Source of the photos and some information: The lure of Alaska by Harry A. Franck, 1942.
Publisher: J. B. Lippincott Company
As stated in the reference, two million pelts were taken the first year after the islands were discovered whereas the price/piece fell to $1. By 1834 only 8,000 skins were taken. Accordingly, Russia stopped seal fishing for thirty three years. After the purchase of Alaska by the United States in 1867, the herd of seals was estimated at 4,000,000 keeping in mind that the seal fishery was highly considered when USA purchased Alaska from Russia. Afterwards, and when the expanding fur trade for lady fashion and hence the pelagic sealing was found seriously threatening the seals population in Alaska, an international treaty to stop pelagic sealing was signed on December 15, 1911 between England (that is, Canada), Russia, Japan and the United States, and has since been renewed. The two photos show the fur cleaning by an Alaskan woman and fur display in a fashion shop in Alaska during early 1940s or before.
Source: The lure of Alaska – Author: Harry A. Franck
Publisher: J. B. Lippincott Company Year: 1942
The fish wheel shown in the photo is a sort of fish trap that was common in Alaska during 1940s and before. These wheels work all night as well as all day long. The wheels are anchored to the shore and turned by the current, they lift a broad scoop high twice each revolution and run their fish, if any, off to the bank.
The majority of stakeholders (official and private) showed negative opinions against fish trapping which led to bills before the Congress stating that the elimination of all fish traps in Alaska would require five years.
The caption of the photo reads: the current-operated fish wheel is the most persistent work of man along the Yukon
Les photos montrent le rôle des femmes dans l’ostréiculture au Sénégal. Les femmes qui s’investissent dans cette activité.
Elles sont entrain de confectionner des guirlandes avec les d’huitres déjà consommées.
Elles sont au bord de la route, sur la partie descendante, cette partie permet de relier les différentes guirlandes en un seul collecteur guirlande. Et en même temps cela permet de voir si les guirlandes ont été bien faites et bien relier.
La seconde montre la photo les collecteurs confectionnés sont attachés sur des bambous en vue du captage de naissains.
La troisième photo montre les femmes sont entrain de faire la récolte des huitres sur les racines des gisements naturels des mangroves.
The video was taken at the freshwater aquarium, Sea World, San Diego, USA.
General: The Bala shark, Balantiocheilos melanopterus, is not a real shark this is also known as the tricolor shark, silver shark, or shark minnow, and silver bala is a cyprinid and type of minnow freshwater fish species. The nickname “shark” has been given to this bony fish because of their torpedo shaped bodies and long fins; “bala” is an abbreviation of the scientific name. Bala shark can grow up to 33-40 cm with larger males than females of the same age. Therefore, young bala sharks could be kept in most aquariums; otherwise, larger aquariums will be required. The life span of bala shark ranges from 8-10 years.
This species performs best in small groups of 3 or more. They are considered peaceful especially when they are schooling with other bala sharks. However, they may turn slightly aggressive, nervous and/or stressed if kept alone or in a small tank. Bala sharks are very energetic fish and are known to jump which means a tight fitting lid is highly recommended.
Appearance: These fish have a shiny silver body and with yellow and black dorsal and caudal fins. They have big eyes to find and catch their prey. Their mouth is somewhat downfacing and without barbles.
Distribution and habitats: Wild Bala shark is found in Asia; in the Mekong and Chao Phraya River basins, around the Malay Peninsula, Borneo and Sumatra. They are found in midwater depths of large and medium-sized rivers, streams and lakes. The existence of aquatic plants is of particular importance for providing shelters and hiding spots to bala shark.
Feeding habits: Being omnivores, Bala shark feeds in nature on phytoplankton, but mostly on rotifers, insects, insect larvae and tiny crustaceans. Full-grown Bala shark has been known to eat very small fish such as neon tetras and guppies. It may worth mentioning that the proper diet will intensify the colors in the fins.
In aquariums, bala shark will accept variety of food including flake foods, freeze-dried bloodworms and tubifex, as well as plant-based foods. It is a scavenger and will search for food on the bottom of the tank.
