Jun 11 2014

Hawksbill sea turtle, Eretmochelys imbricata (Description – feeding – reproduction) – Video

By aelgamal in Aquarium fishes, English, Gallery, Videos
June 11, 2014

Credit for the video: Glenda Vélez Calabria (Colombia)

Review: Abdel Rahman El Gamal (Site and video channel founder)

This video was filmed at mundo marino and te mostramos lo que pasa en el fondo, Colombia

Introduction: The hawksbill sea turtle (Eretmochelys imbricata) which belongs to the family Cheloniidae has a worldwide distribution and occur in tropical and subtropical waters around the world. The species is named tortue imbriquée (French), and tortuga de carey (Spanish).

Description: The hawksbill has an elongated head with a sharp and curved beak-like mouth. Their top shell (carapace) is dark to golden brown. Their flipper-like arms are adapted for swimming in the open ocean. The species is distinguished by its saw-like appearance of its shell margins. Hawksbills have two pairs of prefrontal scales on the top of the head and each of the flippers usually has two claws. The weight of average adult ranges from 45-70 kg with an average length from 65 to 90 cm.

Feeding: Even though the hawksbills are omnivorous, sea sponges are its principal food where in some habitats, sponges constitute 70–95% of their diets. In addition to the sponges, the hawksbills may also feed on algae, invertebrates, comb jellies and other jellyfish, and sea anemones. Hawksbills are resistant to eating some of toxic sponges. The shape of the mouth allows the hawksbill turtle to reach into holes and crevices of coral reefs to find sponges and other invertebrates.

Reproduction and life history: Sexual maturity of Hawksbills is influenced by biotic and abiotic cues including individual genetics, foraging quantity and quality and/or population density, and hence the age at sexual maturation and nesting varies from as low as 10 years to as high as 30 years. Male hawksbills mature when they are about 70 cm long while females mature at about 80 cm. Even though hawksbills are solitary for most of their lives; they meet only to mate.

Hawksbills mate every 2-3 years. After mating and during the night, female turtles reach the nesting beach where she was born. The female clears an area of debris and with the help of her flippers she digs a nesting hole in which she lays an egg clutch of about 130-140 eggs and covers them with sand. Generally, a female hawksbill lays 3-5 nests per nesting season. Afterwards, the female returns to the sea.

After an incubation period of about two months, eggs –during night- hatch into baby turtles of about 15-20 g weight and 25-40 mm long. The newly hatched turtles crawl into the sea and then entering the pelagic phase that lasts for about 1 to 4 years. When juveniles reach around 35 cm, they switch from a pelagic lifestyle to the benthic phase and live on coral reefs until their sexual maturation.

Note: If you are interested to know about the threats to the Hawksbill sea turtle and conservation measures, you are kindly requested to visit this post on the site.

average weight and length, clutch size, Colombia, Eretmochelys imbricata, feeding habits, Hawksbill sea turtle, incubation, life phases, mundo marino, nesting, sexual maturation, tortue imbriquée, tortuga de carey, toxic sponges

Permanent link to this article: https://fishconsult.org/?p=10968

Jun 09 2014

Red Sea fishes – Steinitz Goby, Amblyeleotris steinitzi (Distribution – description – feeding)

By aelgamal in Aquaculture, Gallery, Photos
June 9, 2014

The Steinitz Goby, Amblyeleotris steinitzi is also known as Steinitz’ Prawn Goby, that is a small size species which belongs to the family Gobiidae. It is found from the shallow parts of the Red Sea through the Indian Ocean to the western Pacific Ocean. The species inhabits sandy bottoms on seaward reefs and is found at moderate depth of about 20 meters. The Steinitz Goby is hardy and highly disease resistant species.

Steinitz’ goby has an elongated body with protuberant eyes. Its body is white with about five broad, transverse, reddish-brown bands with some fine pale yellow lines between them.

The species lives in association with analpheid shrimp where both animals share a large burrow system in which the shrimp does all the excavation in a sandy or silty area of the seabed. The shrimp being a detritus feeder that constantly disturbs the sediments and hence exposes organisms which the Steinitz’ goby feeds upon including mainly small invertebrates and other edible matters.

In aquariums, the Steinitz’ goby requires a meaty diet and could be fed live, fresh and frozen brine shrimp, mysis, finely chopped fish or shrimp flesh.

Amblyeleotris steinitzi, aquarium feeding, association with analpheid shrimp, feeding behavior, Red sea, Steinitz Goby, Steinitz' Prawn Goby

Permanent link to this article: https://fishconsult.org/?p=10964

Jun 09 2014

Fishing canoes at the Kpong landing site, Manya Krobo (Ghana)

By aelgamal in Aquaculture, Gallery, Photos
June 9, 2014

Credit: Patrick Appenteng (Ghana)

The photo shows two man-paddle canoes of length 3-5m long at the Kpong landing site in the Lower Manya Krobo District of the Eastern Region of Ghana.

Dominating some section of the Volta Lake is in the area is massive aquatic weed growth. These have over the past few decades posed a lot of environmental concerns both to the fisher folks who live along the periphery of the catchment as well as other stake holders in the fishery industry.

Although, occasionally these water weeds are removed to be used as compost by some commercial farms in the area, the nuisance caused by these water weeds still lingers on.

aquatic weed, canoes, compost, environmental concerns, fishing boats, ghana, Kpong, Lake Volta, landing site, Manya Krobo, Volta Lake

Permanent link to this article: https://fishconsult.org/?p=10960

Jun 09 2014

Artisanal fishing boats at “Ambowe”, landing site, Libreville, Gabon

By aelgamal in English, Fisheries, Gallery, Photos
June 9, 2014

Credit: Chantal Sengue Ngoulou and Jean Michel Megne Me Zeng (Gabon)

The photo shows the landing of artisanal fishing boats at the landing of Ambowe north of Libreville, Gabon. There are twenty docks and around Libreville. These canoes have an average length that ranges between 4-8 meters. Much of these canoes are motorized. The white objectives shown on the boats are old freezers which are used by fishermen to keep their fish while fishing. Also, fishermen secure their requirements of ice upon starting their fishing trip. Depending on the size of the boat, the fishing crew could be 2 or 3 per boat.

