Alligator Gar: The Gator Fish

It swims like a fish but has elongated jaws with sharp teeth that are visible when it opens its mouth, similar to an alligator or a crocodile. So is it a fish? Or is it an alligator? I am not sure who had named this fish which has been scientifically described in 1803, but it has been given a common English name to match its characteristics. The fish is named Alligator Gar.
The fish is generally olive green or yellow and has a heavily scaled body. A tooth-filled mouth and wide, alligator-like snout give the species its name. With a prehistoric look, the Alligator Gar is one of the largest freshwater fish. Its name is derived from the alligator-like appearance of these teeth along with its elongated snout, and is indeed the largest freshwater fish in North America. A mature Alligator Gar fish can grow up to 10 feet and can weigh over 90 kilograms. It has been one of the largest and toughest fish, and the alligator gar is a favourite target of anglers who love this particular sport of fishing.
The alligator gar has a streamlined body to facilitate swimming and its dorsal and anal fins are located very far back on the body. Gars’ bodies are covered by ganoid scales, which are thick overlapping scales that create a protective covering similar to medieval chainmail – like those worn by heroes of favourite movies such as Robin Hood or Gladiators.

The river giant
These menacing-looking fish are indeed prehistoric. Scientists track the gar’s tenure on earth back to 150 million years to about the time birds began to fly. Although fossils of gars have been found in North America, Central America, Europe and Asia, the living members of the family are restricted to seven species living in North and Central America.
The Mississippi River in North America is recorded to be the alligator gar’s main hideout. They can live in fresh and brackish water bodies. The fish, despite its giant size, is relatively passive and prefers to live a solitary life. Alligator gar can also breathe air directly which allows them to survive even in murky waters. According to some literature, there are records of alligator gar having lived on land, and that is something people find surprising. They have been known to survive on land for a period of up to two hours. They may be on land to look for food or to escape from predators.

Predatory fish
Alligator gar is a carnivore fish as anybody can guess by seeing their sharp teeth. Alligator gars have two rows of teeth. The inner row of teeth is palatine and is longer than the outer row of teeth which gives them a good bite of their prey. The teeth of the alligator gar are long, slender, and fang like, giving them a good bite of their prey. They have ambush techniques in hunting prey, feeding by lurking amongst reeds and other vegetation. They like staying hidden and launch their attack on the unwary prey, and generally the prey doesn’t even know the gar is present until it is too late. They lie still in the water until an unsuspecting fish swims by, and then lunge forward and lash the head from side to side in order to capture the prey. Many times gars will lie still at the top of the water for long periods of time, appearing like a log.
Alligator gars prey on fish but they are opportunistic and have been known to feed on everything from waterfowl and small turtles to carrion. Alligator gars have been reported to attack duck decoys and eat injured waterfowl shot by hunters.
There are also speculations that larger alligator gar attack humans. But there has been no confirmation of such attacks. Though they wouldn’t attack human, their eggs, if ingested, are poisonous to humans.

Popular aquarium fish
All the Gar species are popular aquarium fish and quite interestingly the alligator gar is one of the most popular. But they are quite demanding, needing clean water as well as lots of space as they grow. In the Dehiwala Zoo the alligator gar has a moderately spacious tank. The tank has been enriched with suitable habitat to the alligator gars with some decayed logs and large stones placed within. Alligator gar like such hiding places.
Records show that there are seven gar species in the world. The alligator gar is the largest. Of the seven known gar species, the alligator is the largest and the heaviest. They weigh around 300 pounds (140 kilograms) according to records.
The breeding habits of alligator gar still remain largely unknown, but it is believed that they spawn on flood plains that expand towards the river ecosystems. Alligator gars are thought to spawn in the spring by congregating in large numbers with a female and one or more males on either side to fertilize the eggs. Web resources indicate that females generally carry an average of 138,000 eggs. The eggs are released and fertilized by the male outside of the body. They sink to the bottom after being released and stick to the substrate due to an adhesive outer covering. The eggs are bright red and poisonous if eaten. Alligator gars are thought to spawn in the floodplain of these large rivers mainly to give their young protection from predators.
They grow slowly and take a long time to mature. Females mature at 11 years and live up to 50 years. Males mature at six years and live to at least 26 years.

