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Mature Fish Are Found In Deeper Water Because of Humans (arstechnica.com)
An anonymous reader quotes a report from Ars Technica: When studying populations of a flounder-like North Sea fish called plaice in the early 1900's, a man named Heincke noticed that older, larger fish are found deeper in the water than younger, smaller fish. The same phenomenon was subsequently found for other North Atlantic species like cod, haddock, pollock, and some species of flatfish; it was thus dubbed Heincke's Law and treated as an established fact. Biologists assumed it was ontogenic in nature, meaning that it must be connected to how the fish age and mature.
All the species in which older, bigger fish are found in deeper water have something else in common: we eat them. Could it be, some Canadian scientists wondered, that all the big fish are found in deeper water because we fished them out of shallower water? Apparently (and somewhat astonishingly) this possibility had never been evaluated. And the scientists found that not only could this be the case -- it in fact was. "[T]he researchers added a simulation in which the depth and mass of fish were tied to the rate of mortality by fishing," the report adds. "When set to mimic the actual fishing rate over the two decades spanning the dataset, the model outcomes were consistent with both the new and old fish data. When fishing mortality rates were increased in the model, larger fish moved progressively deeper. And when fishing rates were set to zero in the model, there was no age-related deepening seen at all." The study has been published in the PNAS journal.
All the species in which older, bigger fish are found in deeper water have something else in common: we eat them. Could it be, some Canadian scientists wondered, that all the big fish are found in deeper water because we fished them out of shallower water? Apparently (and somewhat astonishingly) this possibility had never been evaluated. And the scientists found that not only could this be the case -- it in fact was. "[T]he researchers added a simulation in which the depth and mass of fish were tied to the rate of mortality by fishing," the report adds. "When set to mimic the actual fishing rate over the two decades spanning the dataset, the model outcomes were consistent with both the new and old fish data. When fishing mortality rates were increased in the model, larger fish moved progressively deeper. And when fishing rates were set to zero in the model, there was no age-related deepening seen at all." The study has been published in the PNAS journal.
"Apparently (and somewhat astonishingly) this possibility had never been evaluated."
Gee, I wonder why no one ever "researched" this. Maybe they can study why wolves aren't commonly found around major cities next.
Suicide cults support overpopulation so they won't die alone.
They Will Be Eaten
When They Get Hooves That Are Not Kloven Then They Can Be Safe
It Is So Written And So It Shall Be
"When set to mimic the actual fishing rate over the two decades spanning the dataset, the model outcomes were consistent with both the new and old fish data. When fishing mortality rates were increased in the model, larger fish moved progressively deeper.
I think this falls under confirming the obvious. Our fishing creates an evolutionary pressure. Fish that survive our hunting will tend to be the ones that prefer places where our nets don't reach as often. As long as we don't hunt them to the point where the population collapses it's perfectly obvious that we would see them evolve in response to our fishing tactics over time.
When I reach into my change jar and remove all the quarters I can reach, there are no longer any quarters where I can reach.
I can't believe I didn't have to spend $3M in taxpayer money to find that out!
"Fish go to where humans aren't catching/killing them"
This is supposed to be a scientific "ah-ha!"?
Very interesting. The abstract of the paper is somewhat more clear than the summary on Slash Dot. We need to teach the public about how these simple simulations relate to reality and help avoid the magical thinking that 'the simulation finds this effect' so it must be the key to the story when the effect was basically put into the simulation. The key piece of rigorous thinking that justifies putting this paper in PNAS is that using a simple model with empirically measured fishing rates for various sizes of Cod, they reproduce 70% of the observed deepening of large fish, suggesting that selective fishing is the largest contributor to the observations that led to Heincke's Law.
Better way to find out is to go to very remote region where no one is fishing and see if bigger fishes are more likely to be found in shallow water.
But I guess it's easier to just run simulation... But what does it simulate anyway? if simulation basically subtracts # of bigger fish of being fished out, of course there will be less fish in shallow water. You don't need simulator to find that out. Unless it can simulate brains of millions of fishes, I don't see the point of this.
Even in a controlled environment like a fish tank, in lots of species, the younger fish hang out at the top of the water more than older fish. (now the reverse can be true in some species if the fry hide at the bottom instead- but most fry go to shallow or higher waters). No one is fishing fish out of my fishtanks.
In the ocean (or a pond, or a fishtank) small microscopic lifeforms are found in higher densities at the surface- because that is where the sunlight is. Whatever eats those lifeforms needs to be nearby... whatever eats those needs to be near them.
The larger you get, the more varied food you can eat- you don't necessarily have to stick with micro-fauna and micro-flora at the surface.
It may be that we eat the fish at the surface- and that's why no big ones there... or it could be because large fish simply don't NEED to be near the surface like small ones do.
"That's the way to do it" - Punch
...news at eleven.
Seriously, how is this a surprise to anyone?
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
Anyone sick of this stupid algorithm yet?
Mature Fish Like It Deep, Really Deep
This could have been your headline Slashdot but you blew it. ;)
Anons need not reply. Questions end with a question mark.
Older/larger fish are found in deeper water because they frequently ambush smaller fish from below.
Well duh... they're heavier... so they sink to the bottom.
Older fish are bigger and heavier too, so they should sink more. /sarcasm
Just another day in Paradise
So...model built to simulate preconceptions of researchers somehow coincidentally validates those preconceptions?
That's idiotic.
At least in lake environments, younger fish stay in shallower water for several pretty obvious reasons:
- there's more aquatic plant life, providing them cover
- the shallowest water
- they have little or nothing to fear from predator birds (Well, filter-feeders now have evolved to defeat that....)
