Mitigation of rising salinity in Lake Qarun – Egypt

Video credit: Patrick Appenteng (Ghana), Charles Makuya (Malawi), Djouani Marcelin (Cameroon), and Marx Garcia (Philippines)

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

Lake Qarun (Fayoum – Egypt) was directly connected with River Nile in ancient times and so forming a natural reservoir of freshwater before being disconnected. Since then, the lake (~23,000 ha), turned into a closed basin relying solely on agricultural drainage water and hence resulting in a steadily rising of water salinity mainly due to the evaporation of lake water. The salinity of lake water ranges from 35 to 40 g/L in the present time.

The threatening of salinity increase to the lake fishery called for mitigation approaches especially when we know that the total build-up of salt in the lake is estimated by about 600,000 tons annually. Among various suggested strategies, salt extraction from the lake water has been recommended as a realistic and effective approach.

The inserted video has been mainly filmed in a large salt extraction factory (Emisal). The infrastructure and so the technologies in practice allow the extraction of about 300,000 tons of salt/year from Lake Qarun, sorted as follows:

  • Anhydrous sodium sulfate (120,000 tons/year)– Used in the manufacturing of dry detergents
  • Refined sodium chloride (edible – 150,000 tons) and vacuum sodium chloride (90,000 tons)/year
  • Magnesium sulfate (27, 000 tons/year)- used in the fertilizers’ industry

It may be worth noting that about 18 million tons of dissolved salts have been excreted from the lake during the period from 1984 to 2018.

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Seed production of red abalone (Haliotis rufescens) in Monterey region – California (USA) – Video

Video description: Peter Hain (USA) and Abdel Rahman El Gamal (Founder of the video channel)

I filmed this video during my visit to this facility on 22 January 2015 where I received a warm welcome from Mr. Peter Hain, the manager of the facility who toured me around the facility. This facility is located in “Moss Landing” in the Monterey region, California.

This facility could be classified as possibly the smallest commercial hatchery/nursery in the state. The collaborators are Monterey Abalone Company collaborates with the Moss Landing Marine Laboratories.

During the visit and as seen in the video, the hatchery component was described verbally as we were out of the spawning season for the abalone, while the spat nursing was adequately covered. The hatchery and nursing facilities and operations are described in the following components:

Source of hatchery broodstock: There are two sources of the red abalone broodstock:

From the wild:  Gravid abalone females and males are collected in season at a site north of Fort Ross, California, under permit from the California Department of Fish and Wildlife.

From other farms/hatcheries:  Gravid females and males are also purchased as needed from two commercial abalone farms and are spawned together with Monterey Abalone Company broodstock and the wild broodstock to increase and maintain genetic diversity.

Sex ratio of broodstock:  In general a ratio of three females to every male is used when spawning commercial farm broodstock.  The ratio can be reversed if crossing large wild females with smaller farmed males.

Spawning season: Wild abalone broodstock from the Northern California coast are generally gravid during the months of March and April, sometimes into early May.  Collection trips are planned to take advantage of favorable weather.  The hatchery phase generally begins in May and extends into June and July.  If any of the initial settlements are poor then additional spawns can occur in August to early September.

Water source and quality during the hatchery operations:

Filtration: Filtration through sand filters (20 microns).   Sand filtered seawater is delivered to the hatchery from the pumping station.  The seawater intake is located approximately 300 meters offshore at 16.6 meters depth.  Hatchery water is further filtered through 20 microns, 10 microns, and 5-micron cartridge filters.

Sterilization: A UV sterilizer is used during the spawning of the adults and hatch-out of the larvae.  The UV sterilizer is generally turned off on Day 3 of the eight to nine-day larval cycle to introduce the larvae to the natural mix of bacteria present in the seawater.

Fecundity:  Large wild females can spawn upwards of eight million eggs with smaller, 4-5 inch, farm animals producing up to one million each.

Incubation: Fertilized eggs will generally hatch in eighteen to twenty hours, dependent on temperature, as trochophore larvae at which point they are transferred to a conical bottom tank with flow-through water and retained with 70-micron banjo screens.  Water flow is maintained at six exchanges per day as the larvae, now veligers, develop.  Generally by Day 8, once again dependent on temperature, the larvae are beginning to show settling behavior.  The larval foot has developed and once this final development stage is reached the larvae are settled the next day into the nursery tanks. 

Larvae develop in the incubator but should be moved to the nursery before the settlement (Should not allow settling in the incubator).   Red abalone larvae in particular are capable of adhering strongly to surfaces and should not be kept in the Larval Rearing Tank any longer than necessary.  

Larval rearing tanks: The conical bottom larval rearing tank holds 454 liters and the ideal density is around five larvae per milliliter.

Production cycle: The hatchery production cycle lasts 8-9 days, depending on temperature, generally 13-15 C.

