Low fish catch – India

Maharashtra witnessed lowest fish catch in 45 years in 2019. Fishers have also reported a 50% decline in their annual fish catch, attributing recurring cyclones for reducing their fishing window. Fish migrate from warm waters to cool waters, a phenomenon that has already begun as the Indian ocean is warming up is one of the reasons for lower fish catch. The marine algae that is the base of aquatic food web has been disappearing in the western Indian Ocean owing to rising sea temperatures.

Global Warming

Warming Waters Inhibit Fish from Reproducing

As many as 60 percent of the world’s fish species could struggle to breed and reproduce if climate change causes the Earth to warm by 5 degrees Celsius over the next 80 years, the current projection for what will happen if greenhouse gas emissions continue unchecked, according to a new study.

A study released Thursday in the journal Science that examined nearly 700 species of freshwater and saltwater fish found that 6 in 10 species would be affected if bodies of water around the world continue to warm. If global warming was limited to 1.5 degrees Celsius, the study’s authors added, that number falls as low as 1 in 10 species.

Species unable to reproduce in traditional habitats may either move to deeper water or further north and would result in local extinctions.


Farmed Fish Are Becoming More Dangerous to Eat

A report in Nature Communications has linked global warming to spreading antibiotic resistance in farmed fish and shellfish. This is why? Because seas and lakes are warming, albeit slower than our air; bacteria adore this warmer environment; fish farmers are dosing the hapless sea-life with ever increasing doses of prophylactic antibiotics, in the fond but futile hope of keeping them healthy long enough to be sold as food. All of this drives the development of antibiotic-resistant bacterial species – which can and do confer their resistance unto nonresistant bacterial species. Aquaculture is now responsible for more than half the fish and seafood consumption around the world.


Insectageddon: They’re starving

A host of sources warn that locusts aside, insects are declining, which is seriously bad news for posterity. Now a study done in the canton of Zurich, representative of all central Europe, and reported in Ecological Applications, has isolated a cause beyond rampant pesticide use and habitat devastation: they’re starving. Farming has “captured” vast areas and the diversity of food plants the insects need has dramatically shrunk over the past 100 years, leaving bees, butterflies and, yes, flies unable to find the food they need. Even leaving aside fly rights, this is seriously bad news because insects play an unimaginably enormous role in the ecology.

Global Warming

Climate change shrinking fish populations worldwide

Warming oceans from human-caused climate change has shrunk the populations of many fish species around the world, according to a study released Thursday.

Overfishing and poor fisheries management have only intensified the problem.

Some of the biggest drops were In the seas near China and Japan, where fish populations dropped by as much as 35 percent from 1930 to 2010, the decades analyzed in the study. Globally, the drop is 4.1 percent for many species of fish and shellfish, according to the study.

Keeping fish stocks plentiful is vital, the study says, since Earth’s oceans have become a crucial source of food for the planet’s rapidly growing population. In fact, more than 50 million people around the world earn a living by fishing, and seafood provides about half of the protein eaten by people in developing nations, according to the study.

“We recommend that fisheries managers eliminate overfishing, rebuild fisheries and account for climate change in fisheries management decisions,” the study said.

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Huge muddy plume of water seeps into Great Barrier Reef

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Images show Australia’s Great Barrier Reef being hit by an “extremely large” patch of muddy flood water that experts say could harm the world wonder. The polluted floodwater is flowing out as far as 60 kilometres from the Queensland coast following weeks of heavy rain.

It’s thought that around 600km of the reef’s outer edges have been affected by the dirty water. Scientists say that the water is likely to contain nitrogen and pesticide chemicals that could potentially kill coral and seagrass should it stay around for some time.

Smart Swimmers

A lowly reef-dwelling fish known as the cleaner wrasse has been elevated into an exclusive club in the animal kingdom whose members have the ability to recognize themselves in a mirror.

Other than humans, only great apes, killer whales, Eurasian magpies and bottlenose dolphins had demonstrated that ability. The trait is viewed as an indication of self-awareness.

The cleaner wrasse had previously been observed living complex social lives where it formed allegiances and even demonstrated the capacity for deception. “These fish are fascinating in their breadth of cognitive abilities – and underappreciated,” said Alex Jordan, a biologist at the Max Planck Institute and the study’s lead researcher.

Global Warming

Climate Change Is Causing Fish to Shrink

Fishermen over the past several years have noted that fish appear to be shrinking. That observation was validated in 2014 by research that found commercially important fish stocks in the North Sea, such as sole, herring, and haddock, have decreased in maximum body size over a 40-year period.

New research published in the journal Global Change Biology explains that these species and many others are ectotherms, meaning that their body temperature depends on environmental temperature.

