White Gold of Bangladesh, Bagda or Prawn Fish

Black Prawn is one of export oriented product in Bangladesh. These exported in many countries of this world specifically in Europe, America and some Asian country. There was a time it was one of the top most exported product in Bangladesh. These are mostly farmed in our Khulna Division, Barisal Division, Chittagong Division and Satkhira District. Most of the people there earn their livelihood by farming these. Our countries weather is very favorable for farming these. It is very tasty and nutritious fish. Lot of people love to eat these in their lunch or dinner as curry. These are mainly farmed in salty water near river and sea flow by barricade. So these can be farmed until we have these salty water river and sea flow.

A freshwater prawn farm is an aquaculture business designed to raise and produce freshwater prawns or shrimp1 for human consumption. Freshwater prawn farming shares many characteristics with and many of the same problems as, marine shrimp farming. Unique problems are introduced by the developmental life cycle of the main species (the giant river prawn, Macrobrachium rosenbergii).

Lifecycle of White Gold or Prawn Fish:

Prawns can live for two to three years. They mature at about six to eight months of age, and spawning occurs in offshore waters. King prawns tend to spawn throughout the year while tiger prawns mainly spawn during spring and summer. A single prawn can spawn more than once in any one year. The female releases hundreds of thousands of eggs.

Fertilised eggs hatch within 24 hours and larvae spend time floating in the water, developing through a number of stages, as they drift shoreward to shallow, hypersaline (highly salty) waters. When they reach these shallow waters, they’re called ‘postlarvae’, and are ready to settle on the bottom, where they develop into juvenile prawns.

They remain in the nursery areas for up to six months before they reach a size (near their size at maturity) when physiological changes demand they move back to oceanic waters to mate and spawn, completing their lifecycle. 

During this migration, the prawns enter the trawling grounds (mainly sandy or muddy-bottomed areas) where they can first be caught commercially. These areas are generally offshore, in waters 10 to 30 m deep. This migration takes place in summer and autumn each year and is known in the industry as ‘recruitment’.

Diet of Prawn or White Gold or Bagda Fish:

Prawns eat plant material, decaying organic matter, micro-organisms, small shellfish and worms. King prawns are sensitive to light so they bury themselves during the day and feed actively at night. Tiger prawns tend to be active day and night.

Prawn of World:

Prawn is a common name for large swimming crustaceans, particularly in Britain and Commonwealth nations, and are also called shrimp. Significant commercial species valued for food tend to be large, and thus tend to be called prawns. Shrimp that fall in this category often belong to the suborder Dendrobranchiata. The term is used less frequently in North America, and typically for freshwater shrimp.

In the United Kingdom prawn is more common on menus than shrimp, while the opposite is the case in the United States. The term prawn also loosely describes any large shrimp, especially those that come 15 (or fewer) to the pound (such as king prawns or jumbo shrimp).

Bangladeshi Mugger Crocodile

The mugger crocodile is a Bangladeshi crocodile and it’s found beside river in Sundarban of Bangladesh. The mugger crocodile can be found some near country of Bangladesh, India, Sri Lanka, Pakistan, Nepal, the southern tip of Iran, and probably in Indo-China and at one point, even in Southern Iraq. It is one of the three crocodilians found in Bangladesh, the others being the gharial and the saltwater crocodile. It is a medium sized crocodile that mostly inhabits freshwater lakes, ponds, sluggish rivers, swamps and marshes. Males of the species may grow 4 m (13 ft) to 4.5 m (15 ft) in length, but rarely exceed 3.7 m (12 ft). As with other crocodilians, females are smaller. The mugger crocodile has the broadest snout of any extant crocodile, giving it an alligator-like appearance. It is a more heavily armored species with enlarged scutes around the neck. Adults are dark grey or brown, while hatchlings are tan colored.

