A species of trout is splitting into two camps

[splashhopper]

Toronto Star

Kenneth Kidd Feature Writer

 

The first thing to know about baby brook trout is that they are not devoted viewers of Disney.

 

Not for them all the massed choreography of Finding Nemo, where entire schools of tiny fish move as one, virtually no member distinguishable from any other.

 

Brook trout, it turns out, aren’t like that at all. From the earliest age, they start acting differently, a diversity of lifestyles that could have serious evolutionary implications.

 

So varied are their behaviours, that brook trout might even be in the nascent stage of separating into two distinct species — one timid and sedentary, the other bolder and more active. Scientists could end up with front-row seats to evolution.

 

“The level of diversity of behaviour, and the diversity in their diets that we see associated with that behaviour, are amazing things that I would never have expected when I trained,” says Robert McLaughlin, a biology professor at the University of Guelph.

 

Back when he was a student, the prevailing wisdom included something called optimal foraging behaviour. This was a kind of Darwinian fitness test, and the result was that animals all get to some point where they derive the most energy from their environment in the most efficient fashion available.

 

If you studied the habits of a single animal, in other words, you could safely assume the other members of this species in that particular place behaved in pretty much the same way.

 

Except, this isn’t always the case in the field.

 

So, scientists have since been moving to notions closer to game theory, which allows for much greater diversity and competition between members of the same species.

 

Which is where brook trout come in — or brook charr (to use the traditional British spelling favoured at Guelph), since brook trout, Salvenus fontinalis, aren’t technically trout.

 

Along with Alexander Wilson, one of his former graduate students, McLaughlin studied 89 wild brook charr in seven still-water pools along the west branch of the Credit River.

 

Not just brookies, mind, but virtual newborns. Although the fish hatch in mid-winter, they remain in the river’s gravel bed, feeding on their yolk sac, until they start emerging in very late March and April.

 

This is more or less when McLaughlin and Wilson started studying the fish in the spring of 2004, although their paper has only just been published in the journal Behavioral Ecology and Sociobiology.

 

The brookies were tiny, measuring just 2 or 3 cenimetres in so-called fork length — the distance between their snout and the middle of the fork in their tails.

 

But even at that young age, the fry split into two camps, with a few undecided in between.

 

A lot of the fish acted like riverbank couch potatoes. They stuck very close to the bank, and ended up mostly feeding on tiny crustaceans.

 

Yet others were soon foraging well away from the riverbank and in the upper portion of the water, where they largely fed on midges and flies.

 

The fish didn’t look markedly different, nor was it a case of the bigger ones being the more aggressive.

 

“They don’t differ a lot in morphology, at least externally, but they differ a lot in behaviour,” says McLaughlin.

 

The reason for the varied lifestyles, or at least a clue to the ultimate reason, lies in their brains.

 

After the behaviour of an individual fish was recorded, it was captured and sent to the lab for detailed measurements.

 

It turns out that the telencephalon, the part of the brain linked to movement and spatial abilities, was relatively larger in the fish that went foraging away from shore, where they would have to recognize underwater landmarks to navigate and avoid becoming prey themselves.

 

But this raises other questions. Were the fish reacting to their environments differently, and developing separate behaviours in consequence?

 

A study now being completed by another of McLaughlin’s former students, points in that direction.

 

The brook charr that hugged the bank have higher levels of the hormone cortisol, which is associated with stress, so perhaps worry keeps them home.

 

Still unanswered, though, is whether the foraging fish do so because they have bigger telencephalons, or whether they end up with bigger telencephalons because they are foraging.

 

The brain, as we now know, is fairly plastic, responding almost like a muscle to exercise, striving to meet the demands placed on it. Hence the adage, use it or lose it.

 

Then again, the presence of larger telencephalons could simply be a genetic endowment, in whole or in part, which the foraging fish take advantage of.

 

At least with brook charr, the answer still awaits further study. “That’s the direction we’d like to move in,” says McLaughlin. “We have some candidate genes we want to look at there.”

 

By which point, we may have a clearer idea of just how much evolutionary change is now at play on the outskirts of the city.

[Grimace]

Really cool stuff. Thanks for the read.

[Dave Bailey]

Nature is magnificent!

[alexcba]

thats pretty awesome. great read.

[TC1OZ]

I enjoy the study of animals but we don't have the humane race figured out yet. Maybe in the future.

[Musky or Specks]

Really enjoyed that thanks

[splashhopper]

the most important thing I learned from that article was what one of our fellow OFC'ers chat name meant ! Guess which one

LOL

Edited July 25, 2010 by splashhopper

[MJL]

the most important thing I learned from that article was what one of our fellow OFC'ers chat name meant ! Guess which one

LOL

 

2 possibilities come to mind

 

1. Doc Salvelinus

 

or

 

2. Nemo (From Finding Nemo )

[splashhopper]

2 possibilities come to mind

 

1. Doc Salvelinus

 

or

 

2. Nemo (From Finding Nemo )

 

u one funny guy...

my name is Memo and i am powerless over fish !

[BillsTheBassMan]

Great Read Ron - some very interesting stuff there . . . Im going to read it again later!

 

Thanks for Sharing!

Ryan

[camillj]

Cool ! But where are the pics ?

[Twocoda]

Very interesting ....next time we are fishing together ...bring this subject up and ill put a spin on it...i havent the energy to type it all out right now...

 

Thanks for sharing that ...now ya have me thinking ...