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Fish-vegetable-horticulture integration in Malawi

Photo credit: Madalitso Magombo (Malawi) Description: Madalitso Magombo and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows an integrated farm of fish and vegetables as well as bananas (horticulture) that does exist in Zomba, Malawi and run by one of the fish farmers in the area.

The integrated aquaculture-agriculture (IAA) technology was introduced to Malawi in 1986 as a means to enhancing household food security, income and environmental sustainability. As shown in the inserted picture, the agricultural crops (vegetables and banana) benefit from the fish pond water with its load of nutrients and hence enhancing the plant growth and reduce their need for external fertilizers. On the other hand, the residues of the vegetables are also fed to the fish or used as manure representing an environmentally way of recycling.

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Permanent link to this article: http://fishconsult.org/?p=15172

Tilapia aquaculture in Guatemala

Photo credit: Andria Melissa Ochoa Rodas (Guatemala) Description: Andria Melissa Ochoa Rodas and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows an earthen pond while prepared for tilapia culture. The pond is in Escuintla which is located in south central Guatemala. As shown in the picture, heavy machinery are used in the preparation process that ultimately targets the lining of the pond with proper liner sheets of 12×20 m each.

Unlike shrimp farming in Guatemala which mainly targets the international markets, the internal consumption is the main target of tilapia aquaculture.

According to FAO, the interest in tilapia culture in Guatemala began in 2004, upon the construction of the Sabana Grande training and fish breeding station.

As reported in FAO statistics, total fish produced from Guatemala aquaculture amounted about 26,000 tons in 2017; out of which close to 10,000 tons belonged to tilapia. The strains of Nile tilapia (Oreochromis niloticus) have been introduced into Guatemala from Mexico and USA over the years 2003 and 2004.

Permanent link to this article: http://fishconsult.org/?p=15168

Ovulation in koi carp – Video

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

This video has been filmed in a koi hatchery in Vietnam.

The focus of this short video is to share how the ovulation looks like in Koi carp which will be almost the same in most fish species. It should be emphasized that the spotting of ovulation time is critical regarding the subsequent phases including fertilization till hatching bearing in mind that if ovulated eggs are not stripped within specific period, eggs turn overripe and hence cannot be fertilized.

The video shows two female undergoing the stripping process. The first females seems not ovulating yet and she may ovulate shortly after as batch of eggs obtained was unnoticed. On the other hand, the second female was ovulating as the stripping went easy and eggs are flowing freely uninterrupted. There are several observations which could be mentioned here including that the handled females were not anesthetized probably because of their relative to medium sizes. Instead, eyes are covered and caudal peduncle that proved to calm the fish.

Permanent link to this article: http://fishconsult.org/?p=15162

Risk of excessive crowding of fish fry

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

The inserted picture shows an excessive crowding of tilapia fry. The crowding condition is not unique and is commonly witnessed in hatcheries and done for easy scooping and bagging. It is commonly believed that because of the short crowding period, no harm to handled fish is expected. However, this assumption cannot be true in all situations. Let us agree that scooping would require a level of crowding but this should consider some precautions. Local oxygenation will be helpful to avoid the drop of oxygen within such crowded fish mass. Another scenario is portioning the total number of the hapa into batches and hence the crowding of a batch enables the scooping in much shorter time with less handling harm.

Permanent link to this article: http://fishconsult.org/?p=15160

Construction of a small fish pond in Madagascar

Photo credit: Marcel Jean Adavelo (Madagascar) – Review: Marcel Jean Adavelo and Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows the construction of a small fish pond in Madagascar. Typically, such small-size ponds do not justify the use of machinery. Added to that, the farmer usually does not have the cash needed for the construction. Instead, members of the community including relatives and neighbors help the pond owner in the construction at no cost except what is offered by the farmer of food –and alcohol- during the work until the completion of the pond. As shown in the picture, the tools used in the construction are made from locally available materials.

Permanent link to this article: http://fishconsult.org/?p=15156

Tilapia zillii – unwanted in fish ponds but highly demanded in markets in Egypt

Photo credit: Suzan Alfred and Mekki Zakaria (Sudan) – Review: Abdel Rahman El Gamal (Founder of the website)

The inserted picture shows a batch of fish ready for the market. The traditional basket has mainly two fish groups; soles and green tilapia (Tilapia zillii).

Whether caught from natural resources such as lakes (like the attached picture) or accidently found in fish pond, Tilapia zillii with its small size attain much higher price than other tilapias of much larger size. Unlike mouth brooder tilapia, T. zillii is are substrate spawners and mature at earlier age of around 3 months with small sizes. The high consumer preference is because the relatively large egg roe that fills most of the body cavity. Added to that, the taste of its flesh is usually appreciated especially when caught from saline waters.