As the oceans warm up, their bodies will do so as well. Higher temperature within the scope that the fish can tolerate generally increases the rate of biochemical reactions in the fish’s body and thus increases their body metabolic rate. Metabolic rate refers to an animal’s oxygen consumption, which also naturally increases as fish grow into adulthood because their body mass becomes larger.

One might wonder why fish and other marine ectotherms aren’t just taking in ever more oxygen to coincide with this natural growth due to maturation and the rise of ocean temperatures. They don’t because at a certain point they cannot keep up.

The researchers point out that the surface area of an animal’s gills — where oxygen is obtained — does not grow at the same pace as the rest of its body. This is because gills, in order to work, must function as a two-dimensional surface — width by height — and thus cannot grow as fast as the three-dimensional volume — width by height by depth — they have to supply with oxygen.

The reductions will be in the range of 20–30 percent if ocean temperatures continue to climb due to climate change. At the higher end of that range is one of the world’s most important commercial fish: tuna.

Tunas are active, mobile, and fast-swimming animals that need a lot of oxygen to maintain their lifestyle. They have to keep swimming non-stop in order to get more water through their gills to obtain sufficient oxygen. Thus, when temperature increases, they are particularly susceptible to not having sufficient oxygen to support their body growth.

For a 2 degree Celsius (3.6 degree Fahrenheit) increase in water temperature, which is approximately what is expected to occur in oceans around the world by the mid-21st century, tunas such as the Atlantic bluefin tuna will potentially decrease in body size by 30 percent.

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Nature – Images

Interesting Images

Deep-Sea Stroll: This fish, an armoured sea robin, ‘walks’ on the ocean floor – these fins are made for walking.

Noaa sea robin


Fish prefer to eat plastic over food – and it is killing them

Microplastic particles appear to be killing fish because their larvae prefer to eat them rather than their actual food, researchers have warned.

With fears that the amount of plastic in the oceans could soon equal the weight of fish in the sea, scientists have become increasingly concerned about the effects on the marine environment.

Now a study published in the journal Science has found that baby perch will actively choose to eat plastic over the plankton they would normally feed on. The researchers said this greatly increased mortality rates of the perch, stunting their growth and appearing to change usually innate behaviour. For example, they seemed to lose the ability to smell a predator that made them much more vulnerable.

When placed in a tank with a pike, perch exposed to microplastic were eaten four times more quickly than perch that had not been eating plastic. All the plastic-fed fish had been killed within 48 hours.

Microplastic is produced as larger pieces of plastic waste are broken down in the environment, but vast amounts of microfibers from synthetic clothes – things such as fleeces are essentially made of plastic – are produced each time they are washed and are small enough to pass through sewerage treatment plants and get into the sea. Cosmetics companies are also continuing to put plastic microbeads into their products.


Fish May Experience Emotion and Conciousness: Study

Fish have been observed exhibiting “emotional fever” when placed under stress, leading researchers to suggest that the creatures may experience emotions and consciousness.

Emotional fever, or the tendency to have higher body temperatures when stressed, had been thought confined to more complex animals.

A University of Barcelona team placed zebrafish in a tank with compartments at various temperatures.

The group that was exposed to stress, then released, mainly moved toward warmer water, increasing their body temperature by 3.6 to 7.2 degrees Fahrenheit.

“These findings are very interesting — expressing emotional fever suggests for the first time that fish have some degree of consciousness,” said researcher Sonia Rey.


First Warm-Blooded Fish Found

The car-tire-size opah is striking enough thanks to its rotund, silver body. But now, researchers have discovered something surprising about this deep-sea dweller: It’s got warm blood.

That makes the opah (Lampris guttatus) the first warm-blooded fish every discovered. Most fish are ectotherms, meaning they require heat from the environment to stay toasty. The opah, as an endotherm, keeps its own temperature elevated even as it dives to chilly depths of 1,300 feet (396 meters) in temperate and tropical oceans around the world.

The opah, also known as the moonfish, has relatively small red fins decorating its large, round body, which can grow up to 6 feet (1.8 meters) long. These fins, which flap rapidly as the fish swims, turn out to be important in generating body heat for the opah.

Researchers first suspected that something might be strange about the opah after analyzing a sample of the fish’s gill tissue. According to the new study, published May 14 in the journal Science, the blood vessels in the tissue are set up so that the vessels carrying cool, oxygenated blood from the gills to the body are in contact with the vessels carrying warm, deoxygenated blood from the body to the gills. As a result, the outgoing blood warms up the incoming blood, a process called counter-current heat exchange.

“There has never been anything like this seen in a fish’s gills before,” Wegner said in a statement. “This is a cool innovation by these animals that gives them a competitive edge. The concept of counter-current heat exchange was invented in fish long before [humans] thought of it.”

