Hatchet fish: Characteristics, habitats, care and more

Some fish not only resemble other animals, but also bear similarity to certain objects. This is the case of the Hatchet fish (Carnegiella Strigata) which have an expanded belly similar to a small ax. Today you will know everything about these fish in this post.

Hatchet fish belong to the Gasteropelecidae family. They are striped-fins fish from South and Central America, the common hatchet fish (Carnegiella Strigata) being the most popular member among the aquarium fans.

Taking their common name from the extreme convexity of their ventral surface hatchet fish have a flat back, straight and backwards sweeping pectoral fins. These fins are considerably stiffer than those of most tropical fish.

These anatomical traits when combined with their highly developed chest muscle makes of hatchet fish, very fast creatures with absolutely superior maneuverability in the water. Able to make very fast and sharp turns, hatchet fish are adept predators of aquatic insects and fry in the wild. In addition, the elongated pectoral fins have become wing projections and interestingly, have wing-like properties.

These fins, which extend up and back from the pectoral joint, not only help hatchet fish  to make extremely sharp turns in the water when they chase their prey or evade predators, but also help them when they perform the curious behavior of jumping out of the water to catch them. We invite you to read our article the anatomy of fish to learn more about such a topic

Taxonomy

Hatchet fish are the family Sternoptychidae of marine fish which is included in the order stomiforms, distributed by the Pacific abyssal waters, Atlantic and Indian Ocean. Their name comes from the Greek: sternon (chest) + ptyx, -ychos (fold)

Anatomy

Hatchet fish have a laterally compressed body, with a very big chest that gives them an ax appearance by which they are given the common name they have.

Interesting note

In 1937, Dr. Hoedeman had several specimens of common hatchet fish to care for and had an extra-large aquarium available for them: 150 gallons. As a precautionary measure, the edges of the tank on the surface of the water were filled with sponge so that the hatchet fish did not damage themselves if they tried to «fly» as they did in nature.

Hatchet Fish tried to fly several times and simply bounced off the sponge protection for the first few days. These fish had come directly from their natural habitat, which was Guianna, in South America.

The fish learned fairly quickly (however, they showed no fear of hitting the spongy rubber) that space was limited and that space to fly was not available. After around 48 hours of attempts, the Hatchet Fish never tried to fly again, although they lived some years after that first day.

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Main Species Of Hatchetfish:

Let’s meet the main species of this family

Common Hatchet fish (Carnegiella Strigata)

This is a freshwater fish, which has a rather small mouth that points upwards, with a series of dark lines that runs all over his body. The fins of the chest are transparent, and they develop in a way that they resemble small pointed wings which grow oriented towards its back. Their dorsal fin is located rather delayed and they lack adipose fin.

Sizehatchet fish: common hatchet fish

The common hatchet fish can reach up to 5 centimeters in length, and the female is somewhat smaller than the male and with less coloration on her body.

Color

The coloring of this peculiar fish is greenish, with some shades of yellow, pink, and silver areas. Their body is flattened on the back, with a very bulging ventral area and a straight profile back. Their abdomen is curved and thin.

How Do Common Hatchet Fish Reproduce?

In a captive situation, their reproduction is quite complicated. In order to be successful, fish need to be fairly well nourished with live food, and to be in specific conditions such as dark water.

When the male is ready to start, he waves his pectoral fins in a place where the female can observe him, always trying to stay in front of her. Next, the female deposits her eggs at the bottom of the aquarium, between the plants, while the male fertilizes them. Once reproduction is achieved, it’s necessary to remove both parents from the aquarium so that they don’t depredate their own larvae or eggs.

Taking Care of Common Hatchet Fish in Aquariums

  • the fish tank should have an approximate capacity of 200 liters, which will allow them to move without any impediment.
  • It must have a filter, since they are fast swimmers and like to stand against the current.
  • It’s recommended to Place a peat on the filter, to darken the water a little.
  • The water temperature should be about 22 to 28ºC.
  • The water must be acidic and aerated.
  • The water should be changed gradually.
  • Must have abundant vegetation, in addition, place small plants and decorative objects.
  • the lid of the fish tank must be well adjusted, since they can be removed when they perform their conquest maneuvers in the reproduction phase.
  • Introduce a leaf litter, in order to create colonies of microorganisms that serve as food.
  • Provide a diet as varied as possible, you can give mosquito larvae and fruit flies frozen or alive.
  • Maintain eye contact with the fish in order to detect any change in their skin color, which may be due to some disease.

