Fish aggregates at coastal waters – linked with weather changes


Last week, this blog reported about mass influx of Dragonflies that usually occurs in this period of time. This week, the fishermen got a bumper harvest from fish aggravate in coastal waters..!! 

Reports from East coast indicated that the fish has come to areas near shore giving bumper harvest

Malu, Malu, Malu: Thousands of fish were washed ashore yesterday due to changes in the weather pattern and the temperature of the seabed. Children and other residents of Beruwala are seen collecting the fish, dead or alive, with experts saying the fish was not harmful for consumption. Pic by S. Siriwardena/SundayTimes

to the fishermen. This is been reported mainly in Kanthamkudi and other areas in Batticaloa, but our correspondents from Beruwala too reported lots of fish been found making it maritime for fishermen.

But this has puzzled general public where many fears it is a sign of an incoming disaster. SundayTimes asked the Oceanography experts to find out the reason for this phenomenon. Dr.K.Arulananthan – the head of National Institute of Oceanography and Maritime Science based at NARA said has been caused due to changing patterns of Oceanic Currents.

Sri Lanka is now experiencing the second Inter Monsoon Rains. According to Dr.Arul, During the South Western Monsoon, the East Indian Coastal current flows from Arabian see toward Bay of Bengal via Southern tip of Sri Lanka. But on the North-western Monsoon; the direction of this East Indian Coastal Current reverse and it happen during the Inter-monsoon season. This brings cold water from Bay of Bengal region and this change of temperature assist growing of Algae and Planktons that leads to algae bloom. Little fish gathers to feed on these microscopic plankton and even big Pelagic fish lives in open seas follows the smaller ones making this present fishing frenzy in many areas, explained Dr.Arul.

The Sardines or Keeramin and Skipjack Tuna are the most notable fish gathered in numbers during past few days. The said phenomena is more applicable for pelagic fish, comments Dr.Arul. The expert also explains another possibility of getting some of the dead fish washed ashore. The Algae is also perform Photosynthesis which consumes the Oxygen in the water. In the waters where Algae bloom, the fish find lack of Oxygen and many dies. Some of these dead fish washed ashore while others sunk deep down to bottom. The decaying bodies of fish at the bottom deplete the Oxygen in that region which affect the bottom dwelling fish like Eel or Ray fishes.

This year Sri Lanka experienced a delayed South West monsoon and perhaps these climatic changes aggravated the differences of the oceanic current to make it more observant. However, Dr.Arulananthan calls it is a normal phenomena and nothing to worry. But the Climate Change may bring more such abnormal changes of weather patterns that leads to phenomenas like this in the future fears the experts.

Many fears that this could be bad omen remembering that just before 2004 Tsunami, loads of fish aggravated in similar manner. Dr.Arul reminding that Tsunami came in December and this phenomenon of changing of East Indian Coastal Current occur during October or November that could have triggered fish aggravation in 2004. He also says the underwater earthquakes might make bottom dwelling fish lives in the deep to migrate to other regions in sea via Oceanic currents, but the fish caught during last few days are not abnormal species, but the common ones usually found in our oceans.

However, it is interesting to know that how the changes of climatic patterns effects the animal behavior as only last week SundayTimes reported about a Dragonfly Migration that follows Inter Tropical Convergence Zone which falls on the same time period across Sri Lanka.

Beruwala too records mass fish death

Meanwhile a large scale of fish deaths was also reported in Beruwala. Hundreds of fish were found dead in a stream called ‘Sellie Ela’ according to NARA sources. This waterway is getting full with water brought in by rain and the nutrients brought in with water increased the algae growth making an algae bloom. Dr.Rekha Maldeniya of NARA said when that the algae emits oxygen during day time when doing photo synthesis and emit carbon dioxide at night while absorbing oxygen in the water. So this deplete the Oxygen in water killing the fish. It is also reported that the water in this ela is now turned into blackish, and Dr.Maldeniya said it is due to died algae. These algae when dead can emit toxics which cause the death of fish. Dr.Maldeniya said these 2 factors were the reason for Beruwala fish death.

Some of these dead fish ended up in the sea.

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. The researchers have studied change of body size of some 600 species based on models between 2001 and 2050.

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 the fish and this study will be another blow. The researchers pointed out that worst impact could be observed in the tropical regions, so countries like Sri Lanka will be expected to be badly effect.

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