Superfish
OSU researcher uses a combination of hormones, selective breeding to create bigger bluegill

Sunday, April 26, 2009 3:33 AM
By Doug Caruso
THE COLUMBUS DISPATCH
<p>OSU researcher Han-Ping Wang shows how male bluegill are larger than female.</p>
Jeff Hinckley | DISPATCH



PIKETON, Ohio -- All of the fingerling bluegill swimming in the gray tank with a scarlet 36 on it look about the same.

But a quarter of them are "super males."

They're the key to growing ponds full of all-male bluegill. Since male bluegill grow twice as large as females, fish farmers can provide larger fillets for people's dinner plates. That would mean larger profits.

Han-Ping Wang, principal research scientist at Ohio State University's aquaculture lab in Piketon, is close to achieving that goal using a process that starts, oddly enough, with turning all the fish into females.

He introduced estrogen to tanks of bluegill that had a natural population of about half male and half female. In the right amounts, the hormone turns all the fish into egg-producing females.

Then Wang let genetics take over.

First, a quick primer on genes and gender: Genetic males have an X chromosome and a Y chromosome. Genetic females have two X chromosomes.

If the male's Y chromosome links up with the female's X chromosome, the offspring is male. If the male's X chromosome links up with a female X chromosome, the offspring is female.

In nature, it's a coin toss -- about half the babies turn up male; about half turn up female.

And it's all up to dad's genes.

So what happens when dad also lays the eggs?

Though they now produce eggs, the half that started as males keep their male X and Y chromosomes after the hormone treatment.

Those fish laid their eggs this past winter, and untreated males fertilized the eggs.

The result: Half the brood should be male with an X chromosome and a Y chromosome. A quarter should be female with two X chromosomes.

Another quarter should be "super males" with two Y chromosomes.

"That's what we need," Wang said.

Right now, Wang knows only that 75 percent of the fish in tank 36 are male. You can't tell bluegill fingerlings apart by looking at them, so he's developed genetic tests that reveal the gender. But he doesn't know which males carry the double-Y chromosome combination he's looking for.

When you put YY males in a tank with XX females, it's like making a coin toss with a two-headed quarter: Bet on boys every time because each offspring will get a Y chromosome from super dad and an X chromosome from mom.

In the next step, Wang will put individual males in breeding tanks with females. Whenever he sees an all-male brood, he'll know that the male has two Y chromosomes.

Wang knows that there's concern about hormone-treated food and hormones escaping into the environment where they can affect the natural breeding of species.

But he says that his method removes the hormone treatment from the farm.

He's also looking for hormone-free ways to get more male bluegill. Simply by controlling the temperature of the water in the first weeks of a brood's life, he's gotten as many as 90 percent of the fish to turn out male.

There is a market for bluegill, but prices are too high, said Doug Denny, owner of the Fish Guys in the North Market.

He sells whole bluegill, which he buys for $4 per pound. He estimates he'd have to charge about $9 per pound to offset the work put in to scale and fillet the fish. That puts it at about the same price as lake perch, which comes to him already processed.

"If I could get fillets at $6 a pound, I could sell it," Denny said.

At the U.S. Department of Agriculture's last count in 2007, there were 144 bluegill farms in Ohio, said Laura Tiu, an OSU aquaculture extension expert in Piketon.

She's the one who helps transfer research to the farmers who can use the information to produce bigger fish faster and potentially bring down the price.

Once he's identified the super males, Wang plans to look for genetic markers and develop a test to quickly identify them by clipping a bit of fin and analyze it in the lab.

They're looking for distinct genetic markers to help them identify the fish. They already have found seven such markers that help determine whether a young bluegill is male or female.

If he can grow enough super males, he can send them to farmers who can breed them with females to produce all-male broods.

Wang wants to treat some super males with estrogen to turn them into egg-producing females with two Y chromosomes. Call them "super mamas."

Breeding super males with super mamas would produce nothing but super males.

