Ten fold increase in reproduction by fish.

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Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Wed Jun 06, 2018 11:38 pm

Recent research here in NZ has shown that the important food fish species known as snapper (P. auratus ) produces offspring at a rate ten fold higher per hectare from a protected marine reserve than they do from waters that are fished. The specimens inside the reserve grow much larger and are much better breeders. I think there is a message here for the commercial fishing people !

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Wed Jun 06, 2018 11:45 pm

Lance Kennedy wrote: I think there is a message here for the commercial fishing people !
Yes indeed. Inside preserves is where you get your largest catches................
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Re: Ten fold increase in reproduction by fish.

Post by Matthew Ellard » Thu Jun 07, 2018 1:30 am

Lance Kennedy wrote:Recent research here in NZ has shown that the important food fish species known as snapper (P. auratus ) produces offspring at a rate ten fold higher per hectare from a protected marine reserve than they do from waters that are fished.
For the last two months I have been reading about the history of Cod fishing from this book.
Cod Book.jpg
Cod was the first fish known to be over-fished. There were some really interesting stories.

During WWII most UK and European fishing trawlers were converted to mine sweepers. As Iceland was neutral it became the Cod hunting monopoly. After the war, many european mine sweepers were converted back to fishing trawlers with more powerful engines. Therefore...... Iceland had three "Cod wars" against the UK and European countries after WWII. Iceland's coast guard drove over UK and European fishing nets dragged behind their ships. [/color]

Aldous Huxley, who wrote Brave New World, claimed it was impossible to over-fish Cod as they had millions of eggs. (He was 100% wrong as not enough fish matured to 10 years old to breed more Cod)

The English government promoted "Fish and Chips" at the end of the 19th Century as a dish for workers, as Cod was a really good source of protein and vitamins and potato provided carbohydrates.

Newfoundland's economy was destroyed by the over-fishing of Cod and thus joined Canada to obtain social security.

Soooooo.....Amanda and I went to a Portuguese restaurant that specialised in traditional Cod recipes to see what it tasted like. It was nothing special. :D
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 1:57 am

Yeah....just a bland white fish. All the taste is in the oil its fried in. I make my own about 3-4 times a year. I like it...... the oil that is. Doesn't matter what the batter is hiding.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Thu Jun 07, 2018 2:23 am

Matthew

You say of fish and chips that fish provides vitamins. Actually, potatoes provide more. You can readily get your entire vitamin C requirement from them, for example. Plus lots more. Potatoes are one of the most underrated foods.


As far as the fish is concerned, right now it's long term availability is under threat, by too many commercial fishing people.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 2:30 am

Yeah....generally FLESH is not known for vitamins. Fats and proteins==>the other good stuff.
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Re: Ten fold increase in reproduction by fish.

Post by Matthew Ellard » Thu Jun 07, 2018 4:25 am

Lance Kennedy wrote:As far as the fish is concerned, right now it's long term availability is under threat, by too many commercial fishing people.
Well I think you and I would agree....it's not only that there are too many fishing boats.....but rather too many people wanting to eat fish.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 5:20 am

I think its more too many fishing boats: all willing to take the last fish. Otherwise fishermen would voluntarily DEMAND that protected areas be promoted in order to revive the stocks.....but its not happening. Its a classic tragedy of the commons scenario.

when people don't want to eat fish, they catch them anyway and use the bodies for fertilizer.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Thu Jun 07, 2018 8:40 pm

Yes.

There is a global trend to establishing marine reserves. It needs to be accelerated. Right now, there is a proposal for a major Antarctic reserve, but it will be opposed.

Here in NZ we have a proposal for a major reserve around the isolated Kermadec Islands, which still are largely untouched. Sadly, it has been put on the back burner by arseholes claiming indigenous fishing rights. A crock, since the Maori never fished there. But political bull-{!#%@} can be based on fiction.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 8:44 pm

Lance: any idea and what would need to be done to repopulate the Atlantic Cod fishery? Why not cod hatcheries like we have for trout and salmon? HAH!==>or indeed just a 20 year moratorium wherever cod actually breed and then NOT ALLOW Japan to fish there anyway?
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 8:48 pm

Here's an idea: genetically modified some kind of white fish that eats jellyfish? That would be a two-fer.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Thu Jun 07, 2018 10:07 pm

Bobbo

Re cod.

