Study shows invasive blue catfish can tolerate high salinities

NOVEMBER 6, 2019

by David Malmquist, Virginia Institute of Marine Science

A new study by researchers at the Virginia Institute of Marine Science warns that blue catfish—an invasive species in several Chesapeake Bay tributaries—tolerate salinities higher than most freshwater fishes, and thus may be able to expand their range downstream into mainstem Chesapeake waters, and from there into new Bay tributaries and even Delaware Bay.

Conducting the study, reported in the November 5th issue of PLOS ONE, were Ph.D. student Vaskar Nepal of William & Mary's School of Marine Science at VIMS and VIMS fisheries professor Mary Fabrizio.

Nepal and Fabrizio undertook the study to better constrain the salinity tolerance of blue catfish in their non-native Chesapeake Bay habitat. The value used in the 2014 report that currently guides management of invasive Bay catfishes was based on a study of blue catfish from their native range: the fresh waters of the Mississippi River basin. Evidence suggests that populations of "blue cats" and other fishes may become more salt tolerant when exposed to brackish estuarine waters.

"We wanted to see how long blue catfish can survive at a given salinity to help us better understand the extent to which they can colonize areas other than those where they were originally stocked," says Nepal.

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Swordfish as oceanographers: Satellite tags facilitate research of ocean's 'twilight zone' off Florida

NOVEMBER 5, 2019

by Hannah Hickey, University of Washington

Researchers from the University of Washington are using high-tech tags to record the movements of swordfish—big, deep-water, migratory, open-ocean fish that are poorly studied—and get a window into the ocean depths they inhabit.

The researchers tagged five swordfish in late August off the coast of Miami: Max, Simone, Anthony, Rex and Oliver. Their movements can now be viewed in near-real time. And although swordfish are a prized catch, these ones aren't at higher risk, researchers say, since the website updates only every few hours and these fast-swimming fish spend most of their time far from shore.

"These are animals that migrate into the ocean's twilight zone that we know next to nothing about," said Peter Gaube, an oceanographer at the UW Applied Physics Laboratory. "Swordfish in different regions have very different behavior. We hope to learn more about these amazing animals and their environment as they migrate between regions."

This is the first time satellite position tags have successfully been placed on swordfish caught off the coast of the United States.

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Extinction of lowland tapir and white-lipped peccary would impair forest diversity

NOVEMBER 5, 2019

by FAPESP

According to a team of researchers affiliated with São Paulo State University (UNESP) in Rio Claro, Brazil, the extinction of South America's two largest herbivores—the lowland tapir (Tapirus terrestris) and the white-lipped peccary (Tayassu pecari) - would cause a significant decrease in forest diversity throughout the continent.

The results of experiments that began ten years ago showed that plant communities are more diversified in areas where both species are present and less diversified in forests inhabited by only one species. The two species have complementary ecological functions.

The study, which was supported by São Paulo Research Foundation—FAPESP, is published in the British Ecological Society's Journal of Ecology.

It was conducted as part of the Thematic Project "Ecological consequences of defaunation in the Atlantic Rainforest," led by Professor Mauro Galetti under the auspice of the FAPESP Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA-FAPESP).

Tapirs and peccaries used to be found almost everywhere in South America's forests, but both species are now endangered in many localities owing to poaching and deforestation for agriculture. According to the researchers, the ecological roles of these species and their importance in the ecosystem services of the forests (biodiversity, nutrient cycling, carbon storage and maintenance of water sources, among others) are poorly understood.

Peccaries consume large amounts of seeds and seedlings. They live in large family groups that can exceed one hundred individuals. Their foraging habits and soil trampling help significantly reduce understory growth in tropical forests.

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Time ticks away at wild bison genetic diversity

NOVEMBER 3, 2019

by Morgan Lee

Evidence is mounting that wild North American bison are gradually shedding their genetic diversity across many of the isolated herds overseen by the U.S. government, weakening future resilience against disease and climate events in the shadow of human encroachment.

The extent of the creeping threat to herds overseen by the Department of Interior—the backbone of wild bison conservation efforts for North America—is coming into sharper focus amid advances in genetic studies.

Preliminary results of a genetic population analysis commissioned by the National Park Service show three small federal herds would almost certainly die off—extinguishing their DNA lineage—within 200 years under current management practices that limit transfers for interbreeding among distant herds.

The study is awaiting peer review by other scientists. It does not include Yellowstone National Park's herd of some 5,000 unfenced bison, the largest federal conservation herd that's seen by millions of people who visit the park annually.

"Some of these herds that lost the most genetic diversity do have a high probability of going extinct, due to the accumulation of inbreeding," explained Cynthia Hartway, a conservation scientist at the bison program with Wildlife Conservation Society who led the analysis.

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Echolocation found to be cheap for deep-diving whales

NOVEMBER 1, 2019

by University of St Andrews

A new international study led by Aarhus University in Denmark, in collaboration with the Universities of St Andrews and La Laguna, Tenerife, reveals how whales have evolved to live in the world's deepest oceans.

Many whales and dolphins, including the champion deep-diving beaked whales, use echolocation, the ability to locate objects by reflected sound, to find food in the dark of the deep ocean. Scientists have not been able to agree on how much energy this remarkable sensing ability takes, until now.

A new study published today (Thursday 31 October) in the journal Scientific Reports reveals that, at least for short-finned pilot whales, echolocation is cheap. This may help explain how echolocating whales evolved to live in deep waters throughout the world.

In a throwback to terrestrial ancestors, whales use air to make their intense echolocation click sounds and this raises a problem for deep divers. Air compresses with depth so that at 700m deep, where pilot whales hunt, a lung-full of air has shrunk to 1.5% of its volume. But the new study shows that pilot whales use tiny amounts of air to make each click so this volume goes a long way. Even so, whales need to capture the air used by each click and recycle it, like a SCUBA rebreather, to be able to echolocate throughout their dives.

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