Apr 26 2015

Cage culture of sturgeon in Uruguay

Credit: Facundo Marquez (Estuario del Plata – Uruguay)

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

Cage culture of sturgeon in Uruguay (02) Cage culture of sturgeon in Uruguay (01)

 

 

 

The two photos show the river culture of sturgeon in cages in Uruguay. Cages used are square where each cage measures 6m x 6m x 3m depth. The three species/varieties of sturgeon are: Russian sturgeon (Acipenser gueldenstaedtii), Siberian Sturgeon (Acipenser Baerii) and Sterlet (Acipenser Ruthenus).

It is believed that raising sturgeons in River Negro (Rio Negro) for all time provides a culture environment similar to the wild conditions and hence enjoy excellent sanitary conditions as reflected in the ideal maturation as well as the high growth rates.

After two years of initial stocking, sturgeon stocks are sexed whereas females are directed to caviar production (when they are mature) while males are directed to fattening units for meat production.

 

 

Permanent link to this article: https://fishconsult.org/?p=12568

Apr 25 2015

Ovarian development and eyestalk ablation in whiteleg shrimp (Litopenaeus vannamei)

Photo credit: David Kawahigashi (Thailand – David Kawahigashi – Vannamei101)

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

Shrimp stage IV gonads (01) Shrimp stage IV gonads (02)

 

 

The inserted photos were taken in a Thai shrimp facility and shows the gonadal development for a female of white shrimp (Litopenaeus vannaemai) which is carried out. In this particular photo the assessment of the gonadal development is done prior to the ablation of eyestalk which is practiced to stimulate the female shrimp to develop mature ovaries and spawn within as little as 3 to 10 days after the ablation.

In general, breeders classify the ovarian development of shrimp females into five stages as follows:

Stage: I: Immature (ovarian lobes translucent and smaller in diameter than the gut)

Stage II: Developing (ovarian lobes opaque, pale yellow-colored and with a diameter similar to that of the gut)

Stage III: Advanced (Ovarian lobes yellowish and larger in diameter than the gut)

Stage IV: Fully mature (ovarian lobes occupying entire part of the cepahalothorax cavity, strong lemon yellow color

Stage V: Spawned (lobes flaccid and convoluted with ova remains)

In order to check the stage of ovarian development, examined females are exposed to either sunlight or to strong –preferably waterproof- flashlight.

The females shown in the inserted photos are gravid females with highly developed, stage IV ovaries

 

 

Permanent link to this article: https://fishconsult.org/?p=12561

Apr 21 2015

Rationality and impacts of underwater lighting on fish production in cages

Photo credit: AKVA Group

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

 

Undewater lightening (02) Undewater lightening (01)

 

The Underwater lighting when practiced in a given aquaculture operation is often adapted for fast growing species such as salmon, trout, cod and others. In fact, the use of submerged artificial lighting during-night hours is steadily gaining more interests in application.

The purposes of submerged lighting although vary; better productive performance and easier management are the main ones.

When used in salmon farms, the underwater lightening is believed to enhance farm productivity through slowing down the maturation process and reducing the risk of early maturation prior to harvest for the exposed salmon enabling them to grow to larger sizes before sexual maturation. There are reports/observations about these findings for the Atlantic salmon (Salmo salar) and King salmon (Oncorhynchus tshawytscha).

The optimum underwater lightening results in an even light distribution which in turn assists in developing almost uniform densities of fish in culture units and so, improves the utilization of feed especially in farming units with high fish density and high turbidity water.

There are some environmental impacts which may accompany the submerged lightening including –in case of cages- a possible aggregation of aquatic organisms (e.g. zooplankton, bait fish) living in open waters around the illuminated areas of the cages increasing their vulnerability to possible levels of night-time predation.

In regard to birds, the attraction of birds to the artificial lighting over the farming units will depend on the behavior of birds especially the nocturnal birds which are active during nights. The attraction of these birds to lighted areas increases their risk of their collision and/or entanglement with farm structures.

 

 

Permanent link to this article: https://fishconsult.org/?p=12549

Apr 16 2015

The role of women in the value chain of artisanal fisheries in Liberia

Photo credit: David Elliott (Mac Alister Elliott & Pts.) – UK

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

 

Liberian women buying fish

 

Whether women seen in the inserted photo are heading to buy fish for their families or for trade, the Liberian women play an important role in the artisanal fisheries sector. They may support the fishermen especially when faced with difficulties such as the loss or damage of fishing gears or canoes. Women may lend fishermen money or buy fishing equipment required to ensure that they are back on waters. Moreover, Liberian women are usually engaged in fish processing and marketing activities.

As in most African countries, fishermen do the fishing and fix the fishing gear and boat; while women take over once the fish is unloaded from the boats whether through buying the catch or –in case of the wives of fishermen- transport and market the catch, and in some cases transform it into dried or salted fish.