The restriction on fishing the Grand Banks and the slow recovery suggests it just needs time. Makes sense. Organisms living in very cold water tend to reproduce more slowly.

Moral. Stop killing cold water species.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Thu Jun 07, 2018 10:52 pm

No reason to be curious these days:

Both sexes usually reproduce for the first time when 5 or 6 years old. The fecundity (number or eggs produced in a given year) of females increases with size and age. A 40 inch female may lay about 3 million eggs, and a 50 inch female up to 9 million eggs in one spawning season. The Atlantic cod is a winter spawner.Sep 3, 2016
Atlantic Cod,general information,reproduction,habitat,food,fishing ...
www.cptdave.com/atlantic-cod.html

Atlantic Cod | Oceana
oceana.org/marine-life/ocean-fishes/atlantic-cod

Atlantic cod reproduce through a behavior known as broadcast spawning, where females release eggs and males release sperm into the water column above ...
////////////////
I would have guessed the above, but this is new:

Something's Fishy With Cod Evolution | Science | AAAS
http://www.sciencemag.org/news/2004/04/ ... -evolution

Apr 28, 2004 - Overfishing caused genetic changes in Canadian cod that shifted the fish's breeding ... hints that the average age of reproduction had dropped in the 1980s. ... The findings do indeed support the idea that the shift in the cod's ...
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Thu Jun 07, 2018 11:41 pm

Bobbo

That kind of evolution is always interesting.
In this case, not so much over fishing as selective fishing. When the larger fish are selectively removed, it becomes adaptive to evolve to reproduce at an earlier age. The only problem is that such reproduction is less effective, since a smaller body mass cannot produce as many gametes.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 12:12 am

Huge mile diameter nets is not "selective." They just took "everything" leaving the small fish to grow to medium size until they were caught too.

Hmmmm.........seems drop dead simple to me: Catch all the fish you can, THEN RELEASE THE BIG ONES.

.....................but................I've never met a smart fisherman. The young ones will talk a good game, then do the same tired {!#%@}: gotta feed the family, pay for the boat.......SOS.
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 12:22 am

Speaking of huge nets catching everything with no brains applied: I've never understood why they just dump the dead fish they don't want back into the water......like sharks. Shark meat is good......I'm sure the Japanese could chop it up, add some red dye, and call it crab?

Now, I assume they target the fish they want and its easier to process said fish on their combo boats....too bad: want to fish? USE ALL YOU CATCH. Just makes sense..........
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Fri Jun 08, 2018 1:01 am

As I understand it, Bobbo, the cod fishers do release underside fish, and many survive. Enough to drive an evolutionary trend to earlier reproduction. What should be done is to release larger fish, and force an evolution to larger size.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 1:22 am

bobbo_the_Pragmatist wrote:Huge mile diameter nets is not "selective." They just took "everything" leaving the small fish to grow to medium size until they were caught too.

Hmmmm.........seems drop dead simple to me: Catch all the fish you can, THEN RELEASE THE BIG ONES.

.....................but................I've never met a smart fisherman. The young ones will talk a good game, then do the same tired {!#%@}: gotta feed the family, pay for the boat.......SOS.
You do this more than you think.............
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 1:38 am

Lance Kennedy wrote:What should be done is to release larger fish, and force an evolution to larger size.
How would that happen?
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Fri Jun 08, 2018 2:40 am

Technically not too difficult. I have seen a design for a trawl net that ends in a cage that keeps fish alive.

How do you make the fishing arseholes do the right thing ? That is more difficult, but not impossible.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 3:04 am

I was thinking just dump the fish out on deck as they do and have them go over a grate. Fish seem to survive being netted. Cheap, Easy, Fast, No extra work.
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 3:15 am

Lance Kennedy wrote: How do you make the fishing arseholes do the right thing ? That is more difficult, but not impossible.
Easy to inspect the grate for sizing. And maybe more "education" that enforcement. It is after all in the long term interests of the arseholes and a few of the largest fish would not hurt the haul.
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Re: Ten fold increase in reproduction by fish.

Post by Gord » Fri Jun 08, 2018 9:37 am

I saw a video recently, can't remember where it was, that suggested the warming ocean water in the area might be contributing to the slower-than-expected repopulation of the Grand Banks.

