Marine fishes

Marine fishes

Although terrestrial humans refer to our planet as earth, it is really Planet Ocean. Not only is 71% of the planet’s surface covered with water, but because water supports life from the surface down to the oceans’ greatest depths of 11,000 m, the total oceanic living volume is 300 times greater than the terrestrial. Anyone first observing our planet from outer space would be struck by this and surely would name the planet for its blue water cover, unique in the solar system.

Much recent attention has been directed at biodiversity (the numbers of species present) in tropical rainforests. The huge biodiversity in tropical areas is accounted for largely by radiation of one group, the insects. If we turn to the sea, we may not find as many total species, in part because insects have not diversified there. However, at the level of phyletic diversity (numbers of different phyla present), the seas support a greater animal biodiversity than does land. Of 33 animal phyla, 32 occur in the sea, and 15 of these are exclusively marine (Norse 1993).

Major ecological divisions

Four main ecological divisions are recognized among the 16,000+species of marine fishes:

1 Epipelagic fishes, which dwell from the surface down to 200 m, make up 1.3% of the total, or about 360 species.

2 Deep pelagic fishes include about 1400 species, or about 5% of the total. These water column dwelling fishes can be further subdivided into mesopelagic fishes, which live between 200 and 1000 m, and deeper dwelling bathypelagic fishes.

3 Deep benthic fishes comprise about 1800 species, or 6.4% of the total.

4 Littoral or continental shelf species are shallowdwelling fishes that inhabit the shore and shelf above 200 m. They are the largest group, constituting 45% of the total, or about 12,600 species.