As we go down into oceans, seas, lakes, or rivers, when we take a look into any aquatic ecosystem, we are able to see different living or non-living things, with different shapes, colours, sizes, different structures, compositions, and physical appearances – different types of fishes and species. Aquatic ecosystems, covering more than 70 percent of the Earth have lots and lots to offer. Many animals and organisms live or participate in aquatic ecosystems. We can find, catch many fishes such as, generally, milkfishes, angelfishes, butterfly fishes, catfishes, pipefishes, stargazer fishes, threadfin fishes, marlins, tunas, sharks, anchovies, moray eels, skates, and rays. Also, dolphins and whales, otters and seals – mammals that can survive (and able to live) in water. And of course, reptiles like turtles that can live up to hundreds of years, snakes, and alligators that can go back and forth to land and water. In general, these fishes in aquatic ecosystems have fins and scales, they utilize their gills for breathing, and obviously, they are cold-blooded. This includes the bony fishes (belonging to Class Osteichthyes), cartilaginous fishes (belonging to Class Chondrichthyes), and the jawless fishes (belonging to Class Agnatha). And they all have spinal columns which makes them “vertebrates”.

In some dictionaries, the meaning of “fish” is the meat of a fish eaten as food, which is right. Most people know that fishes are only food – white meat, just like that. There are also people, especially children, that haven’t really seen a fish, a real fish, a live fish with fins, scales, gills, bones, and head. Because when they eat fish in restaurants, only the meat is served on their plates. Consider the context that before fishes could be eaten, they also need to eat first, to grow. Even though they differ in their physical appearance, the common denominator of fishes is that they need food, they need to eat to sustain their life – just like breathing. In the aquatic ecosystem, all of them are predators, and there is also a good chance that anyone could be a prey. They need to each other. Unfortunately, in order to live, one must die (or more than one). The smaller and the weaker the fish, the more predators will come after it, the lesser chance for the small fish to find its own prey. If it would hide, it cannot be eaten, but it also have lesser opportunity to eat, it wouldn’t grow, it would die as time pass by. In relation to this consumption behaviour, fishes have different mouth positions. There are three main types of fish mouth positions. The superior mouths, the inferior mouths, and the terminal mouths. Fishes have snouts (it is like their mouths/nose) and it consists the maxilla or the upper part of the mouth, the mandible or the lower part of the mouth, and the gap between the maxilla and the mandible, the gape.

If the mouth is located at the dorsal or antero-dorsal part of the snout, it is a superior mouth. Example is a stargazer fish, having a longer mandible than the maxilla and the gape points upward when the mouth is open. And yes, their mouth is like a scoop to gather foods (fishes) swimming above them. They can wait for food in the surface of the waters and they are also benthic predators, they can find food in the depths of the ocean. Compared to the superior mouth, inferior mouths are just bottom feeders, their mandible is shorter than their maxilla and their gape points downward when their mouth is open, which makes it easier for them to eat their prey swimming below them. The inferior mouth is located at the central part of the snout, one of the best examples is the threadfin fish. And last of the three main types is the terminal mouth, butterfly fishes in the aquariums and aquatic parks which children are very fond of. Unlike the superior and inferior mouths, the terminal mouth fishes has a mandible and maxilla that approximately have equal lengths which influences the gape to just point forward when the mouth is open. They can be found in the middle of the water, eating small fishes passing in front of them (using their terminal mouths that is located at the anterior end of their snouts). This is where diversity comes in. This is why diversity is important. Fishes in any aquatic ecosystems have variations; not just in their physical appearances, nor their composition, nor body shapes, nor mouth positions, but also on how they utilize these adaptations to be their advantage in feeding behaviours – in survival.

We, humans, also have our own ecosystem, living in one giant bowl of aquarium, we’re trying to survive in this great ocean. Diversity of fishes and organisms in aquatic ecosystems is just like the diversity of humans in our community, in our world. Just like the fishes, people also have different physical appearances: we have different body built types, different skin colors, different hairstyles, and different faces. We also have different characters and personalities, different talent and skills. Tragically, there are people who were already born with natural talents, gifted people, born more advantageous. The smaller and the weaker we are, the more we get stressed and the more we get beaten by others, we lose our self-esteem or our self-confidence that we imprison ourselves, keep ourselves away from fighting and surviving in the outside world. Then, we die. Nevertheless, in order to be able to survive, just like fishes, we should develop our adaptations or skills and use it as our advantage to defend and protect ourselves and territory among others, to have a job and earn money to supply our needs – to survive each day, and to live our life.