Maintaining the Aquarium

Having hatchet fish in captivity is more complicated than it seems, since it is necessary to provide a wide space with dark substrate and abundant floating vegetation, since this type of fish spend most of their time near the surface.

The approximate ideal capacity of the pond should be greater than 80 liters, especially if you plan to have pups. This wide space will allow them to move without any type of impediment, since ax fish are fast swimmers and love to swim against the current, so it is very necessary to have a pressure filter that gives them that special condition.

Decorative objects and small plants can be added to the ground. The tall plants should only be on the periphery of the pond. In no way should you sacrifice your area to swim openly

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Marbled Hatchet fish (Carnegiella strigata strigata)

The literally flat form of the back of this species and its dorsal fin almost at the height of the source of the caudal, (it does not have fat fin), clearly show us the area of ​​the water column that inhabits it. This modification of its dorsal fin allows it to move very close to the surface without raising suspicion among its predators. His mouth also directed upward tells us that his way of feeding is only through what he finds on the surface of the water.

Their abdomen is visibly round and disproportionate. It houses the powerful muscles that move their long pectoral fins that allow marbled hatchet fish to take big leaps out of the water in order to escape their predators or hunt an insect in mid-flight.

Size

Up to a maximum of 4 cm.

Habitat

Marbled hatchet fish is widely distributed throughout tropical South America in slow rivers and lagoons mostly in areas with heavily planted shores.

Feeding

This is an omnivorous species that feeds mainly on insects and larvae that it finds on the surface. However, marbled hatchet fish also prey on other small fish especially on fingerlings. In the aquarium they will accept all kinds of food being recommended not to feed them exclusively with flakes and offer them from time to time live or frozen food in the form of brine shrimp or mosquito larvae. We must keep in mind that marbled hatchet fish only take the food that remains on the surface.

Differences between the sexes

It’s  very difficult to distinguish sex. Some authors speak of a greater ventral roundness in females, but it isn’t easy to determine.

Association

Marbled hatchet fish are gregarious shoal fish so we must maintain a group of not less than 6 specimens. Moreover, they a very recommended species for community aquariums not presenting any problem of coexistence with the rest of species. As a single precaution, it is important to bear in mind that maintaining very belligerent species can create a stress situation which can trigger the appearance of a white spot or bacterial infection.

Reproduction

It’s  not easy to carry out since marbled hatchet fish require a lot of live food that is not always easy to obtain. In addition, the aquarium must be darkened by using extracts of peat and reduce the Ph between 5 and 6 degrees. The parents should be removed so that they do not depredate the eggs and larvae once the hatching takes place, which will be approximately between 24 and 30 hours. The feeding of the larvae is not easy either, since they must be fed exclusively with plankton at the beginning and later with artemia nauplii.

Aquarium length

Although they are not great swimmers marbled hatchet fish move through fast movements so it’s important that they have enough free space. The aquarium should not be excessively bulky but long enough around  60 cm.

Water conditions

Due to their large distribution the aquatic conditions in which they can be maintained are very variable.

  1. Ph: between 5 and 7.
  2. Very soft to moderately hard waters.
  3. Temperature: From 23 to 28º C.

Maintenance

Although it is an easy fish to adapt and maintain in the aquarium, it is a species somewhat prone to parasites on the skin as responsible for the white spot. The aquarium filtration system should not create a strong current and should give tranquility to the fish through the placement of floating plants such as Salvinia or Riccia. It is important to keep nitrogen compounds controlled and make water changes of 10 or 15% each week

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Related species

Black wing hatchesfish. This is a fresh water finned-fish original of South America, whose scientific name is Carnegiella marthae. This hatchet fish has a convex body, a very deep ventral profile with its anal fin backwards. Their pectoral fins often extend to half the length of the body.

