Many beginner aquarists feel confused when they start reading fish keeping articles and encounter scientific species names and references to things such as “genera”, “family” and “type species”. By understanding the basics of the biological taxonomy system, you can however turn these confusing terms into highly useful pieces of information.
Okay, first things first. Why use the scientific name for a fish species when the fish already has a perfectly good English name? Well, one of the reasons is to avoid confusion. (There exists some confusion regarding the proper scientific name for many species as well, but we’ll save that discussion for a later article.) The English name “Jewel cichlid” is for instance used for a wide range of different cichlid species.
If you try to discus your “Jewel cichlid” with other aquarists or obtain guidelines regarding its feeding requirements etcetera, you might therefore end up with highly unsuitable recommendations since people might think that you are talking about a completely different cichlid. If you instead know that the scientific name for your particular cichlid is Hemichromis bimaculatus, you can discus your fish with more experienced keepers of Hemichromis bimaculatus and avoid getting advise from keepers of any of the other species referred to as Jewel cichlid. You should also be aware that different English speaking countries often use different English names for their native fish species. A shark that is known by one English name when it is found in the waters outside Australia can be known under a completely different name when seen off the U.S. coast. The scientific name will however be the same all over the world.
When you look at the scientific name of a species, you will not simply find out its international name – you will also instantly know to which genus this fish belongs. This is a very useful piece of information for aquarists, because fish belonging to the same genus is closely related and will often (but not always) have similar requirements in the aquarium.
In biology, all living organisms are classified according to a system invented by Swedish botanist Carl von Linné. This system contains eight different levels.
Phylum or Division
Sometimes we will also include subgroups within these eight basic levels, i.e. subphylums/subdivisions, subclasses, suborders, subfamilies and subspecies.
The scientific name of a fish contains two parts. The first part tells you to which genus this species belongs, while the second part of the name distinguishes it from all the other species in this genus. The name Xiphophorus maculates will therefore tell you that this fish belongs to a genus named Xiphophorus. Xiphophorus maculates is actually the name for a very common aquarium fish that you might already have encountered – the Southern Platy. A close relative to the Southern Platy is the Green Swordfish.
Understanding from the English names that these two species are related is naturally impossible. If we instead look at their scientific names, we instantly understand that they belong to the same genus, since the scientific name for the Green Swordfish is Xiphophorus hellerii. So, why is it important to know the family tree of your aquarium fishes? Well, as mentioned above related species will often have similar requirements. Another important thing to take into consideration is that closely related species sometimes interbreed when placed in the same aquarium. If you place Southern Platy and Green Swordfish of different sexes in the same aquarium, it can actually result in hybridization.
The family Gobiidae, in which you will find all the Goby species, is a very big family that comprises more than 2000 species. Many Goby species are today kept by aquarists, including the Bumblebee goby from the genus Brachygobius and the fascinating Mudskippers that can breathe oxygen directly from the air and use their strong pelvic fins to walk on land.
A majority of the Gobies are small, and well rarely grow bigger than 4 inches (10 centimetres). Some of the smallest vertebrates known to science are actually Gobies. In the genera Pandaka, Tyson and Trimmaton you can find several Goby species that never exceed 3/8 inch (1 centimetre). You can however find Gobies that exceed 1 foot (30 centimetres) in length as well, e.g. some of the Goby species in the genera Periophthalmodon and Gobioides. Small Goby species are more popular among aquarists, since they do not need very large aquariums.
Gobies can be found in a wide range of different habitats. Most Gobies species inhabit shallow parts of the ocean where they stay near corals reefs or sea grass meadows. In areas where freshwater rivers reach the ocean and form brackish mangrove swamps you can also expect to find plenty of Gobies. Only a few species of Goby are freshwater dwellers, e.g. the Australian desert goby (Chlamydogobius eremius), the European freshwater goby (Padogobius bonelli) and the Asian river goby(Rhinogobius spp.).
Aquarists that keep Gobies will often find these fishes attached to the glass or to aquarium equipment. The pelvic fin of the Goby fish has developed into a disc-shaped sucker that the Goby use to attach it self. You will a similar anatomical feature on Lumpfish, but Lumpfish and Goby fish are not closely related. The fact that they both have suckers is instead an example of so called convergent evolution.
As mentioned earlier in the article, the Bumblebee goby (Brachygobius nunus) is one example of a popular aquarium fish from the Goby family. It has a beautiful coloration and does not need a large aquarium since it will stay around 1 ½ inch (4 centimetres). Warm, tropical water temperatures and a pH value above 7.0 are recommended. Most Bumblebee gobies are found in freshwater aquariums, but they can adapt to somewhat brackish environments. The Bumblebee goby is a very peaceful fish, so when you feed your fish you must make sure that the Bumblebee goby actually gets any food. Keeping Bumblebee gobies with aggressive species should be avoided, and since the Bumblebee goby is very small it must naturally be kept in an aquarium where there are no larger predators around.
The interesting Mudskippers are usually placed in their own subfamily Oxudercinae within the family Gobiidae. In the wild, these gobies are typically found in regions affected by significant tidal waves. The Mudskippers can therefore absorb oxygen directly from the air and survive even if they become stranded as the water returns out to sea. The Mudskippers have also developed strong pelvic fins that they use to transport themselves over land. If the mudskipper is stranded for any longer period of time, it will dig a hole in the ground and stay hidden until the water comes back.
