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

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