Their body color is silver with patches and black stripes; however, depending on the angle of light the colors may vary. It has a line that is usually of gold hue which is stretched horizontally from the gill and covers the base of the tail. The Black wing hatches fish can reach up to 3.8 centimeters in length.

They are located locally in Caño de Quiribana, near Caicara, Venezuela, and are thought to extend throughout the upper Orinoco drainage in Venezuela and the drainage of the Negro River in the Brazilian Amazon with occasional samples collected from the Madeira River. They can also appear in Colombia in the tributaries of the Vichada River and the Inirida River.

Spotted Hatchet Fish

They are small mesopelagic striped fin fish that inhabit the deep marine bottom.  Spotted hatchet fish belong to the Sternoptychinae subfamily and their scientific name is Gasteropelecus maculatus.

Main Characteristics

They inhabit the tropical, subtropical and temperate waters of the Atlantic, Pacific and Indian Oceans.  Spotted hatchet fish are small deep-sea fish that have developed a peculiar body shape. A very distinctive trait of these fish is given by their bioluminescent photospheres which allow them to use the counter-lighting to escape from predators. Gasteropelecus maculatus usually occur a few hundred meters below the surface, but their entire depth range extends from 50 to 1,500 meters deep.

Their body is deep and laterally compressed (similar to an ax) with the thorax being the blade and caudal peduncle being the handle.

Their scales are silver and delicate with blade-like thorns in front of the dorsal fin. The anal fin has between 11 and 19 radii and in some species it is divided into two parts. Almost all spotted hatchet fish have a fat fin and their large and sometimes tube-shaped eyes can collect the dimmer light and concentrate well on near and far objects.

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Diaphanous Hatchet fish (Sternoptyx diaphana)

This is a small fish that lives in the abyssal marine areas. Their body is small and compressed, with an extravagant external appearance, like most species that live at great depths and, therefore, with very little light. It’s for this reason (the conditions of inaccessibility in which they live) for which we know very little about Diaphanous hatchet fish

Around their belly and eyes, which are very developed and have a tubular shape, diaphanous hatchet fish have luminous organs that help them see any source of light. As far as their chest Diaphanous hatchet fish have large contracted blades, that when stretched, allow them to enlarge their size, something useful when they eat fish or other types of animals larger than them.

Their body color varies between green and violet, maintaining always its very bright tones. In addition, these abyssal creatures have a strip that goes from their operculum (bone fin that protects the gills) to the caudal fin that is pale in its upper part and becomes darker as it descends. On the other hand, the fins are usually transparent.

As for their size, diaphanous hatchet fish can reach up to 8 centimeters and until now, no great differences have been found between males and females. In this regard, the way they reproduce is the most common among fish, where the female lays the eggs and the larvae wait 36 ​​hours until they reach full development.

It should be mentioned that within the hatchet fish category, two sub-categories can be distinguished: salt water hatchet fish, which belongs to the abyssal fish class and the freshwater ax fish, which lives in the tropics.

Common Diseases in Hatchet Fish

Hatchet fish are prone to develop ick (white point) especially when they are first introduced into a new aquarium. Newly acquired specimens must be kept in a quarantine tank before being introduced into a community. Even so, they will still be susceptible to drying out if the water doesn’t remain soft and acidic.

As most freshwater fish, hatchet fish are prone to skin lesions, parasitic infestations (protozoa, worms,) bacterial infections (in general) and bacterial diseases. They are extremely resistant and diseases are not usually a problem in an aquarium in good condition.  However, these facts don’t’ mean that you won’t have to deal with health problems or diseases.

Remember that anything you add to your tank can introduce diseases. Not only other fish, but also plants, substrate and decorations can harbor bacteria. Be very careful and be sure to properly clean or quarantine everything you add to a set tank so as not to disturb the balance.

A good thing about Hatchet fish is that, because of their resistance, an outbreak of any disease can often be limited to just one or a few fish if it is treated at an early stage. When more sensitive types of fish are maintained, it’s common for all fish to become infected even before the first warning signs are noticed.

The best way to proactively prevent disease is to provide your pets with the right environment and a well-balanced diet. The more the environment resembles their natural habitat, the less stress these fish will have, making them healthier and happier.

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