Then those super males can be sent out to breed with untreated females to produce ponds full of all-male fish.

Another option is harvesting the super male sperm, freezing it, and sending that out to the fish farmers.

"We would create the first bluegill sperm bank," Wang said.

"Our parents would be so proud!" Tiu joked.

dcaruso@dispatch.com

Wow. Neat story.

I'll put my money on Bruce's male "super fish," though.

Holy sunfish! I must have had 19 1/2 inch long Male BG in my pond last year!

Don't be surprised if Bruce is already making plans to take advantage of this technology. I know I will.

Males grow twice as large as females? That's news to me.

Four out of the last six bluegill I saw that were legit two pounders were females.

Very interesting story. I wonder if this is one of those stories where they say it's just around the corner, and it ends up being 40 years.

I should mention that out of the last batch of CSBG I selected the 200 biggest fish and eventually reduced this group to the fastest growing 80. When I stocked them a couple of weeks ago, it looked like approximately 65 of the 80 were males.

Bruce are you breeding your CSBG with super female BG?

I agree, some of the biggest BG I have seen have been females, for some reason they are much rarer than big male BG.

The article says the females grow more slowly but I don't recall it said they were necessarily smaller? But I did scan it so I may have missed it.

One thing to keep in my is many times these writers misquote or take things out of context especially when it deals with science because they don't have the background. Dr. Wang is doing some impressive stuff, which has included producing a strain of yellow perch that have an increased growth rate of 40 percent over others.

Bluegills : Biology and Behavior , Spotte 2007 , AFS pg 124

Females are reported to lag behind males through age-0 , but no supporting data have been presented. After the first year the sexes appear to grow at similar rates, although territorial males ultimately grow larger. I analyzed age 1 through age 5 data ... from 4 Indiana lakes without finding significant differences in fork length. However in age 2 bluegills in Michigan ponds the males averaged 154.1 mm TL and females 142.6 mm , a 7.5 % disparity.


Handbook of Freshwater Fishery Biology V II , Carlander 1977 pg 105

Males grew more rapidly than females in some populations , but the differences were usually small. In other lakes no sexual difference in growth was detected , and in a few, females grew larger than males. (Cites omitted)

That's spot on with my experience. Good information.

I wonder if they fish they are playing mad scientist with are being kept in a closed facility. I don't know if I would want their mutated genes and hormones getting lose in wild populations of fish... Interesting work though!

Nope not closed to the public and one can visit or see the latest research on their website at any time. Basically they are working on producing the fastest growing bluegills and yellow perch they can for aquaculture purposes. However most of it is selective breeding. I do know they got yellow perch from several states to determine which grew the fastest and went from there.

I meant more of the genetically and hormonally altered fish and escaping into wild waters and screwing things up... Kinds like salmon with halibut genes getting lose!

The way it's done with the hormones the hormones aren't passed on. As far as selective breeding that's been going on for a long long time with domesticated animals. I don't think it's something to be afraid of.

I think you may be reading into the study some threats that really don't exist. I think that if all the fish escaped all it would mean is that you'd have a few extra males in the next generation. The rest is just simple selective breeding. Certainly nothing more than has been done with hogs, dogs, cattle, etc for centuries. Just being done with a little more sophistication maybe...

...actually, humans are treated with estrogen all the time, and we're not worried about it escaping into the wild. Hormones aren't contagious.

Yes, and I had some real doozy females this year!!! I sampled three females that were over 11 inches since January 1! All of them are in the "program".

My issue is, there aren't wild native cows, chickens etc in North America. There are wild BG and YP... Escaped fish with genetic alterations can cause issues with wild populations. We see that with pen raised quail getting lose and messing with the genetic integrity of wild quail for example. I'm a realist though and realize man has been moving fish all over the world and screwed most things up to a point of no return, so what the heck if some funky BG or YP get lose?