Conservation
The alligator gar is disappearing from many parts of the range, and declining in population everywhere due to over-fishing and the construction of dikes, dams, and other flood control mechanisms resulting in loss of key breeding habitats. The alligator gar was once reported as common and even numerous in much of its northern range. Now it is rare in the northern parts of its range with reports of valid sightings coming in once every few years.

http://www.lakbimanews.lk/index.php?option=com_content&view=article&id=7129:the-gator-fish&catid=41:mag&Itemid=12 

Marine biodiversity takes centre stage - One Ocean,Many Worlds

22nd May is dedicated to Biological Diversity and is celebrated worldwide as International Biodiversity Day. This year it is themed on ‘MARINE BIODIVERSITY’ and emphasizes the importance of the diverse forms of life in the oceans. ZooLander dedicates his column to marine biodiversity, paying tribute to an important segment of the ecological system.

The ocean is home to the blue whale, the largest animal ever to have lived on earth, and to billions upon billions of the tiniest: there are more microorganisms in the sea, than there are stars in the universe. Oceans cover 71 percent of the surface area of the globe, and constitute over 90 percent of the habitable space on the planet, making it one of the most important habitats of the world.
From sandy shores to the darkest depths of the sea, the ocean and coasts support a rich diversity of life. People have lived near and fished from the ocean for thousands of years and even today, an estimated 41 percent of the world’s population lives within 100 km of the coast, and fisheries provide over 15 percent of the dietary intake of animal protein as per statistics of the Convention of Biological Diversity (CBD) which selected “Marine Life” as the theme for the International Day on Biological Diversity.

How much life in the Ocean..?
From 2000 to 2010, in an unprecedented international collaboration, scientists around the world, set out to try and determine how much life there is in the sea. Dubbed the ‘Census of Marine Life’, the effort involved 2,700 scientists from over 80 nations, who participated in 540 expeditions. They studied surface seawater and probed the deepest, darkest depths of the ocean, sailed tropical seas and explored ice-strewn oceans in the Arctic and Antarctic.
By the time the census ended, it had added 1,200 species to the known roster of life in the sea; scientists are still working their way through another 5,000 specimens to determine whether they are also newly-discovered species. The estimate of the number of known marine species - the species that have been identified and the ones that have been documented but await classification, has increased as a direct result of the census, now making it around 250,000. (This total does not include some microbial life forms such as marine viruses.) In its final report, the census team suggested it could be at least a million. Some think the figure could be twice as high. So these figures alone highlight the importance of marine life which thrives in the oceans.
Marine life are found in the coastal areas, the continental shelf, the open ocean, the deep ocean and can be in some of the different ecosystems within the ocean world itself, making it one ocean, many worlds.

Along the Coast
Coastal areas, often among the most dynamic and productive of environments, are in many ways the definition of living on the edge. Waves crashing against rocky cliffs or rolling onto sandy shores, form estuaries that exhale the last breath of river systems, the frenetic riverine pace yielding to a sprawling mixture of fresh and saltwater.
In the warm estuarine waters of the tropics, hot and humid mangrove forests are a hybrid of terrestrial and marine life: above the water, they host insects, birds, monkeys, alligators and large mammals like deer and even tigers; beneath the water’s surface, fish swim among mangroves thick roots, which are covered with filter feeders like oysters, mussels, and anemones, while the muddy banks are inhabited by amphibians and crabs.

Continental Shelf
The area fringing coastal landmasses is known as the continental shelf; during ice ages, when sea levels were lower, the shelf was the boundary of the continents but now extends offshore underwater by an average of 80 km. Continental shelf waters are relatively shallow, generally between 100 and 200 metres deep; because their shallowness means they are bathed in sunlight in their upper layers and because their relative proximity to shore provides them with ongoing sources of nutrients from land, they are some of the most productive waters in the ocean. Coral reefs, sea grasses and kelp forests are all in continental shelf waters, as are the vast majority of the world’s fisheries.

The Open Ocean
Peering over the sides of a ship steaming over its surface, it might appear that the open ocean is one big, boundary-free expanse of water – its wildlife swimming back and forth, from surface to depths, without constraint. But marine life researchers found that, although many areas of the open ocean may look equal, to marine animals there are clear differences. The researchers found, for example, that white sharks congregate in an area off Hawaii that scientists dubbed the “white shark cafe‚”, and that several species of turtles, seabirds, seals, whales and sharks all congregate at ‘hotspots’ as in the California Current.
The top 100 meters of the ocean is the zone within which most of the life with which we are instantly familiar -- fish, turtles, and marine mammals, as well as the microscopic plant and animal plankton that forms such an important part of the marine food web – exist. Much deeper where sunlight struggles to penetrate, its another story.  Six hundred meters deep, sunlight in the ocean is as bright as starlight on the surface; at 693 meters it is approximately ten-billionth its surface brightness; and by 1,000 meters, the sea is completely dark. And yet, even here, there is life.

