The first-ever comprehensive global report on the state of shellfish has been released by The Nature Conservancy at the International Marine Conservation Congress in Washington, DC.

This one of its kind report is a collaborative work carried out by scientists from five different continents employed by academic and research institutions as well as by conservation organizations.

The report, which focuses primarily on the distribution and condition of native oyster reefs, show that 85 percent of oyster reefs have been completely destroyed worldwide and that this type of environment is the most severely impacted of all marine habitats.

In a majority of individual bays around the globe, the loss exceeds 90 percent and in some areas the loss of oyster reef habitat is over 99 percent. The situation is especially dire in Europe, North America and Australia where oyster reefs are functionally extinct in many areas.

“We’re seeing an unprecedented and alarming

decline in the condition of oyster reefs, a critically

important habitat in the world’s bays and estuaries,”

says Mike Beck, senior marine scientist at The Nature

Conservancy and lead author of the report.

Many of us see oysters as a culinary delight only, but oyster reefs provide us humans with a long row of valuable favours that we rarely think about. Did you for instance known that oyster reefs function as buffers that protect shorelines and prevent coastal marshes from disappearing, which in turn guard people from the consequences of hurricanes and other severe storm surges? Being filter feeders, oysters also help keep the water quality up in the ocean and they also provide food and habitat for many different types of birds, fish and shellfish.

Even though the situation is dismal, there is still time to save the remaining populations and aid the recuperation of damaged oyster reefs. In the United States, millions of young Olympia oysters have been reintroduced to the mudflats surrounding Netarts Bay in Oregon, in an effort to re-create a self-sustaining population of this native species. The project is a joint effort by government and university scientists, conservation groups, industry representatives, and local volunteers.

“With support from the local community and other partners, we’re demonstrating that shellfish restoration really works”, says Dick Vander Schaaf, Oregon director of coast and marine conservation for the Conservancy. “Expanding the effort to other bays and estuaries will help to ensure that the ecological benefits of oyster reefs are there for future generations.”

If wish to learn more about the global oyster reef situation, you can find the report here.

A study published in the online scientific journal PLoS Biology on October 27 with the provocative headline “Dams make no damn difference to salmon survival”[1] is now being questioned by a number of scientists, including several co-authors of the study.

According to the study, young fish running the gantlet of dams on the Snake and Columbia rivers did just as well as youngsters in an undammed river. Dams are widely regarded as one of the main reasons behind the sharp decline of salmon in North America’s western rivers and a study claiming that dams make no damn difference for salmon survival is therefore destined to receive a lot of attention from dam proponents and dam critics alike.

While a number of scientists, including several co-authors, are questioning the results and cautioning about what conclusions can really be drawn from them, lead-author David Welch stands by his report. “We’re not saying that the dams have never had an effect,” says Welch. “What we all have to ask ourselves is, if survival is up to the level of a river that doesn’t have dams, then what’s causing survival problems?”

Welch has already warned against overstating what the study proves, and continues to do so. According to Welch, the results of the study do however suggest that dams might not play such a big role in the fate of endangered Columbia River salmon today, and that the situation in the ocean – where the salmon live until it migrates upstream to spawn – is of higher importance than river conditions.

Michele DeHart, manager of the Fish Passage Center[2], strongly disagree with the conclusions drawn from the study. “There’s a huge mass of scientific literature that documents the impacts of dams. It’s just huge,” says DeHart. “It’s like saying, ‘Gosh, I just did this comparison and smoking does not cause cancer.’ Would you change your mind?”

In the study, the survival rate of young salmon and steelhead heading for the ocean (so called smolts) was measured in the rivers Columbia and Snake, which are heavily dammed, and in Fraser River, which has no dams at all. To the researchers’ surprise, the recorded survival rate was around 25 percent for all smolts, regardless of whether they travelled in dammed or undammed waters. If you take into account that smolt in the Columbia River actually have to travel a longer distance, it even looks as if smolt traversing dammed waters are doing better than their counterparts in the undammed Fraser.

