Jul 11 2012

Natural spawning of African catfish (Clarias gariepinus) in Egypt – Video

Video credit: Lylian Lugobola (Tanzania)         Information: Ismael Radwan (Egypt)     Text: Abdel Rahman El Gamal

This video shows the natural spawning of African catfish, Clarias garepinus which is claimed (by many producers) to be easier and more economical as compared to artificial spawning especially in the light of its reasonable productivity. The dimension of the spawning tank in the hatchery is 3×8 m. To ensure at least one successful spawn in each tank,   the tank is stocked with 2 males and 2 females of catfish broodstock. About 5,000 – 6,000 catfish fry are produced in each tank. After about 10-15 days of broodstock stocking, hatched fry are collected and moved to a well fertilized 1000-m2 outdoor earthen pond which is stocked at the rate of 50,000 – 60,000 fry/pond. Palm tree leaves placed in the spawning tanks are believed to provide substrates to fertilized eggs and hatched larvae.

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Permanent link to this article: https://fishconsult.org/?p=3453

Jul 07 2012

Electric eel, Electrophorus electricus (characteristics, distribution, feeding, reproduction, electric charges) – Video

This video was filmed in the Freshwater Aquarium, Sea World, California, USA (June 2012)

Review: Abdel Rahman El Gamal (Founder of the website and video channel)

Characteristics: Despite its name, electric eel is not true eel but more closely related to catfishes. They have elongated, cylindrical, non-scaled bodies, typically growing to about 2 meters in length, and 20 kilograms in weight. Male electric eels are also much smaller than the female electric eels. They can live from 10 to 22 years in captivity. Electric eels are obligate air-breathers and hence they rise to water surface every about 10 minutes to gulp air before returning to the bottom. As the name implies, the species is capable of generating electric shocks which it uses for different purposes. The coloration of electric eels helps them to blend in very well with their surroundings. Although they do not have very good vision, they enjoy a great sense of smell that they rely upon.

Distribution and habitats: Electric Eel is found in freshwater bodies in South America such as Amazon and Orinoco Rivers. They also live in locations that provide them with food supplies including river floodplains, swamps, creaks and coastal plains. They often live on muddy bottoms in calm water and in stagnant rivers.

Food habits: Adult electric eels feed on invertebrates, fish, and small mammals. The young of electric eels may develop cannibalistic behavior whenever their favorite food is not sufficient. In this situation, they may eat eggs, embryos or younger hatchlings. The juveniles of electric fish feed mostly on invertebrates such as shrimp or crab.

Reproductive behavior: The mating is prepared for by the male who create the mating nest from his salvia. The female will enter the nest where she lays about 1,200 – 3,000 eggs. Laid eggs are fertilized by the male’s sperm. Afterwards and because fertilized eggs are left unattended, they will experience high losses due to predation ending by low survivors which become adults.

Electric eels in captivity: Keeping electric eels in captivity is difficult and mostly limited to zoos and aquariums. Whenever intended to keep them as pets, special precautions must be secured. As expected, electric eels cannot be kept with any other fish.

Electric discharges: The electric eels produce powerful electric charges through special organs located in the tail. Electric charges produced by electric eels could be either low intensity (voltage) impulses or high intensity impulses. The low impulses are used for sensory perception and would make up the poor vision of electric eels especially in muddy waters. The high intensity charges can reach up to 500 volts or more. Such lethal charge is used during eel’s for stunning or killing eel’s prey but the charge is also used for self-defense. This high charge could be fatal to human. The electric charges emitted by electric eels is related to their size as smaller eels (about 10 cm in length) can produce charges of up to 100 V while eels with 1-m length or more can produce charges of 450 to 650 volts of electricity with 500 V as the most accepted value.

References: The Physics Factbook, Wild Facts, BioExpedition in Animals, Wikipedia, and Species poster, Freshwater aquarium, Sea World

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Permanent link to this article: https://fishconsult.org/?p=4271

Jul 06 2012

Marketing of fresh fish in South Sudan

Credit: Juma Frezar (South Sudan)

The two photos show a traditional marketing of fresh fish in Bor city, South Sudan.  One of the photos was taken in front of the fisherman’s home whereas his catch of “weer”, Gymnarchus niloticus is offered for sale whereas the second photo shows a small pile of “Nauk”, Heterotis niloticus which is offered for sale along the shore of River Nile. Usually, the price of fish is based on size or numbers rather than weight. 