Just to be clear, there's a difference between genetic alterations, and genetic manipulation. When you say "genetic alterations" that says to me that something on the DNA strand has been spliced, replaced, etc.

I don't think that's what's happening here.

I think they're just using basic math (and hormones) to change frequencies of X and Y chromosomes. That's "genetic manipulation". Zero risk to wild populations. Hormones aren't a dirty word. They're as natural and ubiquitous as blood, and interstitial fluid, and vitamins and keratin, etc. etc.

Seriously though, human's are treated with estrogen all the time, and then released into the wild population. I don't think there's any risk to those around us.

That being said, the individual fish being treated with hormones could be an issue if ingested, provided that the hormone used has a detrimental effect on the consumer. But I don't think that's what we're talking about.

I guess I'll just respectfully disagree that this sort of study poses a risk to mankind. If anything I think it has fabulous potential to benefit humans. Bluegill are delicious, but they're not really economical for growout. If it weren't for science and their efforts to improve food production I'd shudder to think where this world would be.

I had a perch producer and extension agent at Ohio State tell me to use the largest males in my breeding to produce the largest female perch. Perhaps those large females would play more of a part than you are aware of?

We had chickens once that put on weight so fast some of them could not support their weight on their legs. Now if a bluegill grew that fast he wouldn't be so bad off underwater.

If we could grow bluegills as large as tires it would be almost impossible to get them in with an brush or trees around!

I guess I wasn't clear in what I was trying to say. It doesn't appear they are genetically altering the fish. They are just selectively breeding them for desired traits and then treating them with hormones.

The odds of it affecting wild fish populations is probably slim... For one, the odds of the fish escaping is unlikely. Fish treated with hormones are not going to affect other wild fish even if they did escape. My concern is what the affects of selectively bred fish would have on the gene pool of wild fish should they escape. Would the addition of genetics not necessarily found in wild fish be harmful to the wild population should fish escape and successfully spawn with wild fish?

Even though fish maybe the same species or even the same subspecies, even fish populations from adjacent drainages have often been separated for thousands of years. This separation has no doubt led to genetic differences(however slight they may be), between the populations in each drainage. Although the biotic and abiotic factors in each drainage are similar, they are slightly different and each population will evolve to best survive those conditions.

When humans remove fish from the wild and breed them in an aquaculture facility, even if no intentional selective breeding is done, the selection if over a long enough period is going to be for survival in a aquaculture facility, not in the wild. Rainbow trout are a prime example of this... Many strains have been in captivity for so long, they do very poor when released into the wild.

IMO, when it comes to BG and YP or most other species of North American fishes, this is a minor worry compared to the many other more serious threats wild fish populations face in a human altered world...

And yes, there would be a lot more hungry and even starving people if it weren't for genetically altered and selectively bred food products, everything for soybeans to corn and chickens to cows... However, some of those genetic alteration and selective breeding have affected the wild populations from which those original food species came from. Its just the price we pay for being in a modern world where humans have far out surpassed the natural carrying capacity. Humans are just smart enough to alter their environment to allow more humans to live with a set amount of natural resources.

Very nicely stated.

I don't think there's really any difference in what we're stating. Just slightly different angles of perspective, so I'd like to move away from anything that would seem like an argument.

What I'd like to do, with your permission, is use this thread to broaden the discussion.

I'd like to pose the following questions. They may seem somewhat rhetorical, but in actuality, I don't know the answers.

How do we define "wild" populations? It seems like we sometimes stray a little when we use this term. Is it a term that encompasses populations that were present from a particular point in time? If I genetically alter pheasants, then release them on my farm, can they affect the "wild" population? Or is that population not wild because they were brought from China a few decades ago?

What constitutes genetic change? Does it have to be man-made, or does it include the natural selection process that occurs in only a few generations in a sequestered group of individuals? In other words, if you willingly move fish from a creek to a pond, is that any different than moving "laboratory" fish into a stream? If the fish in the creek are selected to "creek life" after several generations, is that not the same as moving "laboratory" fish into a creek? Just wondering...

