Jun 01 2016

Culture of olive flounder in South Korea – Video

Video credit: Hisham El Gazzar (Egypt)

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

Olive flounder in South Korea

 

The olive flounder (Paralichthys olivaceus) is also known as “bastard halibut”. The flounder has been cultured in South Korea since 1980s when 19 tons of farmed flounder were produced in 1980. Afterwards, the production of olive flounder has witnessed a steadily and sharply increase, peaking to 54,432 tons in 2009 then fluctuating from year to year amounting 42,133 tons in 2014 (FAO statistics).

The olive flounder, being a high-value fish, has ranked at the top of aquaculture production of finfish in Korea. The development of olive flounder farming has been supported by its high growth rate, better feed efficiency, and its tolerance to water temperature changes. Moreover, the availability of year-round hatchery-produced seeds is an important factor in the development of flounder aquaculture.  Also, South Korea is by far the top global producer of olive flounder; in 2005; Korea produced more than 42,000 tons of olive flounder representing more than 70% of the global supply of the species.

The olive flounder is mainly farmed in flow-through systems at land-based facilities located on the coast. Usually, farms of olive flounder have access to seawater, which is pumped directly from the open sea into the head tanks and subsequently supplied to the fish tanks. The largest quantity of Korean flounder is produced in Busan.

The olive flounder is very popular among Koreans for its good taste and for being one of the most species for raw fish dishes on the Korean market.

 

Permanent link to this article: https://fishconsult.org/?p=13351

May 29 2016

Excessively crowded Snakehead fish in a thin film of water – Video

Video credit: Hai DO Xuan (Vietnam)
Review: Abdel Rahman El Gamal (Founder of the video channel)

Snakehead in excessive density

 

 

 

The video has been filmed in a temporarily aquaculture facility in Vietnam.

One can easily see how specimens of snakehead in such excessive density while sliding, jumping and moving in such thin film of water.

Snakeheads are extremely hardy and tenacious fish. They breathe using both gills and a lung-like accessory breathing organ and so fish may survive out of water for days as long as their skin remains moist.

They hibernate in winter, and aestivate during summer droughts. These characteristics enabled the farming of snakehead in very high densities wherever its culture is allowed (e.g. Indonesia, Vietnam, and Cambodia).

Permanent link to this article: https://fishconsult.org/?p=13345

May 28 2016

Culture of Dorado (Salminus brasiliensis) in Argentine – Video

Video credit: Herman Hennig (Argentina)

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

Dorado in Argentina

 

 

 

The video was filmed in a fish farm located in Misiones Province, San Jose. The earthen pond shown in the video is about 3 ha whereas “dorado” (Salminus brasiliensis) is being cultured; fish feeding practice is shown in the video.

The excellent quality of its flesh along with reduced stocks in several South American river basins, places “dorado” as a species with the highest potential for fish farming especially the species is characterized by its high growth rate.

According to FAO statistics, there were no records on the production of dorado from aquaculture before 2010 whereas only one ton was produced followed by nil production and one ton again in 2011 and 2012 respectively. However, the emerging interest in the culture of dorado could be reflected in the increase of its production in 2013 (19 tons) and in 2014 (20 tons). Being a piscivorous species, a protein-rich diet would be needed for the culture of the species.

 

 

Permanent link to this article: https://fishconsult.org/?p=13341

May 25 2016

Sucker fish (remoras) and turtles in a commensal relationship

Photo credit: Mohamed Hassan (ORCA, Marsa Alam)

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

Sucker fish and turtle (Marsa Alam)

 

 

The Remoras are a group of fish that belong to the family “Echeneidae” and may be called suckerfish. They lack swim bladder; instead they use a sucking disc on the top of their heads to attach themselves to larger marine animals such as sharks, turtles, and manta rays in a model of commensal relationship.

The inserted picture was photographed in a diving site close to Marsa Alam (Red Sea), and shows several remoras specimens riding a sea turtle.

In such symbiotic relationship, remoras remove the parasites (such as copepods) found on the host turtle and clean sloughing epidermal tissue as well as ingesting scraps of food, feces, and small nekton and zooplankton. On the other hand, remoras benefits by using the host as transport and protection, and also feeds on materials dropped by the host.

This symbiotic association between remoras and turtles have been recorded including remora species such as (Echeneis naucrates and Remora remora) and turtle species including the loggerhead sea turtle (Caretta caretta), green sea turtle, (Chelonia mydas), leatherback sea turtle, (Dermochelys coriacea), and hawksbill sea turtle (Eretmochelys imbricata).

 

 

Permanent link to this article: https://fishconsult.org/?p=13337

May 24 2016

Hand signals in recreation diving

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

 

Hand signals in recreation diving

 

 

 

 

Recreational divers do not usually have access to voice communication equipment and instead they use hand signals as the primary method of underwater communication especially whenever they can see each other. These signals are also used in general use as an alternative by professional divers.

