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Ecological role of fish

Ecological role of fish

Fish are a heterogeneous group of basically aquatic vertebrate organisms, covered with scales and equipped with fins, which breathe through gills.
These living organisms, with over 32,000 species currently known, cover almost 50% of the total species of the vertebrata subphylum.
Fish have colonized any sea, ocean, river or lake on the planet, with different shapes, colors and sizes.
There are species typical of mountain watercourses (such as the Salmonidae or Cyprinidae) or lakes (such as the common carp – Cyprinus carpio), suitable for life on the seabed in search of food. Sometimes species may be endemic to restricted habitats.
Environments with variable salinity, such as river estuaries and lagoons, host species specialized in withstanding even large changes in the concentration of dissolved salt, called euryhaline (the Mugilidae, for example, including the common gray mullet – Mugil cephalus), on the contrary species unable to adapt to environments with variable salinity are called stenohalines.

Ecology –
Fish perform, like all living beings, an undoubtedly very important ecological function. In fact, by feeding on the plant and animal microorganisms that populate the waters, they regulate their development so that they do not spread excessively. Furthermore, fish represent the nourishment of numerous other animals: whales, dolphins, seals, aquatic birds, etc. If there were no fish, these animals mentioned would become extinct and the biological balance would be irreparably disturbed. In fact, it has already occurred that, following the disappearance of fish in some polluted streams or lakes, quite a few bird species have migrated to other regions, causing serious repercussions on ecology.
For this reason, in recent decades, among the new generation bioindicators, fish have taken on a growing interest in the assessment of environmental quality in various continental aquatic ecosystems (rivers, lakes, coastal lagoons, estuaries).
The need to use fish for environmental monitoring, according to classification and evaluation procedures increasingly based on an ecosystem approach, has been highlighted in the legislation of the USA (already for over twenty years), of other industrialized countries and only recently in Europe , through the 2000 WFD (Karr and Chu, 1999; European Union, 2000; Kurtz et al., 2001).
The use of fish as indicators in aquatic ecosystems is based on the assumption that fish species and communities are sensitive indicators, capable of highlighting environmental changes.
Some ecological-evolutionary characteristics represent its strong points for its use in environmental assessments:
– Long evolutionary history;
– Wide adaptive spectrum;
– Colonization of all aquatic environments.

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