Fish species in the family Eleotridae are sometimes referred to as “Sleeper gobies”, but only species within the family Gobiidae are considered true Gobies. The members of the Eleotridae family are quite similar to the real gobies in regard o size, shape and habits, but they lack the fused pelvic fin.
Fish Breeding in Aquatic Habitats
As novice fish breeders usually find out sooner or later, there are many fish species that readily spawn in captivity. They do not need any special food, temperature adjustments or aquarium decoration to start breeding – some female fishes do not even need a male partner around to start reproducing! A majority of these highly prolific aquarium species are livebearers, which means that they give birth to free swimming fry. Females from several species of livebearers can store sperm inside the body for prolonged periods of time, and this is how they manage to reproduce even in aquariums where there is no male present. If your female livebearers start giving birth to fry without any male around, they have mated in the wild or in the pet shop and stored the sperm since then.
A majority of the worlds’ fish species are however not livebearers but egg layers. The egg laying species can be categorised into four main groups based on their reductive method: the egg scatters, the substrate spawners, the bubble nest builders and the mouth brooders. There are other ways of categorising the egg-layers, but these for groups are used by many aquarists.
An egg scattering species of fish will simply release the eggs into the water. The male will fertilize the eggs as they are released and the eggs will then either sink to the bottom or stay afloat. This reproductive method is especially common in species that inhabit streams and rivers where the water flow will transport the eggs and distribute them over a larger area. Since these species are not used to having their offspring around, they will often eat their own eggs and fry if kept in the same aquarium.
Substrate spawning fish species do not want their eggs to be transported away by currents. Substrate spawners will therefore often (but not always) produce sticky eggs that can be attached to a substrate. Some substrate spawners will attach their eggs to virtually any surface in the aquarium, while others are extremely picky. If you take a look at the native habitat of the species, you can often figure out which type of substrate that they will appreciate. Species living in densely grown waters will often attach their eggs to plant leaves and stems, species in rocky environments will often keep their eggs hidden inside caves and crevices, species living near sandy bottoms might dig a pit and place their eggs inside and so on. Flat rocks and empty shells are also popular among many species. Many species will spend a lot of time searching for a suitable breeding site in the aquarium and vigorously clean it before any spawning takes place.
Types of Breeding for Fish
The bubblenest breeders are truly fascinating to watch when they breed since they produce elaborate nests built from tiny bubbles made from air and saliva. It is usually the male fish that is responsible for the construction of the nest. It is very important not to disturb the bubblenest in the aquarium. Heavy water circulation can for instance need to be hampered to prevent the bubble nest from being crushed.
The mouth brooders will protect their offspring in the safest place possible – the mouth of a parent. Some mouthbrooders carry their eggs inside the mouth, while others carry their larvae. Some species carry eggs as well as larvae. You will also notice that certain species are paternal mouthbrooders, while others are maternal mouthbrooders. Even if only one parent carry the offspring, it is common for mouthbrooding species to form monogamous pairs where both parents care for the offspring. Mouthbrooding is also frequently combined with substrate spawning. The female can for instance deposit the eggs in the substrate, and wait for the larvae to hatch before she or her partner picks them up.
As mentioned in the first part of this article, different fish species have developed very different reproductive methods. Some lay eggs, while others give birth to free swimming fry. Some are devoted parents that spend a lot of time caring for and protecting their offspring, while others will eat their young ones if they get a chance. Understanding the various reproductive methods is of course very important if you want to become a successful fish breeder.
Some fish species are very easy to breed, while others have very specific requirements. There are also many fish species that have not yet been bred in aquariums. If you are a beginner aquarists and with to try breeding fish, you can ideally start with some of the easier species. Platy, Guppy and Molly are almost too easy to breed since they require very little effort from the aquarist. Keep the water quality up and feed your fish and they will probably spawn sooner or later.
If you want to ensure a high fry survival rate, you can move the fry to their own aquarium. You should however keep in mind that since these species are so prolific in captivity, pet stores will not purchase fry from you. They might accept your fry for free, but only to use as food for other fish. Instead of filling your entire home with fry aquariums, you can let the fry stay with the adult fish since this will make the amount of new fish more reasonable. Most of the fry will probably be eaten, but a few will usually survive if you provide them with suitable hiding spots in the aquarium, e.g. densely planted areas or rock formations with small caves and crevices.
The fish mentioned above – Platy, Guppy and Molly – are all examples of popular livebearers. Livebearing fish will perform internal fertilization where they male use his gonopodium to reach inside the female and fertilize her eggs. The gonopodium is a modified anal fin that serves as a reproductive organ. The fertilized eggs will develop inside the body of the female fish. When the fry are born, they will usually look like tiny copies of their parents. It is however common for fry to have a more camouflaging coloration than the adults, and they can also be without certain extravagant anatomical features that are only useful for mature fish.
If you keep more difficult species, you might need to coax them into breeding. The only way to find out what makes your particular species interested in spawning is to research them, since different species have different triggers. Some fish species are for instance very sensitive to temperature changes and increasing (or in some cases decreasing) the water temperature is a good way of coaxing them into breeding.
Other fish species will feel ready to spawn when there is an abundance of live food to be found in the aquarium, or when a larger water change alters the levels of ammonia, nitrite and nitrate in the water. It is naturally always recommended to keep the water quality up, provide your fish with suitable food and make sure that the aquarium is large enough for them. A decorated aquarium resembling the natural habitat of your particular fish is usually a better choice than a barren aquarium if you want your fish to breed. Some fish species have very particular requirements, and will for instance only breed in planted aquariums.