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Controlling invasive crayfish – Video

Video credit: Andres Delgado (Colombia) Review: Abdel Rahman El Gamal (Founder of the video channel)

The video shows a single specimen of red swamp crayfish, Procambarus clarkii while climbing a pond dyke and possibly seeking a nearby body of water while the last part of the video shows the sorting of crayfish from the harvest.

I believe that controlling crayfish biomass is a realistic title than eradicating. These animals are capable to avoid most harvesting gears especially while digging their tunnels in the dykes as well as their ability to move out of water.

Trapping has been used to reduce the crayfish population with some success. Also, drain-drying would be able to help in controlling their biomass. Because these animals are not considered food fish in some locations and fishermen may through the caught crayfish back in the water, it is believed that promoting the consumption of crayfish and would lead to careful harvesting and so achieving some control of their populations, bearing in mind that the full eradication of crayfish would be almost impossible.

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Permanent link to this article: http://fishconsult.org/?p=15655

Skyward vision in flatfish (Video)

Video credit: Patricia Martin Cabrera (United Arab Emirates)

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

Flatfish are characterized by their asymmetrical body shape with both eyes lying on the same side of the head in the adult fish. It may be of interest to know that fishes in this group begin their lives as normal swimming fish with eyes located on both sides like all other fish. Through its development and as the flatfish begin to change and start moving to the seafloor where they spend the rest of their lives, one of the animal’s eyes migrates to the other side ending by having both eyes located on one side of their heads. This could be on the left side or the right one. The flatfishes include flounders, soles, turbot, plaice, and halibut.

Because flatfishes are limited to the seafloor, and in order to avoid possible predation, they are known for their smart and exceptionally quick camouflaging which makes them hard to spot. In the attached video, one watch group of fish with different colors and shapes affiliated to some species. However, if you look carefully at the bottom, you can spot two individuals of flatfish which are perfectly camouflaged and looking skyward.

Permanent link to this article: http://fishconsult.org/?p=15651

Direct fish sales from farm to consumers in Egypt – Video

Video credit: Charles B. Makuya (Malawi) Review: Abdel Rahman El Gamal (Founder of the video channel)

This video was filmed in a marine fish farm located along Damietta-Port Said road whereas marine fish are farmed. Two species are shown in this video; meagre (Argyrosomus regius) and grey mullet (Mugil cepahalus). Usually, the market size of meagre is about 1.25 kg and above, and around 500-600 g/for mullet.

The cottage shown in the video belongs to the fish farm and is used for the direct sale of fish harvested from the fish ponds located few meters away.

Consumers usually trust the quality of fish directly bought from the farm. Also, this type of fish sale is advantageous for the farm, especially when located along a road like this one. Through batch harvest, the farm can market a great portion of its harvest. In the case of surplus fish, the fish market is always available. As shown in the video, the farm secures enough crushed ice to be available for fish buyers who bring their iceboxes or similar containers as required.

Permanent link to this article: http://fishconsult.org/?p=15644

Biological filters in intensive aquaculture

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

The inserted pictures show substrates used in intensive aquaculture systems. As shown, the shapes of such substrates may vary although they have a main characteristic in common which is a high surface/volume ratio. Added to that, the substrates used in biological filters should enjoy strong mechanical resistance, limited clogging chances and of course its availability at affordable prices.

No matter what shape and contents of biological filters, its main function of the filter substrates is to create favorable conditions for the two bacterial colonies in order to perform the nitrifying process whereas Nitrosomonas sp. oxidize the ammonia to nitrite, and then Nitrobacter sp. complete the nitrification process through the oxidation of nitrites into nitrates bearing in mind that ammonia is the most dangerous part of the metabolic wastes produced by the fish while   nitrate is almost not toxic to fish.

Biological filters are required in closed systems as it allows for the partial re-use of water as well as saving energy in case of heated water. In addition to reducing heating (or cooling) costs, such filters reduce the impact on the environment through the minimum water discharge.

Typically, a biological filter is submersed in a separate tank and colonized by nitrifying bacteria. In order for the filter to perform the nitrification process as planned, it requires stable physical and chemical parameters, a permanent supply of ammonia and adequate levels of oxygen. The biological filter is, within a re-circulation system, the more complex component, to the extent that it can be considered almost a living organism. As such it requires stable physical and chemical parameters, a permanent supply of food (ammonia) and adequate levels of oxygen.

Permanent link to this article: http://fishconsult.org/?p=15641

Artificial reproduction of Pacu in Paraguay – Egg incubation

Photo credit: Ariel Montiel Benitez (Paraguay) Review: Ariel Montiel Benitez and Abdel Rahman El Gamal (Founder of the website)

Pacu (Piaractus mesopotamicus) is an important fish species with high commercial value in Paraguay. The availability of its fingerlings in a sufficient number would be essential towards the expansion of pacu aquaculture in Paraguay.

The inserted picture was taken at the Laboratory of Pacu in the National Center of Production of Alevines of Paraguay. The center is located in the city of Eusebio Ayala.

The picture shows a part of pacu reproduction as fertilized eggs are placed in netting incubators hanged in a rectangular tank. Tanks receive appropriate water flow sufficient to take waste metabolites out. Incubators are aerated in order to secure sufficient oxygen as required for developing embryos.

Under optimum water temperature of about 25C, hatching occurs after about 23 days whereas newly hatched larvae are nursed towards the production of fingerlings.

