What's eating the brains of sharks and rays in California?

 
Between February and July, there have been a lot of incidents, where dying or dead sharks and rays have washed up on beaches in San Francisco bay. What is causing them to die?


According to an article in National Geographic, CDFW senior fish pathologist Mark Okihiro, Joseph Derisi, an expert on the genetics of infectious diseases at the University of California, San Francisco and Hanna Retallack, an MD-PhD graduate student have found the answer.

Their headline reads : "Mysterious Brain-Eating Shark Killer Identified, Though Questions Remain"

  
It looks like the culprit is "a well-known fish-killing parasite called Miamiensis avidus."

The article further states: This appears to be the first case, Retallack said, of Miamiensis avidus infecting wild sharks. It’s noteworthy, she added, because sharks are evolutionarily quite different from the bony fish that have previously been known to suffer infections. 

Read the entire article here

Cheers,
Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

What causes sharks to have crooked spines?

 
Earthtouchnews has an article describing a bull shark with a crooked spine. That shark was found by the shark lab in Bimini. They named him "Quasimido" and are speculating on what caused that deformity.

The Bimini Shark Lab team secures "Quasimodo" for workup (a short checkup that includes taking various measurements of the animal). Image: Chelle Blais/Bimini Biological Field Station

Sarah Keartes writes: "Dr. Natalie D. Mylniczenko, a veterinarian who has spent time with the Shark Lab beforepresented several possible explanations for the bull shark's strange skeleton. It's possible that a deep abscess, granuloma, or slow-growing cancer is to blame – but Quasimodo's overall state seems to suggest otherwise. If disease were at the root of the deformity, we would expect to see at least some abnormal behaviour. The more likely culprit, according to Mylniczenko, is either a congenital or traumatic incident. In either case, this would have occurred when the shark was very young, and over time, his body would have compensated and healed in a skewed position."

Read the full story here: https://www.earthtouchnews.com/oceans/sharks/meet-quasimodo-the-bull-shark-with-a-very-crooked-spine/
 

Image: Chelle Blais/Bimini Biological Field Station

This Bull Shark is not the only shark with a deformed spine. At Guadalupe Island, we have our own Great White Shark with the same deformation. When we first met her a couple of years ago, I nicknamed her "Kinky" because of the very distinct kink in her tail. I have no idea what caused that kink, since she doesn't have any obvious scars or signs of injury. She was named "Screaming Mimi" by someone through the "Sponsor a shark" program of the Marine Conservation Science Institute. That sponsor program, is one of the ways they raise funds for the Photo ID database at Guadalupe Island.
 

"Screaming Mimi"

Just like the "Quasimodo" in Bimini who was seen swimming around a couple of weeks after the people from the Shark Lab examined it, "Screaming Mimi" also seems to be doing well and has been very active around our cages at Guadalupe Island.

If you want to meet "Screaming Mimi", or any of our other sharks at Guadalupe, contact us at 619.887.4275, crew@sharkdiver.com or www.sharkdiver.com

Let's go shark diving!

Cheers,
Martin Graf
CEO Shark Diver
 
About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

What 's hurting the Great White Sharks at Guadalupe?

 
We are coming towards the end of another great season at Guadalupe Island. Just like last year, we added a lot of new sharks to the photo ID database and saw a lot of our regulars that came back. We definitely see an increasing number of sharks, specially for sharks in the 10-12' range. It's great to see that conservation efforts seem to have a positive impact on shark numbers. We regularly see in excess of 20 different sharks on our expeditions, a huge increase over 10 years ago, when we were lucky to see 10 and often went whole days without seeing a single shark.

One thing that I noticed though is the increasing number of sharks with injuries caused by ropes or fishing gear. A couple of years ago it was "Luca" that swam around with a rope around his body. Luckily his rope was cut and he's doing fine. There is just a black scar left that will disappear in a year or so.

Luca with a black scar from a wrapped rope.

This year we saw a few sharks with either fresh wounds from ropes or still having the ropes attached around them. One of these sharks is a new female.

 

 

 

New female with rope around her

The rope around her body is embedded in the gills on both sides.

Her underside shows a faint scar from the rope that was digging into her. (It' kind of hard to see, just in front of her pectoral fins) The rope goes around her head and into the bottom of her gills on both sides, so it looks like the rope is still inside and the wound has closed around it. She must have gotten that rope wrapped around her quite a while ago, for it to be completely embedded.

This makes at least 3 sharks now that had a rope wrapped around them. Where do these ropes come from?

I hope that somehow this rope can get cut, otherwise I fear that this shark is not going to survive.  We also need to find out where these ropes are coming from, so that we might be able to stop the sharks from getting entangled in the future.

Cheers,
Martin Graf
CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com.

Deadly tiger shark stalks stranded diver?

 

The sensationalist media is at it again, or should I say still at it? This time it's an outlet not normally prone to sensational headlines. Sky News has a headline that reads "Deadly tiger shark stalks stranded diver four miles back to shore"

 

Tiger Shark

Turns out that a spearfisherman got separated from his boat and had to swim back 4 miles to shore. What they describe as "A diver who became separated from his boat has said he is lucky to be alive after swimming miles back to shore while being stalked by a large tiger shark." and "He swam…in shark-infested waters. I just can't believe anybody could do that. It's such a massive effort.", was in reality just a really long swim, where he encountered a couple of sharks.

That "deadly" shark was just checking him out and the diver even says that "For about 500 metres the shark swam on the same path as me towards the shore and then in a moment banked and disappeared completely as if to say 'you're OK now, I'll leave you alone'. So the real danger to the diver were not the sharks, but the fact that he had to swim for 4 miles to reach shore.

 

Tiger Shark coming close to a diver

Maybe a headline that says "Diver lost at sea has to swim 4 miles to reach shore" or something similar would be more appropriate than making the sharks out to be those mindless killers again, would be more appropriate.

 

Me with a Tiger Shark ©Rene Buob

We dive with Tiger Sharks in various places around the world and learned that we have to respect them, but there is no need to fear them. They are neither mindless killers, nor harmless pets, but awesome predators that are curious, but in most cases not interested in attacking us.

Cheers,

Martin Graf

CEO Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at crew@sharkdiver.com.