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Ontogenetic Behavioral Shifts


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#1 centrarchid

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Posted 17 October 2017 - 05:33 AM

I have been raising sunfishes in ponds and tanks for some time now and seeing something new that was hidden because of the tank size used and that I am not in ponds every day.  I do get into ponds a lot more than other fish culturist I know.  

 

Bluegill up to about an inch in a pond setting move in roving shoals that approaching schooling behavior.  I am unable to make out home ranges so my thinking is this is the period in life when they are most likely to disperse under their own power.  At some point when they are more than 1" they adopt at least transient home ranges.  In the typical tank settings we use and I observe almost daily, the fish move very little except to get at food.  In circular tanks they form a large torus that does little more than compensate for current of self-cleaning tanks.  You can have 20 tanks in parallel, each with several thousand larvae - fry, and see the same thing in every tank.

 

For another experiment that is still in the acclimation phase, I cleared what we call the teaser system of adults and stocked a little over 100 fry into it.  The tank is 10 feet long.  The fry are moving about in a big way as roving schools that constantly change in make up.  At some point these fish are going to abruptly change their behavior and it is going to be size or age related.  Work with Redspotted Sunfish indicates to me that differences between species with respect to this behavior are likely to be huge.


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#2 itsme

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Posted 17 October 2017 - 08:15 AM

Yes, this is interesting!  Keep us posted, please.



#3 centrarchid

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Posted 19 October 2017 - 09:13 AM

Here is a goody.  When lights went down each evening the number of fry in study tank went down by the following morning.  Sometime in the night the little buggers swam past inlet or over standpipe.  They moved at night.  This crap stopped once number of fish got down to around 15 fry in a 200+ gallon tank.  The remaining fish switched from schooling / shoaling to at least keeping home ranges.  Schooling / shoaling appears to require a minimum number to engage with such small fish in larger tank volume.  I cannot tell how they are keeping themselves dispersed.  Now I must start over by going out to collect and acclimate another batch.


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#4 itsme

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Posted 19 October 2017 - 10:06 AM

Nature continues to reveal itself as deeply complex and adaptive.  Never assume that you understand what is really happening, and what is possible.  Life finds a way by being plastic and only expressing certain strategies when they are called for.  A sunny sits in one spot all summer, then when conditions change, his behavior changes.  Really a lot like Homo sapiens.  We want to simplify to make it easier to understand and predict what's going to happen, but really, we know oh so little about what is really going on and what has gone on and what will happen in the future.  Maybe that's why adaptability is so endemic.  Without it, we'd all have gone extinct a very long time ago.



#5 gerald

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Posted 19 October 2017 - 01:11 PM

Glad to see we have an active ichthyophilosopher once again.


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Hangin' on the Neuse
"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#6 itsme

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Posted 19 October 2017 - 01:35 PM

Glad to see we have an active ichthyophilosopher once again.

 

Glad that you said that as though you thought it a positive development!  :)



#7 centrarchid

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Posted 19 October 2017 - 03:18 PM

Frankly, the babble upset my stomach.  Reading and trying to comprehend was like driving on a bumpy road going nowhere.


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#8 itsme

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Posted 19 October 2017 - 08:06 PM

Frankly, the babble upset my stomach.  Reading and trying to comprehend was like driving on a bumpy road going nowhere.

 

I'm sorry.  I'll try to be more accessible.  Would take a lot more words to really explain all the ideas that were going through my head.  But I was inspired by your research.  It is revealing some very complex behavior of our friendly sunnies.  Keep it coming.  Good stuff!



#9 Michael Wolfe

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Posted 20 October 2017 - 07:28 AM

All kinds of communication styles out there. Im willing to fight through them all. I find it to be one of the beauties of NANFA. I learn from all yall.
Either write something worth reading or do something worth writing. - Benjamin Franklin

#10 centrarchid

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Posted 20 October 2017 - 01:11 PM

"Cage match" is now setup.  I constructed mini-feeding cylinder, that is normally used to exclude big fish like grass carp from eating applied feed.  Baby BS are dripped down into the feed cylinder where fry are waiting for it.  Fry are free to come and go.  The feed cylinder also provides cover which may or may not complicate things later.  Fry are already stacking up inside the feeding cylinder.  Smaller fry are staying away.  Are the smaller fish excluded by larger or avoiding cover?  I do not know what size the fry change from being pelagic associating with cover.  There is a transition that has a genetic basis.


