"Fresh fish is very perishable product and spoil due to microbiological activity, chemical oxidation of lipids and autolysis. However, microbial spoilage is the main mechanism affecting fresh fish quality. As the bacteria grow they utilize nutrients and produce byproducts.
It is well established that the accumulation of metabolic products is the primary cause of the organoleptic rejection of fresh fish. It is also known that spoilage is caused only by a fraction of the initial microbial population, known as specific spoilage organisms (SSOs), which produce metabolites (chemical spoilage indices-CSIs) responsible for off-flavours and cause the organoleptic rejection of the product.
The fraction of the initial micro-biota that dominate and the metabolic products that are produced are determined mostly by the temperature and atmospheric conditions during storage"