Environmental groups are now claiming that comparing the different rivers with each other is like comparing apples and oranges, and co-author Carl Schreck, head of the Oregon Cooperative Fish and Wildlife Research Unit at Oregon State University, warns that the study could have failed to account for fish that die in the ocean due to the stress they have been subjected to while traversing dams in Columbia and Snake.

Ed Bowles, biologist and head of fisheries for the Oregon Department of Fish and Wildlife, says that it would be better to compare how similar fish, e.g. spring Chinook, do when they spawn in the same river – some above dams and some below.

In May this year, hundreds of Asian swamp eels were discovered in and around Silver Lake in historic Gibbsboro, New Jersey. This was the first finding in New Jersey, Asian swamp eelbut not the first finding in the United States. Unlike Florida, Georgia, and Hawaii – the three other U.S. states where this species have been discovered – New Jersey is however subjected to harsh winters and a breeding population of Asian swamp eels in New Jersey confirms the suspicion that this Asian invader has no problem adjusting to the
chilly climate of northern North America.

The Asian swamp eels were found by a local college student checking on frogs and turtles in the Silver Lake. As he spotted snake-like heads peeking from the water, he decided to photograph them and post the pictures online. This lead to the “snakes” being identified as Asian swamp eels, Monopterus albus, and prompted a call to the local authorities.

In its native environment in Asia and Australia, the swamp eel Monopterus albus inhabits gentle hill streams, estuaries and lowland wetlands, and it is a common species in rice paddies. It has developed a long row of traits that makes it an apt survivor in many different kinds of environments. Unfortunately, these traits also make it the “perfect” invasive species and biologists fear that the Asian swamp eel may wreck havoc with existing North American ecosystems, especially if the predatory species of these systems prefer to target familiar prey rather than catching the newcomers.

– The Asian swamp eel can survive long periods of drought by burrowing in moist earth, and can therefore take advantage of seasonally appearing, short-lived bodies of water.

– If its home becomes unsuitable, e.g. because of drought, this eel simply crawls ashore and make its way to a more suitable home by slithering over land, just like a snake. This makes it hard to eradicate from bodies of water using poison or similar; there is always the risk of at least two specimens getting away over land and forming a new breeding colony in nearby waters.

– The Asian swamp eel can tolerate a wide range of oxygen levels in the water since it is capable of absorbing oxygen from the air above the surface through its skin. This skill doesn’t only come in handy in oxygen depleted waters; it is also what makes it possible for the fish to travel impressive distances over land.

– This eel prefers freshwater habitats, but can tolerate brackish and saline conditions, which increases its chances of always finding a suitable home.

– It eats all sorts of prey, not only fish, crustaceans, amphibians, and other aquatic animals, but detritus (decaying organic matter) as well. Highly specialized feeders have a much harder time adjusting to new habitats and are therefore less likely to become problematic invasive species.

– This eel is a protandrous hermaphrodite, which means that it can change its sex. All specimens are born male, but can turn into females if necessary. This means that if an aquarist releases two male specimens into a lake, one of them can turn into a female to make reproduction possible.

In Georgia, the first specimens of Asian swamp eel was discovered in 1994, and three years later eels were found in Florida as well. The Hawaiian history of combating swamp eels is much longer as the first specimens are believed to have been released in Hawaiian waters about 100 years ago. In Georgia and New Jersey, biologists blame aquarists of having caused the situation by releasing their pets into the wild. In Florida and Hawaii however, Asian food markets and fish-farmers are considered more likely sources. Asian swamp eels are typically sold fresh in food markets and can be kept alive for long periods of time as long as their skin is kept moist.

New Jersey authorities are now focusing on containing the creatures while trying to figure out a way of annihilating them. “We’re not panicking yet,” says Lisa Barno, chief of the New Jersey Bureau of Freshwater Fisheries. “It’s more that it’s just an invasive species we’d rather not have. We’re still documenting the true extent of the problem, but right now it seems to be fairly contained.” One of the immediate goals is to prevent an expansion downstream to the Cooper River and a watershed leading to the Delaware River. Since May, only one Asian swamp eel has been discovered outside the Silver Lake.