It is mindboggling that we know much more about the moon than we know about our own planet’s oceans. In the dark, deep, chilly depths of our oceans, innumerable species exist, hidden from human eyes – and waiting to be discoverred. Our oceans are filled with a wide variety of living things, and fishes constitute a major part of the population, prompting us to take a closer look at these amazing creatures which are so adept at keeping us enthralled while we’re diving. Here, we pay homage to our finned friends by taking a closer look at fishes in general, as well as an even closer peek into the lives of many of the species we encouter while diving.
Fish, Defined
Fishes are unique to the earth’s oceans and other bodies of water. Scientists are able to track their existence back to approximately 500 million years ago, and like many other life forms, fish are wonderfully varied. Their size can vary from less than a millimeter to several meters. Their weights can be tiny as a few milligrams, or gigantic, in the thousands of kilograms. They exhibit an extraordinary array of colors like no other animal species on earth. Their senses, skill, technique and behavior are uncommonly adroit. Some mate in huge groups and never see their mates again while others, in the manner of some higher animals, mate for many years or even for life. Some are only active during daylight hours while others prefer the cover of darkness. While we are quite familiar with many reef species, there are some fish living at depths which are well beyond our reach. Considering these things, it is no wonder that fish fascinate us, enchant us, beguile us and ignite our imaginations.
But in the end, it all comes down to a simple, scientific definition:
Fishes are cold blooded aquatic vertebrates which posses fins for locomotion and gills for respiration. Their bodies are covered with scales rather than skin or hair. Fish of some kind can be found in almost all aquatic environments, and though there are a few (such as some sharks) which give birth to live young, most of them reproduce by laying eggs.
How do we categorize fishes?
It is rather difficult to draw sharp, dividing lines to classify the more than 21000 species of fishes which are known to exist. However, categorization is a bit simpler, so science has been able to place these species into 11 distinct groups. Let’s take a closer look at each of the eleven.
Butterflyfish, Angelfish, and Surgeonfish
Butterflyfish, Angelfish, and Surgeonfish belong to the family Chaetodontidae, Cichlidae and Acanthuridae respectively. All these fishes are small and generally do not grow to lengths greater than 16 inches. The butterfly fish is the smallest of the three, while the surgeonfish is the largest. Butterfly fishes have a striking similarity to angelfishes in appearance, and surgeonfish share similarities with both. Surgeonfishes are distinguished by the scalpel-sharp spines on their sides, which gives this group its name.
Jacks, Barracuda, Porgy, and Chubs
Jacks, barracuda, porgy, and chubs belong to the Carangidae, Sphyraenidae, and Sparidae families respectively. Barracuda are exceptionally large, with streamlined torpedo-like bodies and sinister, toothy grins; porgy and chubs are streamlined in appearance, however their mouths are much smaller and they are much more docile than their barracuda relatives.
Snappers and Grunts
Snappers belong to the family Lutjanidae; grunts are part of the Haemulidae family. Both of these species generally inhabit deeper reef environments. Both snappers and grunts are fairly common in various places, and both are targeted by commercial fisheries as well as by recreational anglers.
Damselfish, Hamlets and Chromis
Damselfish, hamlets and chromis all are exquisitely colorful fishes with many different body shapes and a variety of patterns. Some types of Damselfishes and hamlets are found in coral reefs whereas their relatives, the chromis, are found only in freshwater environments, and certain damselfish also prefer fresh water. All three types of fishes are popular among aquarists and hobbyists.
Groupers and Sea Bass
Both groupers and sea bass are large fishes with heavy bodies and large bones. Both belong to the family Serranidae. Groupers and sea basses have a number of characteristics in common, including large mouths and a tendency to gulp prey. Groupers can weigh hundreds of pounds, while sea bass are smaller. These fishes are subject to heavy fishing to the point of overfishing; they are vital predators in reef environments, which has prompted governmental agencies to create stricter laws protecting them from their worst predators – humans.
Parrotfish and Wrasse
These are some of the fish we enjoy watching most – partly because of their brilliant colors and interesting habits.
Parrotfishes belong to the family Scaridae, while all wrasses are part of the Labridae family. Wrasses are generally much smaller than parrotfish, and are typically encountered at cleaning stations and in other reef environments; parrotfish can be found nibbling away at reefs, and are sometimes heard before they’re seen.
Squirrelfish, Bigeye, and Jawfish
Squirrelfish, Bigeye, and Jawfish belong to the Holocentridae, Scombridae and Opistognathidae families respectively. These fishes are highly sought by commercial fisheries and recreational anglers, however they are quite common in all the areas where they’re found. While jawfishes are normally quite small, bigeyes can grow to be over fifty inches long.
Flounders, Scorpionfish, Lizardfish, and Frogfish
These fishes are known for their excellent camouflage abilities; they’re almost impossible to distinguish from their surroundings much of the time. Flounders, scorpionfish, lizardfish and frogfish are generally not very large, growing to just a few feet in length at most. Despite their common genetics, all these fishes have unique appearances and a variety of different features from one another.
Filefish, Triggerfish, Puffers, Trunkfish, Cowfish, Goatfish, Trumpetfish, and Drums
All these fishes belong to the order Tetraodontiformes, and all are quite closely related in terms of scientific classification. For example, if you take a close look at a Filefish, and you’ll notice that it looks very much like a flattened trunkfish! A huge number of species belong to these fish families, and almost all are common throughout various parts of the Atlantic, Indian and Pacific Oceans.
Eels
For the most part, eels are predatory fishes. With slender, elongated bodies and the ability to hide in small spaces, they come in sizes from just a few inches long to as much as 4 or 5 meters. Most are capable of swimming freely, but they move differently than other fish; their fins fused, forming a ribbon-like structure that surrounds most of the body’s length and increasing the effectiveness of swimming motions. You might be surprised to learn that there are around 800 eel species throughout the world.
Sharks and Rays
Sharks and Rays are cartilaginous fishes, with flexible skeletons which are not made up of bones, but of cartilage which is a very tough, elastic substance. Both sharks and rays belong to the class Chondrichthyes. Rays have flattened bodies, while sharks have streamlined shapes, for the most part. These amazing animals eat a variety of things – some are filter feeders, some prefer small crustaceans, and others are more predatory, preferring larger fish and marine mammals.
Now that you know a bit more about fish families, take some time to learn which ones are prevalent in the areas where you dive, and learn about their habits, too. Knowing which animals you’ll encounter while diving provides you with better opportunities to watch them in action – and if you’re a photographer,this same knowledge will help you capture even better images!