Aside from fishing activities, women often feel more secure when move in groups especially in relatively distant trips.

 

 

 

 

 

Permanent link to this article: https://fishconsult.org/?p=12545

Apr 14 2015

Trout in Armenian aquaculture

Photo credit: Gurgen Khanamirian (Armenia)

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

This trout farm shown in the inserted photo is located in the north of Armenia and specializes in growing rainbow trout, brown trout and Sevan trout.

Trout culture in Armenia

 

Aquaculture represents the key fishery system in Armenia representing around 90% of total fish production during the years 2010, 2011 and 2012 before declining to 71% in 2013.

Trout aquaculture is a main farming system in Armenian representing 62%, 60%, 54% and 56% during the years 2010, 2011, 2011 and 2012 respectively. In tonnage, trout production amounted 3100, 3800, 4800, and 6500 tons during the mentioned years. The remaining quantities are attributed to cyprinids, sturgeons and European catfish.

The artificial propagation of Sevan trout (Salmo ishchchan) which is indigenous to Armenia was first practiced in the 1920s to support the industrial fishery of Lake Sevan. Afterwards, the introduction of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) took place for aquaculture.

Rainbow trout is the most widely produced trout species in Armenia, although many of the farms also deal with brook trout and Sevan trout.

Although the indigenous “Sevan trout” has a slower growth rate, and is easier to be excited than rainbow trout, the species is gaining popularity among consumers and producers especially in the light of its hardy nature and higher tolerance disease compared to rainbow trout as well as its higher price.

In regard to trout farms, only one trout farm was there in the 1970s, which used underground artesian water resources. The number of trout farms steadily increased reaching about 200 farms of different sizes and productivity. Although some trout farms are made of earthen tanks, almost all of the leading trout-farming enterprises use concrete tanks.

In order to utilize the nutritionally-rich effluent of trout farms, in some farming systems, carp ponds are surrounding trout farms. In such system, carps are not fed with commercial feed while rely only on the nutrients discharged from trout ponds. In addition, the outer carp ponds provide a physical protection to trout properties against illegal visits.

 

 

Permanent link to this article: https://fishconsult.org/?p=12540

Apr 11 2015

Description and management of a fish farm in Bela Vista, Maputo (Mozambique)

Credit: Nick James (Rivendell Hatchery – South Africa)

Description and management of a fish farm in Mozambique

 

The photo shows a fish farm located at Bela Vista 42km south of Maputo on Rio Maputo (Mozambique). The farm consists of 26 of flooded half-hectare ponds, while many more are under construction. It took three years since starting the construction and getting into production. The farm receives its water by pumping from a nearby river.

Each 0.5-ha pond is stocked with 15,000 fingerlings of Nile tilapia “Vilanculos strain” which are acquired from a local hatchery. Because the growth performance of the strain is not as hoped, an improved strain of Nile tilapia would replace the current strain. Consequently, a significant improvement in the growth rate and yield is expected.

This farm is owned and run by an NGO which is a drug rehabilitation center (Healing Wings). Fish side is run by about 4 individuals. The farm has also three x 100m chicken broiler houses with 15,000 chickens that contribute the farm fertilization.

In general, the growing season required to reach an average size of 350 g, ranges from 8-10 months. Harvested fish is locally marketed in Maputo.

 

 

Permanent link to this article: https://fishconsult.org/?p=12536

Apr 10 2015

Fish section in Mongu central market, Zambia

Credit: Numel Phiri (Zambia)

Fish section in a central market in Zambia

 

This picture is for a general market for fish and other goods as well. This is the second biggest in terms of fish trading after the Mulamba Harbor market which is at the hub of fish trading. However, the harbor market is characterized by fish trading structures made out of mud and poles and sometimes reeds.

The displayed types of fish in the present market include fresh, sun-dried, smoked and most recently salted fish. This market turns busiest in the evenings between 18 and 20 hrs.

The majority of fresh fish traders in this market are men whilst dry fish (especially small sized sun dried) is dominated by women. In regard to buyers in terms of consumers mostly are women.

Over 80 percent of fish caught is processed i.e. dried due to inadequate and in most cases lack of cold chain facilities.

 

 

Permanent link to this article: https://fishconsult.org/?p=12533

Apr 09 2015

Tuna caught in Libya and grown in Italy

Photo credit with caption: Greenpeace

Additional review: Abdel Rahman El Gamal (Founder of the website)

Tuna from Libya to Italy

 

 

This photo shows a tug towing a tuna cage between fishing grounds in Libya and tuna farms in Sicily, Italy.

It may worth adding that the fattening of Bluefin tuna in Italy started in 2001 by a 4-cage farm located in Sicily, the number of farms and cages increased afterwards. In tuna fattening, captured Bluefin, go through fattening in large floating cages with a diameter of 50 m and 25 m depth.