The Deep
In the absence of sunlight, many deep sea fish create lights of their own, in the form of bioluminescent symbiotic bacteria that dangle as lures or shine a path ahead like headlights. Marine invertebrates burrow through the silt of the seabed itself. Seamounts, underwater mountains that climb 1,000 meters or more from the ocean floor, often have complex surfaces of terraces, pinnacles, ridges, crevices and craters, and their presence diverts and alters the currents that swirl about them; the net effect is to create a variety of living conditions, providing habitat for rich and diverse communities. There are believed to be in excess of 100,000 seamounts of 1,000 meters or higher, although only a fraction have been studied.

Human Impact and Hope
However, although humanity has frequently benefited from the bounty of the ocean and the wildlife it contains, ocean and marine wildlife has not always benefited from the attentions of humanity. Some species are already extinct, due to unregulated human activities; others, notably the great whales, have been hunted to fractions of their original populations. Commercial over exploitation of the world’s fish stocks is so severe that it has been estimated that up to 13 percent of global fisheries have ‘collapsed.’ Between 30 and 35 % of the global extent of critical marine habitats such as seagrasses, mangroves and coral reefs are estimated to have been destroyed. The burning of fossil fuels is causing the ocean to become warmer and more acidic, with consequences we are only beginning to grasp.
But there is hope. Around the world, species and populations are recovering with effort and intervention from communities and governments; large areas are being established as protected areas, and the Convention on Biological Diversity has established a series of specific targets that require stakeholders at all levels to work together to protect the biodiversity that lives in the ocean, for its own sake and for the benefit it brings to people worldwide.
Fish may be one of your favourite food items. But be mindful that they too are marine life and if we allowed the world’s oceans to be polluted and over exploited,  marine species, we will not get fish for our consumption. Let’s all be mindful of Marine Biodiversity and commit ourselves to take special heed to protect this precious resource. on this International Biodiversity Day!

Past themes celebrated on International Biodiversity Day

Marine Biodiversity is the theme for this year’s International Day for Biological Diversity (IDB). Designation of IDB 2012 on the theme of marine ecosystems provides parties to the Convention on Biological Diversity (CBD) and everyone interested in marine life, the opportunity to raise awareness of the issue and increase practical action. The themes of the past Biodiversity Days are listed below...

2012 - Marine Biodiversity
2011 - Forest Biodiversity
2010 - Biodiversity, Development and Poverty Alleviation
2009 - Invasive Alien Species
2008 - Biodiversity and Agriculture
2007 - Biodiversity and Climate Change
2006 - Protect Biodiversity in Dry lands
2005 - Biodiversity: Life Insurance for our Changing World
2004 - Biodiversity: Food, Water and Health for All
2003 - Biodiversity and Sustainable Development
2002 - Dedicated to forest biodiversity

Published on LakbimaNews on 20.05.2012 

Avurudu Panchi a game with cowries Meet a live cowry at the Zoo Aquarium

Avurudu is still fresh  in our homes. Relatives who have not met up in a while are still visiting and Avurudu games that were forgotten are now being played. The rattle of the Panchi is also heard, though it is not as common as in the past.  But do you know that cowries which are used  in a game of panchi are in fact the shell of a sea mollusc and you can get a rare chance to see one alive, and its in the zoo’s Aquarium?

The panchi rattle was a familiar sound during the Avurudu season, decades ago. This clatter sound brings to mind the shiny stones hitting at one another and which pitch on different sound levels. Even if you have never played a game of panchi before, you would have seen it in Avurudu telecasts. But have you paid attention to these attractive milk white and yellowish cowries used in a game of panchi?

On initial look, these cowries’ looks like some kind of stones. But they are in fact the shells of the marine snail popularly known as cowry.  There can be different colours and shapes of cowry shells that belongs to different species, but the yellowish white cowry known as money cowry is mostly used in the game - panchi.

These cowry shells often float to the beach, and you can pick up plenty of them. But since these creatures live in the sea, only deep sea divers could see them live. But have you thought that you could also get a chance to see a live cowry one day? Yes, you can. What you have to do is to visit the zoo’s aquarium. There is no description about the live cowry in the tank it lives in, but you may go to the tank of the marine moray eel. This eel is a nasty looking neighbour for anybody, but even he seems to be tolerant of the live cowry that has suddenly come to share his tank. There is no description or at least mention about the presence of this cowry in the tank indicating that the cowry could be an accidental addition, by its look this cowry seems to be a tiger cowry.