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

Permanent link to this article: https://fishconsult.org/?p=4250

Jul 06 2012

Manual sexing of Nile tilapia, Oreochromis niloticus in Gabon (in French)

Credit: Charles Ibinga Maganga (Gabon)

Tri et sexage manuel du Tilapia nilotica, élevage monosexe des males et femelles dans des étangs sépares; la mise en charge des males se font à raison de 2,2 poissons /m² à SIAT/Bitam; les alevins sont prélevés dans les étangs de prégrossissements tôt le matin, sont sexes et charge dans les étangs de grossissement; des que le soleil se pointe on arrête le sexage (remarquez l’heure sur la photo) souvent vers 9h30 

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

 

 

 

Permanent link to this article: https://fishconsult.org/?p=4240

Jul 05 2012

Collection of African catfish, Clarias gariepinus in Ntem Minvoul Valley in Gabon (in French)

Credit: Charles Ibinga Maganga (Gabon)

Clarias gariepinus, récoltés par les femmes dans la vallée du Ntem à Minvoul (ville rurale, au nord du Gabon). Ces silures (poissons-chats) sont péchés avec des pièges à poissons (panier conique fait à l’aide des roseaux pour les eaux peu profondes) lors des périodes de remontée d’eau, en début des saisons de pluies.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

 

Permanent link to this article: https://fishconsult.org/?p=4149

Jul 04 2012

Promotion of aluminum fishing boats in South Sudan

Credit: Juma Frezar (South Sudan)

The photo shows a fishing boat made of aluminum. The promotion for this boat which is provided by a company that is working in the field of fishery is based on the better fishing efficiency of these boats. However, fishermen (in Bor city) do not favor these boats as they believe that these boats are more vulnerable to accidents due to its light weight compared to the traditional boats “Aliyab”.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

Permanent link to this article: https://fishconsult.org/?p=4142

Jul 04 2012

Fish smoking and drying research, University of Burundi

Credit: Alain Murekambanze (Burundi)

This photo shows a gentle who is carrying out research on the smoking and drying of Lake Tanganyika sprat (Stolothrissa tanganicae). This fish species belongs to Clupediae family which is endemic to the Lake Tanganyika. This research project is managed by the Department of Water, Fisheries and Aquaculture, University of Burundi, Bujumbura.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

Permanent link to this article: https://fishconsult.org/?p=4128

Jul 04 2012

Research facilities at NaFIRRI, Kajjansi, Kampala, (Uganda)

Credit: Alain Murekambanze (Burundi)

The photo shows the research ponds at the National Fischeries Resources Research Institute, NaFIRRI  at Kajjansi, Kampala,Uganda.  These ponds as well as a modern fish hatchery and a feed production unit have been constructed through the cooperation between Uganda and China.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated

Permanent link to this article: https://fishconsult.org/?p=4117

Jul 03 2012

Launching a sample of an Arabic – English Glossary

Permanent link to this article: https://fishconsult.org/?p=4105

Jul 03 2012

Lionfish, Pterois sp. (reproductive behavior, economic importance, ecological concerns) – Video

This video was taken at Aquarium De la Mer, Sea World,California, USA in June 2012

Reproduction behavior: Usually, a male and few females of lionfish represent a mating group. The male lionfish is highly territorial and protects the mating area. The female lionfish releases between 2,000 and 15,000 eggs (with an average of about 8,000 eggs) into the water which are fertilized by the male lionfish. The hatching takes place in about 2 days whereas hatched lionfish fry remain near water surface and continue to grow. When the lionfish fry reach about an inch in length, they swim down into the ocean to join the reef community.

Economic importance: Although lionfish have been considered as a popular food source in some countries, but are far important in the aquarium trade especially in the light of its spectacular looks and coloration.

Ecological concerns: Lion fish has been widely transferred as aquarium fish been being released into natural waters whether accidently or intentionally. Being able to consume large number of prey species, lionfish are among the top predators in many coral reef environments of the Atlantic in the present. There are studies on the possible role or threat that introduced lionfish may impose on native fish species.

Information sources: NOAA, National Ocean Service, National Geographic, http://a-z-animals.com, Buzzle.com

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Permanent link to this article: https://fishconsult.org/?p=4090

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