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Fish are losing their survival instinct – even becoming attracted to the smell of their predators – as the world’s oceans become more acidic because of climate change, new research said Monday. The study of fish in coral reefs off the coast of Papua New Guinea – where the waters are naturally acidic – showed the animals’ behaviour became riskier.

“Fish will normally avoid the smell of a predator, that makes perfect sense,” lead author Professor Philip Munday from Australia’s James Cook University said. “But they start to become attracted to the smell of the predator. That’s incredible. “They also swim further from shelter and they are more active, they swim around more. That’s riskier behaviour for them they are more likely to be attacked by a predator.”

Munday said the research, published in the journal Nature Climate Change, was important given that about 30 percent of the carbon dioxide released into the atmosphere is ultimately absorbed by the ocean, a process which results in the seas becoming more acidic. Acidification around the reefs studied is at levels predicted to become ocean-wide by the end of the century as the climate changes.

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Science Codex

A new modeling study suggests that fish consumption advisories for expecting mothers are ineffective in reducing infant exposure to long-lived contaminants like persistent organic pollutants (POPs).

The study, performed by a team of researchers including University of Toronto Scarborough PhD student Matt Binnington and Professor Frank Wania, looks at how different levels of environmental contamination, a mother’s compliance with advisories, and the behavior of chemicals in the body influenced exposure in her children.

Their model estimates that women who stop eating fish shortly before or during their pregnancy may only lower their child’s exposure to POPs by 10 to 15 per cent.

“We have to be careful in saying fish advisories don’t work at all because they can work very well for reducing exposure to quickly eliminated contaminants, such as mercury,” says Binnington. “But for POPs we found that they are not very effective.”

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NBC News

A hydroelectric dam building boom in the Pacific Northwest in the past century drove dozens of salmon runs to extinction and has cost taxpayers billions of dollars to try to save the fish that remain. Today, scientists from the region are hard at work to prevent a repeat of history at a time when countries around the world race to wring more energy from rivers to fuel a power hungry and warming planet.

“We’ve made some pretty good progress here in the Pacific Northwest on determining criteria that can help keep fish safe,” Richard Brown, a senior research scientist at the Department of Energy’s Pacific Northwest National Laboratory in Richland, Wash., told NBC News.

Brown and his lab colleagues are collaborating with researchers from Laos, Brazil and Australia to apply what they’ve learned to reduce injury and death to fish passing through dam turbines on their way to the sea.

The change in pressure that fish experience while passing through turbines causes a rapid expansion of a swim bladder used to maintain buoyancy. In some cases, the organ can rupture. The pressure change can also cause pre-existing gas in the body to expand, eyeballs to bulge and stomachs to pop out of mouths. For some species and life stages, injuries from this so-called barotrauma may cause more deaths than lethal injuries sustained when fish are struck by spinning turbine blades, according to Brown.

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PhysOrg

Male cod may ‘sing’ to females during mating, suggests a new study investigating the sounds cod and pollack produce during the spawning season.

The research, published in the Journal of Fish Biology, aimed to learn more about these noises, and why the fish make them. They discovered that the grunts were produced in rhythmic patterns, suggesting that the females in the shoal may use these rhythms to choose a mate.

To investigate the noises, the team studied two populations of fish in tanks at a fishery in Scotland. Cod, had previously been recorded making grunting noises as they got ready to spawn, but the pollack’s grunt had never been recorded until now. You can hear the grunts produced in the recordings on this page.

‘We already knew male cod produce these sounds, we just wanted to dig a bit deeper, and find out if the sound changed over time to indicate that a spawning event might be occurring. But it was really exciting to find pollack also produce these sounds,’ says Lindsay Wilson, a NERC-funded PhD student at the Scottish Association for Marine Science (SAMS) who led the research.

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South China Morning Post

Escalating carbon dioxide emissions will cause fish to lose their fear of predators, potentially damaging the entire marine food chain, joint Australian and US research has found.

A study by the Australian Institute of Marine Science (Aims), James Cook University and the Georgia Institute of Technology found the behaviour of fish would be “seriously affected” by greater exposure to CO 2.

Researchers studied the behaviour of coral-reef fish at naturally occurring CO 2 vents in Milne Bay, in eastern Papua New Guinea.

They found that fish living near the vents, where bubbles of CO 2 seeped into the water, “were attracted to predator odour, did not distinguish between odours of different habitats, and exhibited bolder behaviour than fish from control reefs”.

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The Columbia Basin Bulletin

A study of 91 stream restoration projects in the lower Columbia River and Oregon coastal river basins that added wood to increase pool complexity and pool surface area — better habitat for juvenile coho salmon — found that after six years most of the projects had increased over-wintering rearing capacity for the salmon.
 