I'd submit the logic of the open ocean isn't terribly different - surface churn likely provides a fair amount of camouflage vs predators from below.
-Styopa
Fish that swim in deeper waters survive, and pass their genes on. Fish that swim in shallower waters get eaten.
Evolution takes place over thousands of generations.
Heck... it's hardly migration. "Deepening" differences are measured in ranges from 60 to 120 meters deep.
It's simply the fact that fish live longer lives if they don't get caught. And they don't get caught cause nets don't reach that deep.
In fact, study explicitly states that it's most probably not evolution - but a part of a normal development instead.
Observations of depth distributions of older cod during a moratorium on fishing supported this prediction; however, younger cod exhibited low-amplitude deepening (10-15 m) suggestive of an ontogenetic response.
I.e. Young and inexperienced fish don't know how to hide from the nets OR the easy picking food (bottom dwelling crabs and crustaceans) they're munching on isn't available that deep.
Older, more experienced, fish-munching fish, know how deep they need to swim to avoid getting caught in a net.
Mit der Dummheit kämpfen Götter selbst vergebens
So, where it's easier to go fishing (closer to the coast, in shallower water, nicer weather) you saying fish tend to get fished more and hence not as big of fish. Hmmm, did we need to say this out loud to believe it or couldn't people just connect the dots and figure this out themselves? I like going crabing, and you know what, if I go deeper I tend to get bigger crabs since not all people have the ability to crab there. Shocking.
Evolution takes place over thousands of generations.
No it does not require thousands of generations. Have you ever seen a purebred dog? Humans applied selective breeding and can develop a completely new breed of dog with just a few generations. Evolution CAN happen slowly but it does not have to. It can happen quite quickly given the proper evolutionary pressures.
Heck... it's hardly migration. "Deepening" differences are measured in ranges from 60 to 120 meters deep.
Evolutionary pressure don't not care about what you perceive to be a small difference in distance. All that matters is whether that difference in depth creates an advantage in reproduction. If the difference in depth causes a difference in reproductive rates within a population then voila, you have an evolutionary pressure.
I.e. Young and inexperienced fish don't know how to hide from the nets OR the easy picking food (bottom dwelling crabs and crustaceans) they're munching on isn't available that deep.
The ones that prefer the locations where they do not get hunted (the reasons why don't matter) are the ones that will be selected to breed again. Small fish that don't prefer the deep get removed from the gene pool before they reproduce and so they never become big fish. Do this enough times and you will have selected for fish that prefer deeper waters. That my friend is an evolutionary pressure at work and it happens all the time.
*Yawn*
This is Slashdot. Humans cannot negatively affect the environment, even in principle.
Which is why you can't swim out to sea and physically catch one with your hands, and then kill it (in the sea) with your bare hands and teeth, and then eat it uncooked. (At least not without being viewed as a psychopath, and I bet 99.99% of people can't actually catch a fish in the sea with their bare hands.) Yet no doubt most Slashdotters, rather than questioning what they've been taught is 'natural' and 'normal' all their lives, will try to defend this unnatural act. And the end result is this article: you can't have billions of large mammals (humans are large mammals) eating other animals, because it isn't natural. And thus we run out of fish.
SO, they took a set of data which showed an apparent correlation. Then they used that data to create a model based on the correlation which they thought they saw. Then they modified the data in the model and, low and behold, the model behaved EXACTLY as they programmed it to behave. This does not actually prove that the real world works the way the model does.
I can think of two possible explanations for the observed data. The study does not actually test between them.
Explanation 1: When people fish in an area, fish which escape being caught tend to move deeper in the water. The more heavily fished an area is, the more this happens.
Explanation 2: When people fish in an area, fish which stay in shallower water are less likely to live to an old age than those which move to, or live in, deeper water.
Nothing in this study determines between whether the fish move to avoid the fishing, or the fish that stay in shallower water just do not survive as long.
The truth is that all men having power ought to be mistrusted. James Madison
Sure. You discovered this in one of your highly paramterized computer model.
Now what about fish?
For many decades now it's been illegal to shoot deer that are within a couple hundred feet of a home. How soon are they going to noticeably prefer suburbia over wooded areas? I know that my hometown in New Jersey had no deer 50 years ago, but it's almost overrun with them now.
On the one hand you take life too seriously, and on the other, you do not take playful existence seriously enough. Seth
"a simulation in which the depth and mass of fish were tied to the rate of mortality by fishing" found that "when fishing rates were set to zero in the model, there was no age-related deepening seen at all."
Uh... why would there be? It's a simulation. You can't find age-related deepening in a simulation unless you program age-related deepening into the simulation. And if you do program it in, you will find it.
Seriously, how is this science at all? WTF?
.,,. did not already know this. When I was a kid, and my uncle was teaching me how to fish, I asked him why the biggest fish were in deeper waster, and as I remember it, he basically told me that was because the fish in shallower water were easier to catch and kept getting caught too quickly, so the fish that live to be oldest and biggest are usually found in deep water. Those weren't his exact words, I don't think, but it was something to that effect that I took from what he was saying. I had no idea that he was basically bullshitting me and making stuff up that just happened to be true.
File under 'M' for 'Manic ranting'
We need deeper nets and longer poles. Drag them suckers out of the deep an make America great again!
Adolescent fish are shallow. We all knew that, they only love you for your fins!
Why would any study of marine life in the early 1900's be considered reliable? Underwater technology was almost no-existent so any information from this time would've been based on guessing and black magic.