Cage farming of bluefin tuna (Thunnus thynnus) in Turkey

Credit: Huseyn Ek (Akuakare, Turkey)

The photos are taken in some tuna farms in Turkey whereas the bluefin tuna (Thunnus thynnus) is the species of choice. These cage farms are located in Alanya and Lzmir in Turkey. Tunas required for farming are collected from the nature and stocked in these cage in which they are grown for 6-8 months before harvesting upon reaching weights that could range from 150-600 kg/piece.  The harvested biomass could range from 200 – 400 tons/cage having in consideration that the shown cages are of 66 meters in diameter with a circumference of 207 meters. Fish in cages are fed on big sardines, mackerels and other low market value fishes. These cages are manufactured to resist the worst open sea conditions while having sufficient elasticity and durability in such weather.

Tuna farming in Turkey (01) Tuna farming in Turkey (02)

 

Permanent link to this article: https://fishconsult.org/?p=10699

Constructing a simple net grader for tilapia or catfish fry in Benin

Photo credit: Ismael Radwan (Egypt)

Description: Abdel Rahman El Gamal

The two photos show a simple 2-unit fish grader made of a metal frame and netting materials which are locally available in Benin. As expected, the inner unit which is smaller and shallower should be made of larger-mesh net to enable larger size fry to be retained while allowing smaller size fish to pass through and got retained by the lower unit. The mesh sizes will determine the targeted fish sizes. For example, if the grading is a part of sex reversal of tilapia, the mesh size of the inner unit should retain tilapia fry larger than 11-mm total length and hence the passing through fry are should be sexually undifferentiated and would be expected to respond successfully to the sex-reversal hormonal treatment (This is conditioned to national regulations in regard to hormonal sex reversal).

If this type of graders are used for management purposes to produce batches of fish of homogeneous sizes whether for feeding, marketing or to address a predation phenomenon such as in African catfish, the mesh sizes for both unites could vary according the size of fish being graded.

This two-unit grader can grade three size groups when the bottom unit allows the smaller size to pass through into the holding facility in which the grading takes place.

Benin - fish grader (01) Benin - fish grader (02)

 

 

 

Permanent link to this article: https://fishconsult.org/?p=10693

Round Stingray, Urobatis sp. (Description, feeding, reproduction, threats to human)

Photo credit: Glenda Vélez Calabria (Colombia)      Review: Abdel Rahman El Gamal

This photo was taken in mundo marino and te mostramos lo que pasa en el fondo, Colombia

Introduction: The round stingrays are which belong to the family “Urolophidae” and the genus “Urobatis” are cartilaginous fishes. It is also known as raya redonda (in Spanish). Due to its small size and large tail spine, the round stingray lacks commercial value and even considered a nuisance when they become entangled in the nets of shrimp trawlers are hence they are usually discarded.

Description: The round stingrays are distinguished by the presence of massive pectoral fins which join the boy to form a disc. The enlarged pectoral fins made it possible for these rays to swim by means of undulating or oscillating their fins. These rays have no anal fin. Instead, they have a whip-like tail with a long, thick, serrated stinging spine and with no caudal fin. The width of fin disc in females is larger compared to that in males with a maximum of about 30 cm to 25 cm respectively.

The eyes of the round sting rays are located on the upper side of the head while the nostrils, mouth, and gill slits are on the ventral side of the flattened body.

Distribution and habitat: This species inhabits tropical to warm-temperate waters at depths which could range from their common depth of less than 15 m up to much greater depths. While they prefer the soft-bottomed habitats (e.g. mud or sand), they also occur around rocky reefs. The species is endemic to the eastern North Pacific Ocean.

Feeding habits: The round stingray juveniles feed mostly on benthic invertebrates such as worms and small benthic crabs. As they grow, they feed on bivalve molluscs and polychaete worms. They use their pectoral disc and mouth in digging the pits to uncover buried preys. On the other hand, the round stingrays could be preyed upon by the elephant seal, the black sea bass and sharks.

Reproduction: The round stingray is ovoviviparous, whereas a female bears on the average 1-6 young that measure 6-8 cm at birth after a 3-months gestation period. The female is equipped by organs behind her eyes through which she emits a localized positive electric field, which serves to attract males towards copulation. 

Threats to humans: Numerous incidences of bathers who got stung by round stingrays when they accidentally step on the fish. The wound caused by its venomous spine can be quite painful, but is not fatal. The annual replacement of the stinging spine reduced the effectiveness of a program that targeted the clipping of the spines of the large stingray populations.

Round stingray

 

Permanent link to this article: https://fishconsult.org/?p=10688

Display of smoked stingray in an Indonesian fish market

Photo credit: Anna Jamil (Indonesia)

Description: Abdel Rahman El Gamal

The photo which was taken in a traditional fish market located in Pamulang, Banten Province. The photo shows the display of smoked stingray. Stingray fish is one of the most acceptable and popular fish species to be smoked in Indonesia especially processed traditionally method. There are several dishes made from smoked stingrays which could be mixed with other food ingredients such as tofu, and eggplant with coconut sauce.

