NANFA-L-- Habitat Partitioning in a 100 gallon

Subject: NANFA-L-- Habitat Partitioning in a 100 gallon
From: Todd D. Crail (tcrail-in-UTNet.UToledo.Edu)
Date: Tue Nov 30 2004 - 21:42:49 CST

Howdy folks... A while back I showed some pictures of me dumping 80lbs of
clayey topsoil into a 100 gallon tank. I'm glad to say, the topsoil has
worked wonderfully, I can't harvest the val fast enough (which may or may
not be viewed as a problem :)

I had some trouble with tannins for a bit as well... I'm pretty sure it was
the wood but it might have been the topsoil. At any rate, I can control it
easily with some activated carbon, and now the 5500k halide lights are
definately _not_ yellow Nick ;)

I also experienced some blooms initially that would make it cloudy
gray/white. I threw in some corbicula and haven't had a problem since, and
see them siphoning from time to time. That is just one big anecdote,
however. I plan to try and quantify this in my lab as I begin setting up
tanks for study.

That was phase 1 of what I wanted to accomplish with this aquarium. I can
say I'm 95% behind using topsoil mixed with sand as a substrate is a great
choice for growing rooting plants (still need to see what the 2 year test
proves for the last 5%). And the best part... It's dirt cheap! <groaner>

Now for Phase 2... I've always wanted to play with creating mixed habitat
in a tank on a scale where multiple species could be observed occupying
their niche in the aquarium, with multiple specimens of species able to live
within that niche. I believe I have pulled this off (at least with darters)
and would like to share my experience with you all.

It would probably be most clear to mention this as the difference between
where sunfish typically live and where darters typically live. I think that
is something we've all observed time and time again, and neither are usually
in the same spot (there are _always_ exceptions). The difference in where
those animals live, or the places where those animals occupy space is
something ecologists refer to as "niche", which I refered to above. They
get all ooey gooey about it and try and turn it into models and equations
and other abominations of nature, but I'll stay clear of that, I promise :)

I'm sure in the field, you've also noticed that there's a difference between
where say, fantail, orangethroat, greenside and bluebreast darters are found
(whatever is local to you). They can appear in the same general portion of
a stream, however, it may seem they are concentrated by species or size of
specimens in vastly different places in the column of the stream, depending
on a wide variety of abiotic reasons (flow, substrate, aeration) and biotic
reasons (food, plants).

Something I had noticed-in-the Fox Riffle on Big Darby Creek here in Ohio,
was there were a dozen darter species living in the same 30 meter section of
stream. A 30 meter section that looks pretty much the same... fast current,
cobble. Really monotypic to my human eyes. Beside color, the darters all
kind of look the same... they usually sit on the bottom, and pick off little
invertebrates. But there has to be _something_ different that would allow
them to all use the same space, otherwise, why would they need to be
different? And this is what gets refered to as "partitioning" or a
division of the resources in a habitat that allow multiple species to
co-exist in that habitat.

Food items and physiology related to feeding (biotic causes) can be really
tough to replicate in an aquarium. I generally just dump it in and let them
sort it out. It would be really interesting to see how a fish like a
greenside darter feeds on different things with its underslung mouth, as
compared to a common co-habitant like a rainbow darter which has a very
terminal mouth. But I hoped I could pull it off using abiotic resources in
my aquarium. And having designed it and then added the fish... I can say it
was nothing less than a "snap to it" grid they seemed to have worked out
prior :)

Probably the easiest thing for me to do-in-this point is just show you some
graphics I constructed. These are older pictures and the tank is far more
developed, but they get my point across.

The first picture shows various "zones" I have found the fishes have laid
out amongst themselves. I will address who lives where in a bit (I'm sure
you can already make predictions :)

The second picture demonstrates where currents exist (major and minor). I
guess the biggest thing to notice is how I've taken a Rio 2100-in-the far
left end, that pumps into a "spray bar" I crafted out of an Eheim return
line (pvc or cpvc would work just dandy too). I drilled 1/4" holes in a
very random pattern to keep the current as variable as possible. It worked
out pretty darn well. I get pulses coming and going across the water

The second set of big arrows decending on the right are coming from the
return on my canister filter. I've pointed the line directly down the back,
put a plug in the end, but drilled out a hole so some current comes out of
the end. The prevailing current this generates is geared toward the front
glass across the top and creates all the little vectors you see swirling-in-
the right end.

I will discuss these as zones, as I think that will keep a better handle on
how much I type. Frequency is determined after feeding and when everyone
has settled down. They'll crawl on each other waiting to get fed, and the
only way I can rule out my influence is to give them what they want from me

Zone 1
This zone is kind of like the actual riffle, or the shallow portion where
rocks are exposed. Variegate darters (E. variatum) will sit on the right
end of that gray rock, but this area is dominated by banded darters (E.
zonale). If a variegate or greenside moves through Zone 1, the banded
darters move out, but return quickly once the other species has left.

Zone 2
This is the fun zone. This zone is dominated by varigate darters. They own
it. They defend it. They sit right in the current like it's nobody's
business and also create a hierarchy among themselves. A large greenside
(E. blennoides) will be found in this zone from time to time, ocassionally
smaller greensides if everyone else is "out". As well, the larger greenside
appears in Zone 2 only in the absence of the largest variegates, and upon
their return, he moves back to Zone 3. In the rocks behind zone 2, you can
see banded darters in the rocks on the outside and logperch darters (P.
caprodes) in the back where it's open and gravelly with valiserna.

