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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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Permanent link to this article: http://fishconsult.org/?p=15537

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.

Permanent link to this article: http://fishconsult.org/?p=15533

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.

Permanent link to this article: http://fishconsult.org/?p=15528

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.

Permanent link to this article: http://fishconsult.org/?p=15522

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.

Permanent link to this article: http://fishconsult.org/?p=15519

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).

Permanent link to this article: http://fishconsult.org/?p=15515

Artificial reproduction of Pacu in Paraguay

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 sufficient number of the species fingerlings would be essential towards the expansion of pacu aquaculture in Paraguay.

The artificial reproduction of Pacu is essential to stimulate the spawning in captivity. This has been practiced in Paraguay whereas Prostaglandin F (PGF) and carp pituitary extract (CPE) have been used. The inserted picture shows a batch of Pacu eggs produced through artificial spawning It may worth noting that according to FAO statistics, the production of farmed pacu increased from 308 tons in 2010 to 2432 tons in 2018.

Permanent link to this article: http://fishconsult.org/?p=15510

Fish pond de-silting (Zambia)

Photo credit: John Chiseba Mwamba (Zambia) Description: Abdel Rahman El Gamal (Founder of the website)

As silt accumulates, the overall capacity of a pond decreases. Fish ponds which were not desilted for years, ponds had become shallow, which may aggravate weed growth.

Silt can lead to pond turbidity which interferes with the sunlight penetration and hence limits the phytoplankton production which is the base of the food chain and ultimately affects fish production.

In spawning ponds, silt and mud can cover fish eggs and can also hide the fish feed –in case of sinking feed- and make it inaccessible to pond fish. De-silting of earthen ponds is a typical and periodic operation carried out from time to time. In small ponds as shown in the inserted picture, the de-silting is done manually while machinery such as dredgers, excavators, sludge pumps and agitators may be used in larger operations and lakes.

Permanent link to this article: http://fishconsult.org/?p=15502

Possible use of termites in fish feed

Photo and briefing credit: John Chiseba Mwamba (Zambia) Review: Abdel Rahman El Gamal (Founder of the website)

Historic use of termites: The long winged reproductive termite is edible and highly sought after as a delicacy. Moreover, wild-caught termites have been used as a bait to attract fish and insectivorous birds. Natives of South East Africa consume queens of termites as a delicious dish.

Nutritional merit of termites: The composite analysis of termites showed a relatively high content of crude protein of about 43 to 45% with an adequate profile of amino acids especially in its high lysine content which is an advantageous bearing in mind that lysine is limited in most plant protein sources. The significant high lipid content of termites (~30%) is also advantageous whenever in energy supply and/or in providing specific fatty acids. The overall nutritional merit of termites supports its use in fish feed in a partial replacement of fish meal that is usually the most expensive component of fish feed.

Present and potential use of termites in fish feed: During swarming, significant termite populations are wasted and could be utilized for fish feed production especially fish were observed to consume live termites when they fall into fish pond.

Termite is used regularly as feed ingredient in fish farms in several Asian countries including Cambodia, Thailand and Nepal.On experimental scale, the use of termite has been tested upon partial replacement of fish meal in the feed of “rambur – Macrotermes subhyalinus”, “mud catfish – Heterobranchus longifilis”, “Freshwater prawn – Macrobrachium rosenbergii), and maybe others. The outcomes of most studies recommended replacement ratios in the feed of tested species without affecting its productive performance.  The main objectives of the mentioned studies were to explore practical means to reduce the feed cost through a partial replacement of fish meal with a cheaper source of protein; termites.

Permanent link to this article: http://fishconsult.org/?p=15493

Extensive farming of red tilapia in Colombia

Photo credit: Andres Delgado (Colombia) Review: Andres Delgado and Abdel Rahman El Gamal (Founder of the website)

The inserted pictures show the culture of red tilapia in small ponds at Ricaurte which is a town and municipality in the Nariño Department (Colombia). In such small ponds, extensive farming system is typically applied as locally available feed is made of sown forages that are grown around the pond. As shown in the picture, a mesh nets are used to protect the farmed fish against possible predation by birds and/or mammals. In such system, an average size of about 300 g for harvested fish has been achieved after 8 months of culture.

Permanent link to this article: http://fishconsult.org/?p=15488

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