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Comment by specialp | Hacker News Reader

When a fishery crashes, it is dramatic and takes a long time to recover if ever. There's been plenty of fisheries like cod that one could not conceive being depleted but it has been now for decades.

Estimates of catches, mortality, existing stock are prone to error because we don't really know much about how fish live and their overall population. But once that crash happens it is known and too late. Cod crashed in 1992 and still hasn't recovered

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Yes, seen this happen in Tasmania, Australia with crayfish, scallops and orange roughy. Each went from free-for-all to highly managed quotas within a few years. Roughy fishing stopped completely back then, don't know what the status is now.

> we don't really know much about how fish live and their overall population

Absolutely yes. Orange roughy is a good example - it was caught by trawlers when they were massed in huge balls near the surface. Easy to get a big catch quickly. Turns out this was when they were spawning, so breeding cycle was being interrupted, which led to catastrophic declines very quickly.

My understanding is that the cod fishery decline in Atlantic waters has had limited recovery because the ecological niche that the cod fish occupied has been taken over to some extent by a small shark species. The wikipedia page mentions 'trophic cascade' so larger populations of prey species but does not mention the shark takeover. Either way cutting the harvesting won't bring the fish back.

> because the ecological niche that the cod fish occupied has been taken over to some extent by a small shark species.

That is very interesting, I wish this kind of things were taught in school. Too many people think that animals just exists in the current state for ever. When in reality it is a dynamic system that once changed cannot be brought back.

There are two sides to it. The other side is: what people consider current "balance of nature" is just a transient state. Species die off all the time, ecosystems last millenia and then suddenly collapse, then rebound and look completely different. Protecting the habitability of our planet is paramount, but overindexing on how any particular aspect of it looks at any moment is a fool's game.

The planet will literally survive anything. Life finds a way. There were supervolcanoes that blanketed the skies for millions of years.

But human civilization as we know it is fragile.

> Species die off all the time,

This species didn't just die, it was exterminated by humans. It is the difference between someone dying fro a sickness and from a bulled to the head.

> overindexing

How can be stop fishing species to extinction "too much"? How can you justify that way of thinking in this concrete case?

>This species didn't just die, it was exterminated by humans.

Which species? The (non-extinct, not exterminated) cod fish whose ecological niche has been taken over to some extent by a small shark species?

Scale matters and modern humans drive species to extinction faster than the historical average by several orders of magnitude. Even if you value non-human intelligent life at zero, which I think is morally reprehensible but know plenty of others disagree, this kind of destruction has significant hard to predict impacts.

But from a purely selfish and human centered perspective we can also demand preservation just so that future humans also get to enjoy what the previous generations had. I wish humans didn't kill off the dodos! I want my grandchildren to be able to eat ocean fish. And I'm willing to reduce my own fish consumption if that means the fisheries live on into my grandchildren's times.

This is true of trees even. People think forests have looked the same for all time but trees are frequently pushing each other out of areas. Disease and pests play a huge role as well.

There's some amount of introduced pressure due to invasive species of both trees and pests but it's always been this way. Everything is in flux all the time.

Stable pockets exist but they're relatively rare.

Too many people think food grows on a grocery store shelf. If they've never grown a plant from seed and eaten the result, it is hard to internalize the reality of the supply chain.

Replying to my own post as well past edit timeout.

I can't find anything about niche occupancy replacement at all on the Web. Searches lead to information about the trophic decline in prey species after an initial boom when the North Atlantic cod went down to something like 1% of previous volume. Some mention of harp seals competing with younger smaller cod for available food (which is scarce now apparently).

Could be a case of a small effect earlier in the timeline masked by huge changes resulting from warming water &c.

To be fair, we used to catch decades-old (and probably centuries-old) gigantic cod. There hasn't been enough time to rebuild those giant predators back into the system, which has broad effects.

It's like clear-cutting an old-growth forest, and then replanting acorns. The forest simply won't return to anything like its original state for many decades - if ever.

So we need to start hunting shark?

Start a viral trend and they'll be gone too in 5 years.

And that's with management. Here on the east coast of Canada cod was a big industry and was managed by Dept of Fisheries and Oceans aka DFO. The problem was foreign fishing freezer ships just over the maritime border. They took whatever they wanted to and were no restricted even by their own countries. Canada almost went to war with Spain and Portugal we even sent warships to the area.

That's the scary part. By the time the data is unambiguous enough for everyone to agree the stock has collapsed, you're already dealing with the collapse rather than preventing it

Seems like a pattern with environmental problems.

Unclear signals and long lag times make systems management a real bear.

Also it doesn't help there are people whose income depend on the system collapsing

Quite.

Perverse incentives, generalising.

Turns out, it is hard to understand a potential future problem if your salary or comfort in the present depends on you not understanding it.

Climate change is pretty much the same.

Not all fishery crashes are the same. Alaskan sockeye had a huge crash in 2014 which was immediately followed by huge gluts in 2015-2017. Same thing happened last year after a terribly weak run in 2024. Important to look at specific facts and context

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