I have a hunch the distributions would change dramatically if I were to
remove the variegates. My guess is the greensides would own the area,
expanding and merging Zones 2 and 3. What I hope to do is get ahold of some
bluebreast darters (E. camurum) and see what happens. Will a Zone "2.5" be
created, or will other species just get pushed to different areas?

One of the northern hogsuckers (H. nigricans), the larger, faster growing
specimen, spends all of its time in Zone 2 and the black redhorse (M.
duquesnei) spends about 50% of its time here as well. Another hogsucker
will spend time in Zone 2 but is more frequently found in Zone 8, where the
black redhorse is found the other 50% of the time. A shorthead redhorse (M.
macrolepidotum) is also in this tank, but he's too large to work into a
habitat. He spends most of his time behind Zones 2 and 3, and occassionally
comes out in the riffle.

Zone 3
AKA "the minnow zone". This is where the shoal of minners hangs (SRBD,
redside dace, spotfin, silverjaw, suckermouth). If the pump is clogged up a
bit, they'll move into Zone 2 (less current). But for the most part,
they're right here in Zone 3. I don't even want to try and guess what the
partitioning is among the cyprinids. My best guess would be stream size and
historic volume, along with biotic reasons such as mouth shape. That's
asking a little much for an aquarium, as I explained earlier.

However, underneath all this minnow mass... Our evolutionary late-arriving
darters have sorted their way into the fray. The dominant darter in this
zone are the greenside darters, however, large rainbow darters (E.
caeruleum) will move in and out, as will the logperch darters.
Occasionally, banded darters are found here with brief appearances by large
orangethroat darters (E. spectabile). I think this is a pretty typical
distribution we find in Ohio when working reasonable stream riffles.
Especially once I discuss Zone 4.

But there's a part to Zone 3 that has really suprised me. Blackside darters
(P. maculata) hang right in there with the minnow mayhem, swimming along in
the water column like they're part of the gang. They do this before feeding
and after digesting for a while (they'll go hide in the valiserna). Many
times, they'll take a break in Zone 4, but this is brief, due to another
species, and they're right back in the swimming.

Zone 4
This is fantail darter (E. flabellare) country. It's his. Period. You
stop in for a visit, you're getting bit... this includes aquarist fingers!
I need to add another large male fantail to see the outcome, and I hope they
sort it out better than the last two I tried together (they killed each
other). I was suprised he didn't also use Zone 1. He roams-in-times, but I
would say 95% of his time is right here in this little home range he's
picked out.

Zone 5
Dusky darters (P. sciera) <you have to sing "dusky darter"... it's a
requirement> This is my favorite spot in the tank. The large dusky sits
here, in the water column, all the time. He'll investigate that piece of
wood like you wouldn't believe. Upside down, no problem. He just goes in
circles around that little arch. The other smaller ones join him from time
to time, which are my favorite times... but they seem to spend more of their
time over by the wood in zone 8. In any case... if you're looking for dusky
darters in the wild... Check the root wads ;)

A longear sunfish (L. megalotis) likes to spend a lot of his time in this
area as well.

Zone 6
The topminnow zone. Notice how the current "comes too" these areas.
Blackstripe topminnows (F. notatus) are found in one of these three places.
I would like to get some western banded killies (F. diaphanus menona) from
Michigan and see what kind of trouble I can create :)

Zone 7
I don't know what Zone 7 is. I guess I was trying to show current, before I
got smart and then, like, um, showed current in the other figure. Let's
just act like 7 never happened, okay? Thanks.

Zone 8
Get pushed out by other species? No problem... we have Zone 8 for you.
This is where our generalists hang out, or species you can find on riffles
in the absence of the other darters, or in pools where the rest are present.
Orangethroat darters, johnny darters (E. nigrum), and small rainbow darters
are the gang in here. When not in the minnow mayhem of Zone 3 or hiding in
the val, the blackside darters are generally found in Zone 8 as well.

I was suprised about the rainbow darters (I thought for sure they'd be
duking it out up in Zone 2 and 3) but as I think of it now... these rainbow
darters came from a ditch co-occurring with orangethroats. It would be
interesting to get some rainbows from riffles out of the Darby, where
they're co-occuring with varigate and bluebreasts. Hmmm... Good thing they
look different, huh? ;)

As I mentioned earlier, the smaller dusky darters hang out around the wood
in Zone 8 as well.

Okay... So that's kind of a wrap. There are also tadpole and brindled
madtoms, and two pirate perch... But they're so cryptic (I'm sure they're up
under that wood)... I only see them when they come out to feed. Which, by
the way, I'm having excellent success with the pirate perch in the community
tank. They'll come right out and graze after the mayhem has settled down.
There are also hornyhead chubs (N. biguttatus) present, but they are new
additions and I've yet to figure out their habits.

Hopefully you've found this as entertaining as I have. If not, I can always
try and stuff this into more of a model, and try and get a pub out of it.
But that's like, um, work. :)

The Muddy Maumee Madness, Toledo, OH
It's never too late to have a happy childhood.

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: Fri Dec 31 2004 - 12:42:57 CST