Fish Identification Guide

In the second part of our fish Identification guide we look at other visible fish anatomy characteristics such as Barbels, Cirri and fish mouth positions, which aid scuba divers or snorkelers correctly identify the species of fish they encounter.

Barbels

Barbels are a whisker like organ found near the mouth of certain fish. These organs are sensory organs that help the fish locate food in murky waters, acting as taste buds or nostrils. Most fish possessing barbells are bottom dwelling fish such as catfish, carp, goatfish and some sharks, that primarily hunt, or scavenge for food in murkier waters, such as sea beds, or lakes.

 

The Brabels on this catfish are prominently visible

Cirri

Cirri are short bristle-like projections from the fishes body, usually over the head appearing like eyelashes of the fish. Cirri also perform a similar function to barbells.

 

the cirri on this tompot blenny is distinctly visible above the eye

Mouth Positions

The position of a fish’s mouth can tell you a lot about the feeding habits, living style and type of behavior it exhibits. A fishes mouth type may be broadly divided into three categories,  midwater ( Terminal),  Surface feeders (Superior) and bottom-feeders (inferior).

Superior

This kind of fish has an upturned, scoop-like mouth which is designed to feed  on prey that swims above the fish, or perhaps on the surface of the ocean or lake, such as insects or plankton. Surface feeding fish usually have an undershot or upturned (superior) mouth for feeding on insects or floating prey.However a superior mouth doesn’t automatically signify a surface swimming fish; fish with this mouth position feed on food that is above them and are either a predator or a strainer.

Inferior/ Sub-Terminal

Bottom feeding fish generally have an underslung or inferior mouths. ventrally-oriented mouths or mouths located under the fishes head that are adapted for scavenging or grazing on algae, invertebrates or mollusks, and are usually seen in fish such as the catfish or flatfish like halibut or plaice.

Terminal

Fish with a terminal mouth position have a mouth in the middle, or center of their head.  These fish either chase their food or feed on what is ahead of them.  The terminal mouth position is considered the “normal” position, and most fish inhabiting the middle levels of the oceans or lakes possess terminal mouths.