Friday Fishy News - August 17

[Flattieman]

First, a bit more on one of last week's stories:

Fossil Fish Jaws Give Information On Our Own Remote Ancestors

Science Daily

August 17

The dentary from Andreolepis was found in Gotland, Sweden. The scale bars in pictures a-c equal 1 mm. All in all, the jaw is about 5 mm long. (Credit: Image courtesy of Uppsala University)

When we lose our milk teeth they are replaced by new permanent teeth growing out in exactly the same positions. This is an ancient part of our evolutionary heritage and an identifying characteristic of the largest living group of backboned animals. Now, an international team including two scientists from Uppsala University has uncovered ancient fossil fish jaws that cast light on the origin of this group and its unique dentition.

Together with scientists from Spain, Germany and France, Professor Per Ahlberg and Assistant Professor Henning Blom at the Department of Physiology and Developmental Biology have been studying two of the earliest bony fishes found in Sweden and Germany, managing to show that they belong to the same group of vertebrates as ourselves, the Osteichthyes. Their findings are published in this week's Nature.

The backboned animals or vertebrates comprise three main groups. The primitive lampreys and hagfishes have neither jaws nor teeth. The cartilaginous fishes or Chondrichthyes (sharks and rays) grow new teeth on the inner face of the jaw; these gradually move up to the jaw edge, row upon row, and push out the old worn teeth. The third and much bigger group, the Osteichthyes, includes both bony fishes and all land vertebrates. In nearly all osteichthyans teeth are shed one by one and replaced by new ones growing up in the same place. Osteichthyans also carry their teeth on special jaw bones - the dentary in the lower jaw, maxilla and premaxilla in the upper - that have no equivalents in other vertebrates.

Although the Osteichthyes are a big and important group, we know little about their origin. Their fossil record goes back to early bony fishes some 416 million years ago, but then it cuts out abruptly. However, in rocks of the Silurian period (some 420 million years ago) are found fossils of two fishes, Andreolepis from Gotland in Sweden and Lophosteus from Estonia and Germany, that could be very primitive osteichthyans.

”The problem is that until now no complete specimens have been discovered, only hundreds of scales and small bone fragments. Some researchers have denied that these fossils are anything to do with osteichthyans,” says Per Ahlberg.

Now, the discovery of two jaw bones, a dentary from Andreolepis and a maxilla from Lophosteus, settles the identity of these fishes once and for all: they are the earliest known osteichthyans. Curiously, however, the teeth on these bones are not quite arranged in the osteichthyan fashion. Several rows are present, and it appears that new teeth were added along the inner edge of the jaw without the old teeth being shed. In some respects this is more like a shark dentition - not the modern kind, but the sort seen in the earliest fossil sharks.

”This suggests that Andreolepis and Lophosteus belong to the stem group, or common ancestral stock, of the osteichthyans, and also hints that the superficially very different dentitions of sharks and osteichthyans may ultimately be derived from the same ancestral pattern,”says Per Ahlberg.

Andreolepis and Lophosteus may thus help us to understand how the first osteichthyans, our own remote ancestors, evolved from more primitive vertebrates.

Free fish for thousands

Fishupdate.com

August 13

THOUSANDS of people were treated to a free fish feast at the weekend - everything from cod and haddock to salmon and prawns. The only snag was that anyone in Britain who wanted to take up the offer had to fly hundreds of miles north to Iceland.

The fishing port of Dalvik, on Iceland's most northerly coast, which has a population of just 2,200 people, swept aside concerns over new fishing quotas to celebrate Fish Day on Saturday when local processors and townsfolk invited anyone who could get there to a seafood buffet totally free of charge. The goal of festival is bring people together to have a good time while enjoying the harvest of the sea without spending a single krona.

Officially called The Great Fish Day, this celebrated event is an annual summer festival in Dalvíkurbyggð (to give the port its full name) held on the first or the second Saturday in August.

The Great Fish Day has been such a successful event that during the first six years more than 130,000 people have taken part in this gourmet village feast.

While most visitors are Icelandic,The Great Fish Day now attracts an increasing number of tourists from Britain and Europe. Dalvik is a typical Icelandic fishing port where most people are totally dependent on fishing and processing. But thanks to its spectacular mountain scenery it also an increasingly popular tourists area.

As anglers age, fishing industry targets kids

Arizona Republican - USA

August 11

Long a favorite American outdoor activity, fishing has been slipping in popularity. You can see a trend in the mostly older men who line the lagoon near Chicago's Lincoln Park with rod and reel.

Fishing sales nationwide have stagnated, according to the results of a U.S. Fish and Wildlife Service survey released in May. The survey, conducted every five years, found that U.S. anglers spent $40.6 billion last year. That total was similar to 2001's but down 16 percent from 1996s.

The recreational fishing industry is using promotions and fishing clinics to draw youngsters.