The Recreational Scuba Training Council agencies (RSTC) have recognized a standardized set of hand signals intended for universal use. These signals are taught to diving students early in their entry level in the diving courses. These hand signals could be sorted in various categories indicating the followings:

Position: (e.g. ascending, descending, leveling-off at this depth)

Giving instruction: (e.g. turn around, slow down, stop ascending at this depth, hold on to each other)

Warning: (e.g. danger in a specific location/direction, we are ascending too fast)

Emergency: (E.g. I am out of breath, give me air now, I am cold, help me now)

Depending on the hand signal could be by palm alone (up/down), fist with hand, hand motion, thumb extended and pointed, hands indicate rising and falling chest and so on.

The inserted picture shows the “OK” hand-signal as shown to me by Mr. Mattiss (in yellow shirt). The signal is a circle made with thumb and forefinger, extending the remaining fingers.

 

 

Permanent link to this article: https://fishconsult.org/?p=13334

May 16 2016

Red Sea fishes: Emperor Angelfish (Pomacanthus imperator) – Video

Video credit: Patricia Martin Cabrera (United Arab Emirates)

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

 

Introduction: The Emperor Angelfish (Pomacanthus imperator), is a reef-associated marine angelfish and is also called the Imperator Angelfish or Imperial Angelfish. The species is one of the most stunning underwater fish. Their color and graceful shape make them one of the top contenders for any beauty contest. It is possibly the most easily recognized fish in the Red Sea. The species makes a fantastic display whether in the wild or in aquariums.

Description: Emperor Angelfish have deep and slightly elongated with small white mouths. Their flattened shape enables them to wind their way amongst the corals as well as to retain their stability when manoeuvring to pick their food. Adults of emperor angelfish vary in size from as small as 10 cm to up to 40 cm in the wild.

The body of an adult emperor angelfish is vibrantly colored, with yellow and royal blue horizontal lines streaming across their frame. It also has a dark mask-like stripe across its eye area which helps the fish to confuse predators. During mating, the color of male’s mask turns dark blue, almost black, while the female’s mask will turn a bland color.

The pretty angelfish juveniles look totally different from adults. They are dark blue with white and electric blue curved strips (rings) and a honeycomb pattern on the top and bottom fin and tail made up of black spots edged in blue. As a juvenile emperor angelfish grows, its color gradually changes towards that of the adult ending by replacing all juvenile color by the adult color characteristics. It takes about 24 to 30 months for an emperor angelfish to acquire its adult coloring.

It is believed that a juvenile 10 -14 cm in length is the best sized emperor angelfish for adjusting to life in a captive environment such as aquaria. Also, the color changes in captivity may occur earlier than it would in the wild, and the final adult coloration may not be as splendid as that seen in a wild-caught adult emperor angelfish.

Geographic range: The emperor angelfish, Pomacanthus imperator, is native to the Indian and Pacific Oceans, from the Red Sea to Hawaii and the Austral Islands. The species inhabits in a wide geographical range of the world’s oceans from the Red Sea all the way east to Australia’s Great Barrier Reef and the Hawaiian Islands. In recent years, the species have migrated through the Suez Canal and started to colonize areas in the Mediterranean coast. As a result of aquarium release, some populations of the species have been observed outside their natural range such as Japan, Australia and others.

Habitats: Emperor angelfish adults live in or close to reefs at depths ranging from 1-100 m. They can be found hiding in caves in areas of rich coral growth on clear lagoon, seaward, or channel reefs. Adults are more often seen patrolling over the open reef. Juveniles and sub-adults inhabit the mouth of caves and surge channels and often found under ledges or in holes of shallow reef flats.

Feeding habits: Adults of emperor angelfish adults are omnivorous feeding on small invertebrates and plants with a preference to sponges and algae. Their bulky and strong jaws enable them to crush hard-shelled crustaceans and to chew the sponges. The digestive tract of the emperor angelfish coats ingested food with a layer of mucus in order to further protect itself from the sponge’s sharp tiny needle-like silica. However, emperor angelfish juveniles feed on parasites as well as dead skin of larger fish and have been sometimes seen cleaning other fish such as moray eels.

Reproduction: Emperor angelfish adults are so territorial, and they will typically defend their living space with often two females. They may even attack other male emperor angelfish who try to enter their territory. The fish are protogynous which means they are born as females and develop later into males.

Upon mating, the pair will leave the reef to the surface whereas eggs are released by females and fertilized by males where fertilized eggs can be taken away on currents back and dispersed in the reef zones where they hatch and continue their life cycle.