Ambowe, artisanal fishery, fishing boats, Gabon, landing site, Libreville

Permanent link to this article: https://fishconsult.org/?p=10954

Jun 09 2014

تفريخ البلطى النيلى وإنتاج الذكور فى أحد المفرخات فى الفلبين

By aelgamal in Aquaculture, Gallery, Photos
June 9, 2014

Credit: Ahmed Zaki (Egypt)

هذة الصورتم أخذها فى أحد مفرخات البلطى فى الفلبين وحيث يتم فى هذا المفرخ تخزين أمهات البلطى النيلى بمعدل 3 إنات لكل ذكر. يتم تجميع الزريعة السابحة من على أجناب الحوض وذلك لنقلها إلى المعاملة بالهورمون الذكرى 17α-Methyltestosterone بهدف إنتاج زريعة بلطى نيلى جميعها ذكور. يصل معدل تجميع الزريعة فى هذا المفرخ إلى ما يزيد عن عشر مرات يوميا خاصة وأن زريعة البلطى حديثة الفقس تسبح فى مجموعات على أجناب الحوض. يعود زيادة عدد تجميع الزريعة خشية تمكن بعضها إذا ما ازداد حجمها أن تنزح إلى وسط الحوض وتتحول إصباعيات يمكنها افتراس صغار البلطى من التفريخات التالية.

يتم تجميع الزريعة من هذه الأحواض على مدى العام وإذا ما لوحظ قلة أعداد الزريعة المجمعة، يتم تجميع الأمهات وفصل الجنسين قبل نقلها للاستراحة إلى أحواض أخرى على أن تستبدل بأمهات جديدة يتم تسكينها فى حوض التفريخ

17α-methyltestosterone, broodstock replacement, fry collection, hatchery, Nile tilapia, Oreochromis niloticus, Philippines, sex reversal, tilapia, البلطى النيلى، تحويل الجنس، إنتاج ذكور البلطى، المعاملة بالهورمون

Permanent link to this article: https://fishconsult.org/?p=10951

Jun 09 2014

Spawning and sex reversal of Nile tilapia fry in a Pilipino hatchery

By aelgamal in Aquaculture, Gallery, Photos
June 9, 2014

Credit: Ahmed Zaki (Egypt)

The photos were taken in a tilapia hatchery in the Philippine. In this hatchery the broodstock of Nile tilapia, Oreochromis niloticus at the ratio of 3 females: 1 male. The swim-up tilapia fry are collected along the pond sides using a long-handled, narrow-mesh deep nets. The collected fry are transferred into special tanks to complete the sex reversal process using the male hormone (17α-Methyltestosterone). Because the newly hatched fry moves along the sides of the spawning ponds in schools and so the daily collections are done for more than ten times per day. This practice target to collect all of the fry because left-over fry when they grow in the spawning ponds will predate on newly hatched tilapia of new generations.

The spawning of Nile tilapia in the Philippines takes place all-year round. When the collected fry are on the decline, the water is lowered and the broodstock are transferred into recovery ponds and replaced by newer spawners in order to maintain a high level of spawning.

17α-methyltestosterone, broodstock replacement, fry collection, hatchery, Nile tilapia, Oreochromis niloticus, Philippines, sex reversal, tilapia

Permanent link to this article: https://fishconsult.org/?p=10947

Jun 05 2014

Small-scale aquaculture in rural development (updated 2014 version)

By aelgamal in A.A. EL GAMAL, English, Lectures
June 5, 2014

This lecture was delivered in the Fish Culture Development training course which is annually organized by the Egyptian International Centre for Agriculture (EICA). The lecture addressed the features of rural communities as an introduction to rural aquaculture. The appropriate farming system had to discuss the farming systems as well as the species. Models of rural aquaculture are discussed including rice-fish culture, cage aquaculture, duck-fish and poultry-fish culture. The key issues related to the promotion of rural aquaculture at national levels have been discussed including the role of extension agents and the importance of the participatory approach keeping in mind the adoption curve. The lecture brought in case studies in which subsidies as well as related issues are discussed. The social dimension has been highlighted throughout the lecture.

http://fishconsult.org/wp-content/uploads/2014/06/Small-scale-aquaculture-in-Rural-Development-EICA-Updated-2014-version.pdf

adoption curve, cages, duck-fish, golden apple snail, participatory approach, poultry-fish, rice-fish culture, rural aquaculture, Rural communities, simplicity concept, subsidies, top-bottom approach

Permanent link to this article: https://fishconsult.org/?p=10943

Jun 05 2014

Use of air injectors in a marine fish farm in Egypt – Video

By aelgamal in A.A. EL GAMAL, Aquaculture, English, Farmed species, Gallery, Gilthead seabream and European seabass, Machinery used in fish farms, Videos
June 5, 2014

This video was filmed in a large marine fish farm in Egypt. during May 2014. The key species in the farm are gilthead seabream (Sparus aurata), European seabass (Dicentrachus labrax) and meagre (Argyrosomus regius). The relationship between the capacity of the air injector and fish biomass has been established by the farm as a 3-hp air injector is sufficient to maintain a fish biomass of 4 tons of fish. A high rate of water exchange is performed in the farm that targets a production of 7 tons of fish/acre (16 tons/hectar).