Safe interaction with stingrays in touch tanks (Video)

This video was filmed by the author during a visit to the Sea World, California, USA.

As shown in the video, visitors surrounding the touch tank are trying and actually touching the stingrays which is a unique experience.

In order to ensure a safe touch, the barbs (stingers) of rays are constantly trimmed down like trimming fingernails, so the de-barbed stingrays are safe to interact with and touch. According to large aquariums, the trimming process is done every three months whereas each ray is gently taken out of the water to trim the barbs for about 10 seconds.


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Aquaponics in Togo

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

The inserted pictures show one of the aquaponics projects in Togo. This one is a private farm located in Plateau Region, prefectures of Kpele, and locality of Bodze. This particular farm was established in 2012.

The fish component in this project is represented by Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus). The plant component is almost the typical aquaponics plants such as spinach, lettuce and others. This project relies on underground water.

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Impacts of COVID-19 on aquaculture with a special emphasis in Africa

I delivered this presentation in an online workshop held on 27 July 2020. The management of the workshop took place at the Egyptian International Centre for Agriculture (EICA), Dokki, Egypt. The structure of the workshop included three main presentations (this is one of the three) as well as presentations from selected African countries. By the end of the 4-hour event, there was a question and answer session. This workshop has been sponsored by EICA in partnership with the Japan International Cooperation Agency (JICA).

About a month prior to the workshop, a questionnaire was developed by the author and circulated by EICA among selected African aquaculture specialists. The analysis of the feedback has been done by the author as presented in this document.

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Supersaturation of dissolved oxygen in fish ponds

Photo credit: Samy Ndala (Congo DR) Review: Abdel Rahman El Gamal (Founder of the website)

The supersaturation of dissolved oxygen (DO) is often observed near the surface of water bodies as a result of the strong the photosynthetic activity resulting from phytoplankton abundance. This occurs during bright sunlit days in eutrophic water bodies such as rivers, lakes and/or fish ponds. The supersaturation of oxygen during daylight is always followed by much lower oxygen levels at night when the photosynthesis ceases while the respiration by all living organisms continues.

For illustration, the dissolved oxygen in the inserted photo reads 14.8 mg/l which is much higher that the saturation levels of dissolved oxygen. For example, the 100% DO saturation is 8.09 mg/l at water temperature of 26°C and 7.81 mg/l at 26°C. This photo was taken during August in a freshwater fish pond in Egypt where temperature is usually at highest and so the sun light. One can notice the dark green color of pond water indicating the abundance of phytoplankton in the water. It may worth mentioning that in highly productive fish ponds, some DO may be lost to the atmosphere through oxygen supersaturated surface waters.

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Co-culture and rotated culture of lotus and fish

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

Lotus-aquaculture culture system has been practiced for long time in China and is being evaluated recently in some Asian countries where lotus (Nelumbo nucifera) is native macrophytes. Several fish species have been used in such integrated systems including carps, tilapias and others.

The two culture forms are either the co-culturing of two crops in the same field and for the same time or apply the rotation type in which the culture of each crop is done individually in a one after another pattern.

The evaluation of lotus-aquaculture systems has always considered the technical as well as the economics of such integrated systems. Even the outcomes of the two forms varied and could be related to the culture conditions, there have been some agreements. For example, in the co-culture form, the shading resulting from the shading of lotus leaves which reduce the phytoplankton production and hence the dissolved oxygen in the water. Added to that, if the dead water leaves were not removed from the pond, they decompose and worsen the dissolved oxygen situation which is not in favor of fish production.

Regarding the lotus, fish can feed on aquatic grasses that may compete with lotus for living resources. Also, fish excreta would be a good source of organic fertilizers that leads to enhanced lotus growth.  Feeding fish on harmful pests is another benefit of such co-culture method. On the rotation form of lotus-aquaculture, the main advantage is having two different crops instead of one bigger crop. Also, the fish crop would assist in releasing the trapped nutrients from the pond bottom to be usable in the subsequent culture of lotus in an ideal recycling model.

