Surprising study finds sharks are key to restoring damaged habitats, fighting climate change

Researchers tested how the absence of tiger sharks could affect seagrass coverage.


Alexandra Kelley | March 22, 2021

Im ok with it as long as they stay out of the lineup

They told me they are ok with you so long as you stay out of their kitchen :wink:

I’ve said it before and I’ll say it again.  I have a good relationship with sharks.  I don’t eat them when they are out of the water, and they don’t eat me when I’m in the water.  So far it’s working out great.

That’s always been my agreement as well. But when I lived in Sonoma County, CA, heart of “The Red Triangle” there were a few times, surfing alone at a notoriously sharky beach when I would just get the heebie-jeebies.  Deal or no deal, I’d just get out of the water when that would happen.

The biggest problem with sharks is they have no manners , there is never a “please may I bite you” or “thanks for the piece of foot” .

So far I only eat Mako sharks.

They are “key” to restoring habitat.  Used to be my habit to eat a"Surfer Burger" (breaded and deep fried shark) once in awhile.  Or going out on the nightly shark run out of Mission Bay.  Bring home your catch and smoke it.

Interesting… here, we have a similar issue, though the obverse of this particular coin . we’ve got an overpopulation of seals. Which appears to be an order of magnitude more than at any time in history, including archaeological evidence dating back a few thousand years. 

How come? They’re protected by law, so they have reproduced madly. And their natural predators increase a lot slower. The Great Whites are the fastest and most prolific, Orcas (who take out seals and are pretty much the only thing that takes out Great Whites) a lot slower and fewer offspring each. 

But we’re getting more and more Great Whites. 

Unfortunately, other things look like seals swimming on the surface, like human swimmers, boogie board types and ( uh oh) kneeboarders like me, with our fins and all. Mister Shark comes up to have a taste and equally unfortunately by the time he’s discovered that I’m not a seal and instead old and stringy,  I’m discovering that paddling for shore is a lot less efficient with less legs or circulatory fluid. This has rather put off the sun and fun beachgoers and in turn the tourist businesses. Not least the surf biz. 

Then, well, figure 50,000 plus 100 kg seals, eating something like 10% of their bodyweight in fish every day. As they’re not 100% efficient, at least half of what went in comes out with water quality suffering. Fishermen are unhappy and water quality folks likewise. The seals target smaller, juvenile fish, so inshore populations we were hoping to see recover are instead declining. 

No easy answers. And nobody is quite into patience, they want to wipe out one species or another or both rather than nature taking its course over decades. 

Anybody know of a few hundred orcas looking for a cool place to go? All you can eat buffet? We got just the place…


And almost no one seems to get that you can’t effect or change on thing without changing everything. 

“When we try to pick out anything by itself, we find it hitched to everything else in the Universe.”

~ John Muir ~

And there it is. 

Now, there is always a boom-bust thing going on. For instance, here, in a given year you might see some rabbits.The next year, a lot of rabbits and a few foxes. The next, a lot of both. And after that, more foxes but fewer rabbits, And after that pretty much no rabbits and the foxes are fewer and thin, not doing too well. And after that, you see no foxes but a few rabbits and the cycle begins again. 

Of course, rabbits are not the only thing foxes eat. Nor are they the only thing that eats rabbits. Coyotes, for instance. The place the rabbits dug their burrows may have a parking lot built on it. What they eat may not have grown so well that year, or a rabbit disease made the rounds, or a fox pandemic. It happens. It’s way more complicated than just rabbits versus foxes. 

Nature doesn’t really have a balance or an equilibrium , more dynamic than that, in an incredibly complex set of processes we can only see as a series of snapshots of small parts of it that we think we understand.

We think…


Well said.

Yes, and part of the snapshot on the central coast of CA. is there seems to be a lot more of them. A lot more. Especially, in the spring/summer when the juveniles move in over the sand bottoms for fish I assume. Last year one surfer was killed and two stand up paddlers had their boards hit while paddling outside the kelp forest. A rare event is now becoming quite common. I ve had two ‘encounters’ the last five years after never seeing a thing for over 40. I realize this is annecdotal. Just sayn. Mike

About 20 years ago I often surfed around Bolina (shhhhhh…). Shark bumps and nips stories were a dime a dozen esp amongst the younger, bolder guys who were less hesitant about surfing some of the more sharky spots. A friend flew in a small plane, over a spot out on on Pt Reyes and said he could the silhouettes of BIG white sharks lying on the bottom, waiting for seals (or what might look like a seal) to swim overhead. Then they’s launch like a Polaris missle, straight up for a Scooby Snack. He refused to got there ever after but many Bolinas kids surfed there and I saw more than a few patches on boards that looked like bite marks and stitched up tears in lower legs of wetsuits. Maybe it’s a lot worse now? Maybe thus has it ever been? 

A couple main reasons for rising white shark populations. The Marine Mammal Protection Act enacted back in 1972 ensures a non stop source of food for mature sharks. White Sharks themeselves have been protected in Cali since 1994 and the American Atlantic since 1997. Also, in 1994 California outlawed gillnets in inshore waters allowing a rise not only in shark populations but also the many inshore fish that make up the diet of immature white sharks** and **the furry stuff the big ones eat…       

I’ve had two “close encounters” in the past 15 or so years. One of them really scared me. 

What Doc has been discussing is population dynamics.

Part of the model is that the surfer population has increased exponentially since 1960, attracting more predators.  Lots of apex predators in the ocean with a competitive advantage.

As the prey population increases, the number of predators increases to thin it…

Hey Bill. Yes. Population dynamics. I don’t debate religion with anyone but I doubt whether not eating shark will prevent  get hit by one. I do admit to launching a little prayer before paddling out, though…just in case.  Mike

Sympathetic magic has a very long tradition :wink:

I don’t eat shark becasue they are top of the food chain and so bioaccumulate mucho pollution of all sorts. But that’s just my orthorexia talking HAHAHA!

If humans thin the seal population, the shark problem will likely get worse for surfers.

An increased shark population now has less food available.  They still must eat to survive.

So they go for the next most plentiful prey – surfers…

IMO risk management is effective.

Like fish, Great Whites use more than vision to locate prey.  They are attracted to motion/surface disturbances, e.g. paddling.  They have very effective “lateral lines.”

“Great white sharks have an elaborate sense of touch through what’s called the lateral line – a line that extends along the middle of the shark’s body from its tail to its head. This line, which is found in all fish, is made of cells that can perceive vibrations in the water. Sharks can detect both the direction and amount of movement made by prey, even from as far as 820 feet (250 meters) away.”