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Comment by cma | Hacker News Reader

"They keep our fish stock healthy, they keep the food chain intact, they keep diseases out of other animal populations," she said. "Good luck trying to replace that when we lose them."

Isn't human predation (fishing) a suitable alternative to shark predation for this purpose? I guess they eat a more wide diet of fish types.

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Human predation doesn't apply the same positive evolutionary pressures as apex predators. Typically predators eat the slowest, weakest, dumbest prey. Humans either target the biggest, strongest prey (if hunting individuals) or indiscriminately massacre a swathe of the ecosystem (eg. dragnet fishing).

What is a "positive evolutionary pressure"? Why are fast, smart, strong fish important?

I'd imagine smart fish survive better in general; we're changing the environment, and brains can adapt faster than evolution.

Fast, strong fish are better sources of muscle, which is what we hunt them for.

Don't other apex predators hunt for size as well? And aren't whales similar in some ways to dragnet fishing? They don't target the weakest straggler sardines or the injured phytoplankton only.

Did putting in/replacing a predator in an eco system ever work? I can only think of countless examples where it didn't

There's a widely publicized example where wolves were reintroduced in a national reserve (Yellowstone National Park). The ecological effects were dramatic. Here's a quick video on it (jump to 2:35 for an even quicker viewing): https://www.youtube.com/watch?v=gc52l5ZcAJ0

That was restoring not replacing.

But the OP was asking about sharks as a predator which are clearly being restored.

As a concrete example.

My father in law is a fisherman, of various shellfish. Puts a premium on being sustainable and a lot of his business is farm raised shellfish.

Rays eat the shellfish. They can decimate beds of shellfish.

Sharks eat the rays.

I've joked with him about raising sharks as a farm raised fish. He laughs but gets kinda terrified of the idea because he actually thinks it through a bit half seriously and is nervous about sharks.

I'm surprised there isn't aquaculture programs for sharks though if there's such a demand. Lots of sharks are small.

My impression based on reading a bunch of links is that a bit of genetic engineering and bigger demand would improve yields and efficiency of plant and microbial squalene. It seems like in this type of situation the differential is usually due to historical convenience.

Biomedical research is full of examples of this sort of thing. It's not exactly a beacon historically for animal welfare. Horseshoe crabs are a similar example that come to mind as a para llel.

Human fishing isn't selective, not the way a predator is selective.

Except we farm most of our fish. And sharks are out of the equation?

“Most”, yeah 50%. What about the other half? Just because we farm more fish now doesn’t mean we catch less in the wild. It just means we’re farming more.

And farming is growing. A reasonable projection is, wild fish will matter less over time until they are negligible.

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