The Bangladeshi Mugger Crocodile:

The Bangladeshi Mugger Crocodile is a skilled predator that preys on a variety of species. Like other crocodilians they are ambush hunters and wait for their prey to come close. They wait camouflaged in the murky waters to launch the attack in the suitable moment. They mostly prey on fish, reptiles, birds and mammals. Reproduction takes place in winter months. Females lay eggs in nests that are holes dug in the sand. Temperature during incubation is the determinant of sex in the young. The mugger crocodile possesses the size to be a serious threat to humans but are not as aggressive as some other species, such as the sympatric saltwater crocodiles. They are also observed to usually avoid areas with saltwater crocodiles. Muggers are fairly social species and tolerate their conspecifics during basking and feeding.

Characteristics of Bangladeshi Crocodile:

The mugger crocodile is very dangers when they hunt. It’s like a torpedo in water. Being a giant reptile, the mugger crocodile eats fish, other reptiles and small mammals, such as monkeys. In fact, most vertebrates that approach to drink are potential prey, and may suffer being seized and dragged into the water to be drowned and devoured at leisure. Large adults will sometimes prey on large mammals such as deer, including the 225-kg sambar deer, and the 450-kg domestic water buffalo. Mugger crocodiles have 19 upper teeth on each side; a snout that is 1 to 1½ as long as broad at the base; a rough head but without any ridges; mandibular symphysis extending to the level of the fourth or fifth tooth; pre-maxillo-maxillary suture, on the palate, transverse, nearly straight, or curved forwards; and nasal bones separating the pnemaxillaries above. Four large nuchals forming a square, with a smaller one on each side; two pairs of smaller nuchals on a transverse series behind the occiput. Dorsal shield well separated from the nuchal, the scutes usually in 4, rarely in 6, longitudinal series, those of the two median usually considerably broader than long; 16 or 17 transverse series. Scales on limbs keeled. Fingers webbed at the base; outer toes extensively webbed. A serrated fringe on the outer edge of the leg. Adult blackish olive above: young pale olive, dotted and spotted with black.

The Bangladeshi Mugger Crocodile can achieve speed of around 8 mph over a short distance in pursuit of prey. They can swim much faster than they can run—achieving speeds of 10 to 12 mph in short bursts—and can cruise at about 1 to 2 mph.

Crocodiles of World:

Crocodiles (subfamily Crocodylinae) or true crocodiles are large aquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodylinae, in which all its members are considered true crocodiles, is classified as a biological subfamily. A broader sense of the term crocodile, Crocodylidae that includes Tomistoma, is not used in this article. The term crocodile here applies only to the species within the subfamily of Crocodylinae. The term is sometimes used even more loosely to include all extant members of the order Crocodilia, which includes Tomistoma, the alligators and caimans (family Alligatoridae), the gharials (family Gavialidae), and all other living and fossil Crocodylomorpha.

Although they appear to be similar to the untrained eye, crocodiles, alligators and the gharial belong to separate biological families. The gharial having a narrow snout is easier to distinguish, while morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait is the upper and lower jaws of the crocodiles are the same width, and teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed; therefore all teeth are visible unlike an alligator; which possesses small depressions in the upper jaw where the lower teeth fit into. Also when the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define the family, the species belongs to. Crocodiles have more webbing on the toes of the hind feet and can better tolerate saltwater due to specialized salt glands for filtering out salt, which are present but non-functioning in alligators. Another trait that separates crocodiles from other crocodilians is their much higher levels of aggression.

Crocodile size, morphology, behavior and ecology somewhat differs between species. However, they have many similarities in these areas as well. All crocodiles are semiaquatic and tend to congregate in freshwater habitats such as rivers, lakes, wetlands and sometimes in brackish water and saltwater. They are carnivorous animals, feeding mostly on vertebrates such as fish, reptiles, birds and mammals, and sometimes on invertebrates such as molluscs and crustaceans, depending on species and age. All crocodiles are tropical species that unlike alligators, are very sensitive to cold. They first separated from other crocodilians during the Eocene epoch, about 55 million years ago. Many species are at the risk of extinction, some being classified as critically endangered.

Crocodile is a dangers animal in water without extra safety you don’t swim on water of Sundarban. It’s like a torpedo in water.