Smoked stingrays in Indonesia

 

 

 

Permanent link to this article: https://fishconsult.org/?p=10682

Blowfish (Biology — poisoning — utilization)

Credit of the photo: Glenda Vélez Calabria (Colombia) Description: Abdel Rahman El Gamal (Founder of the site)

This photo was taken in mundo marino and te mostramos lo que pasa en el fondo, Colombia 

Introduction: The blowfish belongs to the “Tetraodontidae” family which includes more than 120 species that occur worldwide. Most of blow fish species are found in tropical and subtropical ocean waters. Although this group is primarily marine and estuarine fish, some fish species live in brackish and even freshwater. Other common names include puffers, swellfish, globefish and toadfish. They are typically small to medium in size, although a few species can reach lengths of greater than 100 centimetres. Blow fish live from 5 to 10 years.

Description and distinctive characteristics: As the family name tells, the species is characterized by four “tetra” teeth “dontinidae” which fused together into a prominent beak. The species have hidden spines which become only visible when fish are puffed up. The eyes of blowfish move independently from one another.

Distribution and habitats: The majority of blowfish lives in salt water and prefers warm, tropical seas or estuaries. Some species live in freshwater environments while a few others are suitable for aquariums. While the group is most diverse in the tropics, they are not common in the temperate zone and completely absent from cold waters. Food habits: Blowfish feed on algae, crustaceans, mollusks and red worms. The four large teeth with the hard peak are used for crushing the shells of crustaceans and mollusks.

Reproduction: The spawning of puffers occurs after males slowly push females to the water surface or join females already present. The eggs are spherical and buoyant. Hatching occurs into tiny fry after about four days. As the blowfish fry mature, they move closer to the shore and become adults.

Natural defenses: The puffer’s distinctive natural defenses help make up for the slow swimming of the fish. The ability of the fish for a sudden evasive as well as the excellent eyesight allows fish to maneuver and avoid predators. The pointed spines after fish inflation with water resulted that fish will turn inedible to possible predators.

Poisoning: Puffer fish are considered the second most poisonous vertebrates in the world (after the golden poison frog). The first recorded instance of blowfish poisoning was from Captain James Cook’s 1774 excursion to New Caledonia. It is believed that the toxicity of tetrodotoxin to humans is hundred times more than cyanide with no known cure.

Puffer poisoning usually results from the consumption of incorrectly prepared puffer soup, or from raw meat (sashimi fugu). Because the levels of toxins vary from a specimen to another and from a season to season as well as from a location to another, the effects that results from the consumption of puffers vary from light-headedness up to death passing by numbness of the lips, dizziness, vomiting, rapid heart rate, decreased blood pressure, and muscle paralysis. It may worth noting that this neurotoxin is found primarily in the liver and ovaries, although smaller amounts and traces exist in the intestines and skin, as well in muscle. Interestingly, the poisoning does not always have a lethal effect on large predators, such as sharks, and lizard fish.

Utilization: Regardless the poisoning risk associated with the consumption of blowfish, this does not deter them from being considered a delicacy and expensive sushi dish in Korea and Japan (bok; sashimi fugu). However, only licensed and trained chefs should be the authorized ones to prepare these dishes. However, for various reasons, the poisoning continues to threat the like of people who are not aware about the whole thing or who could not carry out safe preparation for the fish.

References: National geography, Wikipedia

Blowfish

Permanent link to this article: https://fishconsult.org/?p=10678

Culture of Indian white shrimp, Penaeus indicus in Egypt: Pond preparation prior to stocking (1 out of 6) – in Arabic

Credit: Sherif Sadek and Mohamed Sabry (ACO), Egypt

Reporting: Abdel Rahman El Gamal

 

توضح الصور عملية رئيسية يتم إجراؤها أثناء تجهيز حوض ترابى قبل تخزينه بيوافع الجمبرى الهندى الأبيض Penaeus indicus.  فى هذه المرحلة من إعداد الحوض، يتم استخدام محلول الكلور بالتركيز المناسب حيث يتم استخدام المحلول فى تجمعات المياه وفى أية مناطق يحتمل وجود كائنات غريبة أو غير مرغوبة بها أو تلك التى بقيت من زراعة سابقة. ومن أمثلة تلك الكائنات كما توضحها إحدى الصور الكابوريا والتى تم تجميعها بعد المعاملة بمحلول الكلور وهذه الكائنات تمثل تهديدا خطيرا للجمبرى إن ظلت بالحوض. هذه المزرعة موضوع الصور تقع بمنطقة المثلث بمحاذاة طريق بورسعيد – دمياط.

