Ocean Acidification Could Make Fish Lose Their Fear Of Predators, Study Finds

By Katie Valentine
 

CREDIT: Shutterstock

Add “losing fear of predators” to the long list of impacts acidifying oceans could have on fish and other marine life.
A new study published in Nature Climate Change has found that elevated CO2 levels in marine waters make reef fish attracted to the smell of their predators, rather than being repelled. Researchers looked at multiple species of reef fish living near natural volcanic CO2 seeps in Papua New Guinea, an environment the study says is acidified to levels comparable to projections of what the entire ocean’s acid content will be in the next 100 years. They compared the behavior of the fish living in the acidified environment to fish in nearby, less acidified reefs, and found that, while fish in the nearby control reefs avoided water streams that contained predator odor, fish from the acidified reef spent 90 percent of their time in water streams that smelled of their predators.
On top of that, fish that lived under high-CO2 conditions were bolder than other fish — meaning that they emerged more quickly from their hiding places after a disturbance and ventured farther from their hiding places than other fish — and couldn’t differentiate the smells of different habitats. Fish from the control reef spent more than 80 percent of their time in hiding, while two species of damselfish from the acidified reef spent less than 12 percent of their time in shelter, and two other fish species studied spent no time in shelter, preferring to swim in more exposed, open water
Danielle Dixson, assistant professor at Georgia Tech and co-author of the study, told ThinkProgress that the results of the study were surprising because scientists long believed that fish would be able to deal with ocean acidification due to their natural mechanism for coping with increased levels of CO2. When fish are exposed to high acid environments, they absorb the acid into their bodies, and to compensate for the increased acid, they increase the amount of bicarbonate — a base — their bodies produce.
“The thing that people didn’t really think about was that when they up-regulate all this bicarbonate, it interacts with neurological pathways,” Dixson said.
Dixson said that when there’s too much bicarbonate in the fish’s system, their GABA receptor stops working properly, causing the cognitive issues the researchers recorded. These effects have major implications for the future of the ocean ecosystem. The balance of the acidified reef ecosystem in the study did not suffer as a result of the cognitive problems of the fish, mainly because there were fewer predators in the environment and because, when young fish were killed by predators in the acidified environment, other young fish would migrate from nearby, less acidified reefs to replace them. But when all the oceans are at the level of the CO2 seep ecosystem, this replacement from fish in less acidified waters won’t be an option.
“It is hopeful that there are still fish that live [in the CO2 seep sites] and that they’re metabolically the same as the fish that live in the non-CO2 seep site, but the degree of aid that the control sites are providing the CO2 sites is unknown,” Dixson said. “As the world acidifies — in 100 years when the ocean is expected to be the equivalent of a CO2 seep reef — there won’t be these safe havens that can help.”
The study isn’t the first to document ocean acidification’s wide-reaching effects on fish and other marine species. Another study from August also found that fish could become confused and hyperactive as acid levels increase in the ocean, and also found evidence that the metabolism of fish could change. That study also found that when atmospheric carbon levels reached 500 to 650 parts per million — levels that are predicted by 2100 — corals, echinoderms (such as starfish), mollusks and fish were negatively impacted. Researchers have also predicted that ocean acidification could lead to a decline in shellfish, and that coral will struggle to build its skeleton as acidity rises. The effects of acidification could be so harmful to coral that Oceana predicts some species of coral could become functionally extinct within 20 years.

Source:  http://thinkprogress.org

Khan Traders Fish Meal — Karachi

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When male fish turn female!

Written by Oman Observer



In what can be termed as a perfect case of gender-bender among fish, biologists have found evidence of “feminisation” of male fish in the estuaries in the Basque coast of Spain. Pollutants acting as oestrogens are responsible for this phenomenon which, among other changes, is causing ovocytes — immature ova — to appear in male fish, biologists claimed. The acquisition of feminine features by male fish has been detected, to a greater or lesser extent in all the estuaries — not only in the characteristics of the gonads of the specimens analysed but also in various molecular markers.
“The results show that endocrine disruption is a phenomenon that has spread all over our estuaries, which means that, as has been detected in other countries, we have a problem with pollutants,” explained Miren P Cajaraville, Director of the group of Cell Biology in Environmental Toxicology at the University of the Basque Country. The team has conducted research using thick-lipped grey mullet and has analysed specimens in seven zones in coastal Spain — Arriluze, Gernika, Santurtzi, Plentzia, Ondarroa, Deba and Pasaia. The results of the research were published in the journal Science of the Total Environment and Marine Environmental Research. — IANS
Source:  http://main.omanobserver.om

Pollution is disrupting these fish and their genitals

by Nicholas Tufnell

Grey mullet fish have been caught exhibiting female gonads

Shutterstock

 

The gonads of thick-lipped grey mullets are becoming increasingly feminised in the estuaries of Spain's Basque Country, according to research carried out by members of the Cell Biology in Environmental Toxicology group from the University of the Basque Country. The cause of this feminisation is thought to be due to certain pollutants, which are increasing oestrogen levels in the fish.
The specimens tested came from six zones: Arriluze and Gernika in 2007 and 2008, and since then, Santurtzi, Plentzia, Ondarroa, Deba and Pasaia. Feminised gonads aren't the mullet's only problem -- the acquisition of feminine features has also been detected in various molecular markers.
According to the director of the research group, Miren P. Cajaraville, the results show that "endocrine disruption is a phenomenon that has spread all over our estuaries, which means that, as has been detected in other countries, we have a problem with pollutants".
The source of these pollutants can be found in products many of us use every day, including contraceptive pills, perfumes, detergents and pesticides. The chemicals inside these products react with the fish, causing endocrine disruption, which can throw some fish hormones into disarray. There is very little known about the full effect of these pollutants as they have only recently appeared in the ecosystem.
According to Cajaraville, "our discoveries are significant, because they enable us to know how far these pollutants have spread in our estuaries and rivers and what effects they have; that way, we will be able to adopt methods to prevent them reaching our waters, like legal regulations governing their use."
The pollutants, it is thought, have started to appear in these estuaries as a result of industrial farming and through cleaning systems in wastewater treatment plants. "Our main hypothesis," says Cajaraville of the Urdaibai Biosphere Reserve, "is that they come from the water treatment plant. It was the first place we studied, and continues to be, by far, responsible for the highest percentage of recently appearing pollutants."
 The results of the research have been published in two papers, one in the journal of Science of the Total Environment and the other in the journal of Marine Environmental Research.
Source:  http://www.wired.co.uk