I don't put any stock into it since it was just some random video that I can't even reference properly, but it has left me interested. I'll be on the lookout for more information on the topic in the future.
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Fri Jun 08, 2018 11:04 pm

Gord: right on. It would be rare for "any" change not to have a reaction to it. More or less of something rather than no effect at all is the general rule. Although, I do "feel for" the deniers.....the degree of change seems so minimal, why would it do anything?

but thats Science for you. Teaching those willing to learn how the Universe actually works.
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sat Jun 09, 2018 12:18 am

bobbo_the_Pragmatist wrote:
Lance Kennedy wrote:What should be done is to release larger fish, and force an evolution to larger size.
How would that happen?
Lance Kennedy wrote:Technically not too difficult. I have seen a design for a trawl net that ends in a cage that keeps fish alive.

How do you make the fishing arseholes do the right thing ? That is more difficult, but not impossible.
I was gonna let it pass, but it is slow, and I think you do have an interest in the subject, so: The SUBJECT of the post was evolution. As you love repeating, I'm not a scientist but I don't think releasing larger fish would force evolution to larger size? So........How would that happen?
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sat Jun 09, 2018 12:49 am

It would not force evolution to a larger size, but it would permit genetic reversion to the previous optimum size. Larger fish produce more offspring, so devoting resources to growth rather than gametes permits more gametes in the long term. Evolution drives genetic change towards an optimal form for survival and reproduction. That larger form is the optimum.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sat Jun 09, 2018 2:02 am

Lance? So, you've moved from FORCED to PERMISSION? Now, not being a scientist myself, just a casual reader on the subject, I have not come across either concept in evolutionary theory....so, how does the permission work? .... Hmmm, come to realize, I have never run across any mention of genetic reversion either. That subscription to Scientific America is really paying off for you?........I do keep thinking I should subscribe. Maybe I should have taken more courses is Logic? What distinction are you making between growth and gametes? More logic/science I never studied beyond intro courses: I thought it was genetic change that drove evolution and not the other way around? Evolution is not a drive at all, but rather a result?

You seem to have backward or made up concepts for EVERYTHING THAT APPLIES to the issue. I sure wish I had studied more science so I could discuss this/learn.

I do agree the larger form is optimum for species survival.........thats why I posted letting the large ones go.

I wonder if the descent into erroneously quibbling and made up words is concomitant with no direct recognition you got it wrong? Knowing one's self. A powerful tool.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sat Jun 09, 2018 3:46 am

Bobbo

Quibbling again about words ?

Evolution selects genetic changes that result in improving survival and reproduction. In this case, it is larger fish which are more effective at reproduction.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sat Jun 09, 2018 5:30 am

Lance, I assume you are refusing the engagement.

Second time: Evolution doesn't select anything. Evolution occurs as NATURAL SELECTION selects those organisms better fitted to their environment than those other species and individuals competing for it. and in this case FIRST TIME: its not evolution nor NATURAL SELECTION: but rather mankind determining who survives to reproduce. What the fishies need to do now is experience genetic changes making their flesh unpleasant to eat by hoomans. aka: a nice trick not yet observed ever taking place: not enough time and no "natural" environment for it to take place in.

I know.....too subtle for you. Come back with anything close to accurate .... and that I haven't already said. You know: try something new.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sat Jun 09, 2018 8:00 pm

OK.
Evolution by artificial selection.

There is no requirement that evolution be natural.

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Re: Ten fold increase in reproduction by fish.

Post by Matthew Ellard » Sun Jun 10, 2018 2:04 am

Lance Kennedy wrote:OK. Evolution by artificial selection. There is no requirement that evolution be natural.
The "Cod" book discusses the reintroduction of "farmed" cod baby fish into the natural environment. The problem is that farmed fish may not have the genetic diversity that exists in natural cod fish and may replace fish with stock that is not genetically diverse enough to live in the natural environment. The book simply states more research is needed.

What interesting is that natural cod, eat crustaceans. As natural cod levels are so low, Newfoundland and other former cod fishing colonies are now fishing for lobsters and prawns....as their stock levels are increasing. :D

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sun Jun 10, 2018 2:54 am

When Atlantic cod first hatch, the fry eat zooplankton and small crustaceans. As they grow, the young fish eat shrimp and small lobsters. Adults eat mainly herring and capelin. Seals are the main predator of Atlantic cod.
Atlantic Cod: Natural History Notebooks
https://www.nature.ca/notebooks/english/atlanticcod.htm
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sun Jun 10, 2018 3:09 am

Lance Kennedy wrote:OK.
Evolution by artificial selection.