Mollusc in the sea

Cowry is actually a kind of a sea snail which is a mollusc which lives in the sea. Scientifically, they belong to a family of Molluscs Cypraea. The cowry shell is oval shaped like an egg, but the underside is flat. There is also a long, narrow, slit-like opening known as the aperture which is often toothed at the edges. The soft body of the sea snail and the broad muscular foot it uses for crawling could be retracted into the shell, when it feels danger approaching.

The cowry shells are extremely smooth and shiny because in the living animal, the shell is nearly always fully covered with a skin: the mantle. The shell-producing this mantle tissue has two special folds that extend outside the shell in the cowry. These mantle folds keep the shell clean and polished, and prevent damage to the shell surface. The mantle is covered with frilly, branched projections called papillae that look like small fingers. The functions of the papillae are not clear: they may provide camouflage for the animal by breaking up the snail’s outline; or may allow absorption of oxygen from seawater.

The cowry uses its mouth tube to feed on. The Algae is its main diet in their natural habitats and is mostly active at night. During day time it usually hides in its natural habitat, but the cowry in the zoo can be seen attached to the glass wall of the tank throughout the day.

Cowri in Dehiwala Zoo with its neighbor
- Murray Eal

Travel using fleshy foot

The cowry travels by using the “foot” that can be extended from the aperture of the underside. This muscular organ is long and is spread underneath the body and the cowry is able to move forward by making a sort of ripping motion using its foot, say marine experts.  When it moves, the snail leaves behind a bit of slime, which coats the area that it is trying to move along on.  If you watch a snail on a dry surface, you can see that it leaves a trail of slime behind it.  Sea snails are very slow moving creatures and could spend the better part of a day just trying to travel across the yard.

The eyes of the cowry can be found at the base of one pair of tentacles; however, some other species of snails don’t have eyes at all.  They breathe through gills or sometimes through a thin tissue layer called the mantle that wraps around the body of the snail like an envelope.  Sea snails use their gills like a fish would, to retrieve oxygen out of the water.  The gills are found in the cavity of the mantle.

Other sea snails

If you visit the beach, you would find many different kinds of cowries and other shells. These are differently coloured and differently shaped. There is enormous diversity of sea snails say marine biologists. Marine snails make up the majority of the snail family population and they can often be found in fresh water as well as in  salt water. 

Sea snails do have teeth -- not in the common perception of what teeth look like.  They technically have radulas, a very hard organ that looks like a ribbon in appearance and has tiny rows of teeth on it. Some will only have a few teeth while other snails have thousands.  As the teeth wear down, new ones grow. They do not exactly chew their food but rather grind and tear it.  Sea snails are often popular in aquariums, as an accessory, to eat debris from the sides of tanks.

Predators of cowry

The very narrow toothed aperture of the cowry shell keeps the adult sea snails out of danger, frustrating predators. However there are some smart predators which learn the art of how to reach the softer parts of the cowry. Some tropical crustaceans can break the dorsum of a cowry shell and some mollusc-eating cones can inject venom to the cowry’s flesh. The cone then extends its stomach into the cowry shell through the slit and completely digests the flesh.

However, the octopuses are the most fascinating cowry hunters. Some octopuses can make a small hole in the strong cowry shell using a special barb/tooth and an acidic secretion. In the beaches, have you noticed some of the cowry shells have strange looking holes on them..? Perhaps those are the unlucky victims of these cowry eating octopuses.

Game of Avurudu Panchi

Being shiny objects, cowries are often used in jewellery by coastal communities. In some other instances, the cowries have also been used as money. These are known as ‘money cowries’ and the ones used in playing panchi. They are small in size and is of a yellowish marble, off white colour.

When playing panchi, there are two groups and they use lead-filled cowries in a coconut shell and rattle it inside shaking hard and releases them on to another coconut shell. After each toss of the cowries, those that had come to rest with the flat surface upturned scores a point. The points scored by each side are registered by moving one or more of a set of pawns, along a pattern of squares outlined on a wooden board, towards a home-base. The first team to take all the pawns to the home base wins.

Remember - the live cowry can be seen in the murray eel’s tank, at the zoo aquarium. So make a visit this Avurudu season to observe a living cowry which is not a common sight.

Published on 15.04.2012

Celebrating Aquatic Animals, Commemorating World Water Day

Aquatic Life in a Water World

March 22 is World Water Day. Water is essential for all of us and we cannot live without drinking water. In fact it is believed the life of the Earth began in water, so Earth is indeed a water planet. ZooLander looks at the amazing diversity in aquatic animals.

