Category Archives: Fish

Shark Bites in the USA

The USA has the most reported shark attacks in the world. What could be the reason for this? Are Americans so well nourished that they taste better? Could be, but all the references I have read say that a shark attack is most probably an “accident”. The shark had mistaken the human for his more usual meal such as a seal or another fish.

One reason the United States is at the top of the list is that the U.S. has a very large combined coastal shoreline. Another reason is the increase of recreational marine activities, and recreational marine activities expose people to all aquatic dangers including shark attacks.

No doubt, a high level of reporting of attacks is also a factor. Not all coastal countries publish a complete record of shark attacks. Publishing such reports could adversely affect the tourist trade. In addition to the USA some of the other countries that have reported shark bites are Africa, Central & S Am, Australia and Pacific Islands.

In the U.S 60% of all shark attacks are reported by the state of Florida. California reports about 15%, this is closely followed by Hawaii. Most coastal states have at one time or another reported a shark attack. Most of the attacks are not fatal. Most of the attacks are done by a contact bite, then the shark swims away. The victim can be left with a maiming wound or deformity. Fatal attacks are mainly due to the bull shark, tiger shark, or the great white shark and the Oceanic white tip shark. (Pictures and information about these sharks can be found at Dangerous animals–Sharks). In recent years the entire east coast has had a growing problem with aggressive sharks. The reason for the increase is being researched.

Overall shark attacks are extremely rare – “Lightning strikes humans more often than sharks bite humans”. The International Shark Attack File reports that world wide there are 50 – 70 unprovoked shark attacks a year. The number of shark attacks is increasing because the human population is increasing and recreational use of the shark habitat, oceans and coastlines, is increasing. Even though there are 50 to 70 attacks a year the number of fatalities are low.

Wikipedia has a list of the fatal, unprovoked shark attacks in the US. The records start in 1779 up to the recent. The more recent records state the age of the victims and other information that is interesting reading and gives some explanation of the event. A summary of the records show that there were 13 deaths from 2000 to 2010. Three of the years, 2002, 2006 and 2007, did not have any deaths. The years 2001 and 2004 had 3 deaths each. So far in 2010 there have been two reported deaths due to shark bites, but the year is not over.

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Dangerous animals–Sharks

We can all hear the ominous music, building slowly, frightfully, until the climax when Jaws attacks! Movies like Jaws have burnt this fearsome group of animals into our psyche, and I think the thought lurks somewhere in our minds whenever we visit the ocean that there are really big fish out there. There are somewhere around 440 species of shark worldwide. They are an ancient group of fish, whose overall lineage dates to before the Age of Dinosaurs. Of these hundreds of species, only 4 are known to have been involved in a significant number of fatal attacks on humans. Worldwide there is an average of 4.3 fatalities per year. 

The four most dangerous species have different habits, and therefore the patterns of attacks and their danger to people are different. They are the great white shark (Carcharodon carcharias), oceanic whitetip shark (Carcharhinus longimanus), bull shark (Carcharhinus leucas), and the tiger shark (Galeocerdo cuvier).

Great White Shark

Great White Shark

The great white, of Jaws fame, is a fearsome predator. Adult sharks are 12-17 feet in length. They are found along both coasts from Mexico into high latitude waters of Alaska, and along the east coast up to Hudson Bay. However, it is also known from deeper ocean waters, and new findings suggest that at least the west coast populations congregate in the open ocean between California and Hawaii for parts of the year. They are predators of marine mammals, turtles, large fish, and even whales. Humans are incidental targets.

During the hot summer of 1916, the Jersey Shore was the scene of a series of attacks that shuck the public, and was the inspiration for the book Jaws. Between July 1 and July 12, four people were killed. The great white is often blamed, but it could have also been a bull shark. Why there were so many attacks at that time is hard to say, and has not been repeated since.
Oceanic Whitetip Shark Oceanic Whitetip Shark

 

The oceanic whitetip shark is actually responsible for more fatal attacks on humans than all other species combined, and it does not even frequent the coasts. It is found worldwide, and prefers warm waters and deep ocean areas. It is the unfortunate events of the twentieth century that allowed this shark to become superlative in human fatalities—it is the shark reasonable for attacks on survivors of shipwrecks and downed aircraft. During the war in the Pacific, when ships and planes were regularly shot down, many hundreds of stranded sailors were attacked and killed. Horrific stories from survivors testify to this gruesome bloodshed and led to much research by the Navy in shark repellents. Hopefully, this scale of human carnage will never occur again. And while this species is the most deadly shark, its habits make it of little concern to the average beach-goer.

Tiger Shark Tiger shark

 

The tiger shark is found worldwide in mostly equatorial waters. It prefers tropical and sub-tropical warm water, and does not get into the high latitudes like the great white. It tends to stay in deep waters that line reefs, but it does occasionally move into shallow water and channels where it might encounter people. This shark is large, commonly attaining lengths of 10-14 feet, but because of its habits encounters with humans are relatively rare.

