Is fish biodegradable? (5 methods of fish preservation)

This article shall answer the question of the biodegradation of fish.

It shall also look into other areas such as:

  • Process of biodegradation.
  • Fish spoilage and storage.
  • Effects of fish degradation on the environment.

Is fish biodegradable?

Yes, when fish dies, its body components are broken down by its endogenous enzyme and microorganisms such as bacteria and fungi to produce small biomass and gases such as carbon dioxide, methane, water vapor, and other gases depending on the types of biodegradation and the agents involved.

What is biodegradation?

Biodegradation is the process by which naturally occurring organic materials are broken down by microorganisms such as bacteria and fungi into small particles which are not harmful to the environment.

Biodegradation is carried out by different agents such as UV radiation, light, wind, and water but the most effective agents of biodegradation are bacteria and fungi.

Biodegradation occurs in three distinct stages: biodeterioration, bio-fragmentation, and assimilation.

The biodeterioration process loosens up the structure of the organic substance. For instance, the cell wall of plants is weakened by light, wind, water, and UV radiation.

Bio-fragmentation involves the breakdown of organic matter into smaller, nontoxic particles by bacteria and fungi, releasing water and carbon dioxide in the process.

Assimilation is the last stage of biodegradation and it involves the microorganisms taking up the products of bio-fragmentation into their biological machinery to be used to make energy.

Biodegradation can either involve the microorganisms using oxygen, aerobic biodegradation or it can involve the microorganisms which do not use oxygen, anaerobic biodegradation.

Types of biodegradation.

There are two distinct types of biodegradation.

  • Aerobic biodegradation.
  • anaerobic biodegradation.

Aerobic biodegradation.

This is the process of biodegradation that involves the use of oxygen.

The microorganisms such as bacteria and fungi use oxygen to break down organic matter into small biomass and carbon dioxide and water.

Most organic matter contains proteins and carbohydrate compounds that are broken down by endogenous enzymes into small particles such as amino acids and glucose.

The remaining proteins and carbohydrates, together with the amino acids and glucose are broken down into carbon dioxide and water, in the process, small biomass is formed.

Aerobic biodegradation is very fast.

The ammonia in the dead organism is broken down into nitrates and nitrites by the nitrogen-fixing bacteria which enrich the soil and supply the plants with necessary nutrients.

Anaerobic respiration.

This is a type of reaction that involves microorganisms that do not require oxygen.

The microorganisms use other chemicals like hydrogen sulfide to break down organic matter into small biomass, carbon dioxide, and methane gas. 

The process of anaerobic respiration is very slow but very efficient. Composting is a type of controlled anaerobic reaction.

How is Fish preserved?

Fish is one of the most perishable foods. It has a very short life due to its aquatic habitat, and therefore, it requires a lot of proper handling and storage to regulate its spoilage.

To increase the shelf life of fish, it has to be preserved using different methods to avoid spoilage.

The different methods of preservation include ancient methods such as; drying, salting, pickling, and smoking.

These methods are still in use but large-scale preservation employs modern techniques such as freezing and canning.

Before fish can be preserved, it is first cleaned, scaled, and eviscerated.

The drying method involves exposing the fish to sunlight or an alternative source of heat. The heat dries the water in the fish making it dry. This prevents the growth and spread of bacteria and fungi, which thrive in moist environments.

Salting involves using salt or brine. Cleaned, scaled, and eviscerated fish is then laid between layers of salt or immersed in a pool of brine.

Salt preserves fish by absorbing water and also by raising the pH of the fish environment. These conditions are not conducive to the growth of bacterial or fungal populations.

Smoking preservation involves drying using a creosote component, and fish is drawn near the source of heat where it is dried. The methods of salting, smoking, and drying all work on the same principle of absorbing water from the fish so that microorganisms can not grow.

The freezing method involves the storage of fish under very low temperatures. The ice conditions prevent the growth and activities of bacteria and fungi.

Most bacterial microorganisms are inactivated at low temperatures, their enzymes become inactivated and hence they stop multiplying.

The inactivity of bacteria means that fish products remain fresh.

The freezing method involves the use of storage cans to preserve fish and other food substances.

Storage cans are first cleaned and heated at very high temperatures using equipment such as an autoclave.