Shrimp pond preparation (01) chlorine Shrimp pond preparation (02) chlorine Shrimp pond preparation (03) crabs

 

 

 

 

Permanent link to this article: https://fishconsult.org/?p=10672

Culture of Indian white shrimp in Egypt: Nursing of post larvae (2 out of 6)- in Arabic

Credit: Sherif Sadek and Mohamed Sabry (ACO) – Egypt

Reporting: Abdel Rahman El Gamal

عادة ما يكون الطور اليرقى 15 هو الذى يتم شراؤه من مفرخات الجمبرى حيث يتم تحضينها فى حضانات المزارع لفترة حوالى شهر قبل تخزين اليوافع بأحواض التربية وذلك كما هو الحال فى المزرعة التى تمثلها الصور الحالية والتى تكون فيها الحضانات على هيئة تجهيزات مبطنة بالبوليثيلين. خلال فترة الحضانة يتم تغذية الجمبرى بغذاء متخصص بمستوى بروتينى ثابت (34%) ومحتوى دهون (15%) طوال فترة التحضين وتمتد بعدها للتربية وإن اختلف حجم حبيبات الغذاء الذى يتراوح فى البداية من 6, 0 ملليمتر متزايدا طوال فترة النمو حيث ينتهى بحبيبات ذات قطر قدرها 2 ملليمتر وذلك فى نهاية فترة التحضين وعندها تصل الجمبرى إلى يوافع بمتوسط وزن حوالى 2, 1 – 5, 1 ملليمتر والتى يتم حصادها من الحضانات وتخزينها فى أحواض الترابية. تقدر معدل البقاء أثناء التحضين بحوالى 75%.   

Shrimp culture (Nursed shrimp) 01 Shrimp culture (Nursed shrimp) 02 Shrimp culture (Nursed shrimp) 03

 

Permanent link to this article: https://fishconsult.org/?p=10666

Threats and conservation efforts of the Mekong Giant Catfish, Pangasianodon gigas in Thailand

Photo credit: Wanna Thawinwan (Thailand)

Review: Abdel Rahman El Gamal

General: The Mekong giant catfish, Pangasianodon gigas is the world’s largest freshwater fish which is native to the Mekong River basin in Southeast Asia. It is also called giant Mekong catfish and also “Pla Beuk” in the Thai language. There are records about specimens of the species with lengths of up to 3 m and a weight of about 300 kg. In regard to their life-span, the species is among the long lived ones and can live more than 60 years. The species which belongs to the family Pangasiidae is the most threatened species in the Mekong River and has been considered critically endangered as listed in the IUCN Red List.

Threats and conservation: The decline of the populations of the Mekong giant catfish is an example that of the drastic decline of fish population where there stocks dropped by about 80-90% over the past century. Overfishing, destruction of spawning and breeding grounds and damming contributed to the series declines of the species.

Because of the importance of this species, national and international efforts have been paid to save the species. These efforts included the banning of the fishery and trade of the species, research and raising awareness, and release of captive-bred adult specimens. Also, there is a captive breeding program which is carried out under the responsibility of the Thai Department of Fisheries. The photos are taken during a recent work on the artificial reproduction of the Mekong giant catfish.

References: National Geography, Wikipedia, RelivEarth, WWF Global, Fish Thailand

Mekong giant catfish 01 Mekong giant catfish 02 Mekong giant catfish 03

 

 

 

Permanent link to this article: https://fishconsult.org/?p=10658

Hand-feeding of African catfish broodstock in Benin

Video credit: Ismael Radwan (Egypt)
Review: Abdel Rahman El Gamal

The video shows how peacefully the broodstock of African catfish, Clarias gariepinus repeatedly pick the feed pellets from the operator,s hand. We notice the tank has a net coverage to keep the catfish from jumping out of the tank.

Permanent link to this article: https://fishconsult.org/?p=10656

Culture of Indian white shrimp in Egypt – Stocking in grow-out ponds (3 out of 6)- in Arabic

Credit for the photos and information providing: Sherif Sadek and Mohamed Sabry (ACO)- Egypt

Reporting: Abdel Rahman El Gamal

 

توضح الصورتان تخزين يوافع الجمبرى بمتوسط وزن حوالى الجرام والتى سبق تحضينها فى أحواض التربية التى سبق تجهيزها وخاصة التخلص من الأسماك غير المرغوبة وكذلك الكابوريا. من الأهمية بمكان وضع تجهيزات سلك على نظامى الرى والصرف تلافيا لدخول أى كائنات غير مرغوبة. فى مزرعة الجمبرى الحالية، ينم تخزين يوافع الجمبرى بمعدل 6 يوافع جمبرى للمتر المربع. وكما هو واضح من إحدى الصور، يتم إجراء أقلمة الجمبرى لمياه الحوض. هناك من مزارع الجمبرى ما تفتقد إلى إمكانيات تحضينية وفى هذه الحالة يتم تخزين أحواض الإنتاج مباشرة باليرقات المتقدمة التى تحصل عليها من المفرخ  ويتم ذلك بمعدلات تخزينية أعلى لتعويض ما هو متوقع من معدلات فقد عالية.

تتبنى المزرعة الحالية نظام الاستزراع المختلط والذى فيه يتم تخزين 2500 إصباعية للفدان من أحد أنواع البورى (السهلية) مختلطا مع الجمبرى وذلك بمتوسط جرامان للوحدة

Culture of Indian white shrimp in Egypt (stocking in the grow out ponds) 01

Culture of Indian white shrimp in Egypt (stocking in the grow out ponds) 02

 

 

Permanent link to this article: https://fishconsult.org/?p=10653

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