There is no requirement that evolution be natural.
Well, congrats. A baby step, but a step nonetheless. While communication is always an art, I'm thinking the main subject of your response was the evolutionary direction of the cod? You posted that releasing the larger cod would cause an evolutionary shift to larger cod.

My question is still: How would that work?
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sun Jun 10, 2018 3:58 am

The word 'evolution ' comes from a Latin word meaning to unroll. It actually was used mostly in reading a scroll. Unrolling a scroll was a kind of continuous development of the theme of the scroll.

Darwin recognised three kinds of biological evolution.
1. Humans breeding changes into animals. What I called artificial selection .
2. Natural selection.
3. Sexual selection.

But it is also entirely correct to call a number of non biological developments evolution also. Eg. Social evolution, as shown by Stephen Pinker, as humans develop a less violent society.

Releasing larger cod would lead to a development of genetically larger cod, because being larger would be selected for. There is always heaps of genetic variability in any population. Some smaller. Some larger. If the larger ones are more likely to survive (by getting released), then the percentage of cod in that population with the genes for larger size will increase. More larger cod.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sun Jun 10, 2018 5:05 am

Lance, I agree that is the "straight forward" application.....but it niggles at me. How does one "get large" and not turned into fish and chips when you were at the smaller size? All the fishies went thru that smaller size and were not "Large" until SAVED by the grate. I have rough drafted that its the difference between growing fast and being large.....but it niggles at me.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sun Jun 10, 2018 9:23 am

Bobbo

Fish spawn millions of larvae. Most get eaten, but there are still vast numbers of small fish. A lot of small fish end up as fish and chips or food for bigger fish. But there are so many small fish that this does not matter too much. The smaller number of survivors then grow. The end result is a much smaller number of big fish. But those big fish are wonderfully able to churn out larvae by the millions. Since the number of big fish is limited, fishing for them has a disproportionate impact on the population, removing the best breeders.

It is much better to remove a lot of small fish than a lower number of big ones.

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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Sun Jun 10, 2018 9:37 am

Lance.....you make only wanting to be friendly somewhat difficult, irrelevant/repetitive as you so often are. As usual, your post does not engage the subject, it only repeats/rephrases what is the premise of what has already been said.

What is the effect of releasing the largest of the species? Does that affect evolution....or only the sustainability of harvesting a crop? Curious non-scientists want to know............
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Re: Ten fold increase in reproduction by fish.

Post by landrew » Sun Jun 10, 2018 5:31 pm

There's a reason why birds lay dozens of eggs, and some fish lay thousands; the survival rate can be very low, or nonexistent at times. However, when opportunities arise, the high birth rate allows a species to quickly occupy a niche in the biome.
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Re: Ten fold increase in reproduction by fish.

Post by Lance Kennedy » Sun Jun 10, 2018 8:37 pm

Bobbo

You missed the point.

The point is that, because small fish are there in large numbers, they are not limited. Large fish, though, being the one in a million survivors, are there in small numbers. So killing large fish has a much bigger impact than killing small fish. Since the large fish are the main breeders, they have a big impact on the genetics of the population , and hence evolution . If you kill off the large fish through fishing, you leave a big hole, which is filled by smaller fish evolving to breed earlier. Permit the large fish to survive, and evolution causes small fish to devote their resources into growing rather than breeding, so that they can become the successful breeders when they grow.

In terms of evolution, when large fish survive, it is a better reproductive strategy to devote resources to growing big before breeding. But when large fish are selectively removed by fishing, it is a better reproductive strategy to start breeding early. Meaning small fish evolve to devote resources to breeding rather than growth, and hence fish remaining small.

bobbo_the_Pragmatist
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Re: Ten fold increase in reproduction by fish.

Post by bobbo_the_Pragmatist » Mon Jun 11, 2018 1:28 am

Lance: on first read, what you post makes sense except where you say the large fish are removed selectively as the issue exactly the opposite. Currently, big fish being taken the same as the small fish with a possible insight from us that it makes sense to selectively release the big fish. The thread has stuck on you saying releasing big fish would tend to cause an evolution of the cod into big fish, but you continue to misstate several key issues and terms. I think the, or maybe just me, confusion is because man would be "managing" a food source.....not much natural selection going on to favor Big Fish but rather fish that grow fast.

somewhere, we have a disconnect.
Real Name: bobbo the existential pragmatic evangelical anti-theist and Class Warrior.
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