Abalone Nursing

Nursing capacity: Based on the current volume of nursery tanks, the capacity of the nursery facility is 120,000 – 130,000 abalone spat (seed).

Water source and management: Monterey Bay is the source of water whereas water is pumped from 300 meters offshore and from 16.6 meters under the surface. Water passes through sand filters which filter down to around 20 microns. The filters are backwashed as required by a PLC monitoring system. Filtered water is directed to nursery tanks as required.

Water temperature: 15C is considered ideal but the range is generally 12 to 16C.

Water salinity: Abalone prefers oceanic salinity of 32-36 g/L and will suffer mortality if salinity drops below 25 g/L for an extended time.

Water renewal throughout the nursing:  During the majority of the nursery phase a renewal rate of every two hours is sufficient to maintain water quality although that rate would be increased if, for instance, heavy rain were forecast.  Once the juvenile abalones are beginning their transition to macro seaweed the renewal rate is increased to once per hour.

Nursing tanks: There are four nursery tanks of 5×10 feet with a depth of 50 cm and four tanks 2×8 feet.

Nursing tanks are equipped with settling racks, holding corrugated fiberglass sheets, are locally made of PVC to provide a large surface area.  The surface area available for settlement in each of the large tanks exceeds 125 square meters.  The smaller tanks each have 46 square meters available. The tank standpipe is fitted with a 100-micron banjo screen which is taken out the day after the larvae are settled. The settlement racks sit off the tank bottom on an aeration manifold made of PVC pipe.

Two layers of shade cloth, 85%, are fitted to each tank and a third shade is available for the initial settlement phase.

Management of nursing phase:

Nursing tanks are filled with the filtered water 3-5 days before the introduction of larvae from the hatchery and a slow flow is maintained over the settlement racks.  This practice allows a bacterial coating, the first food of the abalone, to be established on the corrugated sheets. Abalone larvae are settled into the tanks and distribute themselves onto the corrugated sheets.

Diatoms of 10 microns are inoculated into the tanks the day after settlement of the abalone larvae.

Tanks are left uncovered for several days until the diatoms are established and then the tanks are shaded with the three layers to slow further diatom growth.

Spat-diatom ratio: Once the settled spats are seen grazing on the diatoms, one of the three shades is removed to encourage the growth of diatoms. The same process is repeated depending on the spat-diatom ratio. Diatom growth is strictly regulated so as not to overgrow the abalone while at the same time keeping sufficient diatoms available as the juveniles graze. 

Supplemental food: Diatoms growing on the corrugated sheets can be supplemented in the later stages with the addition of dried diatom powder, artificial abalone feed wafers and with wild Ulva sp. that grows in the tanks.  About two months before harvest the juveniles are introduced to macroalgae which may include Ulva, Palmaria, or Gracilaria sp.

Note: I have been told that one kg of diatom was found sufficient for the production of the 120,000 spat. In fact, one kg of live diatom (Navicula incerta) was purchased from a commercial producer and used to inoculate two newly settled tanks as well as being used to inoculate an unsettled tank.   Diatoms were later harvested from this tank for further inoculations in later settlements.

Collecting grown spats: When the spats are ready for farming, they are collected and graded. During the visit, there were four graders. The largest size could reach about 1-g while the smallest can be 0.25g

Note: The largest spat seen during the visit was introduced in the nursery facility six months before and will be ready for farming about three-four months after the visit.

Sampling: Settled juveniles are counted when they become visible so that populations can be adjusted as necessary.  Periodic length measurements are taken to check the rate of growth.

Settlement success: The ratio between the larvae and produced spats can vary from year to year and from tank to tank.  Temperature, genetics, tank management and diatom diet all factors contributing to survival. This nursery operation plans on 2% survival which gives sufficient grazing surface per animal until they reach a size that they can be weaned onto macro seaweeds.  Survival at greater than 2%, if not dealt with by early population reduction, will lead to overcrowding and reduced growth rate.

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Biofloc culture of red tilapia in Colombia – Video

Video credit: Sandra Sanchez (Colombia) Description: Sandra Sanchez and Abdel Rahman El Gamal (Founder of the video channel)

The inserted video shows a typical model of intensive culture of red tilapia (Oreochromis spp.) in Colombia. The culture takes place in ponds with geomembrane liner. The technology applied depends on biofloc.  

In such intensive system, up to 100 kilos per cubic meter can be achieved conditioned to optimum design of rearing facilities as well as the high technical management of the farm. According to experts, it is possible to establish 10 circular tanks on an area of less than half a hectar (5000 m2). It was possible to produce between 4 to 5 tons of harvested fish per month. In this typical system, the tanks are placed above the ground and hence there is no need to dig in the soil.

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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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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.

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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.

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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.

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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.

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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.

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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.

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