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#11 centrarchid

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Posted 21 October 2017 - 07:07 AM

The 10' raceway as part of an RAS.

 

DSC04149.JPG

The feeding cylinder.  The container on top serves as hopper BS drain from slowly into the "cage" below.

 

DSC04150.JPG

 

Can you see the single fish on the outside of the cage roughly above center of the image?

 

DSC04151.JPG

 

All fish concentrated around that cage.


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#12 centrarchid

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Posted 21 October 2017 - 07:31 AM

Home ranges evident with at least some of the fry.  Largest fry are concentrated in or around feeding cylinder.  Their home ranges are tight and overlapping.  Fry with home more than a couple feet away have much larger home ranges with no overlap.  Very cool!  BS density much higher in feeding cylinder and fish swim much less between taking prey items.


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#13 centrarchid

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Posted 21 October 2017 - 09:55 AM

Once fish with bigger home ranges get relatively full, they move somewhere else in tank.  Larger fish with tighter home ranges staying there.  First sign of pecking order in feeding cylinder may have been noted at end of my shift.  My hours in lab on weekends from 0500 to 0800 which limits my ability to properly track fish.


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#14 gerald

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Posted 21 October 2017 - 09:33 PM

That feeding cage could be a useful contraption for feeding slender darters in a tank with sunfish or shiners, if you can find the right size mesh that'll just let darters slip through.


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Hangin' on the Neuse
"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#15 centrarchid

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Posted 22 October 2017 - 05:35 AM

It functions as a creep feeder as well allowing small fish to feed away from larger fish of the same species.


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#16 centrarchid

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Posted 23 October 2017 - 11:56 AM

Fish are nearly invisible until they start feeding, then they are very obvious.  Fish feeding on BG likely have same issues I have.

 

 

 

When BS available they (BG) switch over to hawking not unlike chickens in video below. 

 

https://youtu.be/NuhB8rvxLBc

 

 

They catch only prey that are moving.  The forager keeps going over same area over and over again.  Area is a function of density / encounter rate with forage.  The more forage, the tighter the area foraged.  I can not get BG fry to show up with current camera setup.


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#17 centrarchid

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Posted 25 October 2017 - 11:31 AM

Four remaining fish now foraging as a shoal away from feeding cylinder except when BS present in and around cylinder.  Fish promptly return to feeding cylinder when I approach it.  There may be evidence for pecking order when shoaling and possibly when in feeding cylinder.


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#18 centrarchid

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Posted 26 October 2017 - 03:09 PM

Behavioral modes apparent when volume / habitat complexity allows.  Something really neat going on.

 

 

School                              - Shoal                          - Individual

No obvious home range     Home Range                Overlapping Home Range to No Overlap

Blanched                            Barring                          More interesting to even more interesting


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#19 centrarchid

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Posted 27 October 2017 - 04:37 PM

Yesterday I added five larger fry.  One disappeared.  Remaining for have roughly similar movement patterns as the remaining four smaller originals.  Color pattern very different.  Larger fry a lighter in coloration and have bars.  Color differences not likely genetic or age related since full-siblings with same spawn date.  Smaller fry spent a nearly 45-day stint in outdoor tank where there was natural forages, more variable and lower temperatures, and more space.  The larger fry are showing a clearer pecking order.


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#20 centrarchid

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Posted 31 October 2017 - 10:20 AM

I am withholding feed to later in the day in part to allow someone to learn how to harvest BS.  Fry of concern are starting to get agitated.  They search about in half of tank were BS are dripped in.  When they see me approach they rush over and stack up where BS actually falls in.  They are swimming about relatively fast as they wait.  It takes a few minutes after I walk away before they disperse.


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