We can live for a few days without food, but can we even think of surviving without water. But there are some animals that need water based mediums to live in, as if their very survival is dependent on water. These are aquatic animals and live in water for most or all of their life. We breathe through our lungs, but most of these aquatic animals, like fish, use their gills, a special organ that can extract the oxygen from water. However there are other aquatic animals such as whales and dolphins that breathe air directly from the atmosphere.
The environments these aquatic animals live in are of two types - freshwater or saltwater. Creatures that live in saltwater mediums like the oceans are known as marine species. Zoos and aquariums are the best places for observing these animals and the best place in Sri Lanka to study marine species in captivity, is at the aquarium in the Dehiwala zoo. Diving or snorkeling is the other option, if you want to see them in their natural habitat.  As many of us cannot swim or dive in to the vast oceans and as it is also a specialized technique that needs to be learnt and practiced, the majority has to go to aquariums to study these beautiful animals.
The zoo aquarium is full of freshwater fish. There are lots of endemic fish species that are native to Sri Lanka, which cannot be found anywhere else in the world. This section in the aquarium is the most important and interesting corner to watch. There are other interesting river fish from other parts of the world too that you can observe at the aquarium. Zoolander has previously reported on the aquarium’s freshwater inhabitants - the giant Amazonian fish Arapima, notorious Piranha and the endemic Sri Lankan fish Pathirana Salaya. There are other  interesting fresh water fish swimming in lit-up tanks, placed in darkened passages.
The aquarium is also home to many varieties of marine fish. Those who are associated with corals are the most beautiful of them. Can you recall the Moray eel that Zoolander reported on sometime back? It’s an interesting creature found in coral habitats. On a visit to the Dehiwala zoo, one can observe many such aquatic creatures in the aquarium.
Whales and Dolphins are the most popular aquatic mammals, but none of them can be seen in captivity in Sri Lanka. However, the Dehiwala zoo is not without a representative of the aquatic mammal family. The performing sea lion is the only aquatic mammal at the Dehiwala zoo and with the daily performances, it is one of the most popular characters, entertaining visitors.
Amphibians are another aquatic form of animals that can live both on water and land and the aquarium still has its corner for frogs.

Fish gills
Have you gone to the fish market to buy fish? Or have you seen the fish on the kitchen table ready for cooking? If not, have a look at the head of a small or medium sized fish and you will notice the gills, which are used for breathing by taking oxygen from water. But how do these gills function? Have you ever given a thought to it?
The gills allow fish to absorb oxygen from the water and in the fish they do the work, of lungs. In lungs, blood in tubes flow near the surface of tiny air sacks, oxygen transfuses from the air in the sacks into the blood, and carbon dioxide transfuses from the blood to the air in the sacks. A fish’s gills work exactly the same way, except that it is water in the gill structures that handle the transfusion, and are visible dangling in the open water instead of being hidden inside the lungs.
Gills themselves have a car radiator-like appearance. Most fish have 4 gills on each side, consisting of a main bar-like structure that has numerous branches as those found on a tree, and the branches consisting of even smaller branch-like structures. This arrangement of cells allows for a very large surface area when the gills are immersed in water.
Functionally, the mechanism for pumping water over the radiator-like gills seems to vary depending on the species of fish. In general, a fish is able to reduce the pressure in its mouth cavity by lowering the floor of the mouth and widening the outer skin flap that protects the gills, called the operculum. This increase in volume lowers the pressure within the mouth causing the water to rush in. As the fish raises the floor of their mouth, an inward fold of skin forms a valve of sorts which doesn’t allow water to rush out. The pressure is then increased compared to the outside of the mouth and the water is forced through the operculum opening and across the gills.
This wonderful organ, the gill, has allowed fish for millions of years to enjoy the wonder that is underwater basket weaving. The next time you see a fish swimming around you can smile to yourself knowing that they are working much harder than us to breathe.

Fish that can live outside water
If you happen to watch the popular Sinhala TV programme Atapattama, you may have seen a large Gourami fish that comes out of the water and even allows children to cuddle it for about 15 minutes outside water. It became fascinating news and got much publicity. But fish experts say this is not a new phenomena and fish like the Gourami have the ability to live outside water for a longer time as they have another special organ in addition to gills that allows them to absorb atmospheric oxygen. This organ is called a labyrinth organ which acts as a lung helping the fish to breathe in air, allowing labyrinth fish to take in oxygen directly from air, instead of taking it from the water in which they reside with the use of gills. The labyrinth organ helps the inhaled oxygen to be absorbed into the bloodstream. As a result, labyrinth fish can survive for short period of time out of water, as they can inhale the air around them, provided they stay moist.
Labyrinth fish are not born with functional labyrinth organs. The development of the organ is gradual and most labyrinth fish breathe entirely with their gills and develop the labyrinth organs when they grow older as per the experts who studied this fish variety. It is not unique to  Gouramis -- if you remember ZooLander wrote about this special organ, when reporting about the zoo aquarium’s Dino Fish - Arapaima. The Arapaima lives in the Amazon and they too have the labyrinth organ.
Aquatic creatures are very interesting animals, even though we are not as familiar with them as with land animals. The zoo’s aquarium will provide a good opportunity for you to observe these fish. How they breathe underwater, how they swim, how they interact. Why not make a visit to the zoo once again and carefully observe these aquatic marvels and be delighted by them

