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As bizarre as it sounds, there is plenty to learn about fish just by looking at them. Anglers who take the time to study fish features and their functions will undoubtedly possess more knowledge.

This attention to detail will provide insight into fish behaviour and ultimately deliver a greater capacity to catch them.

They say not to judge a book by its cover, but in the case of fish, it may be the exact opposite. Here are five features to examine on a fish that will give you valuable insight into how they behave, hunt and feed.


The most obvious observation of a fish is its general body form. The body shape and profile will provide huge clues about the habitat in which a fish resides, how it hunts and its swimming ability.

The most obvious case is that of Flathead or Flounder. Their flattened profiles clearly suggest that they spend most of their time on the sea floor. In contrast, the streamlined torpedo-like profiles of Tuna and Mackerel suggest fish built for high speed, stamina and strong oceanic currents.

Body shape indicates the preferred habitat, behaviour and swimming ability of a target species.


The eye size on a fish provides a good indication of the importance of vision to that particular species. Fish with large eyes usually require good vision for hunting or low light conditions. Large eyes are often characteristic of deep water fish species.

The position of the eyes can also provide clues on where a fish lives or how it hunts. Eyes positioned toward the top of the head suggest that the species spends much of its time looking up and can indicate either a benthic (bottom) residing species (Flathead) or a species that prefers to eat at the surface (Saratoga).

Eye size provides a good indication of the depth that your target species may inhabit and its ability to spot your line or offering.


Great insight into the feeding habits of a fish species can be gained by examining the shape and position of the mouth of a fish. Fish with an upward opening mouth (Saratoga) are designed to feed at the surface or high in the water column. Fish with a downward pointed mouth primarily feed on the substrate (Golden Trevally and Carp). Fish with a horizontal positioned mouth are more versatile and are likely to feed at different depths in the water column.

Small beaked mouths are designed to pick at molluscs and crustaceans from rocks (i.e. Leather Jackets) while large bucket mouths that create a vacuum are designed to inhale baitfish (Barramundi).

Mouth shape provides a strong indication on where you should ideally be placing your baits or lures in the water column.


Teeth provide insight into dietary habits. Toothy critters with large razor teeth are designed to bite and tear at flesh (Mackerel and Mangrove Jack). Small, fine teeth are designed to grip and grab prey (Flathead, Estuary Cod), while relatively toothless or bucket mouths are designed to inhale prey whole (Australian Bass and Barramundi).

Behavioural differences can even be observed through observing teeth within the same species. In particular, pay close attention to any bream that you catch. Some Bream possess sharp pointed teeth that indicate a diet of fish and prawns, while other bream possess flat rounded teeth that are used for grinding molluscs and other invertebrates from rocks, pontoons and boat hulls.

Teeth provide a good indication of what baits or lures to use.


The size and shape of fins suggest swimming proficiency. Large rounded caudal (tail) fins are indicative of a fish capable of short powerful bursts, but reduced stamina (Estuary Cod, Flathead and Pike). Large forked and rigid caudal fins suggest an ability to deliver sustained power and are usually present on muscular pelagic species (Trevally and Tuna).

Undulating dorsal and anal fins (Leather Jackets) typify species that require fine accurate movements for feeding or positioning. Some species possess a compromise between all of these features to deliver an all-round performance in swimming, manoeuvrability, and stamina (bream, snapper).

Fins provide insight into swimming performance and manoeuvrability.


A host of other unique features on fish provides insight into their behaviour and habits. The whiskers on a Catfish and the tendrils on a Threadfin Salmon help them sense prey in murky water. The horn (enlarged dorsal fin) on a Leather Jacket acts as a deterrent to predators and helps them lock into rocky reefs so that predators can’t pull them out. Although the purpose of the bill on a marlin is debated, it undoubtedly plays a role in their ability to swim, manoeuvre and target prey at high speed.

Unique features can reveal all sorts of additional insight into the ways that fish hunt or the habitats that they reside in.

Next time you examine a fish in a book, an aquarium, or at the end of your line, give these aspects some thought. Use the knowledge and insight to help tailor your fishing efforts to the right conditions, habitats and methods to catch your preferred species. Attention to detail counts, so look carefully at your catch.


Is there anything you would like to add to this article? Share your experience with everyone through the comments section below.

Peter Hollingsworth
Peter Hollingsworth

Peter has been fishing all around Australia since he was a boy. He loves camping, fishing and kayak fishing.