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Traditional fishery in Gorgol River (Mauritania)

Photo credit: Vaghih El Bechiry (Mauritania)      Description: Vaghih El Bechiry and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows a group of fishermen while fishing in Gorgol River “Gorgol Noir” which is an open fishery resource and hence there is no fishing license is required. In order to achieve enough sustainability of fishery resource, the fishery department determines the mesh size of the fishing seines to be not less than 40mm. There is ongoing stock enhancing program whereas fish fingerlings are stocked in the river. In fact, the plan is to establish a fish hatchery in Lakleta for supporting the stock enhancement program.

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Training small-scale fish farmers in Cambodia

Photo credit: Nyro Tum (Cambodia) Description: Nyro Tum and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows a field day tailored to make potential small-scale farmers acquainted with aquaculture. Field days are typically conducted to train farmers who are already practicing fish farming targeting to introduce enhanced technologies and/or addressing current problems. Preparing such field days usually requires technical and financial information.

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Collection and preparation of mangrove oyster by Senegalese women

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

In Senegal, the mangrove roots and mud are home of several hundreds of known species of fish, bivalves and oysters, and crustaceans, which are very important especially for domestic consumption.

Women are the ones who are in charge of the collection of oyster from mangrove forests as well as in the processing of collected oysters. Women have the experience in identifying the sites that are still in good condition in regard to the oyster density and those with low density or exhausted.

Women access the mangrove sites either on foot or in small rowing canoes. For oyster harvesting, women use simple tools are simple including a spoon to dig up the shells, a knife for the oysters, and baskets for the harvest. Upon harvesting, women have the experience that the practice needs to preserve the resource mainly through keeping the green (live) roots of the mangroves undamaged except in certain conditions such as the wood is dead or when the roots are very dense bearing in mind that the roots of mangrove trees where the oysters are found. After harvesting, women also process the harvested oyster. They usually have the experience to crave the oysters out of their shells using a proper knife.

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Pangasius feeding in Vietnam – Video

Video credit: Mohamed Atta (Egypt) Review: Abdel Rahman El Gamal (Founder of the video channel)

Vietnam has the lead in the production of striped catfish (Pangasius sp.) that is exported to over 100 countries. According to FAO statistics, about 1.3 million tons of Pangasius has been produced from aquaculture in 2018.

The culture of Pangasius is mainly practiced in cages, earthen ponds and to a lesser extent in pens.

The inserted video shows the feeding of Pangasius in a commercial fish pond where a small boat is used to spread the feed within the pond. The aggressive feeding is quite obvious as shown in the video. Typically, the stocking rate rages from 20-40 fish/m2, increasing to higher rates in intensive practices with a production of about 250-300 tons/ha/crop. On the average, Pangasius can reach 1.0 – 1.5 kg as an average size after 6 months which is an optimum size for the market.

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Fish production and consumption in Mauritania

Photo credit: Vaghih El Bechiry (Mauritania) Description: Vqghih El Bechiry and Abdel Rahman El Gamal (Founder of the website)

The fish display shown in the picture exists in the central market located in Mokama city, South of Mauritania. The fish displayed in the market are caught from Foum Laklet Lake about 80 km from Mokama. Fish during transportation is usually iced. As normally the case, the man shown in the photo is the fish seller while the buyer is the woman.

Fish displays are often dominated by tilapia, followed by bayad (Bagrus bayad). During the rainy season, African catfish (Clarias gariepinus) contribute to the fish trade in the market. In addition to the mentioned species, other less important species may be displayed in the market.

As the case with traditional fish market, there are wholesalers who deal directly with fishermen while retailers have their displays and sell directly to fish buyers. It may worth noting that the capture fish production from Mauritania in 2017 amounted 794,580 tons while the per capita consumption of fish was 8.2 kg/year in 2016 bearing in mind that most of produced fish is exported (449, 835 tons in 2016).

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