Bony Fish

Bony Fish

There are a great many bony fish species, as they have evolved and adopted to live in all kinds of habitats, both in salt water and fresh water. Although there are different biological or taxonomic groups to which the bony fish species belong, they are also grouped according to ecological factors, such as the types of habitat they inhabit and the lifestyles they lead within these habitats. Unfortunately, some species of bony fish are becoming extinct because they only live in particular habitats that are now being polluted or destroyed.

All fish living in salt water are properly known as marine fish, while those that live in habitats such as those that live in habitats such as rivers, lakes and swamps are properly described as fresh water fish. There are species that break the rules and prefer brackish water, which means the water is slightly salty, where rivers pour into oceans in estuaries and deltas. Good examples are the mudslippers (oxudercinae), which are also amphibious, meaning they are able to leave the water by using their pectoral fins as limbs. There are also species that spend parts of their lives in either salt water or freshwater and are known as either anadromous or catadromous. Atlantic salmon (salmo salar) are anadromous, as they breed in freshwater and their offspring then travel to salt water to grow and mature into adult fish where as European eels are catadromous, as they breed in salt water and their young travel to freshwater to grow and mature into adults. As water provides a three- dimensional environment, many fish have a tendency to spend most of their time in particular regions of the water. Fish that frequent the seabed or riverbed are described as benthic species. Some rest on the sediment, while others hide within it. Above the benthic zone there is the demersal zone and above that is pelagic zone, both of which are home to particular species of fish, too. Where the water meets the land at its edges there is a fourth region, known as the littoral zone, which also has its specific species. In oceans, this is often described as the intertidal zone, as the water`s edge moves up and down with the tide. In order to find food, fish need to move about, or migrate. Some species move only short distances within their habitat, while others may migrate over significant distances or even to different parts of the world. Changes in the seasons may cause these geographical migrations across oceans or along rivers. Fish will also travel to different depths, according to day and night, because food animals do the same. This is known as circadian migration.

The bodies of bony fish are covered with overlapping scales, which protect the body but also allow flexibility. The scales also serve to provide fish with colours and patterns. These can be for various purposes, such as indicating the sex of a fish, to camouflage it from predators or prey or to warn enemies that a fish is poisonous. Scales may also be smooth or textured for similar reasons. Fish with silvery scales use them to reflect light as a way of confusing attackers. Many open water fish display counter shading, too. This means that they are dark above and light below so that a predator is less able to see them against the bottom or against the sky respectively.

The heads of bony fish are covered with plates that provide armor for protection. The eyes are able to move but they are unable to close as they have no eyelids. The mouth is equipped with functional jaws, which allow fish to open and close their mouths. Some species have lips because they feed by sucking in and sifting detritus, while others have teeth because they feed by biting their food, whatever it happens to be. Some species have teeth that have been fused into a beak- like structure as they peck at their food. Behind the head, on each side, there is a gill cover, or operculum. Each gill cover can open to expel water from which the gills have removed oxygen, as that is how fish breathe without needing to come to the surface to breathe air. The gills are red, feathery organs, which allow blood to come close to the surface over a high surface area, so that as much oxygen as possible can be absorbed. Typical bony fish include species from the mackerel and tuna family (scombridae), the trout and salmon family (salmonidae), the carp and goldfish family (gadidae), the sea bass family (moronidae), and the mullet family (mugilidae). Most typical fish belong to the perciformes order, which happens to be the largest order of vertebrate species, with over 7,000 members.

Reference

1. Britannica Reference Encyclopaedia

2. Knowledge Encyclopedia Animal!: The Animal Kingdom as you've Never Seen it Before

3. Images are taken from Zoo-Que and Google.

4. In Defense of Plants: An Exploration Into the Wonder of Plants

5. A Naturalist’s Guide to the Birds of India

6. Earth: A Sustainable Planet

Also See

• Migration & Navigation of Birds

• Archaeopteryx – The First Bird`s Fossil

• Parrots

• Bats