Interesting facts about fish and other aquatic creatures

1. Sea turtles absorb a lot of salt from the sea water in which they live. They excrete the excess salt from their eyes, which makes them look as though they’re crying.
2. Prehistoric turtles may have weighed as much as 5,000 pounds.
3. As it gets older the cockle just adds another layer to its outer shell. To work out their age you can count the rings on them just like on a tree.
4. A goldfish has a memory span of three seconds.
5. A male angler fish attaches itself to a female and never lets it go. Their vascular systems unite and the male becomes entirely dependent on the female’s blood for nutrition.
6. Beavers can hold their breath for 45 minutes under water.
7. The sailfish is the fastest swimmer, reaching 109 km/h (68 mph).
8. The slowest fish is the sea horse, which moves along at about 0.016 km/h (0.01 mph).
9. The heart of a blue whale is about the size of a small car.
10. The tongue of a blue whale is as long as an elephant.
11. The largest jellyfish ever caught measured 2.3 m (7’6”) across the
belly with a tentacle of 36 m (120 ft) long.
12. Fish and insects do not have eyelids - their eyes are protected
by a hardened lens.
www.whereincity.com

About World Water Day

International World Water Day is held annually on March 22 to focus attention on the importance of fresh water and advocating for the sustainable management of fresh water resources.
An international day to celebrate fresh water was recommended at the 1992 United Nations Conference on Environment and Development (UNCED). The United Nations General Assembly responded by designating 22 March 1993 as the first World Water Day.
Each year, World Water Day highlights a specific aspect of fresh water. This year’s theme is “water and food security”.

Published on LakbimaNews on 25.03.2012 

Visit Zoo to see Amazon's Largest Fish

The zoo’s aquarium is the home for large fish. Among them, you’d find one of the world’s largest freshwater fish, a habitant of the Amazon River - arapaima. They are true giants and ZooLander recommends that you closely observe these large fish.

At a quiet corner of the aquarium is a large tank. In it swims a group of large fish. They are well near 5 or 6 feet long, and are surely the heaviest fish in the aquarium. Everybody wants to have a peek at these monster fish, but the little known fact is that they are in fact one of the world’s largest freshwater fish.

Named arapaima, these fish are inhabitants of the biodiversity rich Amazon River. In local Amazonian languages, this giant fish  is also called pirarucu or paiche. Because of their enormous size, this giant is also mentioned in the legends of the local Amazonian tribes. According to legend, Pirarucu is the disrespectful and cruel son of an Amazon chief. God has struck him down to the depths of the river, and it became the arapaima. Brazilians and locals still refer to the fish as pirarucu.

Whatever the legend holds, the monster fish is also referred to as a living fossil by historians. They believe these fish have inhabited these Amazonian regions since the Jurassic age, millions of years back. The fossil records too supports this theory making the arapaima a living fossil fish and a true prehistoric river monster. In other words theyt could have been there during the same time as dinosaurs and can truly be called Dino-fish from the deep.

They are truly giants in freshwater, and records indicate that fish as long as 9 feet are caught from the Amazon River. An unconfirmed record from  the 19th century also reports of fishermen having caught an arapaima the length 14.8 ft (4.5m). A full grown arapaima can weigh as heavy as 440 pounds (200 kilograms). Arapaima has a wide, scaly, grey body and a tapered head. This gives them somewhat of a bizarre look and establishes their name as a monster river fish. This dino fish is indeed a predator of the deep. Usually they hunt other fish, crustaceans and other small animals. It is also claimed that the arapaima sometimes feed on water birds that are low flying or swimming without a sense of the lurking dangers that lie beneath.

Most of the fish breathe through their gills, and can stay underwater without a problem. But the arapaima is strangely an air breather, getting oxygen from air inhaled through the mouth. Arapaimas can stay underwater for 10 to 20 minutes, and tend to remain near the water’s surface, where they hunt and emerge often to breathe with a distinctive coughing noise, say experts.

