Overfishing Has Caused Cod To Halve in Body Size Since 1990s, Study Finds (theguardian.com) 50
Overfishing has led to a collapse in the eastern Baltic cod population, but over the past three decades the size of the fish themselves has also been dramatically and mysteriously shrinking. From a report: Now scientists have uncovered genomic evidence that intensive fishing has driven rapid evolutionary changes that have contributed to these fish roughly halving in average body length since the 1990s. The "shrinking" of cod, from a median mature body length of 40cm in 1996 to 20cm in 2019, has a genetic basis and human activities have left a profound mark on the population's DNA, the study concluded.
[...] The dramatic shrinking of cod has been a source of concern for several decades, but it was not clear to what extent the phenomenon has been driven by environmental factors such as hypoxic conditions caused by algal blooms, pollution and more extreme marine seasonal temperature changes. [...] The study used an archive of tiny ear bones, called otoliths, of 152 cod, caught in the Bornholm Basin between 1996 and 2019. Otoliths -- a bit like tree rings -- record annual growth, making them valuable biological timekeepers.
[...] The dramatic shrinking of cod has been a source of concern for several decades, but it was not clear to what extent the phenomenon has been driven by environmental factors such as hypoxic conditions caused by algal blooms, pollution and more extreme marine seasonal temperature changes. [...] The study used an archive of tiny ear bones, called otoliths, of 152 cod, caught in the Bornholm Basin between 1996 and 2019. Otoliths -- a bit like tree rings -- record annual growth, making them valuable biological timekeepers.
Cod works in mysterious ways (Score:3)
And apparently also small ways.
Re: (Score:3)
Oh my Cod! He died for our sins on a plus-shaped skewer.
Looks like (Score:5, Funny)
I'm gonna need a smaller codpiece.
Evolutionary pressure (Score:5, Interesting)
DISCLAIMER: I am not a biologist of any type, but as a layman...
I'm guessing that smaller fish had a better chance of escaping from the nets, so the next generation tended to be smaller.
Re: (Score:1)
We are over fishing and killing their habitat and their food supply.
Doesn't make sense. If we are overfishing the cod, that would leave more habitat per fish as well as more food supply per fish for the survivors.
The article actually states what PP surmises: The smaller fish have an easier time escaping the nets. And this is by design.
Re: Evolutionary pressure (Score:1)
Yes and next year those smaller fish have grown and get caught in the same net they escaped. We don't see bigger fish or lobster or crab like we used to because they are all over harvested and not allowed to grow to the sizes they are capable of. Same reason we never or very rarley see 20' sturgeon. We kill them before they can get that big. Stop harvesting the cod for a decade or two and they'll be back to the sizes they used to be.
Re: (Score:2)
It doesn't always work the way you want; there may not be a commercial interest in what replaces the fish you remove. For example, globally, jellyfish populations are soaring [smithsonianmag.com] - because we've been (A) removing their predators, and (B) leaving more food behind for them.
Some people eat jellyfish, but they're comparably a tiny market.
(That said, due to the low cost, maybe their popularity will increase. Lobster used to be seen as poor-people's food after all, disgusting bottom-dwelling crustaceans, before the
Re: (Score:2)
At least he read the summary:
Now scientists have uncovered genomic evidence that intensive fishing has driven rapid evolutionary changes that have contributed to these fish roughly halving in average body length since the 1990s. The "shrinking" of cod, from a median mature body length of 40cm in 1996 to 20cm in 2019, has a genetic basis and human activities have left a profound mark on the population's DNA, the study concluded.
You do understand that DNA changes are, in fact, genetic? Don't you?
Don't you?
Re: (Score:2)
Back at you with your smartass response.
Most fish have minimum size regulations. I'm not sure about current limits, but as of 1975 [nafo.int], for cod in Iceland, the minimum length was 43cm. Cod under 43cm have to be thrown back. If you're going to argue that this doesn't impose massive evolutionary pressure for cod to slow size increases and max out at just under 43cm (focusing their energy intake on reproduction rather than growth), you know nothing about evolution. If you went around every year and randomly sh
Re: (Score:2)
(And even if you don't have a size limit, as others note, nets let smaller fish escape, and in effect impose their own sorts of size limits. Even longlining with given-sized hooks and specifically chosen baits favour fish of certain sizes)
Re:Evolutionary pressure (Score:5, Informative)
"Trawling is intended to be size selective, with legally binding minimal mesh sizes designed to protect smaller individuals and allow fish to reach maturity and spawn before being caught.
However, this may have had the unintended consequence of producing a strong selective evolutionary pressure in favour of smaller fish, which would be more likely to escape the nets."
Re: (Score:2)
I think it is indistinguishable from the selection of older, larger fish not escaping the net. No other genetics required.
Now show me that the population is markedly not growing pas that minimum size, and to show it is not caused by catch selection...
Re: (Score:2)
Evolution works regardless of whether you think it should or not.
If you stand a high chance of being killed if you exceed a given size, that is intense evolutionary pressure to stop using your energy resources on growth as you near that height, and instead focus it on reproduction.
Whether you think that evolution should just stop working and cod should just keep growing the same as before regardless of whether it gets them killed (and thus unable to reproduce further), it will continue to work on the specie
Re: (Score:2)
** near that size
Re: (Score:2)
I would contend there is a difference between evolution and commercial selection. Wild Atlantic salmon have so overfished that they are within real risk of extinction. yet the farmed fish are now 'different' from the wild population, they have no discernable spawning urge, no selection of a specific river to spawn in. When they escape and join schools of wild salmon, they follow along to the Atlantic coast, and there get confused. And there are other interesting problems. That is not evolution, it is an int
Re: (Score:2)
Re: Evolutionary pressure (Score:2)
I think selection via harvesting is being mistaken for evolution. And I doubt marine biologists can precisely judge age by size/weight. Either way, overfishing will have to stop.
