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Cage Culture: Raising Fish in Ponds

[drum beat] For thousands of years before the first settlers arrived on
these shores the nation’s oceans, estuaries, and lakes provided bountiful harvests of seafood Exploring what they were to call
the Chesapeake Captain John Smith and his men found fish lined so thick with their heads
above the water (Smith later wrote) as for want of nets, we attempted to catch
them with a frying pan Neither better fish, nor plenty, nor variety
have any of us ever seen Over the years waters along the Eastern seaboard have
continued to provide mightily Flounder, cod, bluefish, mackerel shad, striped bass, salmon, perch, trout However, even as fishermen were
hauling in these rich natural harvests there were always those who sought to
cultivate fish to rear them under controlled conditions In fact, as ancient Chinese
tombstone rubbings and woodcuts show the cultivation of fish — or aquaculture goes back nearly 5,000 years An early 19th century photograph
taken in China shows a man-made pond and the net which
has been used to harvest cultured fish In the United States, cultivation of
trout first got started on a large scale in the eighteen
hundreds Hatcheries, such as this one, rear hundreds
of thousands of trout a year for stocking streams and rivers Only in the last 20 to 30 years,
however has the cultivation of other commercial
species begun to expand in this country most recently, the cultivation of striped bass hybrids This expansion is in response to growing
public awareness of the nutritional value of seafood,
increasing demand for good quality fish year-round, and the declines of popular
natural stocks On average, over the last two decades Americans have been eating more
seafood each year While major fish wholesalers like this one in Jessup, Maryland, are
largely receiving ocean and river harvests of
fish and shellfish these harvests may not be sufficient to
satisfy the public appetite for seafood High-quality farm-reared fish could
relieve harvest pressures that commercial and sports fishermen
place on natural stocks Already, cultured striped bass hybrids,
such as these are coming from farm ponds
to wholesale and retail markets For some years researchers like Reggie Harrell, a
fisheries scientist and Sea Grant Extension specialist at the University
of Maryland have been working with
fish growers to raise fish more effectively and profitably Basically, fish can be reared in ponds
in one of two different ways You can either rear them in
the open pond itself where they’re free to roam and find
the optimal conditions in the pond Or they can be raised intensively in
enclosed structures, such as cages or net pens A cage or net pen culture has advantages
over the open pond for harvesting For instance, if you have a pond that has
stumps or logs or things like that in it, that you
can’t drag a seine through or you can’t drain the pond, a cage
or a net pen affords you the opportunity to harvest the pond by either
dipping the fish out of the pond or removing the cage structure itself Concentrating so many fish in an
enclosed area, however brings with it a number of
responsibilities It requires close care in stocking
the cages, feeding the fish monitoring water quality, maintaining good records,
and keeping cages clean You can easily construct cages at home with
materials that are readily available For instance, fiberglass rings
or PVC pipe can be used for cylindrical cages Rot-resistant wood for square
and rectangular ones For the enclosure material itself,
plastic mesh or nylon, or polyethylene netting Cage size and design are limited
only by your imagination and practicality In making a cylindrical cage,
you will measure the amount of mesh
material for the bottom frame first and cut it You can then attach the mesh to the
hoop by sewing with wire or heavy-gauge
monofilament line or by using plastic ties When you finish, trim the ends of the ties This will reduce the chance of floating
materials hanging up on the cage Once you decide on the
height of the cage measure the amount of mesh you will need and cut You can then sew or use plastic ties again
for attaching mesh to the bottom frame You will want to make sure all gaps are closed up After measuring the amount of material
you will need for the top of the cage you’ll next secure the frame to the mesh
to make the cage more rigid Because cages provide a ready perch for
birds to feed a secure covering will protect the fish At the same time you need access to the cage
for feeding, for cleaning and for monitoring water quality One way to do this is to fasten the top
covering only halfway around the perimeter This leaves a flap that can be secured
with a bungee cord and snap to prevent predators from
getting to the fish In larger, more rigid cages, you will probably
want to use a covering that can be tacked down, but that still has
access for feeding and cleaning Of course, you will need to carefully sew the
vertical seam and other openings Once the cage is complete attach buoyant material such as
styrofoam so that the structure can float You will want to balance the flotation to prevent
the cage from tipping over in strong winds The amount of styrofoam will depend on
how large the cage is Mesh openings come in different sizes and it is important that you choose a
mesh that will match the size fish you begin with The mesh must be small enough to hold
the smallest fish in the cage and yet large enough to allow as much
water to flow through as possible to remove waste products and
