Hello and welcome to Conservation Skills
in 10 Minutes or Less.
The series of short, skill based videos
is brought to you by the US Fish and Wildlife Services National
Conservation Training Center in Shepherdstown, West Virginia.
If you have a couple of minutes, pull up a chair,
and pick up a new conservation skill,
or maybe refresh an old one, on topics ranging
from fish culture to bird identification
to stream restoration.
Enjoy.
Hello.
My name is Matthew Patterson.
And I'm a course leader at the National Conservation Training
Center.
And I'm going to lead you through a skill exercise today.
So what's the topic for today?
Today's lesson is on calculating flow index.
So what is flow index?
Well much like density index and exchange rate,
flow index is attempting to assess the carrying
capacity of the raceway.
I'd like to point out right now that this
is part of a video series on carrying capacity.
So if you're interested in also calculating
density index and exchange rate, please check out those videos
as well.
So in this case, instead of space,
how much space do the fish have, which
is what we were interested in with density index,
we're now interested in the amount
of water needed to both provide oxygen and remove waste
from the raceway.
And much like density index, of the fish do not have enough
oxygen or waste products are building up in the raceway, ,
growth survival, and the general health of the fish can suffer.
So it's really important to keep track
of things like the flow index.
So how do I calculate flow index?
Well typically, you would use a spreadsheet in Microsoft Excel
to calculate flow index.
But we want you to know how to calculate these things by hand,
so that if your spreadsheet gives you
a number that sort of doesn't make sense, then
you can make those corrections.
And you know what's running behind the scenes.
So here's the formula for calculating flow index by hand.
It's f equals w divided by l times i.
What does that mean?
f is, of course, the flow index.
w is the fish weight in pounds.
And this is all fish in that raceway.
l is the fish length in inches.
And i is the inflow or, the gallons per minute of water,
that are entering that raceway.
So just like our other videos, we're
going to have a skill demonstration.
I'm going to show you how to do the calculation.
And then you'll have a chance to practice.
So here's the skill demonstration.
Raceway 2a at the Shangri-La Fish Hatchery
is holding 2,100 pounds of 7 inch rainbow trout.
The raceway is currently receiving 200 gallons
per minute of spring water.
So let's calculate the flow index.
You'll remember from density index
that you also needed to calculate the volume
of your rearing unit.
We're not interested in the volume of the rearing unit
here, because that had to do with how much space you needed.
We're interested in how much water is coming in.
So for our skill demonstration, remember, the inflow
is 200 gallons per minute.
Our fish length with 7 inches, and the weight
was 2,100 pounds.
So we plug that information into our equation,
f equals w over l times i, and we get a flow index of 1.5.
OK, and like I mentioned, you now get a chance to practice.
It's your turn.
So I would suggest, after I read through this example skill
practice, that you pause the video,
go through the calculation.
And then when you resume the video,
we'll provide the answer for you.
So here is the skill practice.
At the Wonderland Hatchery, you are holding 1,200 pounds
of fish in a raceway.
Your fish are 4 and 1/2 inches long.
And the raceway is receiving 150 gallons
per minute of well water.
What is the flow index?
So go ahead and pause it here.
And when you come back, we'll walk through the answers.
OK, welcome back.
we're going to provide now the skill practice answers for you.
Remember, your equation-- f equals w divided by l times i.
In our skill practice, we had 1,200 pounds efficient
the raceway.
They were 4 and 1/2 inches long.
And the inflow was 150 gallons per minute,
if you plug those into your calculator,
you should get a flow index of 1.8.
Hopefully, that's what everybody got.
OK, so now we know how to calculate flow index.
What does that mean?
What is a good flow index?
If you remember back to density index,
we had a general rule of thumb.
We didn't want the density index to go above 0.5.
But a big flow index depends on a couple key factors.
One, what is the water temperature at the hatchery?
And two, what is the elevation of the hatchery?
And if you remember, we're interested in how much oxygen
we're delivering, in this case.
Obviously, both water temperature and elevation
can affect the amount of dissolved oxygen in the water.
So what do we do?
We go to this table.
And this is table eight from the first edition of Fish Hatchery
Management.
And let's assume that the well water at Wonderland Hatchery
is 52 degrees Fahrenheit, and the hatchery
sits at an elevation of 3,000 feet.
So if we follow this table, and we
go across the top, that shows elevation,
we see the 3,000 foot elevation column.
We follow that column down to 52 degrees Fahrenheit.
And what does that give us?
That gives us a maximum flow index of 1.5.
So we don't want our flow index at this hatchery
to go above 1.5.
Now in the skill practice, you calculated
that the wonderland hatchery had a flow index of 1.8.
So what do we do?
In the case of density index, we split the fish
right so that we could give them more space.
In this case, we have a couple of options.
We could still split the fish, because that
would reduce the weight in our equation or split the weight.
But we could also increase the flow rate.
So if you look at the equation, remember,
weight is in the denominator.
So if you increase the weight by splitting,
you decrease the flow rate.
But also, the increased flow rate,
you can decrease the flow index.
You want to learn more about flow index
and other skills like it?
I would suggest checking out our course called Cold Water Fish
Culture that's offered at the National Conservation Training
Center.
And if you hang on after this video,
I'll provide a quick tutorial on how
you can access this course on our website
and get more information.
Now you have questions about this particular skill
or any other skill related to cold water fish culture,
or any class that we offer at the National Conservation
Training Center, feel free to contact me
at my email address here or on my phone number that's
attached.
Thank you for listening, and we'll see you next time.
OK, as promised, I was going to show you
how to find cold water fish culture on our website.
Best thing to do is just go to Google
and type in National Conservation Training
Center and hit Enter.
Typically, the first search that comes up, open our website,
and then go to the Search bar here.
And type in the cold water fish culture.
Hit Search.
The first PDF that comes up we'll take you to this PDF
with more information about the course,
including course description, course objectives, target
audience.
And then down at the bottom, you see
what course is coming up next.
Thanks again for joining us for Conservation
Skills in 10 Minutes or Less.
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Have a great day.
And always remember, the beautiful thing about learning
is that no one can take it away.