Re: (Score:2)
That's not how it works. This generation of cod's parents were able to escape the nets because they were smaller than their larger counterparts. Hence, the genes for smaller cod were more likely to be passed on, simply because of the survival bias of smaller fish.
Humans would "evolve" basically the same way given similar circumstances. It's no secret that having relatively tall parents commonly corresponds to relatively tall offspring. If suddenly all of the relatively taller adults were decapitated by
Re: (Score:3)
This issue occurs in other fisheries.
Sport fishermen on the Atlantic coast are not permitted to take striped bass less than 28 inches or longer than 31 inches in length. This ensure there is at least one opportunity to spawn, and hopefully more than one, before they are taken. Populations of striped bass have been resurging over the past few years, mostly due to reduced fishing pressure. Sport fishing is not permitted in the Exclusive Economic Zone.
The lobster fishery off the coast of Maine observes a size
Re: (Score:2)
The suggested regulations I've seen to counter these evolutionary pressures are IMHO pretty clever: you impose both minimum *and maximum* sizes on your catch. You can only keep fish that are between the minimum and maximum sizes. So growing fish have a certain size where they're in the "danger zone", but if they get bigger than it, they can keep spawning to their heart's content with no danger from humans.
Re: (Score:2)
They can keep spawning with limited danger from humans. Poachers, illegal catch, all threats. Minimized hopefully.
Much better management of these finifsh resources run up against commercial interests. Fishermen need to make a living. Some are part of multigenerational enterprises. Hard to put them out of business, though that has been attempted several times.
Re: (Score:2)
It doesn't need to change the total catch. You can lower the minimum size if you impose a maximum size. Same fraction of the total fish allowed to be caught. Large fish tend to be much better reproducers than small ones, so you may actually be able to allow an even larger fraction of the fish to be caught each year.
Re: Evolutionary pressure (Score:2)
The general goal of Georges Bank fisheries management has been to protect juvenile fish and extra-mature fish, permitting more spawning and thereby increasing the sustainable catch. American fisherman have largely complied, but the Exclusive Economic Zone is regularly violated by fishers of other nations. And every reduction in catch is fought as further penalty for commercial fisheries. They really need to reduce the catch for a decade, defend the EEZ, and make further instruments in research and marine b
Re: (Score:2)
Other nations regularly poach in the Georges Bank? That's pretty crazy.
Re: Evolutionary pressure (Score:2)
That's normal. The whole world 'poached' Atlantic Salmon between Greenland and Norway, Greenland and Canada, all in international waters of course. The Russians actually fished salmon with factory ships that produced meal for livestock, a horrible waste. The Japanese and Norwegian fleets harvested salmon for food, understood. Overfished and struggling to spawn in polluted US rivers, the wild stock dwindled. The Connecticut, Hudson, Merrimack, Kennebec, and Penobscot Rivers saw thousands of fish, teeming, ea
It's not environmental, it's legal (Score:5, Interesting)
Re: (Score:2)
As a complement: minimum size for professional fishing of Gadus morhua (codfish) is 35 cm in the North sea (France/UK), 30 cm in the waters of Denmark. Source: https://www.fishbase.se/countr... [fishbase.se]
Classic tragedy of the commons (Score:5, Insightful)
Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.
-- Garrett Hardin
https://en.wikipedia.org/wiki/... [wikipedia.org]
No mention of China (Score:1)
The hidden war at sea: China’s illegal fishing explained [youtube.com]
China's fishing fleet is causing havoc off Africa's coasts [economist.com]
Re: No mention of China (Score:2)
Re: (Score:2)
farming optimization (Score:2)
Cod Only Knows What I'd Eat Without You (Score:2)
http://slashdatpedia.com/brian... [slashdatpedia.com]
Born Brian Gadus Morhua
June 20, 2012
Georges Bank
Died June 11, 2025 (aged 13)
Brian Gadus Morhua, known as "My Cod", was an Atlantic cod,
widely known for its mild, delicate flavor and firm,
flaky white flesh, making it a popular choice for various
culinary applications. Cod was also a versatile fish that
co
We need more Game Wardens to harass fishermen... (Score:3, Insightful)
Stop commercial fishing (Score:2)
Seriously, we farm the plants and animals that we eat. We should farm the fish we want to eat, as well.
But it's tradition!
Lot's of things were once tradition. Then civilization happened. Also, you can't feed 9 billion people playing hunter-gatherer.
Re: (Score:2)
Re: (Score:2)
> We should farm the fish we want to eat, as well.
We do, we produce more by fish farming than catching. Yet this doesn't stop us from devastating everything.
https://ourworldindata.org/ris... [ourworldindata.org]
Re: (Score:3)
The fun part is that it would seem our fish farming is actually worse than simply going out to catch them.
https://www.newscientist.com/a... [newscientist.com]
Reducing meat consumption is the only way.
I'm trying, it's a learning curve...
Re: (Score:2)
The fun part is that it would seem our fish farming is actually worse than simply going out to catch them.
It's not that simple and not what your link claims. The link claims fish farming of predatory fish is worse than previously estimated in "weight of wild fish that die to feed farmed fish".
1. Wild salmon still eat fish. It's not a given that a wild salmon would have caused fewer prey fish deaths than a farmed one.
2. A lot of the additional weight as compared to other estimates is in the by-catch that dies in catching prey fish for the farmed fish. This is (ironically) an issue in the fishing methods, not in
poor cod (Score:2)
Pity the poor cod. They are scrod.