To confirm that these special gills helped the opah stay toasty, the researchers tagged a number of moonfish with temperature monitors and tracked the fish as they dove. The fish spend most of their time at least 150 feet (45 m) below the ocean surface. No matter how deep they dive, however, their body temperature stays about 9 degrees Fahrenheit (5 degrees Celsius) warmer than the surrounding water. Fat deposits around the gills and muscles help insulate the fish, the researchers found.

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Pollution Believed to Be Sickening Fish of the Deep

A groundbreaking study of the health of fish living in the depths of the continental slopes suggests that some species may have developed liver diseases, tumours and other health problems that could be linked to manmade pollution.

The research took place at depths between 2,000 feet and 1 mile in the Bay of Biscay, off the western coast of France, and revealed the first case of a deep-water intersex fish species.

Such conditions, in which the fish displays a blend of male and female reproductive organs, have also been found among fish in far more shallow and polluted waters from Europe to North America.

“In areas ranging from pristine, high mountain lakes of the United States to ocean waters off the coasts of France and Spain, we’ve now found evidence of possible human-caused pollution that’s bad enough to have pathological impacts on fish,” said fish disease expert and report co-author Michael Kent of Oregon State University.

While no clear evidence of a major pollution source was found near the deep-water diseased fish, the species there mature at a relatively old age.

Researchers believe they could have accumulated dangerous amounts of pollution during their lifetimes.

Global Warming

Warming Oceans Bring Big Challenges for Fish

Marine researchers have found that many species of fish around Australia are moving southward or otherwise shifting their ranges and egg-laying patterns in response to warming ocean waters.

Using a network of 62 GPS stations across the volcanic island, lead researcher Kathleen Compton of the University of Arizona found that some sites are rising as much as 1.4 inches per year.

“We found a mixed bag—some positive and some negative,” lead researcher Gretta Pecl told The Guardian. “Some species are shifting south and increasing their range while others are already at their tolerance for temperature, and as it warms, their range will shrink.”

The University of Tasmania scientist said that ocean temperatures off southeastern Australia are warming four times faster than the global average.

Other warming hotspots include the Atlantic off Brazil, parts of the Indian Ocean and the North Sea.

Pecl says species that are highly sensitive to temperature, will see their rate of growth and amount of energy needed for oxygen consumption will be altered by the warming.

Research published in 2013 found that fish species were being pushed towards the poles by warming oceans at a rate of about 4.3 miles every year, chasing climates in which they can survive.


Global Warming

Fish migrating to North-South poles due to global warming

A new study from University of British Columbia has claimed that a large number of fish are moving away from the oceans towards the poles at 26 kilometres per decade because of massive climate changes. The temperature of earth’s water is experiencing a incremental surge every year. As a result, fish are moving towards the poles and by 2050, there will be a huge vacuum of fish that are presently found in the oceans.

The study however concludes that there will be new species of fish and other sea animals to fill up this vacuum in the arctic ocean. Fisheries near the topical areas will suffer, according to the experts. The main reason behind this is the fact that many areas near the sea shores rely heavily on the sea food. The local inhabitants have developed a taste and liking to sea food that is present in deep waters for years. The fleeing of fishes will create the absence of sea food for these populations living near the coast.

The study depicts that, under best-case scenarios, fish will move towards North and South Poles at a speed of 15 kilometres a decade. William Cheung of the University of British Columbia says that many Scandinavian countries are already taking steps to prepare for this massive fish migration.

Migration of fish


Amazon’s Biggest Fish Faces Threat of Extinction

Measuring 10 feet (3 meters) long and weighing in at more than 400 pounds (180 kilograms), it’s hard to imagine that the arapaima, the largest fish in the Amazon River basin, could ever go missing. But these huge fish are quickly disappearing from Brazilian waterways, according to a new study.

A recent survey of fishing communities in the state of Amazonas, Brazil, found that the arapaima is already extinct in some parts of the Amazon basin. In other parts of the Amazon, its numbers are rapidly dwindling.

However, the researchers also uncovered some good news: In communities where arapaima fishing is regulated, the species is actually thriving, giving the researchers hope that conservation of the species is still possible.

Arapaima pirarucu 2007


Global Warming Causing Fish Heart Failure

It seems that some species of fish just don’t have the heart to endure a warming climate.

A New Zealand scientist says that climate change could be a leading factor in heart failure for some fish because the creatures aren’t able to maintain an optimum body temperature in the warmer waters.

The University of Auckland study found that when three fish species from various environments were exposed to warmer water, their hearts failed to function as temperatures increased.

Biologist Anthony Hickey said the Australian tropical fish known as moon wrasse proved to be the most sensitive to the warmer water.

Hickey said the fish can withstand a rise in temperature of only a few degrees before cell structures in their hearts, known as mitochondria, fail to function.

The findings could have implications for the world’s food supply.

The moon wrasse, found in Australian waters, is among the fish species most sensitive to warming waters.