Bangladeshi Dolphin

Bangladeshi Dolphin a toothed whale that is related to the porpoise. The dolphin has a long, streamlined body and some species have a prominent beaklike snout. The dolphin travels in schools and can swim at a speed of up to 25 mph (40 km/h). After a gestation period of one year, the female gives birth to one young. The young suckles for up to two years in bay of bangle waters and rivers in Bangladesh.  Dolphins are cetacean mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves and are carnivores, eating mostly fish and squid. The family Delphinidae, the largest in the order Cetacea, evolved relatively recently, about ten million years ago during the Miocene.

Bottlenose dolphins are well known as the intelligent and charismatic stars of many aquarium shows. Their curved mouths give the appearance of a friendly, permanent smile, and they can be trained to perform complex tricks.  In the wild, these sleek swimmers can reach speeds of over 18 miles (30 kilometers) an hour. They surface often to breathe, doing so two or three times a minute. Bottlenose dolphins travel in social groups and communicate with each other by a complex system of squeaks and whistles. Schools have been known to come to the aid of an injured dolphin and help it to the surface. Bottlenose dolphins track their prey through the expert use of echolocation. They can make up to 1,000 clicking noises per second. These sounds travel underwater until they encounter objects, then bounce back to their dolphin senders, revealing the location, size, and shape of their target.

When dolphins are feeding, that target is often a bottom-dwelling fish, though they also eat shrimp and squid. These clever animals are also sometimes spotted following fishing boats in hopes of dining on leftovers. Bottlenose dolphins are found in tropical oceans and other warm waters around the globe. They were once widely hunted for meat and oil (used for lamps and cooking), but today only limited dolphin fishing occurs. However, dolphins are threatened by commercial fishing for other species, like tuna, and can become mortally entangled in nets and other fishing equipment.

Swimming upside down may also help the dolphins see. Even though their eyes are small, these dolphins do have good eyesight. But their puffy cheeks may be a problem. It’s hard to look down over those cheeks! The dolphins may be able to see prey better while swimming on their backs. A sleeping dolphin usually rests at or near the surface of the water. That way, the dolphin is not too far from the air it needs to breathe.

A sleeping dolphin usually has one eye closed. The dolphin’s breathing rate slows down. Still, it seems to be aware of the fact that it is breathing. When you sleep, you are not aware of your breathing. You don’t need to be conscious in order to breathe. But many scientists think that dolphins do need to be conscious. River dolphins usually live in fresh water or in water that is only slightly salty. Sundarban river dolphins may be bright pink, bluish-gray, or off-white in color. They have humps instead of dorsal fins. And they have long, narrow beaks that they use for feeding.

Shark in Bay of Bengal Waters

Many type of shark live in Bay of Bengal waters. These range from the 30cm pygmy shark to the world’s biggest fish, the gentle whale shark, which grows up to 12m long and is a popular feature of the Bangladesh sea tourism sector. The presence of many species of shark as 'apex predators' – occupying the top level of the food chain – is an indication of a healthy marine environment. Despite their reputation, sharks seldom cause harm to humans, however, when incidents do occur the results can be devastating.

Biology of Sharks:

Sharks are typically slow growing, late maturing, long-lived and produce only a few young per year, making many species particularly vulnerable to overfishing. Like rays and skates, sharks belong to a class of fish called Chondrichthyes which have skeletons made of cartilage not bone. Sharks are covered in tough scales known as dermal denticles  making their skin extremely tough and abrasive.  Sharks have between five and seven external gills. Some sharks which live on the seabed, such as angel sharks and wobbegongs, have a flattened shape like rays and skates.  However, most sharks have a torpedo-shaped body. A large triangular dorsal fin on top of the shark keeps the shark stable. Large, stiff pectoral fins behind the gills are used for steering. The tail or ‘caudal’ fin powers the shark’s swimming. Many sharks must keep swimming in order to breathe.