Since humans are animals too, are our actions considered "unnatural" just because we're human, or are our actions "natural" because we're part of nature? Why does human activity get special labeling? Is it because we're smarter? Or do we just think we're smarter?

If humans willingly eradicated elephants from the world in the next five years, which we undoubtedly could do, why is this considered tampering with, and negatively affecting nature? If we're part of nature itself, isnt' this natural? Just wondering....

If a population of coyotes eliminated all of the worlds remaining black-footed ferrets, is this a "natural" or "unnatural" act? Is it different than the humans eliminating the elephants? Or do we just "know better"?

Just wondering....

BTW, we'll never be able to answer these questions....only speculate. Our part in nature makes it impossible for us to objectively view the questions. JMHO.

Sorry for hijacking this thread, I'll make a new post for Bruce and I as well as others to expand on this topic...

I'm especially interested in those wild human populations.

Normally, it takes a large effort to create a populaiton of genetically manipulated creatures. When left to themselves, they quickly revert to their natural state. Animal genetics that have evolved over millions of years are very powerful. Even true genetic alteration will quickly be supressed unless it creates a powerful reproductive or survival advantage, which is unlikely.

I would love to have a commercial source for some of those maga-males!

Hasn't this exact thing already been done with Tilapia and the reason most tilapia stock for grow out purposes are 98% male? I don't think the concept is new by any stretch, maybe just new to bluegill. I'd be really interested in female only LMB, especially feed trained...same for perch too.

You and me both. I think there is market potential there for a creative entreprenuer. My state however says it doesn't allow geneticaly altered fish. Funny someone needs to tell them the triploid carp are genetically altered as are triploid rainbows which are common place now if you get the eggs from Trout Lodge.

Luara Tiu of the Piketon research center has already responded back to some questions I had namely more specifics on what temperatures or temperature ranges will skew bluegill offspring to mostly males. She has promised me Dr. Wang will get back to me and I'll be glad to share it with you all here.

If I could skew smallmouth bass to primarily males that would be a plus too as although there isn't much of a size difference in the two sexes, one large aquarium has told me they have problems with egg bound females.

Considering my fish are not for the food market I'm going to look more into using hormones to influence sex also. Male perch except for broodstock are virtually worthless for me as they are the runts of the two sexes.

Interesting stuff. I seem to vaguely remember from back in the days that I raised tortoises that the sex of a clutch of tortoises could be some what maniupulated by controlling the air temperative of the of the incubation chamber. Just a mere few degrees one way or the other can have an impact on the number of males or females hatched.

Good memory JHAP, most reptiles are like that... Anything from fence lizards to box turtles to alligators!

Yes temp and pressure have been used along with food laced hormones and other ways to make all one sex fish or to make them triploids and tetraploids.

Don't you mean haploid, or triploid? I thought the diploid state of genes was normal?

Trying to go to fast. -

Neither I fixed it now. Triploids and tetraploids.

See this is why science drives me crazy:

Triploid = (three sets; 3x) Makes sense tri as in tripod, triangle.

Tetraploid = (four sets; 4x) Tetra??? What? Why not quadraploid?

Pentaploid = (five sets; 5x) Got it. As in Pentagram (leave pentagrams alone, according to all of the movies I've watched messing with pentagrams can be dangerous stuff).

Hexaploid = (six sets; 6x) Sure as in hexagram.

Octaploid = (eight sets; 8x) Of course, behold the Octopus

Decaploid = (ten sets; 10x) Yep as in Decade.

Dodecaploid (twelve sets; 12x) WHAT? Why not Dozenaploid?

Tetraploid = (four sets; 4x) Tetra??? What? Why not quadraploid

JHAP, everything cant be based on Espanol. Where's the Greek love?........Dont answer.

Ok I'll restrain myself.

Theo? Brettski?

I have temporarily misplaced my 10 foot pole.