Fish ashore at coastal waters in many areas

Last week, fishermen and the community in the East coast were surprised by the influx of fish on the shore. Experts say this is due to a coastal current that resulted in the fish being washed ashore.

It was frenzy of fishing at the coastal areas in the east last week. Lots of fish had been swept ashore enabling the public to catch them by simply using a net or a piece of cloth. Many gathered to see this phenomenon and get fish for a free meal. Some of course kept their distance fearing that the aggregate of the fish could be some bad omen like the advent of another tsunami. Sardines were the most commonly found fish in addition to the skipjack tuna among the schools of fish.
Reports of fish being washed ashore had puzzled the general public even in other areas; some feared that this could be the sign of an incoming disaster. But oceanography experts say that there is nothing to worry and the sudden aggregation of fish is normal. They connected this to the changes linked with the monsoonal patterns. Oceanography expert Dr. K. Arulananthan at NARA (National Aquatic Research and Development Agency) confirmed that this was due to the changing patterns of the East Indian coastal current.

Change of temperature
Sri Lanka is now experiencing the second inter-monsoon rains. According to Dr. Arulananthan, during the south western monsoon, the East Indian coastal current flows from the Arabian Sea towards the Bay of Bengal via the southern tip of Sri Lanka. But with the north-western monsoon the direction of this East Indian coastal current reverses and this happens during the inter-monsoon season. This brings cold water from the Bay of Bengal region and the change of temperature assists in the growing of algae and planktons that leads to algae bloom. Little fish gather to feed on these microscopic plankton and even big pelagic fish that live in open seas follow the smaller ones making this present fishing frenzy in many areas, explained Dr. Arulananthan.
The sardines or keeramin and skipjack tuna are the most notable fish that had gathered in numbers during past few days. The said phenomenon is more applicable for pelagic fish, comments Dr. Arulananthan. The expert also spoke of another possibility of dead fish being washed ashore. The algae also perform photosynthesis which consumes the oxygen in the water. In the waters where algae bloom, the fish find a lack of oxygen, and many die. Some of the dead fish get washed ashore while others sink deep down to the bottom of the sea. The decaying fish at the bottom deplete the oxygen in that region which affects the fish that dwell in the bottom, like eel or ray fish.
This year, Sri Lanka experienced a delayed south west monsoon and perhaps these climatic changes aggravated the oceanic current to make it more observant. However, Dr. Arulananthan calls it a normal phenomenon adding that one need not worry, unduly. But the climate change may bring more abnormal changes of weather patterns that lead to phenomena’s like this in the future, experts fear.
Many feared that this could be a bad omen as they recalled that just before the 2004 tsunami, loads of fish were seen in a similar manner. Dr. Arulananthan reminded that the tsunami occurred in December and this phenomenon of the changing of the East Indian coastal current was in October. He also said the underwater earthquakes might make the lives of fish dwelling in the deep sea to migrate to other regions via oceanic currents. However, the fish caught during last few days are not abnormal species but ones that are commonly found in our oceans.
However, it is interesting to know that the changes of climatic patterns affect animal behaviour as ZooLander reported recently about a dragonfly migration that follows Inter Tropical Convergence Zone which fell during the same time period across Sri Lanka.

Climate change shrinks fish size, says new study
A new scientific study shows that climate change will shrink the size of fish by 14-24%. This too links to the level of oxygen in the water where scientists say the increase of temperature will reduce the oxygen in the water. Researchers from the University of British Columbia have studied change of body size of some 600 species based on models between 2001 and 2050.
Although data projects relatively small changes in temperature at the sea-bed, the resulting impact on fish body size are “unexpectedly large,” BBC has reported. When compared with actual observations of sizes of the fish, models generated on future sizes of fish seem to underestimate what’s actually happening in the seas. The researchers looked at two case studies involving the North Atlantic cod and haddock. They found that the recorded data on these fish showed greater decrease in body size than what the models had predicted. Other scientists stated the impact could be widely felt.
A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner, the research report states.
The fish stocks around the world are already being depleted due to overfishing.
Climate change due to global warming will also make the ocean acidification that impacts on the fish and this study will be another blow.
According to experts, the ocean acidification is a phenomenon that is triggered by the increase of carbon dioxide in the atmosphere. When the Co2 mixes with sea water, the oceans get more acidic. This impacts the many delicate species and ecosystems as corals on the first wave of attack and then will impact the other fish species too, experts point out.
Other species like the mollusks that have shells that are built by calcium carbonate too could be in danger as another report suggests. Calcium carbonate dissolves in acids and when the sea water gets more acidic, their shells will thin exposing them to predators and other hostile elements.
Researchers point out that the worst impact could be observed in the tropical regions; so countries like Sri Lanka will badly affected. Scientists argue that failure to control greenhouse gas emissions will have a greater impact on marine ecosystems than previously thought, the BBC reported.

How Global Warming affects Biodiversity of oceans

   The ocean has absorbed 80 per cent of the heat added to the Earth’s system by climate change.

    Warmer waters cause coral bleaching, which in turn negatively impacts the entire coral ecosystem.

    Many species will be forced to migrate so they can maintain the temperature conditions they need for feeding and reproduction.

   Alteration to water temperature can directly impact development, age of sexual maturity, timing of spawning, growth, and survival of most fish.

    Decreased upwelling due to warmer waters means that fewer important nutrients from lower in the water column will make it to the surface of the water. Many important marine ecosystems almost completely depend on nutrients from such upwelling areas – for example, marine habitats around the Galapagos Islands and along the US coast of California.  

  Acidification directly harms the many ocean plants and animals that build shells of calcium carbonate – including many tropical reef-building corals, coldwater corals, mollusks and other scallops, crustaceans such as lobsters and crabs, and some microscopic plankton that make up the foundation of the food web throughout most of the ocean.

    Many of those same shell-forming organisms provide critical habitat and food sources for other organisms.

How it impacts human welfare:
As in all instances, people are directly linked to life around them. People and many industries around the world rely on the ocean for food and other natural resources. For instance, upwelling areas provide some of the richest fishing grounds in the world. Likewise, coral reefs provide habitat for fish and other protein food sources for people, as well as important tourism economies in many areas. As warming ocean waters impact life within the ocean, humans and industries dependent on them are likewise impacted.

Source: www.conservation.org

http://www.lakbimanews.lk/index.php?option=com_content&view=article&id=7357:fish-ashore-at-coastal-waters-in-many-areas&catid=41:mag&Itemid=12

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

Piranha - The Amazonian Freshwater Fish

Published on LakbimaNews on 10.10.10

The World Oceans Day

Published on LakbimaNews on 13.06.2010

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