The Recreational Boating and Fishing Foundation has four initiatives under way: signing up youths for fishing programs; getting states to send license-renewal notices and to recruit anglers more actively; a collaborative campaign for the boating and fishing industries; and its year-old Anglers Legacy program, designed to mobilize anglers to take someone fishing.

"Living Fossil" Fish Making Last Stand in China

By Stefan Lovgren

National Geographic News

August 15

It's known as the "mother species" and the "panda under the water."

Yet the nickname that most aptly describes the Chinese sturgeon, a giant fish that's been around since the age of the dinosaurs, may be "living fossil."

Now conservationists are locked in a race against time to save this ancient river titan from extinction.

Adult sturgeons, which can measure up to 4 meters (13 feet) in length and weigh 1,000 pounds (450 kilograms), migrate from the East China Sea into the Yangtze River to spawn.

But the Yangtze's deteriorating environment and increased shipping traffic have taken their toll on the mammoth fish.

Thirty years ago there were 2,000 spawning Chinese sturgeons in the Yangtze River every year. Now that number is down to several hundred.

There may be only a thousand of the animals left in the river, said Wei Qiwei, a lead researcher at the Yangtze River Fisheries Research Institute in Jingzhou

Wei and other scientists hope to reverse the trend by breeding sturgeons in captivity and putting them back into the river before the species disappears the wild.

"The Chinese sturgeon is very precious to us," Wei said. "I don't want it to disappear on my watch."

Sexual Maturity

Wei's institute operates a breeding base tucked into a sleepy farming community outside Jingzhou.

A slogan on a wall greeting visitors reads, "Love the Chinese Sturgeon, Our National Treasure."

Inside, a hatchery facility the size of two football fields contains rows and rows of tanks holding sturgeons in varying stages of development, from larvae to one-year-old fish.

Sexually mature sturgeons taken from the wild are kept at the hatchery to provide eggs for breeding.

"The short-term goal is to preserve the fish in captivity, but the long-term goal is to preserve the fish in the river as part of the ecosystem," Wei said.

To do that, scientists want to keep some of the newly hatched sturgeons in captivity until they are sexually mature before releasing them into the wild.

But the reproductive capacity of the fish is poor; it takes more than ten years for the Chinese sturgeon to begin spawning.

It will take at least another five years for the oldest fish at the hatchery, which are kept in holding tanks outside, to reach sexual maturity, the scientists estimate.

"The critical issue for us is to make brood stock [from the fish taken from the wild] and then to release them again," said Zeng Lingbing, director of the institute's Fish Pathology Laboratory.

"But we have not come full circle yet, so we don't know if this will be possible."

Boat Traffic

Fisheries biologist Zeb Hogan heads the National Geographic Society's Megafishes Project, a three-year program to document the world's largest freshwater fishes.

Hogan recently visited the hatchery and said Wei's breeding program could help offset the many threats now facing the Chinese sturgeon in its native waters.

"This breeding program is like an insurance policy to make sure this ancient fish does not disappear," said Hogan, standing waist deep in the green waters of a holding tank with a seven-foot (two-meter) sturgeon in his grip.

The fish can grow twice that size, but no sturgeons that big have been seen in the Yangtze in the past 20 years, Wei explained.

The Chinese sturgeon moves from seawater to fresh water to spawn. It has the longest migration of any sturgeon in the world and once migrated more than 2,000 miles (3,500 kilometers) up the Yangtze.

That was before the Ghezouba Dam was built on the Yangtze River in the early 1980s, cutting off the sturgeon's migratory path, just as it did for the critically endangered Chinese paddlefish.

All of the sturgeon's original spawning grounds were located upstream from the dam, Wei explained.

"There used to be spawning grounds totaling more than 600 kilometers [375 miles] in the river," Wei said. "Now there is less than 30 kilometers [19 miles]."

Increasing boat traffic on the Yangtze is a major threat to the sturgeon, which frequently swims near the surface. Every year, about ten Chinese sturgeons are killed by boat propellers.

The sturgeon is also highly sensitive to increased noise on the river caused by growing traffic.

In addition, Wei speculates that worsening water contamination from industrial runoff and other sources may be causing sturgeons to change their sex.

"After 1995 the ratio of male to female has totally changed," he said. "It used to be one to one, but now there may be up to ten females for every one male."

Habitat Restoration

In addition to restocking the river with fish, Wei is also trying to find ways to create artificial spawning grounds in the Yangtze River.

"Habitat restoration is another way to save the species," he said.

Hogan, who is a National Geographic Emerging Explorer, says there is no umbrella solution for saving megafishes like the Chinese sturgeon.

"If we look at rivers around the world, we see all kinds of problems—habitat fragmentation from dams, pollution, invasive species, overfishing," he said.

"There are a lot of threats to large-bodied species of fish, and we have to look at each river separately to find the best way to save these amazing creatures."

Flattieman.