Bull shark Bull shark

 

In contrast, the bull shark is likely the most dangerous species to humans overall. It too is common in warm waters along coasts, but it also tolerates fresh water, and can migrate into rivers. They have been found far up the Amazon River in South America, and as far north in the Mississippi River as Illinois (yikes!) (Thomerson et al. 1977). These sharks are unpredictable and are often aggressive, and because of their habit of being in shallow waters are probably responsible for the majority of near-shore attacks.

However, having said all of that, the chances of being attacked are very remote. You can see the per year compared with other animals on the chart. Was that deep, ominous music I just heard?

Average number of deaths per year caused by various animals

Average number of deaths per year caused by various animals

Thomerson, J. E., T. B. Thorson, and R. L. Hempel. 1977. The bull shark, Carcharhinus leucas, from the upper Mississippi River, near Alton, Illinois. Copeia 1977(1):166-168.

Several of the images come from sources recommended in the Nature Wallpaper post.

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Shark bites in the Cretaceous Sea

One of the most exciting things in paleontology is being able to definitively establish the interaction of two species from the fossil record. It is thrilling to picture a moment in time, millions of years ago, when two animals were at the same place, at the same time, and be able from fossil evidence to glean something about their interaction and behavior.

One dramatic example of this is finding a fossil with clear evidence that it was bitten by a shark. During the Late Cretaceous, North America was cut in half by an interior sea that extended the Gulf of Mexico across the mid-continent to connect with the Arctic Ocean in the north, effectively creating two land masses where today there is one.

In this last period from the Age of Dinosaurs, fantastic and strange creatures swam the seas. Today, the sediments from that ocean are exposed in badlands across much of western Kansas, Nebraska, and South Dakota. These geologic formations, like the Niobrara Formation, preserve a rich record of the ocean life, and clearly show what a scary ocean it was.

Tylosaurus model from the Carnegie Collection

Tylosaurus model from the Carnegie Collection

Giant marine lizards thrived in the sea. These beasts, close relatives of modern snakes and lizards, were called mosasaurs. There were several kinds that likely had different modes of life, some making use of resources close to the surface, and other species specializing in deep-water feeding, with the largest of them reaching 50 feet in length. They were joined by another group of marine reptiles called plesiosaurs. Plesiosaurs occur in two basic body plans, with the unimaginative names of long-necked and short-necked for obvious reasons.

Long-necked plesiosaur Styxosaurus

Long-necked plesiosaur Styxosaurus

The long-necked plesiosaurs have been described as looking like a turtle with a snake threaded through its shell. They had a stocky, turtle-like body, enormously long necks capped by a remarkably small head, and stumpy tails. They had four large flippers that helped to propel them through the water as well.

Short-necked plesiosaurs had large heads attached to short, thick necks. The long-necked forms most likely specialized in eating smaller fish with their small heads, maybe using their long necks to “snake” their way amongst their prey before being noticed. The short-necked forms obviously ate large prey, as evidenced by their massive heads and powerful jaws. (You can find models of both long and short-necked forms, as well as mosasaurs as part of the collection of dinosaur toys).

Living alongside these giants of the sea were animals that we would easily recognize, at least for their general body plan—these were the sharks. There was a significant amount of shark diversity in the Interior Sea as well, from relatively small forms that likely ate near the sea floor, to mid-sized forms that ate smaller fish and scavenged on dead carcasses, to several very large species that rivaled the modern great white shark in size and ferocity.

On occasion, when finding remains of fish or the marine reptiles, we find evidence of those remains having been bitten by sharks. The most compelling evidence is when teeth are found embedded in the fossil remains, but also punctures and tooth scratches can be a telltale sign.

Several plesiosaurs have been found as partial skeletons, with bites in several areas of their body, suggesting that after they died and settled to the ocean floor their carcass was scavenged by mid-sized sharks.

Cretoxyrhina bites the back of a mosasaur in the Late Cretaceous

Cretoxyrhina bites the back of a mosasaur in the Late Cretaceous. Painting by Dan Varner.

And in one dramatic example, the great white of the Kansas seas bite the back of a mosasaurs, cutting a section of vertebrae completely out of the giant lizard. The section of back, with its included vertebrae, was later spit out by the shark after having been mostly digested. The gristly remains settled to the ocean floor to lie there for millions of years before being found and placed in a museum.

Today we are fascinated by tales of shark attack, with the movie Jaws being a prime example. You can learn about these dangerous animals in another post, but perhaps it gives you some comfort to know that the denizens of the ancient seas also were subject to shark bites!

Additional information about this specimen can be found at Oceans of Kansas.

