Amazonian catfish’s 5,000-mile migration endangered by dams

singular Amazonian catfish is capable of an amazing feat: hidden from human eyes, the species travels vast distances over its lifetime, making a round trip covering more than 8,000 kilometers (nearly 5,000 miles), to return to its natal breeding grounds, a new study confirms.

But even as this record-setting feat — the longest freshwater migration in the world — is scientifically confirmed, the species is threatened by hundreds of planned Amazonian dams.

Brachyplatystoma rousseauxii is a commercially valuable catfish species and an apex predator, growing to 3 meters (more than 9 feet) long. Understanding the migratory patterns of the fish, whose range spans six Amazonian countries, “is paramount for designing adequate conservation and management strategies, especially in view of the current and proposed hydroelectric development throughout the Amazon basin,” the researchers write in the Journal of Applied Ecology.

Observations in the 1990s concerning the size distribution of catfish caught along the length of the Amazon River first led researchers to suggest that long-distance homing migration might be taking place, explained study lead author Fabrice Duponchelle of France’s Institute of Research for Development. Subsequent genetic analyses were consistent with that hypothesis, but still didn’t offer definitive proof.

Intrigued by the possibility that catfish might be homing over such vast distances, Duponchelle employed an innovative technique in the new study to get conclusive evidence: chemical analysis of the otolith, a type of ear bone.

As otoliths grow, their chemical composition changes to reflect the background levels of particular chemical elements found in the environment. Like tree rings, the layers of bone relate to their age: the center, innermost layer of otolith is the oldest, and reflects life as a hatchling; the outer edge is the most recent, and reflects the last stage of the fish’s life.

Read the full article, originally published on Mongabay, here

The giant Amazonian catfish is a valuable commercial species, an apex predator, and the world's long distance freshwater fish migration record holder. Photo courtesy of the USGS Columbia Environmental Research CenterThe giant Amazonian catfish is a valuable commercial species, an apex predator, and the world’s long distance freshwater fish migration record holder. Photo courtesy of the USGS Columbia Environmental Research Center.

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Orangutan reintroductions could risk population survival, study warns

An estimated 1,500 orangutans now live in rescue and rehabilitation centers located across Sumatra and Borneo. As habitat loss due to deforestation and forest fires continues, these institutions are struggling to keep up with demand.

Release into the wild is the ultimate, urgent, goal for most of these animals, but a new study warns that there could be serious genetic implications for the offspring of reintroduced animals — and orangutan populations in general — if those rescued from one region are released into a different region.

The study, led by primatologist Graham Banes, examined the genetic consequences when orangutans from different, divergent, subspecies interbreed. Borneo’s three recognized subspecies — from three distinct regions — are thought to have diverged from each other 176,000 years ago, meaning that hybridization between them may result in negative genetic effects. If hybrid offspring reproduce, combinations of genes that were beneficial for one lineage can be disrupted, resulting in poor health and reduced reproductive success, the researcher said. These effects, known as “outbreeding depression,” could threaten the survival of individuals and populations in the long-term.

Read the full article on Mongabay.

A Bornean orangutan in a rehabilitation center in Sabah. Photo by Rhett A. ButlerA Bornean orangutan in a rehabilitation center in Sabah. Photo by Rhett A. Butler

Dams threaten future of Amazonian biodiversity major new study warns

Amazonia’s surge in hydropower development threatens numerous species with extinction, and puts unique habitats at risk, warns a recent study.

River dolphins, giant otters, turtles, fish, birds and monkeys will all have their habitats altered by hydroelectric dams, with some species likely to be completely wiped out, says an international team of biologists that looked at all impacts associated with 191 existing Amazon dams, as well as the 246 dams being planned or under construction.

What’s more, the researchers identified a network of negative interactions between dam construction, mining, climate change, human migration, and biodiversity and ecosystem services which illustrates how impacts can cascade in multiple, devastating ways.

In environmental terms, the most obvious and direct impact of dams reported by the study are on water flow and connectivity. Nutrients that flow downstream from the Andes are interrupted by dams; flood pulses that form a vital part of many species’ lifecycles are modified by the reservoirs and flow patterns that dams create and control; habitat complexity is lost; and species such as river dolphins become isolated in the stretches of river between hydropower developments, which leaves smaller sub-populations vulnerable to decline.

To read the full article, orginally published on Mongabay, click here.

River turtles in Colombia. Turtles, dolphins and otters are among the aquatic species threatened by dam construction, but risks extend to birds, bats and terrestrial animals too. Photo by Rhett A. ButlerRiver turtles in Colombia. Turtles, dolphins and otters are among the aquatic species threatened by dam construction, but risks extend to birds, bats and terrestrial animals too. Photo by Rhett A. Butler

 

Rising CO2 is reducing nutritional value of food, impacting ecosystems

Among the myriad impacts climate change is having on the world, one in particular may come as a surprise: heightened atmospheric CO2 levels might be adversely affecting the nutritional quality of the food you eat. As carbon dioxide in the atmosphere continues to increase, you could end up eating more sugar and less of important minerals such as zinc, magnesium and calcium — without even realizing it. Those effects could also be reverberating up the food chain and altering ecosystems in as yet poorly understood ways.

