Sardines are saltwater fish.

Sardines are warm-water fish, which means that they live where the sea water is warmer, i.e., at lower latitudes. At higher latitudes, sardines are very rare due to the cooler temperatures. There are many different species of sardines, and their specific sea areas of distribution are also different.

For example, there is a species of sardine called the "European sardine", which as the name suggests is found along the coasts of Europe, and also along the northwest coast of Africa near the equator. Another example is the small sardine, which contains more than 20 species and is mainly found in the western part of the Pacific Ocean. On the southeastern coast of China, there are also some sardines distributed, which belong to the genus Sardinops.

Sardines have been living in the ocean for a long time, and have adapted to the ocean environment, their body structure and regulatory mechanisms are in line with the conditions of the marine environment. Therefore, they can not live in fresh water, if they suddenly let them to live in fresh water, they are likely to die because they can not adapt.

Feeding Behavior of Sardines

Sardines mainly feed on zooplankton, and the types of zooplankton that sardines feed on are as follows: bacteria, coelenterata, mollusks, protozoa, decapods, juvenile barnacles, fish eggs, methanogens, and copepods. The seasonal bait composition of sardines varies with hydrologic conditions. During periods of intense upwelling, the bait composition is dominated by phytoplankton, while during periods of weak upwelling, the bait composition is dominated by zooplankton.

Sardines are filter feeders, filtering seawater through their gills and catching plankton that passes through them. In addition sardines have lens eyes, which greatly increase resolution and image brightness. So they can also use their vision to track prey filtering through the water.

The amount of food that sardines eat depends on their weight, their environment and their food supply. Depending on food availability, sardines eat 2-5 percent of their body weight each day. Sardine larvae eat the same type of food as sardine adults, but they rely primarily on phytoplankton for survival. When sardine larvae grow up they will prey on larger organisms. In the meantime, they may pick up parasites from other fish or peck at other debris in the water.