Warmer seas spell unsolvable trouble for Bangladesh’s national fish Hilsha

As the world gets warmer, fish stocks in the oceans face devastation particularly in tropical countries like Bangladesh, researchers say.

News Deskbdnews24.com
Published : 13 Jan 2017, 05:05 PM
Updated : 13 Jan 2017, 10:29 PM

The Hilsha and the Bombay Duck, or ‘Loitta’ are at risk as ocean temperatures rise, according to a study led by Jose Fernandes of the Plymouth Marine Laboratory.

With rising temperature, fish seek cooler waters and head to higher latitudes.

The study said measures against overfishing and sustainability may reduce the damage caused by warmer waters but these stocks will still face significant harm.

According to the Guardian report that mentioned the study, fish provide 60 percent of animal protein in Bangladesh.

The climate change would affect nutrient flows in coastal waters, ocean temperatures and sea levels, causing crisis to millions that inhabit the areas, particularly fishermen whose livelihood depend on these stocks. 

“If you look at the world’s fish catches as a whole, you find they are made up, more and more, of warm-water species as opposed to catches in previous years which had more species that were from cooler waters,” said Andrew Bakun, marine biologist at Miami University.

Despite the huge strides made in fishing technology, the world’s annual catch continues to decline by more than 1 million tonnes every year due to over-exploitation, writes the Guardian.

Now with the rise in temperature, fish are moving hundreds of miles from their old grounds and, in some places, beyond zones set up to protect them.

“All the world’s oceans are facing intense problems but the problem is going to be particularly serious for tropical countries, which are often underdeveloped and are far less able to maintain sustainable management regimes for their fisheries,” said York University marine biologist Callum Roberts.

The oceans resources provide critical source of protein for more than 2.5 billion people, the report said.

As species change their distribution for changes in their environment, measures taken by governments for sustainability are bound to lose effectiveness, said another study headed by scientist John Pinnegar.

In addition to overfishing and warmer seas, acidification, due to oceans absorbing the increased amount of carbon dioxide from the atmosphere, was endangering marine life.

Coral reefs are home to thousands of different species of fish and in Australia, vast swaths of Great Barrier Reef Coral was killed last year by a combination of acidity and a rare underwater heatwave.

Scientists have warned that all coral reefs are at the risk of being destroyed by the end of the century even if carbon dioxide emissions are relatively contained in the coming decades.

Apart from coral, the effect would be dire on crustaceans because acidic water disrupts the formation of their shells made from calcium carbonate.

George Waldbusser of Oregon State University explained the ‘death race’ of an oyster to Climate News Network.

“From the time eggs are fertilised, Pacific oyster larvae precipitate roughly 90 percent of their bodyweight as calcium carbonate shell within 48 hours.

"They must build their first shell quickly on a limited amount of energy – and, along with the shell, comes the organ to capture external food. It becomes a death race of sorts. Can the oyster build its shell quickly enough to allow its feeding mechanism to develop before it runs out of energy from the egg?”

The research concluded that the impacts of climate change, under greenhouse emissions scenario A1B, are likely to reduce the potential fish production in the Bangladesh exclusive economic zone by less than 10 percent.

"However, these impacts are larger for the two target species. Under sustainable management practices, we expect Hilsa shad catches to show a minor decline in potential catch by 2030 but a significant (25%) decline by 2060," it said.

"However, if overexploitation is allowed, catches are projected to fall much further, by almost 95% by 2060, compared with the Business as Usual scenario for the start of the 21st century," it added. 

It also said the results demonstrate that management can mitigate or exacerbate the effects of climate change on ecosystem productivity.

According to the Ministry of Fisheries and Livestock, 11 percent of the fish caught in Bangladesh annually are Hilsha, which contributes 1 percent to the country's GDP.

World Fish says catches in Bangladesh make up 65 percent of the Hilsha caught across the globe. Around 2 million people directly or indirectly depend on Hilsha.