In fish ponds and because of the reproduction behavior of green tilapia, the species is highly undesirable as their reproduction could disturb the management of fish ponds. Regardless the control measures taken in fish ponds to prevent the entry of tiny organisms, the fertilized eggs of T. zillii with its small size may find its way to fish ponds where they hatch, grow and interfere with the pond management.

Permanent link to this article: http://fishconsult.org/?p=15153

Adipose eyelids and their functions in fish

Photo credit: Marx Perfecto C. Garcia (Philippines) Review: Abdel Rahman El Gamal (Founder the website)

The inserted photo shows the eyelid in a mullet specimen (Mugil sp.).

There are several theories related to the possible roles of eyelids in fishes. It is generally accepted that the eyelids may play a role in affecting the vision and enhance the ability of fish to focus on specific objects. This is supported by the presence of eyelids in deep sea fish whereas better vision and focusing would be of top importance for the survival and well-being of fish in the deeper part of ocean as the visibility is severely reduced. It is also believed that eye lids serve as a physical barrier and protect fish eyes against foreign objects in the waters.

It is questionable whether the adipose eyelid could block out ultraviolet light and so prevent the UV damage to the fish’s retina in some species. Apart from above, the eyelids served as a taxonomy tool in some fish groups such as mullets. In flathead grey mullet, Mugil cephalus, the adipose eyelid is well developed, covering most of pupil with only a narrow slit over the pupil, while in thin-lip grey mullet (Chelon ramada), the adipose eyelid is poorly developed.

Permanent link to this article: http://fishconsult.org/?p=15150

Bamboo fish graders in China

Photo credit: Marx Perfecto C. Garcia (Philippines Description: Abdel Rahman El Gamal (Founder of the website)

The inserted picture was taken in an aquaculture facility in China and shows several sizes of bamboo graders.

The use of bamboos in aquaculture goes back to about a century when bamboo cages were used in Indonesia. In countries where bamboos are abundant, bamboos have been introduced more in aquaculture as an eco-friendly material with lower cost and easier maintenance. Fish graders have been added to the use of bamboos.

Bamboo graders are commercially produced at the moment. As the case with other bar graders, the thickness of bamboo stems as well as the distance between them would determine the size of fish retained above the grader and those that passes through for a given species. That is why; graders are numbered according to the space between bars for easier use. It may need mentioning that freshly cut green bamboo are often flexible and can be shaped and manipulated for various uses including graders. Other treatments may be applied for the same purpose including the use of heat.

Permanent link to this article: http://fishconsult.org/?p=15147

Removing the premaxilla of tilapia males

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

The removal of the premaxilla of bone of the upper lip of tilapia males goes back to the late 1970s. The purpose of such practice is to reduce the aggressive behavior of tilapia males and hence reduce the possible injuries and/or mortality of females during the spawning season especially when the mating takes place in confined places such as hapas or tanks whereas females can be exhausted or experience scale loss that may lead to their death. This harm is more frequent when males are much larger than females. The clipping of the premaxilla is done using sharp scissors or razors.

As expected, in open pond breeding, the aggressive behavior of males is not common as females usually have more chance to escape such harassment and hence the removal of the male premaxilla is not usually required. The same is true when females are mated with similar-sized males.

The resulting wound should be disinfected using proper disinfectants such as potassium permanganate or a 10% solution of Betadine. It may worth noting that the removal of the male premaxilla does not interfere with the reproduction or feeding activities of treated males.

Permanent link to this article: http://fishconsult.org/?p=15144

Fish hatchery management (2019 updated lecture)

This lecture on the management of fish hatcheries was delivered in Fish Culture Development training course during August 2019. The lecture starts with general information related to the various modes of reproduction among aquatic animals of finfish, shell fish, mollusks and others including substrate spawners, mouth brooders till giving birth. The levels of parental care have been also addressed. Relying aquaculture on wild collected seeds has been covered along with less reliability of such approach and hence the necessity to have fish hatcheries. The focus of the lecture has been placed on the hatchery technology of fish species giving examples of various groups of finfishes and crustaceans in freshwater and marine waters including acquiring broodstock, hatchery facilities, reproduction technology (natural – artificial) and the relationship between adopted technologies and the biology of fish as well as the economic considerations. The lecture addressed the quality of hatchery production whether through genetic enhancement or biosecurity measures such as vaccination or disease-free protocols.

http://fishconsult.org/wp-content/uploads/2019/08/Fish-Hatchery-management-Updated-2019-version.pdf

Permanent link to this article: http://fishconsult.org/?p=15128

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