The photo shows a grow-out tank for tilapia located in Lake Amatitlán, Guatemala. The lake is one of four major lakes in Guatemala. The water supply to tilapia tank is pumped from a depth then pass through a filter of volcanic rocks and geotextile to reduce its ammonia content before reaching fish tank. The biological filtration is of top importance especially when knowing that Lake Amatitlán receives waste water of more than 2 million people that live in the upper part of the basin of the lake. The water hyacinth, Eichornia crassipes which is epidemic to the lake and seen floating in tilapia tank has been introduced to provide food supplements to tilapia in the form of natural food as represented in the macro-invertebrates attached to the roots of this weed. On the other hand, the presence of the weed in tilapia tank reduces the water quality within the grow-out tilapia tank. The lake is furnished with fourteen 5-HP aeration pumps which target to reduce the accumulation of blue green algae in the shoreline of the lake and in the same time to enhance the level of dissolved oxygen within the lake.
This video was taken at Lake Peten Itzá, Guatemala
Introduction: Great Egret, Ardea alba (ex Casmerodius albus) has several common names including common egret, large Egret, White Egret, Large Egret, Great White Egret, and Great American Egret.
Description: Great Egret adults are entirely white bird whose neck and legs are thin and long, with orange-yellow bill, green facial skin and bare blackish legs and feet. The bird has a distinct kink on the upper neck. In the breeding season, the bird develops long delicate plumes on its back which extend about ten centimetres or more beyond the tail. For other times of the year, the bird loses its plumes. Males and females of the Great Egrets are alike. The average weight of an adult bird ranges from 0.7 – 1.5 kg with length 80-104 cm, and 130-170 cm for wingspan.
Distribution and Habitats: The species inhabits all kinds of aquatic systems throughout the world including and depending on locations river margins, lakes shores, marshes, flood-plains, rice-fields, coastal wetlands, aquaculture ponds, and others. In general, the great egrets are distributed across most of the tropical and warmer temperate regions of the world. They migrate from cold weather to winter in North Africa, India, Southeast Asia, South America, Australia, New Zealand or warmer locations within the same country.
Feeding behavior: Great Egrets are often observed wading in shallow water (fresh or salt), hunting and catching their prey that pass by the bird. They mainly feed on fish, but they may also feed on crustaceans, aquatic insects and small vertebrates such as amphibians. In drier habitats, the bird may eat terrestrial insects, lizards, small birds and even mice. Great egrets are diurnal feeders but are most active at dawn and dusk. They may feed solitarily or in small groups of 10-50 individuals. However, they may form flocks of hundreds where food is abundant.
Reproduction: The breeding season varies according to geographical location whereas the birds in the temperate zone breed during spring and summer while in the tropics, they may breed during the rainy season when the food supply is more abundant. Often, the bird breeds in colonies of tens, hundreds or even a thousand pairs. The breeding birds mate in their nests that are constructed from sticks and vegetation and placed above ground or water surface at a height of about 5-12 m in sites that are protected from ground predators. Building of the mating nest is the responsibility of the male. A female egret lays a clutch of eggs that consists of three to four eggs that are incubated by both parents for about 23 to 26 days. Hatched young are fed by regurgitation. They usually leave the nest 30 to 42 days after hatching where they remain dependent on their parents for some time afterwards.
Threats and conservation: The major threat occurred to the bird populations was during the late 1800s and early 1900s, when egret plumes were in great demand for decorating women’s hats and dresses. Knowing that one kilogram of plume is produced by killing 300 birds which indicates the large numbers of the birds that were killed for decorating ladies hats and dresses. Luckily and before reaching close the extinction level of the great egret, the bird lovers, who formed the Audubon Society, were able in 1901 to get legislation enacted to ban the feather trade and hence to stop the bird slaughtering.
The loss and degradation of habitats and the illegal collection of eggs and chicks by local peoples are added the threats which are sporadically practiced in some places.
However, because the bird has an extremely large range, its population size is very large, and since the decrease in its populations –if occurs- is not the rapid, hence the bird population are not neither vulnerable nor threatened in the present.
Review: Abdel Rahman El Gamal (Founder of the website and video channel)
Introduction: The spotted Gar (Lepisosteus oculatus) is a primitive freshwater fish of the family Lepisosteidae, native to North America. Its name Lepisosteus which is Greek means “bony scale”. The spotted gars are among the few fish species with ganoid scales. Females on average are known to live longer than the males whereas male’s average lifespan is 8 years old while the average lifespan of females is 10 years with a maximum lifespan for the species is 18 years old.
Distribution and habitats: The spotted Gar is native to North America and found throughout the rivers and streams that feed into Lake Michigan and Lake Erie, the Mississippi River, and rivers along the northern coast of the Gulf of Mexico from lower Apalachicola River in Florida to Nueces River in Texas, USA.
The species prefers and inhabits clear, quiet water with abundant aquatic vegetation. Even though it is a freshwater species, it occasionally enters brackish waters along the Gulf Coast. The species is tolerant to warm water with low dissolved oxygen levels. The degradation of the spotted gar habitats in some locations had negative impact on the species. Such degradation could be reflected in siltation, dredging, filling and in the decrease or disappearance of aquatic vegetation.