The restoration projects placed large logs in small to medium sized streams that had been damaged by years of neglect and that had lost much of the natural stream’s complexity of pools and gravel. The projects’ design was to use wood without cabling to hold them in place in areas that would be expected in a natural stream. After six years of monitoring, biologists saw an increase in the surface area of pools and an increase in gravel.
 
However, the amount of large wood that had been installed declined over the six years in almost 75 percent of the projects and few sites collected new wood. But even with this decline, wood remained on average 100 percent of the pretreatment levels of wood.
 
In addition, changes in channel complexity and flood plain connectivity, the more wholistic and desired outcomes of the projects, were not observed.

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The Columbia Basin Bulletin

Juvenile wild steelhead are smaller than hatchery fish when they reach the ocean, but have a higher feeding success, are in better condition and grow faster than hatchery fish once they arrive in the marine environment, according to a recent study.
 
“Juvenile steelhead enter the marine environment each year at a similar size and condition, yet after a short period in the marine environment, they are feeding and growing at a much higher rate than in the estuary as they quickly move offshore and this growth depends on ocean conditions,” said Elizabeth A. Daly, senior faculty research assistant for the Cooperative Institute for Marine Resource Studies (Oregon State University and NOAA Fisheries), which is located at the Hatfield Marine Science Center in Newport, Ore.
 
The Bonneville Power Administration since 1998 has funded NOAA and CIMRS/OSU on an ongoing ocean research project on juvenile salmon marine survival.
 
The study measured and weighed both wild (unmarked fish) and hatchery juvenile steelhead in the Columbia River estuary and in the ocean. According to the report, wild steelhead were slightly shorter than hatchery fish as they entered the ocean, but were overall healthier, fed with greater success and grew faster than the hatchery juveniles.

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Livescience

The Mexican blind cavefish does not have eyes, but it can “see” obstacles in dark caves by puckering its mouth and producing bursts of suction, according to a new study. The research describes this unique form of navigation for the first time.

Scientists previously thought the eye-less Mexican cavefish navigated by sensing changes in water pressure produced by waves sent off from the fish’s own body. But when the researchers examined the fish, they found some problems with this explanation. For example, larger fish, which would presumably produce larger waves, should be able to identify objects from farther away than smaller fish. In fact, larger fish detected objects at about the same distance as smaller fish did.

Researchers at Tel Aviv University in Israel decided to investigate the sightless navigation further, conducting an experiment in which they counted the number of times the fish opened and closed their mouths when near objects the fish were familiar with. The researchers then moved the objects and observed changes in the fishes’ mouth movement in the unfamiliar environment.

The fish opened and closed their mouths more than twice as frequently in unfamiliar surroundings, and more frequently when approaching an object than in the open, with no objects nearby, suggesting this behavior plays a role in detecting the fish’s environment.

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FIS

A team of researchers from the Institute of Marine Sciences (ICM) discovered a new hormonal mechanism that controls the formation of spermatozoa in fish.

According to Joan Cerdà, initiative leader and researcher at the Institute of Agrifood Research and Technology (IRTA) of the Higher Council for Scientific Research (CSIC), this finding could help clear up the mystery about the causes of male infertility in fish.

The authors of this research, whose results were recently published in the journal Proceedings of the National Academy of Sciences (PNAS), focused on studying the causes of infertility of Senegalese sole males bred in captivity.

One of the hypothesis to explain this is that this is an epigenetic problem during larval development due to a still undetermined cause.

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Science Codex

A new study showed that several Gulf of Mexico fish embryos developed serious defects in heart development following exposure to crude oil from the Deepwater Horizon oil spill. The study is the first to analyze the effects of the primary toxic agents released from crude oil on several commercially important pelagic fish species that spawn in the Gulf of Mexico.

The research team, which included five researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, concluded that, “losses of early life stages were therefore likely for Gulf populations of tunas, amberjack, swordfish, billfish, and other large predators that spawned in oiled surface habitats.”

“This study is the first to understand the impacts of the Deepwater Horizon oil spill on the early life development of commercially important fish in the Gulf of Mexico,” said Daniel Benetti, UM Rosenstiel School professor of marine affairs and policy and director of the Aquaculture Program. “The findings can be applied to fisheries management questions in marine regions where crude oil extraction is prevalent.”

The study, published in the March 25 issue in the journal of the Proceedings of the National Academy of Sciences (PNAS), assessed the impacts of polycyclic aromatic hydrocarbons (PAHs), a toxic agent released from crude oil, from Deepwater Horizon oil samples on embryos of bluefin tuna, yellowfin tuna, and amberjack. Embryos were exposed to two different oil samples, one collected from surface skimming operations in the Gulf of Mexico and another from the source pipe attached to the damaged Deepwater Horizon wellhead.

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