Permanent link to this article: http://fishconsult.org/?p=15632

In-pond raceway in Egyptian aquaculture (Video)

Video credit: Marcel Adaveleo (Madagascar) and Danial Osiyoye (Nigeria) Review: Abdel Rahman El Gamal (Founder of the video channel)

Historic information: As reported, the “In-pond raceway technology – IPR” was first developed in 2007 on a channel catfish farm in West Alabama, USA. Afterward, the technology was transferred to China in 2013 and then to more Asian countries including Vietnam, and India. Currently, the technology has been introduced to more countries around the globe. This video was filmed at the WorldFish Center in Egypt whereas Nile tilapia (Oreochromis niloticus) is the cultured species.

System description: The system relies on the creation of water circulation within the raceway units located in earthen ponds as well as on the removal of the organic wastes. The water circulation is done using paddlewheel aerators and/or air blowers. The use of low-speed paddlewheels provides a constant water current through the raceways. The aerators should be of capacity sufficient to create water flow of enough volume with particular velocity in the raceway cells which ultimately determines the frequency of water renewal within the raceway that in turn is a function of several parameters including the species, stocking density, and fish biomass.

In regard to the waste removal, the water and sludge are moved from the raceways into a waste-settling zone in the open pond from where the water is filtered before re-circulation, while the organic wastes are periodically collected using mechanical collectors. The organic waste products in the open pond are carried into the open pond area where they are processed naturally and at the same time stimulate the growth of natural organisms that in-turn becomes good food for other fish species especially in the open pond.

Typically, the raceways are constructed in parallel in a chosen corner of a traditional earthen pond with a center baffle to provide for a continuous circulation pattern around the pond and through the raceways. 

Advantages: The IPR as mentioned ultimately targets higher production of high-quality fishery products that result from the healthy environment that ensures higher growth rate and survival, efficient feed conversion ratio, and other production traits.

Permanent link to this article: http://fishconsult.org/?p=15624

Use of cribs in the organic manuring of fish ponds in Togo

Photo credit: Sabi Asma (Togo) Description: Sabi Asma and Abdel Rahman El Gamal (Founder of the website)

The structure shown in the corner of a fish pond in the inserted picture is typically used in the organic manuring in Togo as well as in other African countries. Instead of spreading the organic materials over the entire water surface, it is placed within the crib whereas the decomposition takes place and the nutrients are filtered between the bars of the crib and with the water current in the pond, the whole pond is fertilized.

This simple system is usually adopted in small-scale fish farms where farmers rely on organic manure. While only the nutrients dissolve into the water and used for the fertilization, the undissolved bulk of the manure remains within the crib and hence could be easily moved without disturbing the entire pond water.

Permanent link to this article: http://fishconsult.org/?p=15616

Shrimp culture in Guatemala – Video

Video credit: Alejandro Joachin (Guatemala) Review: Alejandro Joachin and Abdel Rahman El Gamal (Founder of the video channel)

The inserted video was filmed in a shrimp farm in Aldea El cebollito, Monterrico (Guatemala). The farm consists of three ponds of 1-ha each. The white leg shrimp Litopenaues vanammei is the species farmed in the farm.

The stocking density in this project is 250 shrimp PL/m3. As shown in the video, the shrimp ponds are furnished by paddle wheel aerators sufficient to maintain optimum dissolved oxygen throughout the growing season. The salinity of the farm water is 15 gram/liter. As the temperature in the region throughout the year suits the growth of this species of shrimp, four production cycles are practiced every year of a 12-week each. The biggest shrimp harvest is targeted in the month of April (Eastern week) whereas the maximum demand on shrimp occurs and so the highest market value. The average size of harvested shrimp is about 14 g.

According to FAO statistics, the total production of shrimp from aquaculture in Guatemala amounted 17,273 tons in 2018.

Permanent link to this article: http://fishconsult.org/?p=15612

Pit fish smoking in Chad

Photo credit: Saleh Abakar Oumar (Chad) Review: Saleh Abakar Oumar  and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows a simple traditional smoking facility in Chad that is made of a pit (hole) dug in the ground. The soil selected for the pit digging should be stable to help the pit keep its shape and prevent the pit from caving in. A metal mesh is placed over the pit above which the fish is placed.

The logs and so the fire are produced in the bottom of the pit. Bearing in mind the simplicity of such smoking pits, and the escape of generated smoke, the cooking time ranges from 12 to 24 hours depending on fish type and size.

Permanent link to this article: http://fishconsult.org/?p=15607

Promoting aquaculture in Namibia – Video

Video credit: Kaulo Salushando (Namibia) Description: Kaulo Salushando and Abdel Rahman El Gamal (Founder of the video channel)

This video was filmed during an official harvesting that took place in Fonteintjie fish farm which is a governmental farm. The harvest was covered by media and attended by the minister and top officials as well as invitees from the community including a number of school children who witnessed the harvest. The event targeted to promote aquaculture especially in the southern part of Namibia.

We can see that tilapia is the main species cultured in the farm along with some common carp.

The national strategy strongly advocates for aquaculture in that it empowers people, provides employment opportunities and provides food security for communities. It may worth noting that aquaculture in Namibia still in its infancy stage as according to FAO statistics, aquaculture in Namibia amounted 647, 626, 605, 587 and 472 tons during the years from 2014 to 2018 respectively.

Permanent link to this article: http://fishconsult.org/?p=15603

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