Description: The spotted gar Lepisosteus oculatus are notable for being one of the few extant fish species with ganoid scales. These scales are diamond in shape and are shiny and very tough. They are cylindrical and long which can grow up to 90 cm and weigh of about 3.5 kg with an average length of about 75 cm. They have long, beak mouth with many sharp prominent teeth used to eat their prey of fish and crustaceans. Their upper body is brown to deep olive-green, and yellowish or whitish below. The species is distinguished by the dark spots on the body, head and fins. The spotted gar has a special swim bladder which enables them to gulp air and live in very poorly oxygenated waters.
Feeding habits: The spotted gar is a voracious predator that feeds on various kinds of fishes and crustaceans starting when juveniles feeding on small crustaceans, mosquito larvae and similar organisms before they quickly shift to prey on fish such as sunfish, gizzard shad, topminnow, shrimp and others as the gar matures. The adult spotted gars do not have many natural predators. However, their early life stages such as fingerlings and juveniles could be preyed upon by a number of fish predators, although the eggs of gar are potentially toxic to many species such as the alligator gar.
Reproduction: As soon as temperature rises to the reproduction optimum temperature, the spotted gars spawn in shallow water with low flow and heavy vegetation. As females are larger than males of the same age, a single female could mate and allow more than a male partner at the same time to fertilize her eggs. On the average, a female lays about 12,000 eggs while could reach up to 20,000 adhesive eggs of green color. Eggs which are laid once/year are attached to the leaves of aquatic plants. There is no parental care after the eggs are laid. Depending on water temperature, eggs hatch after 7-14 days into about 2.5 cm long hatchlings which have specialized pads on their upper jaws that allow them to adhere to vegetation. The larvae remain attached to plants until the yolk sac is absorbed and then the pad is no longer there. Growth is rapid in the first year of life reaching a length of about 25 cm after the first year. Males mature in about two to three years while females mature at three to four years.
Doncella, Pseudoplatystoma is a South American catfish that belongs to the family Pimelodidae. The photo shows one of doncella species; Pseudoplatystoma fasciatum, which is known as “tiger shovelnose catfish”. Doncellas typically inhabit major South American rivers, lakes, flooded forests and other freshwater habitats. These fishes are important as a food fish in addition to the demand they enjoy in aquarium trade. These fishes are primarily predators which feed on fish, crustaceans such as crabs or shrimps. Their predation ability is supported by their large and expandable mouth. Their barbels enable the fish to locate their food in muddy waters whereas the visibility is often poor. The induced spawning of this fish would enhance the possibility of their commercial production through aquaculture.
Las fotos muestran la captura de carpa plateada en estanque de tipo rústico y la selección de carpas comunes y herbívoras en estanques rústicos en la Centro Piscicola Tiacaque, (Jocotitlan, Mexico)
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The photos show the earthen ponds in which silver carp, common carp and grass carp are maintained at the Tiacaque piscicola Center, (Jocotitlan, Mexico)
The photo shows a typical artisanal fishery practice in Lake Peten Itzá, Guatemala. The fishing crew involves two fishermen who both cooperate in setting the fishing seine. Afterwards, a fisherman of the two who stays in the fishing boat (not shown in the photo) beats water surface using a pole to scare the fish in the location towards the seine. The seine is pulled to enable the second fisherman to collect captured fish in the shown container.
The two photos show the middlemen with their bicycles or motorbikes at the Tanji landing site. These middlemen buy small quantity of pelagic fish such as bonga, Ethmolosa fimbriata and sardinella for selling it in nearby villages located about 5-15 km from the landing site. During the trip, fish are carried in baskets with ice or are sometimes kept damp using materials such as wet seaweeds or wet jute bags to protect fish from the sun and hence maintain fish freshness and quality.
The photo shows carrying fish from fishing boats at the Tanji landing site to the shore and trucks. Normally men and women are involved in this task. Fish carriers are usually paid 4-5 fish per trip. It is self- employment.
The two photos show landed fish species of the fishing boats at the Tanji landing site. Displayed fish are placed before customers bargaining price. Two of the photos show displayed bonga (Ethmolosa fimbriata) and sardinella while the third photo shows only bonga which dominates fish catch in Gambia and hence is considered the most affordable fish in Gambia.
The photos show fish sun-drying at Tanji landing site, Gambia. Because of the very warm climate in Gambia especially during the period June-October, and the limited ice supply and cold storage facilities at the fish landing site, landed fish may spoil very fast. Therefore, the sun-drying of fish which are in excess to sold fresh fish is considered a practical method for fish preservation. Sun-drying is carried out by women.
One of the photo shows a large quantity of bonga (Ethmolosa Fimbriata ) which undergoes sun-drying whereas the second photo shows the sun-drying of Aris spp. in the front and bonga in the back. Often, dried fish is only used in small quantities to add flavor to stews.