Labyrinth organ

They have a special organ - the  labyrinth organ which is rich in blood vessels that opens into the fish’s mouth. This also helps the arapaima to survive in waters where the oxygen level is low.  Lakes in the Amazon region which are are isolated from other rivers during the dry season brings down the oxygen levels but this giant fish survives as it has the advantage of the ability to breathe air.

However, this air breathing habit also results in the arapaimas’ downfall. Because they have to surface to breathe, they are easy targets of fishermen, and others who hunt them for fun. Arapaimas are caught using nets or by harpooning. Once an Arapaima is detected, the fishermen can be certain that it could emerge somewhere near and stay ready to harpoon it. This has caused the  decline of the fish population pushing it to Vulnerable and to  Extinction status in the IUCN Red List of Threatened Species. Because the arapaima can be cooked in to “large, boneless fish steaks” it is considered a delicacy, and records show some 7000 tons per year were fished from 1918 to 1924, at the height of it being commercialycaught. But recognizing the threat, the commercial fishing of arapaima has now been banned in the Amazon region. Fishing is allowed only in certain remote areas and on a catch-and-release, basis or harvesting by native people for their consumption. Raising arapaimas for food is allowed.

The reproduction cycle of this giant fish is also interesting. They build a nest at the bottom of rivers where it is muddy. Experts say that the nest is about 50cm wide and 15cm deep. It is said that the arapaima breeds in drier periods where water levels are low or at times when water levels just start to rise. As the water rises the eggs hatch and the offspring have the flood season to prosper, during the months from May to August. Because of this, the yearly  spawning is regulated seasonally in this region.

The father arapaima is truly the most dedicated of parents. “Mouth incubation” is thought to take place. Arapaimas are mouthbrooders with the eggs and young  protected in the mouth. This task is done by the father, who takes on the duty of protecting the babies. The father guarding the eggs is known to take the young and egss in his mouth and move them to another location. The young are led by the male in a group, once they are able to swim. The mother gives protection to the father by staying and swimming close, ready to interfere in case of an attack. This is truly the gentle side of this giant fish.

published on LakbimaNews on 05.02.2012 http://www.lakbimanews.lk/index.php?option=com_content&view=article&id=4412:visit-amazons-dont-dine-on-the-dino&catid=41:mag&Itemid=12

The Beuty & the Beast at Aquarium

Published on 02.10.2011 on LakbimaNews

Zoo's Oceanic Members

Published on LakbimanNews on 11.06.2011

Life in the Deep

Published on LakbimaNews on 18.06.2011

Tilikum: Performing Killer Whale

published on LakbimaNews on 17.04.2011

Piranha - The Amazonian Freshwater Fish

Published on LakbimaNews on 10.10.10

Aimiable lions at sea

The World Oceans Day is celebrated in June and last week, ZooLander visited the Aquarium in search of marine fish. Continuing the exploration of Oceans of Life, ZooLander reports on the life of the only marine mammal in the Colombo Zoo...!! Lions are the kings of the jungles, but why are these marine mammals called ‘Sea Lions’..? Known as Muhudu Sinhaya in Sinhala, this strange name grabs the attention of the zoo visitors who flock to the arena at the entrance to the Aquarium to witness the performances of Chakku and Karl - Colombo Zoo’s pair of sea lions. They are very intelligent and play many tricks in front of you. It is amazing, how they so obediently act on their master’s commands. Playing with the ball is their favourite game and they also like to swim the length of the small pond to show acrobatic skills. After the show, the sea lion would shake hands with the masters and say goodbye to the audience before they go into their dens, located inside.

“It is not that hard to train the sea lions” say the trainers of these marine mammals. The Colombo zoo received Karl only 2 years ago when he was only 1 year old, but he learned the tricks very fast, according to the trainers. The Aquarium has 2 master trainers to look after these sea lions. Both Karl and Chakku like the company of their trainers and they also get little fish as a tip after every performance. Their favourite diet includes hurulla, salaya and cuttlefish. Both of them wait until 4.00 pm in the evening to perform at the special arena near the entrance to the Aquarium.

Chakku is the elder of the two who is now 9 years old. The Colombo Zoo received Chakku from Japan and Karl from Krefeld Zoo in Germany. But sea lions are not found either in Europe or Asia, naturally. Both Karl and Chakku belong to a species called Californian sea lions and as the name suggests, are found in numbers off the coast of California of the United States of America. But their actual range is far more extensive. They inhabit areas from Vancouver Island, British Columbia in the North, to Mexico in the South in the sea around the American continent. An adult sea lion male can be as heavy as 1,000 lbs and 7 feet in length. However, the female does not grow that big and an adult female can at average be 350 lbs in weight and 6 feet in length. Unlike some marine mammals such as whales and dolphins, the sea lions share their life between water and land. They generally haul out of the water to mate, rest, give birth and moult. California sea lions are also very social animals, and large groups often rest closely placed together in their favourite hauling sites. They are also vociferous communicators making ‘bark’ type noises. A colony of a sea lions in the wild can be so noisy -- you would call it as noisy as malu kade if described in purely Sinhala terms.