Caged tuna are fed with herring, sardines, anchovies, mackerel and squid for 3 to 8 months.  Depending on the water temperature the fish are fed 5 to 8% of the estimated body weight/day. This feeding system is extremely inefficient as about 20 to 25 kg of fish is required to add a kilogram weight to the caged tuna. In addition to the increase of tuna weight during the fattening, the increase of their fat content is targeted to allow for better price in commercial tuna markets, especially the Sushi Market in Japan.

Tuna fattening is certainly an important fishery activity throughout various activities including capturing the tuna required for fattening, transporting the captured tuna to fattening cages, capturing the fish needed to feed tuna and move the harvest to tuna markets. However, most of mentioned activities raise negative images which could be summarized in the possible depletion of juvenile tuna population, draining the seas of fish used as tuna food. Moreover, the excess feed and feces of caged tuna are polluting the near shore waters.

In conclusion, the sustainability of tuna fattening in cages will depend on the availability of economically sound methods of hatchery production to avoid the use of wild-caught juveniles. Equally important, is the improvement in artificial feed formulation to eliminate or reduce baitfish consumption.

 

 

Permanent link to this article: https://fishconsult.org/?p=12530

Apr 06 2015

Migration of the gray whales: An extraordinary spectacle to watch – Video

Video credit: Hani El Malky (USA)

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

This video was filmed on 24 December, 2014 during a 3-hour cruise.

This video was filmed during a whale watching cruise on 24 December, 2014. Several operators advertise about this 3-hour whale watching cruise. Even though, whales are the main target for this trip, dolphins and seals could also be watched. Also, choosing the time of these the right period for operating this cruise enhances the possibility of seeing the whales. Of course the experiences of the cruise crew cannot be overlooked.

Many of the tour operators who offer watching excursions have extensive knowledge of the whales and their migration habits.

About 20,000 of gray whales (Eschrichtius robustus); one of the largest mammals on earth are making a 10,000-mile round trip journey from the Arctic Sea south to the lagoons of Baja California, where the females give birth to their calves. The trip takes several months during which whales enjoy the warm water in Baja California water and provide their calves enough time to grow strong to make their journey back home north around April. This trip is the longest known migration undertaken by any mammal on an annual basis.

San Diego seems an optimum destination to watch the whales based on its 70 miles of coastline directly in the path of migrating whales. The whale watching season in San Diego runs from mid-December through April.

As you will see in this video, we were fortunate to see several whales in more than one location. The captain and his crew did an excellent job navigating out and tracking down to show the whales. We were able to see also many dolphins close to the end of this cruise. Throughout the journey, a technical crew member provided through microphone useful information about sea life.

The reaction throughout the journey varied from quietness, waiting turning into a real excitement upon watching the target animals especially the whales.

 

 

Permanent link to this article: https://fishconsult.org/?p=12528

Apr 04 2015

Freshwater aquaculture of rainbow trout in Denmark

Photo credit:Gurgen Khanamirian (Armenia)

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

Intensive trout farm in Denmark

The inserted picture was taken in an intensive rainbow trout freshwater farm located in Central Jutland (Denmark). Fish production in this given farm amounts 100-110 kg/m3. The following review provides some background information on the development of trout culture in Denmark.

Denmark has long been one of the world’s pioneers in the farming of trout whereas pond farming of rainbow trout (Oncorhynchus mykiss ) began to exist around the beginning of the 20th century In 1914 there was 140 trout farms operating in Denmark whose production was primarily for export..

Almost all Danish freshwater trout ponds are located in Jutland (the western part of Denmark) where most abundant flowing streams do exist.

Originally, trout culture in Jutland was practiced in earthen ponds with relatively simple practices using water diverted from a river, led through the ponds and released again into the same river. Not long ago, fish used to be fed minced fish till harvest of about 300-350 g average size.

The growth of trout farming industry has raised environmental concerns due to the disposal of farm effluent (faeces and unused food) in Danish streams causing significant conflicts with the wild fishery as well as other water uses.

Accordingly, gradual changes in the trout farming took place whether in the construction or in operation; concrete ponds have gradually replaced earthen ponds and farm effluents are strictly monitored to reduce the amount of nutrients returning to rivers.

Because most of the suitable freshwater areas (almost all in Jutland) are now in use, the traditional extensive systems are gradually replaced by intensive farming methods conditioned by the necessity to keep effluent discharge in compliance with the environmental regulations which include assigning maximum amount of fish that can be produced from each farm as well as the annual amount of feed which a farm can use and so the allowable effluents a farm can produce.

In order to cope with such strict environmental regulations, many of trout producers have to move towards cleaner practices such as the farms that use recirculation technology while the restricted feeding is widely spread among freshwater trout producers to improve the utilization of provided feed allowances and to reduce losses to the environment.

 

 

Permanent link to this article: https://fishconsult.org/?p=12525

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