The heating kills some microorganisms while also deactivating others. After heating, the fish is stored in the cans and the cans are hermetically sealed to prevent any entrance of even the microscopic organism.

This process of heat at very high temperatures to kill or deactivate microorganisms is called thermal sterilization.

What is the process of fish biodegradation? 

After fish is caught, the process of food spoilage begins. 

A process called rigor mortis brings changes to the fish’s body after its death. These changes include the breakdown of various biomolecules like proteins, lipids, and carbohydrates into their simple forms.

These compounds undergo enzymatic breakdown in a process called autolysis. Also, the chemical oxidation of lipids occurs.

The autolysis process breaks down proteins into amino acids, and the muscles are also broken down. This weakens the fish’s body structure.

The lipids are also broken down or oxidized by enzymes and other oxidative substances such as metals.

The lipids oxidation by enzymes is called lipolysis and causes fish rancidity. 

The activities of enzymes to break down lipids, proteins and muscles produce gases such as ammonia which makes fish produce odors.

Fish death and eventual activities of enzymes weaken the fish structure and also produce substances that lower pH and this coupled with high water activity leads to uncontrollable growth of microorganisms.

The microorganisms, mostly the bacteria, increase in population and start degrading the components of fish. 

The proteins, lipids, carbohydrates, and muscles are broken down to give compounds such as amines, biogenic amines, organic acids such as acetic acid, sulfides such as hydrogen sulfide, and alcohols such as ethanol, aldehydes, and ketones.

These products contain unpleasant smells. The microorganisms continue to grow under those conditions, reducing the fish into small biomass, and in the process, gases such as carbon dioxide, and methane are produced.

Different microorganisms could degrade fish. The types of bacteria found in a degrading fish are determined by: 

  • The living habitat of the fish.
  • The fishing season.
  • The water temperature.
  • The method used to capture the fish.
  • The handling of fish after its capture.

What are the effects of fish biodegradation on the environment?

Different effects result from the biodegradation of fish carcasses depending on the environment.

First, the biodegradation of fish is important in maintaining a clean environment. It prevents the over-accumulation of waste products such as bones in the environment which would pollute the environment.

According to a study, biodegradable fish products can also be used to make biodegradable plastic which will replace the synthetic plastics that cause environmental pollution.

The degradation of fish also improves soil fertility. Degradation produces ammonia which is utilized by the nitrogen-fixing bacteria to provide nitrogen to plants, improving soil nutrients.

However, when fish degrades in the water bodies, it produces nutrients that lead to eutrophication; the process of introducing nutrients to the water.

The eutrophication leads to the uncontrollable growth of aquatic plants and algae which compete for oxygen with aquatic animals, which might lead to their death.

When there is too much fish degradation in the environment, it leads to the over emission of gases such as ammonia, hydrogen sulfide, and carbon dioxide. These are gases that in high concentrations are toxic to plants and animals.


This article has answered the question of the biodegradability of fish.

It has also covered other areas such as:

  • Process of fish spoilage.
  • Process of biodegradation.
  • Methods of fish preservation.
  • The effects of fish degradation on the environment.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is fish biodegradable?

Can I use fish waste as fertilizer?

Yes, fish waste is rich in nitrogenous compounds such as ammonia which are huge sources of nitrogen to plants.

Is food biodegradable?

Yes, food is acquired from organic sources, and plant and animal products are susceptible to microbial degradation.

How do you recycle fish waste?

Fish waste can be recycled by using it to grow crops that use the nitrogen and phosphorus compounds in the fish waste.


J├ęssica Tavares, Ana Martins, Jorge A. Saraiva. Fresh Fish Degradation and Advances in Preservation Using Physical Emerging Technologies.

Retrieved from:

S. K. Wilson, R. Fisher, M. S. Pratchett, N. A. J. Graham, N. K. Dulvy, R. A. Turner, A. Cakacaka and N. V. C. Polunin (March 2010),. Habitat degradation and fishing effects the size structure of coral reef fish communities. pp. 442-451

Retrieved from:

Xiaobao Niea, Xiaoming Chena

Mechanisms underlying the deterioration of fish quality after harvest and methods of preservation

Huss HH (1988) Quality and quality changes in fresh fish FAO Fisheries Technical Paper 348, Rome. ISBN 92-5-103507-5.

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