Lions in Navy
The name “Sea Lion” in fact would have been derived from the little mane developed in the mature males. Though the mane or the coarse hair growing from the crest of the animal’s neck is not as big as that of an African lion’s, it would be enough to win the hearts of the female sea lions in the wild. Males also grow a large crest of bone on the top of their heads as they reach sexual maturity, and it is this that gives the animal its generic name Zalophus californianus (za-emphaticloph-forehead) meaning Californian big-head.

The Californian sea lions are also trained by the US Navy for underwater surveillance. Sea Lions are indeed very intelligent marine mammals and have already been trained to detect underwater landmines, for ship and harbour protection -- and underwater equipment recovery. These trained sea lion comrades can be highly useful as they can reach places inaccessible to human divers. It is estimated that they can dive to 1,000 feet (304 m) and silently swim at speeds of upto 25 miles per hour (40 km/h). So they are being trained for military purposes, since 1960 according the internet sources. It is documented that sea lions have been sent,in the Persian Gulf, to protect U.S. ships from enemy divers. The animals are trained to swim behind divers approaching a ship and attach a clamp, which is connected to a rope, to a diver’s leg. Navy officials say that the sea lions can get the job done in seconds -- and the enemy doesn’t know the clamp was attached to his leg until it’s too late. The US Navy’s Marine Mammal Program sparked cotrovery and was fiecely criticised by the animal welfare activists. However the sea lion’s intelligence, exceptional diving ability, and trainability made it a very useful comrade of the best naval force in the world.

Life of the Lions of the Sea

During the breeding season, California sea lions gather in traditional sites known as rookeries. As per the Sea World institute which had documented much information about the sea lions, at the onset of the breeding season, male California sea lions start establishing breeding territories. Once territories are established, males patrol their boundaries and ‘bark’ when necessary to maintain and defend them.

An intruding male evokes an immediate response from the resident male, who struggles violently to displace the intruder. But they also patrol the aquatic borders of their territories by swimming along the territories’ edges. During the breeding season, adult males fast when defending their territories. Pups are born on land and it is observed that most California sea lion pups are born in June. Recent research revealed that the mother sea lion has the ability to delay the development of the embryo until the conditions become favourable. Delayed implantation assures that the pup will be born when environmental conditions are optimal for its survival. However, females generally give birth to one pup each year and they are well developed with their eyes open. Pups also can swim at birth and within 30 minutes they are able to shake, groom, scratch, and walk. Multiple births have never been observed in the wild according to some sources and once born, the mother nurses them for at least five to six months. This protection sometimes can lengthen over a year where the motherly love grows very intimate. All the pups who live in a large sea lion colony would looks similar, but the mother sea lion can recognize pups on crowded rookeries through smell and vocalizations. It is observed that the female vocalizes often during and immediately after the birth of her pup. The pup instinctively replies and this vocal interaction may continue for 20 minutes or more. Perhaps, this is to register each other’s unique voices. A sea lion’s average lifespan is said to be around 17 years in the wild, and longer in captivity. Their noses are sealed shut, they are able to stay underwater for up to 15 minutes, but have to surface after that period.

Sea Lion Show

The sea lion show is performed every day at a special arena near the entrance to the Aquarium. Have a look at how Chakku and Karl perform on your next visit to the zoo..!! But please pay attention that your cousins of the wild enjoy their freedom ; they who were born in captivity have sacrificed their freedom to entertain you. So be mindful that some of your behaviour can be harmful to these curious animals. Oshin - the partner of Chakku brought from Japan died few years back and a number of coins thrown by ignorant visitors were found in its stomach. So never throw anything to the pool of water where these sea lions perform daily, but enjoy their performances. Also take home the message that Chakku and Karl are trying to convey - “Protect Oceans of Life, so that many species like us get the chance to survive..!!”

Published on LakbimaNews on 20.06.2010 http://www.lakbimanews.lk/archvi/lakbimanews_10_06_20/mag/mag5.htm

The World Oceans Day

Published on LakbimaNews on 13.06.2010

This article has been published on LakbimaNews 0n 17.Jan.2010