Monday, 18 February 2019

Salmon populations may adapt their eggs to survive in degraded rivers

January 31, 2019, University of Southampton
A University of Southampton study suggests that the membrane of salmon eggs may evolve to cope with reduced oxygen levels in rivers, thereby helping their embryos to incubate successfully.
The research, funded by the Environment Agency and published in the journal Royal Society Open Science, has found that differences in the structure of the thin film surrounding a salmon embryo affects its ability to absorb dissolved oxygen from river water.
Atlantic salmon are in decline in their natural habitats and it's thought this is partly due to a reduction in the quality of the water in which they spawn. Sediments washed off the land can starve rivers of oxygen by encouraging more organic matter to grow and by silting up the gravel beds where salmon lay their eggs in nests (redds). The eggs rely on a sufficient flow of oxygen across their membranes to successfully incubate and this latest study examines how the structure of these membranes vary in different salmon populations.
The researchers took a range of measurements from membranes of eggs at a fish farm in Scotland and from conservation hatcheries in four different UK rivers; Dorchart, Tilt, South Tyne and North Tyne. They were chosen for their varying levels of sediment and oxygenation. The results showed membrane thickness, porosity and permeability varied according to each location.

Britain's most endangered species identified for first time as Natural England launches 'Back from the Brink' campaign

1 FEBRUARY 2019 • 10:59PM
Britain's 20 most endangered species have been identified for the first time by a host of wildlife and woodland charities, as Natural England has launched a campaign to bring them back from the brink of extinction.
The charities, including the RSPB and the Woodland Trust, have been given over £7.7 million in funding from the National Lottery and other donors to work together to save the endangered animals and plants.
Since the ambitious project began a year ago, the charities have already managed to reintroduce of the Chequered Skipper butterfly to the Rockingham Forest area of Northamptonshire. It  had been extinct in England since 1976.
Now, the various charities are working together for the first time to safeguard the rest of the animals on the list.
The species include the pine marten, which used to be Britain's third most common predator until it was hunted almost to extinction for its beautiful pelt.
While the population is recovering in Scotland, they are scarce in England. By the conclusion of this project, it is hoped they begin to colonise in Northumberland and Cumbria.
Funding for the project will mean that nest boxes can be built for them in the woodland areas they thrive in, and that the current pairs can be tracked.

Butterflies thrive in grasslands surrounded by forest

February 4, 2019, Linköping University
For pollinating butterflies, it is more important to be close to forests than to agricultural fields, according to a study of 32,000 butterflies by researchers at Linköping University and the Swedish University of Agricultural Sciences (SLU) in Uppsala. The results provide important knowledge about how to plan and manage the landscape to ensure the survival of butterflies.
Semi-natural grasslands are one of Sweden's most species-rich habitats, with a multitude of plants and butterflies. However, the amount of these areas has been reduced by 90% in the past 100 years. Semi-natural grasslands are often preserved as just small fragments in the landscape. Their loss has led to many species of butterfly being decimated, and in some cases eliminated from parts of Sweden. The researchers who carried out the new study, published in the scientific journal Landscape Ecology, have investigated how the landscape around these fragments influences different species of butterfly in southern Sweden. A total of 32,000 butterflies from 77 species were found.
"Several of our results are really exciting, and demonstrate that the species richness of semi-natural grasslands is influenced by other factors than the properties of the grasslands themselves. The surrounding landscape is also important for butterflies. If the semi-natural grasslands are embedded within large regions of arable land, the number of species is reduced", says Karl-Olof Bergman, senior lecturer in the Department of Physics, Chemistry and Biology, IFM.
The species richness of butterflies was in general greater in locations where large areas of semi-natural grasslands lay within 10-20 kilometres around the studied semi-natural grassland. Another important landscape feature linked to a larger number of butterfly species was if the grasslands were surrounded by forest.

Better fish welfare using 'sensor fish'

February 4, 2019, SINTEF
After many decades of salmon farming, recent years have seen studies into fish welfare in connection with issues such as how fish are treated in their cages. In particular, the fish farming sector is looking for better approaches to delousing.
Researchers have now developed an electronic sensor that can be used to measure the external factors that affect fish during processes such as delousing.
The project, Hydrolicerhas, been carried out by researchers to study a mechanical approach to the delousing of farmed fish. The method involves subjecting the fish to turbulence in a water chamber. Currents generated in the water mass effectively "lift" the lice from the fish with no need for chemicals.
"We have progressed from having no idea about what fish are exposed to in terms of mechanical stress to having access to a variety of measurements indicating the types of stresses involved," explains Torfinn Solvang, a research scientist at SINTEF, and manager of the Hydrolicer project.
The researchers discovered that the physical trauma incurred prior to delousing was probably more stressful than the process itself.
"The fish have to be moved from their cages into the delousing chamber using a pump system," says Solvang. "In order to feed the salmon into the pump, they first have to be crowded together so that the system can move fish and not just water. This process can take an hour or more, while the actual delousing is completed in less than thirty seconds," he explains.
The researchers also identified differences between pump systems. So-called ejector pumping, that works using high water pressure, exposed the fish to less physical stress (measured in terms of acceleration) than so-called impeller pumping, which moves the fish using a mechanical paddle installed in the water stream.
The results have encouraged the researchers to start looking for even more data on the stresses that caged fish are exposed to during a variety of operations, not least delousing.

Male killer whales hunt more than females

February 5, 2019, The Company of Biologists
 It's hard to tell just how imperilled killer whales are. With several different forms—some of which may even be different species—it's unclear which are at serious risk and which are less vulnerable. But one group is definitely in jeopardy. 'The southern resident killer whale population was listed as endangered in the United States in 2005', says Jennifer Tennessen from the National Oceanic and Atmospheric Administration (NOAA), USA and the decline of Chinook salmon in the Pacific Northwest—which are consumed by the population of ~75 whales—is believed to be one of the causes. While shipping also poses a risk to the animals, NOAA has been monitoring them for a decade and one of the scientists' main goals was to estimate how much fish the charismatic whales capture. But, with the majority of pursuits occurring beneath the waves, Tennessen and her colleagues needed to develop a technique based on the animals' manoeuvres that would allow them to identify when the mammals were successful. They publish their discovery that killer whale hunts are not always successful and that male killer whales hunt more than females in Journal of Experimental Biology.
Heading into the Salish Sea, between Vancouver Island, British Columbia and Washington State, Tennessen and her colleagues—Marla Holt, Candice Emmons, Brad Hanson, Jeff Hogan and Deborah Giles—attached tags to 21 whales to record their sounds and underwater movements. Then the team followed the animals, noting where they surfaced and what they were up to, in addition to retrieving the remains of any meals. 'Fieldwork is one of the most exciting yet simultaneously challenging aspects of the research', says Tennessen, describing how she and her colleagues tracked the animals from small inflatable boats in all conditions.

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