 

 

Permanent link to this article: https://fishconsult.org/?p=13331

May 15 2016

Raceway culture of rainbow trout in Santander, Colombia

Photo credit: Karen Sachica Cepeda (Colombia)

Review: Karen Sachica Cepeda and Abdel Rahman El Gamal (Founder of the website)

Raceway culture of rainbow trout in Colombia

 

 

 

Rainbow trout (Oncorhynchus mykiss) presence in Colombia dates to the 1930s when it was first introduced to the country while first record of farmed trout should up in marginal quantity (3 tons) in 1971. Afterwards, the production of rainbow trout from Colombian aquaculture showed steadily increase in the beginning peaking to about 9,000 tons in 2000. Afterwards, trout aquaculture fluctuated for variety of reasons ending by about 6000 tons in 2014 (FAO).

The inserted picture shows a private race way trout farm which is located in the department of Santander; a north-central Colombian department in the Andes mountains. At this high altitude of 1005-1200 meters above sea level, water temperature ranges around 15 and 17 ºC suits well the culture of rainbow trout.

Most of trout production is sold locally, with a significant quantity that is exported. In spite of the high potential of trout farming in Colombia and the year-round fingerling supplies, the high cost of trout feed is a significant obstacle towards further expansion of trout farming in Colombia.

 

Permanent link to this article: https://fishconsult.org/?p=13329

May 14 2016

Tilapia in El Salvador aquaculture

Photo credit: Martiza Marroquin de Rivas (El Salvador)

Review: Ana Martiza Marroquin and Abdel Rahman El Gamal (Founder of the website)

Tilapia aquaculture in El Salvador

 

 

Tilapia contributed significantly in aquaculture in El Salvador. According to FAO statistics, the first show-up of farmed tilapia occurred in 1984 where 10 tons of Nile tilapia (Oreochromis niloticus) was produced. Afterwards, there has been a significant increase in the production of farmed tilapia peaking up to 4101 tons in 2011 before declining and reaching 832 tons in 2014 whereas tilapia contributed by about 50% of total El Salvador aquaculture over most of the years.

The inserted picture is for a 3000 m2-earthen pond located in Atiocoyo (Department of Liberty). The stocking rate is 5 fingerlings/m2, and fish has been fed manufactured feed with 32% protein. The average in the mentioned system averages about 10 tons/ha per the growing season.  One may notice the bird threads over the ponds to protect fish against fish-eating birds.

 

 

 

Permanent link to this article: https://fishconsult.org/?p=13322

May 13 2016

Cage culture of tilapia in Lake Manure (Vanuatu)

Photo credit: Secretariat of the Pacific Community (SPC)

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

Tilapia cages in Lake Manuro

 

 

 

The inserted photo shows the floating cages of tilapia in Lake Manure (Vanuatu). The original stock of tilapia has been imported from Fiji where subsequent fry importation of red tilapia hybrids came from Thailand in 2007. There are several of commercial operations working in Lake Manure whereas the strain of Genetically Improved Farmed Tilapia (GIFT) and the red tilapia hybrids are cultured in the floating cages.

In the beginning, commercial feed for farmed tilapia was imported from Thailand while the current trend is to depend more on locally manufactured feed made from locally available ingredients such as tusker brewery waste, Vanuatu abattoir meat meal, copra meal, biodiesel plants, flour and rice. It has been claimed that the proper locally manufactured feed formulas proved to be economically feasible.

In general, tilapia is not the desired fish by local fish consumers in Vanuatu who prefer marine fish whereas Asian community is the major consumers of tilapia especially dark fish.

There are damaging cyclones which could seriously threaten the cage farming in the lake. An example of that is the damage caused during the severe Cyclone Pam of 2015 whereas cages were damaged and tons of caged tilapia swept away.

 

 

Permanent link to this article: https://fishconsult.org/?p=13319

May 12 2016

Out-door nursing of cobia using green water in Vietnam

Photo credit: Hai DO Xuan (Vietnam)

Review: Hai DO Xuan and Abdel Rahman El Gamal (Founder of the website)

Out-door nursing of cobia in Vietnam

 

 

 

 

The inserted picture shows the nursing of cobia (Rachycentron canadum) in Vietnam using green water in a semi-intensive rearing method. This method has been developed in 2005 and got adopted in private hatcheries especially those located in Khanh-hoa province. In this method, relatively large out-door tanks supplied with green water are used.

Typically, cobia larvae are reared first in indoor tanks where they are fed on rotifers for the first feeding stage. In out-door nursing phase as shown in the inserted picture is done in out-door ponds (tanks) with abundant natural zooplankton, mainly copepods is adopted as a means of reducing the cost of live food production.

Before the introduction of the larvae, the out-door ponds are filled up with filtered sea water and then fertilized for enhancing the growth of plankton as larvae rely primarily on zooplankton of the appropriate size as they grow. The density of natural food in nursery tanks is constantly monitored and timely supplementation by natural food from outside sources takes place whenever needed. As soon as the cobia larvae reach more than 3 cm in length, they are transferred to tanks again for weaning.

 

 

Permanent link to this article: https://fishconsult.org/?p=13316

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