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Comment by s_dev | Hacker News Reader

The real problem is that nearly all seafood is unsustainable. Even when using euphemisms like 'farms' make us thing it's somewhat contained to one place and we just throw them some food pellets manufactured from vegetables in another factory. The reality of salmon farms for instance is that for every 1kg of farmed Salmon it takes 20kg of wild fish to feed them to maturity.

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It really depends. The Hawaiians farmed fish several hundred years ago. They built structures (loko i'a) that encouraged certain fishes to congregate and fed/protected them. The caveat is that the fish primarily ate algae and plankton so it is considerably easier to feed the fish.

"ranching" is the right term. Like what we do for lobsters, when we feed and trap them

This 20kg figure sounds wildly inaccurate. Fish feed is in general 75% plantbased. It is also very efficient (in terms of conversion rate to growth). Could this 20kg figure be decades old?

This seems to be a very generalized statement when there is a lot of variation to consider. There are 33,000 fish species, some being specialized feeders of algae, to 100% live fish, all designed for processing each food differently. Are you speaking on a specific fish that is commonly "farmed"? I could see Salmon needing this 20kg and not even contain the quality fats they get in the wild, resulting in a lower quality food on top of being more impactful to the environment.

Also the non plant parts of it could be fairly efficient too. e.g see black soldier fly farming for fish feed. Not that that is a 100% answer for all feed for seafood farming, but interesting options abound.

Personally though, Octopi are too smart for me to eat. I'll always pass on it now.

Whatever happened to the Roach farming as a viable option for quality protein farming? I could see a flow like algae/hemp -> roach -> fish -> human

Soldier fly leaks from farms are more palatable than Roach leaks?

In the 1970's I went on a field trip to a trout farm in New York (USA, obvs.). They fed plant food pellets to this giant whirling silos of fish. Not sure if salmon can eat plants but trout sure can. Of course, that was the 70's, and just one fish farm.

Trout are salmon are trout.

Some species even bridge freshwater to salt. Sockeye come to mind, a few populations are completely landlocked.

Same family, not the same genera.

Tilapia can be raised vegetarian. Salmon eat meat. Lots of fish can survive on mostly insects and water plants. All depends.

The Feed Conversation Rate for fish is between 1.0 and 2.0kg of feed to produce 1kg of fish. For salmon this is 1.2 to 1.5kg. They are replacing the wild fish with alternatives and additives that are more sustainable.

There's a lot of shit ton of algaes blooming due to climate change. Wonder if that can be sourced as protein / feed.

A lot of those algae are poisonous.

The ocean food web rests on algae. Every creature in the sea eats algae indirectly. Every wild-caught fish.

That's not a reasonable way to think about it in this context. If a small fish eats algae that is poisonous to us, it's likely able to metabolize the poison and not itself be poisonous to its predators or to us.

So poisonous that they can't be industrially processed? Or no one has bothered to try for feedstock. Genuinely curious.

So poisonous that when cattle is feed with it daily, its grow is stunted

Metabolically, animals are pretty inefficient, and each trophic level (layer of the food web) only keeps about 10% of its caloric intake as edible flesh for the next layer (https://en.wikipedia.org/wiki/Ecological_efficiency#Ten_perc...).

So if algae feed smaller fish, the smaller fish feed salmon, and the salmon feed humans, to double our salmon, we'd need 20 units of smaller fish and 200 units of algae (edit: oops, math is hard).

That's a lot. Climate change can increase algae productivity, but not by that much unless we want to barbecue the world. Of course there are other avenues (like simply harvesting more of it, or growing crops in areas of land/ocean not suitable for other uses). But there are always knock-on effects too, like algae blooms can be poisonous or deplete nutrients in an area.

The on-land agricultural revolution and improved/modified genetics gave us access to much more edible food, but a lot of that is only 1-2 trophic levels (we eat grains directly or feed grains to livestock that we then eat). The ocean tends to have a lot more layers, and is also not as easy for us to till and fertilize, and not all of it is equal... much of the edible parts are concentrated in certain areas, with a lot of empty water in between.

In general we probably shouldn't be hunting apex predators in the ocean anymore than we hunt them on land. It took 'em millions of years of evolution to reach a relatively stable carrying capacity, but we can drive them to extinction in a few years.

But, hell, realistically there's probably no stopping any of this. One day our kids will read about whales alongside dodos in the history books =/

Climate change may be a contributing factor, but my understanding is that a major driver of the algae blooms is nutrient runoff from agriculture.

> nearly all seafood is unsustainable

If we only could convince vegans to renounce to hoard cats...

All this young anchovies ending in a can tomb just for Mr whiskers appetite... sigh

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