Dying Leopard Sharks in the Bay?

[jacuzzi]

So I saw a local news story yesterday about how they are finding dying leopard sharks in the Bay. Test show that its from massive internal bleeding to the point blood is coming through the skin. People finding them have tried to put them back but the sharks immediately return to the shore as if they are committing suicide. Its a very slow and painful death which disturbs me, being a fisherman I catch and release leopard sharks all the time. Whats weird to me is that scientist say that the cause may be a change in the salinity in the bay because of the recent rain. Doesn't make sense to me, no other fish or sharks are being found so can anyone shed some light on this?

 

[GreshamH]

Link? Kinda sounds fishy given how much rain we got in 82/83 during a stronf El Nino. Surely this years La Nina isn't wetter then that year and I do not recall this as an ebent back then. Time to look into this

 

[sfsuphysics]

Saw a news story on this myself, so no link to an actual story. But from my understanding is it wasn't so much in the bay but little "creeks and streams " next to the bay, where rain water run off could potentially lower the salinity quite a bit more so.

That said, lots of great schools in the area, hopefully one or more will have a project, autopsy, and figure something out

 

[99sf]

Very sad. I've been kayaking in Tomales bay where the leopard sharks breed, and it's amazing to see them in the shallow, calm waters.
AP Article
Marin Article
San Mateo Article
Peninsula Article

 

[sfboarders]

I'm no expert but wouldn't you think they would swim away if the salinity was getting to low? Another link from SF Gate

 

[GDawson]

Interesting..... I wonder if there's any connection to rodent/vermin poisons. The active ingredient in most of them these days is a form of cumadin It's a blood thinner. The animals hemorrhage and bleed out.

-Gregory

 

[phishphood]

A similar die-off occurred in 2006 after heavy rains, said Carrie Wilson, biologist with the state Department of Fish and Game.

Dunno about the significance Gresham. I doubt that it would've occurred in 82/83 w/o any record of it, but at least its been somewhat documented? I hazard a guess that it has nothing to do with salinity, or at least very little.

I like the pesticide idea, but even at the concentration they use on land, it has to be diluted by so much by the time it hits the from creeks etc. But ar these baits or sprays or what? If they're baits, I have a hard time believing enough of the pellets or whatnot came in contact with water and were flushed to creeks/storm drains instead of sitting in the soil.

Just my .02.
PS brain fried from a final an hour ago, please excuse.

 

[99sf]

Support for the salinity hypothesis from the Chronicle article John linked:

Though they don't venture out into the deep sea, they do favor water with salinity levels at the higher end of the spectrum, said Wes Dowd, a postdoctoral scholar at Stanford University's Hopkins Marine Station in Pacific Grove.

Dowd studied the effect of low-salinity water on leopard sharks as part of his thesis. In his experiments, Dowd found that when salinity fell to 19 parts per thousand, the sharks thrust their noses and fins out of the water in an attempt to survive.

Earlier this spring, sensors in some parts of San Francisco Bay recorded salinity levels below 15 parts per thousand, Dowd said. Seawater salinity maxes out at about 34 or 35 parts per thousand. "When (salinity) moves lower ... it becomes harder for the sharks to compensate for that change in their environment," Dowd said. "They don't cope well."

 

[GreshamH]

Support for the salinity hypothesis from the Chronicle article John linked:

Though they don't venture out into the deep sea, they do favor water with salinity levels at the higher end of the spectrum, said Wes Dowd, a postdoctoral scholar at Stanford University's Hopkins Marine Station in Pacific Grove.

Dowd studied the effect of low-salinity water on leopard sharks as part of his thesis. In his experiments, Dowd found that when salinity fell to 19 parts per thousand, the sharks thrust their noses and fins out of the water in an attempt to survive.

Earlier this spring, sensors in some parts of San Francisco Bay recorded salinity levels below 15 parts per thousand, Dowd said. Seawater salinity maxes out at about 34 or 35 parts per thousand. "When (salinity) moves lower ... it becomes harder for the sharks to compensate for that change in their environment," Dowd said. "They don't cope well."

Thrusting ones nose out of the water and bleeding from ones skin and DYING is a rather large stretch :lol:

 

[GreshamH]

Support for the salinity hypothesis from the Chronicle article John linked:

Though they don't venture out into the deep sea, they do favor water with salinity levels at the higher end of the spectrum, said Wes Dowd, a postdoctoral scholar at Stanford University's Hopkins Marine Station in Pacific Grove.

Dowd studied the effect of low-salinity water on leopard sharks as part of his thesis. In his experiments, Dowd found that when salinity fell to 19 parts per thousand, the sharks thrust their noses and fins out of the water in an attempt to survive.

Earlier this spring, sensors in some parts of San Francisco Bay recorded salinity levels below 15 parts per thousand, Dowd said. Seawater salinity maxes out at about 34 or 35 parts per thousand. "When (salinity) moves lower ... it becomes harder for the sharks to compensate for that change in their environment," Dowd said. "They don't cope well."

Wait for the data

Though Wilson acknowledges the possible link between the deaths and the rapid influx of freshwater, she declined to use the term "die-off" and cautioned against jumping to conclusions until all the data are in.

"There have been some wild speculations based on only a few samples," she said. "We don't want to give out any information that's premature."

Omitting that from you post does it no justice!

 

[99sf]

The articles say that a state expert has begun to study the shark deaths. Nobody is jumping to conclusions.

 

[GreshamH]

The articles say that a state expert has begun to study the shark deaths. Nobody is jumping to conclusions.

A word I did not use.

Salinity
Pesticides
etc

have all been put forth as speculations as to the cause and on what evidence have any been put forth to support those speculations? Sure sharks do not like hypo, but nothing they have put forward suggests hypo would make them bleed out of their skin and dye like they did.

 

[GreshamH]

Support for the salinity hypothesis from the Chronicle article John linked:

Though they don't venture out into the deep sea, they do favor water with salinity levels at the higher end of the spectrum, said Wes Dowd, a postdoctoral scholar at Stanford University's Hopkins Marine Station in Pacific Grove.

Dowd studied the effect of low-salinity water on leopard sharks as part of his thesis. In his experiments, Dowd found that when salinity fell to 19 parts per thousand, the sharks thrust their noses and fins out of the water in an attempt to survive.

Earlier this spring, sensors in some parts of San Francisco Bay recorded salinity levels below 15 parts per thousand, Dowd said. Seawater salinity maxes out at about 34 or 35 parts per thousand. "When (salinity) moves lower ... it becomes harder for the sharks to compensate for that change in their environment," Dowd said. "They don't cope well."

Wait for the data


Though Wilson acknowledges the possible link between the deaths and the rapid influx of freshwater, she declined to use the term "die-off" and cautioned against jumping to conclusions until all the data are in.

"There have been some wild speculations based on only a few samples," she said. "We don't want to give out any information that's premature."

Omitting that from you post does it no justice!

99sf... the reason I posted that quote under yours is with out it yours is incomplete and paints a different picture. I'm not saying you meant to do it, but it sure reads different with out the second post I added to it (from the same article).

 

[tuberider]

I'm not buying the rain theory myself, hemorrhagic symptoms don't spell freshwater intrusion. It's like saying "look, the dead guy is all bruised up he must have had hantavirus". Not saying that it couldn't have happened, but when you're finding dead fish in SF and Millbrae, you're not talking about fish in shallow water that is not affected by tidal influence.