Sharks like most fish typically ‘cruise’ at two – four body lengths per second or less. Burst speeds of up to 10 body lengths per second or more are possible for a short periods of time to obtain prey or escape predators. Sharks have an continuous supply of teeth, with worn out teeth being replaced as needed. A shark can have up to 3,000 teeth in its mouth at one time and 30,000 plus teeth over its life. Their teeth vary according to diet. White sharks have large serrated teeth for cutting big prey while grey nurse sharks have long, needle-like teeth, used for gripping. Many rays have teeth modified into grinding plates to grind crabs and other invertebrates.

Shark senses:

Sharks have excellent eyesight and an incredible sense of smell. Like other fish, sharks have clusters of hair-cells called ‘neuromasts’ located in canals just below their skin along the sides of their bodies and around the head and mouth. As with many species of fish, these can sense vibrations caused by fish movements in the water and sound hundreds of metres away. Through pores in their snouts and heads called ‘ampullae of Lorenzini’, sharks also have the ability to detect the weak electrical signals produced by most living organisms. These pores help them find prey buried in sand or hidden by darkness. It is thought they may also help sharks navigate by responding to fluctuations in the Earth’s magnetic fields.

Upper level predators:

Many people are fearful of sharks, but sharks may have more to fear from humans. Their slow rate of reproduction means many species of sharks are highly vulnerable to fishing and may take a long time to recover if stocks are depleted. Sharks can feed on a wide variety of prey, including fish, squid, octopus, crustaceans, mammals, reptiles and other marine creatures. Many species of sharks are specialist feeders, targeting particular prey. Whale, basking and megamouth sharks and others species filter feed on plankton and have relatively small teeth because they do not need them to feed. Modified extensions on their gills allow the plankton to be filtered from the water. Sharks play an important role in maintaining balanced ecosystems, controlling prey populations and removing weak animals while healthy ones survive to reproduce. Because they are at the top of aquatic food webs, sharks have few predators, apart from humans, other sharks and orcas.

Life cycle of Sharks:

Each shark species has its own expected life span and it is difficult to set an average for sharks as a whole. However, very broadly speaking, most sharks live for between 20 and 30 years. The Spiny Dogfish lives for over a century, and some Whale Sharks have been known to do the same. Unlike most other animals, sharks generally do not care for their young. As soon as pups are born into the water, they swim away and care for themselves. Some sharks give birth to litters of up to 100 babies at a time, while others may have as few as two or three. The Great White Shark gives birth to approximately three to 14 pups at a time. In almost all cases, all of the pups are healthy and well-developed. This is in stark contrast to many other animals (such as several fish species and some turtles), which give birth to large numbers of ill-developed young (in effect, producing quantity over quality). This means that sharks are defined as K-selected reproducers. Mating amongst sharks is somewhat elusive, rarely seen by researchers and scientists. Fertilisation of the female egg occurs internally. The male’s pelvic fin (the fin on the underside of the body, close to the tail) has evolved into claspers, a pair of organs that can best be compared to a penis in mammal species.

Sharks use one of three ways to carry their young – 1) Oviparity, 2) Viviparity and 3) Ovoviviparity.

Yolk-sac viviparity or ovoviparity:

Most sharks are ovoviparous – eggs hatch in the mother’s body, nourished by the egg’s yolk and fluids secreted by the mother. In the lamniforme shark, the first embryos to hatch eat the remaining eggs. In some species, including grey nurse sharks, embryos actually feed upon  sibling embryos inside the mother.


A few sharks lay their eggs in water, mostly in an egg case with the consistency of leather, which may be corkscrewed into crevices for protection. The empty cases or “mermaid’s purses” can wash up on shore.


Some shark species have a placenta-like link between the mother and developing young, similar to mammals.

Distribution and habitat of Sharks:

Sharks live in every ocean, estuary and freshwater system. Most species of sharks tend to inhabit shallower continental shelf areas, where rivers deposit nutrients into the oceans, providing the basis of an ocean food web. Megamouth sharks favour the open ocean while bull sharks are often found many kilometres upriver.