Reproduction: Bala sharks are egg scatters and uses external fertilization. In nature, it is known that sexually mature Bala sharks of 10-15 cm long migrate to special breeding ground to be engaged in mass spawning whereas water current is necessary to appropriately spread the sperm of males. Professional efforts have been successful in breeding “Bala sharks” in aquariums whereas hormones have been used to induce the spawning. Bala sharks do not guard their eggs or fry.
Threats: The deforestation of river and stream habitats of Bala shark along with the over collection as demanded by the aquarium trade led to the scarcity or even extinction of the species in many river basins of its native range and consequently listing the species by the IUCN Red List as an endangered. The problem becomes even more obvious when considering their short life.
Conservation: The successful breeding of Bala sharks in captivity is considered a key measure towards the conservation of the species. It is claimed that most of the Bala sharks in pet stores or exported especially from Indonesia and Thailand are captive bred.
References: Aquatic Community,Liveaquaria.com, Aqua Ultraviolet, PETCO, Fish Channel, Wikipedia
The video was taken in freshwater aquarium (Sea World), San Diego, California, USA
Review: Abdel Rahman El Gamal (Founder of the website and video channel)
Introduction and description: Silver dollar is a common name for a fish species that belongs to the Characidae family; Dollar d’argent is another common name. These fishes have metallic color with deep and compressed body. During growth, the depth of the body becomes comparatively less than its length. This growth phenomenon is called negative allometry. While the juveniles are coin-sized, adults can grow to about 20.0 cm TL. The species is almost entirely covered with minute scales. Maximum lifespan of the species may exceed 10 years. Silver dollars are popular for aquarium trade.
Habitats: The native habitats of silver dollars are tropical climates. They prefer soft and slightly acid water with a pH below 7.0 and water hardness of up to 15 dGH. The optimum temperature for the well-being of silver dollars ranges from 24 to 28 °C. They spend most of their time in the mid- to upper-level of the water.
Feeding habits: Silver dollars are herbivore feeding on plant materials while they may feed also on worms and small insects and even fish which can fit in their mouth.
Reproduction: The species prefers to spawn in soft and warm water with dim lightening. When a pair adult spawns, the female lays up to 2000 eggs. Fertilized eggs fall to the bottom of the tank whereas hatching takes place in about three days. After about a week, the free swimming fry will be capable to feed on appropriate food including –in case of aquariums- commercially prepared food, finely crushed spirulina, or freshly hatched brine shrimp. There is no known parental care for this species.
Aggressiveness: The silver dollar is a peaceful schooling fish that swims in schools of 5-7 individuals. They could be classified as semi-aggressive. The aggressiveness could be only noticed when the fish are kept with smaller fish that they can fit in their mouth.
References: Wikipedia, Aquarium poster, Nature Pet Centers
Description: Abdel Rahman El Gamal and Ahmad Yousef alqarain (Jordan)
Rainbow trout (Oncorhynchus mykiss) was first introduced from USA into Korea in 1965, whereas its farming started in Pyeongchang due to its cold, and high quality waters whether from underground or natural waters in mountain areas. Korean trout production from aquaculture has steadily increased reaching about 3,000 tons in 2011. Most of farmed trout is consumed as sashimi at trout farm restaurants as represented by this intensive trout farm along with the restaurant.
The photo shows the fencing of fish ponds using nets and bamboo sticks. The purpose is to prevent the entry of unwanted animals especially snakes and birds.
The male hormone (17 alpha- methyl testosterone) is dissolved in alcohol at the dose of 60 milligram per 500 ml of alcohol and then after the alcohol containing hormone is to be mixed with one kg of fry feed. Treated feed is dried in shade and could be stored in freezer until used. This one kg of treated feed will be sufficient to sex reverse 5000 fry of Nile tilapia, Oreochromis niloticus for a 3-week treatment. One of the photos shows the mixing of hormone with feed while the second photo shows the shade drying of treated feed. One may notice that the person who handles the treated feed through mixing the hormone or spreading the treated feed is using gloves for health protection.
This 2-min video demonstrates the dissecting of a specimen of African catfish, Clarias gariepinus which was completed with the identification of main organs (liver, spleen, stomach, intestine, spleen, and bladder). The testes identified in the dissected match the male morphology of the specimen. On the dissecting plate there is a tilapia specimen which was already dissected.