Giant Cambrian shrimp fossils discovered in Northern Greenland

Both Tamisocaris and its cousin had compound eyes that would later be a defining characteristic of many insects, and also a circular mouth.

 

Science Recorder | James Sullivan | Thursday, March 27, 2014

On Wednesday, paleontologists announced the discovery of a strange sea creature that swam the oceans over 520 million years ago, during the Cambrian explosion, when a stunning array of diversity first appeared on the Earth. The newly discovered creature, a small filter feeding arthropod called Tamisocaris, reached 28 inches long. It is a distant cousin of the famous Anomalocaris, which may have been one of the world’s oldest apex predators, and whose modern day descendants include centipedes.  Although both the Tamisocaris and Anomalocaris are both members of the classification group that includes crustaceans, insects, and arachnids, nothing quite like the Tamisocaris, which was first found in a Greenland shale bed back in 2009, is alive today.
According to the leader of the study, paleontologist Jakob Vinther from Britain’s University of Bristol, the Tamisocaris was one of the largest creatures alive in the Cambrian, making it what Vinther referred to as a “gentle giant.” Although it’s not the same as a whale or a basking shark, it filled a similar ecological role at the time – using comb-like bristles on its appendages to trap bits of plankton and zooplankton – small plants and animals that it would eat, sucking the pieces into its mouth, rather than hunting and stalking prey.
The Anomalocaris possessed a similar pair of spiny, grasping appendages by its mouth, but with the purpose of catching prey, such as trilobites and small jawless fish. Both Tamisocaris and its cousin had compound eyes that would later be a defining characteristic of many insects, and also a circular mouth.  Although legless, it had a number of flaps down its back that made swimming movements possible.
What is significant is that the adaptation of filter feeding may suggest insights into how the similar development happened in whales, which are also plankton feeders, as well as crustaceans, some of which grow fairly large but feed primarily with spiny appendages like Tamilocaris. Both animals lived alongside primitive shellfish, jellyfish, and starfish, as well as jawless fish and a diverse array of trilobites, but the existence of Tamilocaris suggests a greater deal of diversity may have existed among arthropods than was previously thought and that the Cambrian age was home to a number of species that have yet to be discovered.

Source: http://www.sciencerecorder.com

Dead on arrival: Fishermen auction 5-metre-long whale shark

Published in The Express Tribune,

Residents gather around a whale shark after it was brought to Karachi’s fish harbour after it was enmeshed by a shrimp trawler in Balochistan. PHOTO: REUTERS

KARACHI: A five-metre-long whale shark, which was enmeshed by a shrimp trawler in Balochistan, was brought dead to Karachi on Wednesday, where its pieces were auctioned.
The female whale shark was tangled at Phor near Sonmiani. “Soon after its arrival, the fishermen cut it into pieces and auctioned it,” said World Wildlife Fund (WWF)-Pakistan director Rab Nawaz.
“This is an endangered species under the Convention of International Trade and Endangered Species,” he said. “But some cruel people killed it and sold its pieces at throwaway prices. There is no law in Pakistan to protect the shark and take action against the people who violate it.”

WWF-Pakistan has been advocating for the inclusion of this species in Schedule-I of the Wildlife Act of Sindh and Balochistan so that it’s enmeshing, trade and utilisation in any form can be banned. “India has already made the law but we are still waiting.”
The whale shark is found in tropical and subtropical waters of the ocean. It is commonly found in Pakistan. In fact, the first account of their organised fishing is from Pakistan. Luckily this fishery in Pakistan was stopped in the early 1970’s.
Muhammad Moazzam Khan, the former director-general of the fisheries department, stressed on the need to protect whale sharks because the Northern Arabian Sea, bordering the coast of Pakistan, is one of the world’s most important feeding, basking and breeding grounds for them. There are only a few places in the world, including Pakistan and India, where documented records of their breeding are available.
“The whale shark is not consumed in Pakistan but its meat is used for fish meal, the liver is used to extract oil for smearing the hull of fishing vessels and the fins are exported illegally to Hong Kong and China for shark fin soup,” he explained. The fishermen who sold its pieces on Wednesday hardly fetched more than Rs20,000. “This practice should be discouraged by the government.”
Umair Shahid, who has been working in marine fishing for a long time, suggested there should be collaboration between the academia, conservation organisations and fishermen to work towards the conservation of threatened animals. “There is no comprehensive research on biology and other aspects of marine animals,” he said. “All stakeholders should take the necessary steps to protect endangered animals whose population is seriously declining in Pakistan.” He suggested transforming fishing gears to improve fisheries’ management and complying with internationally binding agreements, which Pakistan is a signatory to.
“During the last eight months, four such entrapped whale sharks have been released by the fishermen following an awareness campaign started by WWF-Pakistan,” recalled Khan. “We demand the government to make strict laws and take action against those who kill such endangered species.”
Source: http://tribune.com.pk

Profile and Products of Khan Traders Fish Meal

 By Naeem Khan

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