Fish are one of the oldest known life forms having lived on Earth for over 350 million years! However, due to the fact they live beneath the surface, much remains unknown about their life, habits and environments. Enter the National Aquarium.
Facts about Fish Senses
Fish senses vary between species. For instance, the Sevengill Shark uses taste and smell whereas many other species use electrosense or lateral line vibration. This is where special organs generate an electric field around the fish's body to help them locate food and communicate. Also, did you know...
- Most fish hear with their ears.
- Their body temperature is always the same as the water around them.
- They have scales that overlap and point backwards.
- Some fish can change sex during their lifetime.
- Most fish don't really sleep, they just rest, always conscious ... always aware
Fish Respiratory Systems
Using their gills to extract oxygen from the water, when a fish breathes, the gill cavity expands and water flows in through its open mouth. The exchange of oxygen and carbon dioxide takes place as the water passes over the gills. In the deep sea where there is low dissolved oxygen, some fishes will store oxygen in their air bladder.
Most fish have one of two types of respiratory systems:
- Pump Mechanism (such as Gurnard and Stingray)
- Ram Ventilation (such as Kahawai and Sharks)
Some fish propel themselves through the water with flippers and fins, much like a row boat has oars and a rudder. Other aquatic animals have webbed feet or suction cups to help them get around. Fish also have special bladders to control their neutral buoyancy, allowing them to stay afloat. For instance, an Orange Roughy has a wax filled bladder, a Shark an oil bladder and a Snapper's special bladder uses air.
Fish Feeding & Digestion
Many fish engulf their food whole without breaking it down. Sharks crunch their food with their teeth. Snapper break food into chunks by shaking and ripping it apart. An Octopus bites its prey then injects it with a poison to anesthetise it before consuming.
Aquatic Animal Colouration & Protection
Counter-shading is a naturally occurring feature of many aquatic species, where the underbelly is light (to blend in with the lighter areas above the fish) and the topside is darker (to blend in with the ocean depths). For instance, consider the colouring of Penguins, Sharks and Snapper. Many fish also change colour to alarm, or for breeding purposes.
There are many ways fish protect themselves from predators:
- Wrasse (or Parrot Fish) wrap themselves in mucus before burying into the sand to sleep at night.
- Trigger Fish find holes in rocks or in the sand to hide.
- Crayfish live in holes and are spiny, they can dart backwards to safety quickly.
- Octopus and Squid can change colour and the Octopus can add skin tags at will.
- Eels dig holes in which to retreat.
- Stingrays can change colour quickly and easily for offensive or defensive purposes, they can also bury themselves in the sand.