For plants, a rise in atmospheric carbon dioxide actually boosts productivity by stimulating photosynthesis. They make more carbohydrate and grow larger — seemingly a good thing. But because other nutrients don’t increase and can’t keep pace with the augmented carbohydrate, this potential boon to our food supply isn’t all that it seems: plants end up having a higher carbohydrate to protein ratio, and relatively lower concentrations of minerals.

Put simply: atmospheric carbon dioxide acts as a sort of fertilizer to grow bigger, leafier plants, but those larger broccolis and lettuces actually contain less nutritional value per portion than their predecessors grown in the preindustrial, pre-fossil fuel world.

And that could be a problem for the world’s already malnourished people, for bees seeking protein-rich pollen so they can safely overwinter, and for ecosystems that could be thrown out of balance by changes in plant nutrition.

The human implications of these ongoing changes to our food supply came under the spotlight in April when the US Global Change Research Program (USGCRP) published a major report on the impact of climate change on human health. One of its key findings was that rising carbon dioxide will reduce the nutritional quality of food.

Read the full article on Mongabay

Rice fields in Kashmir, India. Staple crops such as rice and wheat are forecast to become less nutritious as a result of increasing carbon dioxide levels in the atmosphere. Photo courtesy of sandeepachetan.com travel photography on Flickr under CC BY-NC-ND 2.0 licenseRice fields in Kashmir, India. Staple crops such as rice and wheat are forecast to become less nutritious as a result of increasing carbon dioxide levels in the atmosphere. Photo courtesy of sandeepachetan.com travel photography on Flickr under CC BY-NC-ND 2.0 license

Keeping Amazon fish connected is key to their conservation

Imagine a fish isolated in an Amazonian lake — part of the vast freshwater ecosystem of the Amazon basin, an ever-changing network of rivers, lakes and floodplains that extends to 1 million square kilometers (386,102 square miles).

Now imagine that isolated fish as water levels rise during the wet season, and floodplains vanish beneath up to 15 meters (49 feet) of water. The fish — once restricted by the lake’s edge — swims freely into the flooded forest and mingles with others of its kind from elsewhere.

For thousands of years, isolated fish populations across the Amazon have likewise played a game of musical chairs: intermixing between flooding water bodies, migrating short and vast distances between lakes and along river channels, and then as the waters receded, forming new lake and river populations.

This connectivity — with the genetic mixing it affords — is vital for healthy fish populations, but is extremely vulnerable to changes in the annual “flood pulse” that inundates forests.

Read the rest of the article on Mongabay.

A South American Leaf Fish (Monocirrhus polyacanthus). More than 2,000 fish species live in the Amazon, the highest fish biodiversity in the world. That diversity has been greatly enriched due to the periodic isolation and intermixing of freshwater species that occurs across the region. Photo © Rhett A. Butler/MongabayA South American Leaf Fish (Monocirrhus polyacanthus). More than 2,000 fish species live in the Amazon, the highest fish biodiversity in the world. That diversity has been greatly enriched due to the periodic isolation and intermixing of freshwater species that occurs across the region. Photo © Rhett A. Butler/Mongabay

Imperiled Amazon freshwater ecosystems urgently need basin-wide study, management

My latest piece for Mongabay looks at some of the threats facing the Amazon’s freshwater ecosystems, and at how a fragmented protected area network and policy framework – based on terrestrial ecosystems – is failing to protect the connectivity of the freshwater world. As multiple impacts interact with each other the functioning of the whole ecosystem is under threat. You can read the full article here.cropped-p1030605.jpg

Damming the Amazon: new hydropower projects put river dolphins at risk

A little while ago I wrote about the plight of Amazon river dolphins in the face of dam-building across the region. Here’s the opening few lines, but to read the whole piece please follow the link to the original on Mongabay. A National Geographic photographer kindly let us use some of his pictures, so it is worth a look!

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A dam-building boom is underway in the Amazon. More than 400 hydroelectric dams are in operation, being built, or planned for the river’s headwaters and basin. Scientists know that tropical dams disrupt water flow and nutrient deposition, with negative consequences for aquatic animals, especially migratory species. But little detailed knowledge exists as to the impacts of dams on specific species, or as to the best mitigations to prevent harm.

A recent study that tries to fill in that knowledge gap zeroes in on Brazil’s river dolphins. It found that as many as 26 dams could negatively impact dolphin populations and their prey.

The research, led by Dr Claryana Araújo of the Federal University of Goiás, Brazil, focused on two freshwater species: the Amazon River Dolphin, or boto (Inia geoffrensis), which is sometimes famously pink; and the Tucuxi (Sotalia fluviatilis).

The river dolphins of South America are charismatic emblems of rainforest biodiversity, and have captured the public imagination. Swimming in rivers, lagoons, and among submerged tree trunks in flooded forests to chase down prey, they can be found as far inland as the upper reaches of Amazonian tributaries, more than 2,600 kilometers (1,615 miles) from the Atlantic Ocean.

To continue reading, click here.