down and it will decompose a little bit more slowly. This is why it is advisable to keep your fish frozen at all times except when you are planning on cooking or eating them. Freezing fish slows down the decomposition process significantly, sometimes even stopping it all together. This is why you should only thaw your fish out once you are planning on eating it, and even then it is preferable to let it defrost slowly at room temperature rather than in the microwave.
Water Factor
Whether it is fresh water or salt water, water is essential for fish decomposition. Without it, your fish will not decay at all. But having too much water is also harmful to fish decay, especially when it comes to fresh water. Keeping an adequate amount of water in your tank will result in healthier, stronger fish that will allow you to enjoy your time fishing more. Just make sure that the water levels are checked and changed at least once a month, and preferably twice or three times a week simply to ensure that the fish are getting enough oxygen.
Type Of Fish
More and more people are discovering the delights of eating raw fish these days. Whether you are a seasoned angler who has been catching and cooking fish for years, or you are just getting started, knowing the right place to buy fish is essential. If you eat a lot of fish, you’ll find that some of it goes off quickly, and if you aren’t careful, you’ll end up with some very smelly dead fish floating around in your tank! You also need to make sure that the fish you buy are of a good size and have a high nutritional value. Smaller fish, especially those under a pound, have a much lower value and are usually full of parasites and other nasty things that you don’t want to ingest. On the other hand, a really large fish can take a long time to decompose and may contain a lot of cholesterol, which you are advised to limit in your diet. There are also some species of fish that are known to contain a lot of mercury, which you also should avoid eating. This element is very toxic to the human body and even small amounts can be harmful. So make sure that you know which type of fish is safe to eat and which one isn’t.
Marine Vs. Freshwater Vs. Saltwater
Marine fish, those that live in saltwater, and freshwater fish decompose at the same rate, but in different ways. Marine fish have a thick layer of scales that protect them from damage and the sun’s ultraviolet rays, which cause their meat to spoil quickly. Thicker bones also act as natural insulation and keep marine fish warm in the winter, keeping their meat succulent until the next warm season. This makes the toothsome treats much more affordable for our favorite four-legged friend. The opposite is true for freshwater fish, whose thin, transparent skin allows for faster evaporation of their bodily fluids, causing their flesh to spoil quicker than that of a saltwater fish. But don’t worry, freshwater fish also have a longer lifespan than their marine counterparts, sometimes living up to ten years in captivity! So even though they decompose faster, they are also much more useful as food sources due to their longer lifespan.
How Long Does It Take For Fish To Decompose?
With all of that said, how long does it take for fish to decompose? The general rule is about three weeks for most fresh and frozen fish, and up to a month for a few select species. This is assuming that the fish are somewhere around room temperature, which can vary depending on where you are located. For example, it will decompose a lot more quickly in the southern part of the U.S. than it will in the northern part. Similarly, some fish decompose more quickly in the summer than in the winter. In the winter, there is less activity so you will probably have to add more food to make up for it. When it comes to freshwater and saltwater fish, you might have to wait a little longer than you would for a marine fish, especially in the case of freshwater fish. But it is still definitely doable, even for the saltwater fish!
The takeaway from this article is that even though fish decay at room temperature, it is still strongly advised not to keep them at this temperature for very long due to the various hazards that it poses to humans and other living creatures. Freezing fish slows down the decomposition process significantly, sometimes even stopping it altogether. This is why you should only thaw your fish out once you are planning on eating it, and even then it is preferable to let it defrost slowly at room temperature rather than in the microwave. Finally, make sure that you know which type of fish is safe to eat and which one isn’t, as some of them are much more dangerous than others. Never feed a fish that you don’t know what type of food it prefers, and don’t hesitate to throw away any fish that you suspect is infested with worms or other parasites.