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Keep Your Cichlids Healthy – It’s Easy

Guest Post

The hobby of keeping cichlids can be a very enjoyable and rewarding experience. Most people just getting started in keeping these very intelligent aquarium fish have lots of questions. Even as an experienced aquarist, I seem to learn something new everyday. Here are some tips to get you started.

The first thing that you need to do when keeping cichlids is to consider what size that your cichlids will be when they are fully mature. If you have gotten bitten by the Oscar bug and have fallen in love with these very personable fish, you are simply going to need a large tank.

Most people will recommend at least a 55 gallon aquarium to keep a pair of Oscar fish. That is simply the bare minimum for these big guys. If you have a smaller variety, you just need a smaller tank. Simple, right?

Second, ph level and water salinity, among other water chemistry levels, can be very different between the different types of cichlids. Just consider African Cichlids. They are found in different lakes in Africa. Each of these lakes have their own unique water chemistry, so if you are keeping Africans, it is very important to do your research if you are going to replicate their native habitat.

If your cichlids are going to thrive, whether they are African or New World Cichlids, temperature and water chemistry must be monitored.

Plants and cichlids sometimes just do not match well. Many cichlids are very intelligent, but they love to make lettuce out aquarim plants. Its a challenge, but it can be done.

American varieties of cichlids seem to be able to tolerate plants in their aquarium better that Africans do. But having made that point, Oscars love to destroy plant life. Angel fish, on the other hand, seem to tolerate plants very well.

Angel fish can be some of the most enjoyable cichlids in my opinion. They even do very well in community tanks because they are generally docile and tolerate plants very well.

Visit cichlid care to learn how to keep cichlids healthy, colorful and happy. And visit keeping cichlids to learn how to keep your cichlids stress free.

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Fossil ‘discovery’ rewrites history

Originally published in the Hays Daily News 21 February 2010

By MIKE CORN
mcorn@dailynews.net

For nearly 40 years, it’s been tucked away in a storage room at the University of Kansas, little more than a bag of bones that at the time it was collected struck even the most experienced as unusual.

The late Marion Bonner was right: The discovery in 1971 by his son Chuck then 21, was indeed unusual.

On Thursday, scientists announced that it was deserving of its own genus, proving to be something of a missing link between the oceans of 100 million years ago and today.

The announcement was made Thursday in Science Magazine.

The fossil, representing a massive filter-feeder much like the blue whale of today, was named Bonnerichthys, in honor of the Bonner family — responsible for outstanding fossil discoveries in the chalk bluffs of northwest Kansas.

Several of those discoveries are on display at Sternberg Museum of Natural History, as well as other museums.

The Bonnerichthys discovery came not from a recent collection, but from one that Chuck Bonner discovered in 1971 in Logan County while on a fossil-collecting expedition with his family.

“That was pretty nice,” Bonner said Friday. “Pretty nice to have a genus named after us.”

Several individual species have been named for Marion Bonner, who collected fossils alongside George Sternberg, founder of the Sternberg Museum.

While it was discovered by Chuck Bonner, the excavation work fell to his father.

“Dad knew when he was digging on it, it was something different,” Bonner said.

“I tell you what, I wasn’t too excited that day. Actually, I was more excited about Dana finding a turtle up above me.”

While the Bonner discovery — once it was cleaned up — was responsible for the naming of a new genus, there’s another and more complete specimen being prepared.

That discovery, coming from land owned by Mahlon and Carolyn Tuttle, has been donated to Sternberg and will provide even richer detail about the fish.

The Gove County specimen was discovered by Kenshu Shimada, an FHSU alumnus now at DePaul University in Chicago, and excavated by Mike Everhart, adjunct curator of paleontology at Sternberg.

Everhart has been thrilled with the credit given to the Bonner family, as well as the fossil that was collected in Gove County.

The trouble with plankton feeders is they are too much like sharks, in that they have little skeletal structure to fossilize. Much of it is cartilage and tissue.

Bones in the skull, for example, were connected by cartilage.

That made it big, but difficult to find, 100 million years later.

“It is the biggest bony fish feeding in the Cretaceous sea,” Everhart said. Generally, the Kansas variety, which makes up the largest percentage, would have been about 30 feet long.

The discovery, that it was a huge fish that fed on plankton, “filled in the blanks.”

Early on, the fish had been classed as a swordfish, but neither sword nor skull had been found.
Everhart said they have now determined that the fish lived from 170 million to 85 million years ago, dying out at the same time the dinosaurs.

“At the end of the Cretaceous, for some reason, the plankton died off,” Everhart said. That spelled doom for the filter feeders as well.

The chain of events have thrilled Everhart and Bonner.

“It’s very exciting to me,” Everhart said of the discovery and its publication in Science Magazine. “It’s not everyday you get a chance to be published in Science. It’s a pretty prestigious publication.”

Determining the fish was a filter feeder was just as significant.

“It was just an ‘aha’ moment,” he said. “We figured out what was going on.”

“He would have been swelling with pride,” Bonner said of his father.

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