to bring in oxygenated water Greater water circulation generally
means better water quality For example, while you will need a relatively small mesh opening if you begin with 3-inch fingerlings You will eventually need to transfer the growing fish to cages with a larger mesh to ensure adequate water flow through the cage If you are using a feed that floats
or are constructing a cage for larger fish you will need to put in a feeding ring This is simply mesh with a small opening that
can be stapled and/or sewn around the cage perimeter it will prevent small fish food pellets
from floating out of the cage When completed, the cage is ready
for the pond All cages should be securely tethered to
prevent winds or water flow from moving them around
and possibly damaging them While best located in open water where
prevailing winds allow water to move through the mesh cages placed nearer to shore make for
ease in daily feeding and water quality monitoring Once you have contracted with a supplier
you will bring the fish in yourself or arrange for delivery The number of cages or net pens
you can place in a pond or the number of fish you stock in a cage
will depend on the size of your pond the cage size, and the species of fish
being cultured It will also depend on whether you have
the means for aerating your pond Aeration is simply a mechanical method
of moving oxygen-rich surface water
into deeper waters and through your cages In general, without aeration you can
estimate fairly safely raising 1,000 pounds of fish
per acre per year in cages With aeration you might be able
to rear 2,000 pounds per acre or more The particular species of fish and the
type of pond will determine just how many fish you can put in a cage With striped bass or hybrids, for example unless you plan to later thin
down the numbers you should plan on starting with 5
fish per cubic foot Let’s say you have a square cage that is 4 feet by 4 feet by 4 feet the volume is 64 cubic feet This means that, in a one-acre pond
without aeration you can place 320 fish in each cage Using the estimate of 1,000
fish per acre without aeration your one-acre pond could carry 3 cages with
some 320 fish each You may want to divide the fish into as many cages as is reasonable In this way, for example, if one fish
comes down with a disease its spread can perhaps be restricted to
the one cage What you do will depend on your
particular pond and the species you are raising Some species are territorial and,
if given too much room in a cage will fight with each other So, you do not want to divide
the number down too far Naturally, you want your fish to grow
to market size as quickly as possible That growth will depend on a
number of factors among them, the condition of
the fish you begin with the water quality of your pond, and
the nutritional quality and amount of feed You want to provide fish with enough food
to grow to maximum size but not so much that you are wasting it Feed costs can amount to as much as 50 percent of the cost of rearing fish The amount of feed you give your fish is
based on a percentage of average body weight Therefore, every several weeks you will need to take a sample of fish
from each cage or net pen to calculate the amount of
feed your fish require First, fill a large bucket with pond water and mix in an anesthetic Net a sample of 5 or 6 fish and place them in the bucket The anesthetic will make it possible to handle the fish while doing as little harm to them
as possible [Who’s gonna record? You get
the weights, I’ll get the lengths] Length information is sometimes good
to have to evaluate the evenness of growth However, the average weight of the fish
is more important [Background: weight is 311] Weigh the fish carefully
and record weights accurately It is the average weight of
this sample that you will use to calculate just how much feed
your fish will require [Background: 282] Let’s take an example of how to calculate
feed requirements Assume the average
weight of 6 fingerlings in a cage is equal to 1/8 of a pound If there are 320 fish in the cage the total weight of the fish is 1/8 pound multiplied by 320 fish or 40 pounds At a feeding level of 5 percent of
total body weight (the general rule-of-thumb for
fingerlings) You would allot 2 pounds of feed a day for that cage By the end of the first season, let’s
assume the average weight of the fish has increased to 1/4 of a pound However, 40 fish have been lost perhaps because of predation, or
disease, or some unknown cause There are now 280 fish in the cage The total weight of the fish is now 1/4 pound multiplied by 280 fish or 70 pounds At a feeding level of 5 percent of body weight you would allot 3-1/2 pounds of feed a day for that cage However, as the fish get older they can be fed at reduced percentages
of their body weight For example, from 2 to 3 percent Again, this percentage will depend on
factors that are particular to your pond and the species of fish you are raising It is best to feed your fish several times a day You can fill a container with the
day’s ration and then feed them over a number of feedings Also, it is important to remember that unless
you have supplemental aeration you should never feed more than 30
pounds of food per acre, per day, no matter what type of
food you have This is because it is very difficult for
natural processes that occur in a pond to break down that much organic matter,
waste, and metabolites and still have enough
oxygen to keep fish healthy In any type of fish culture, it’s extremely
important that you monitor water quality the most important of these being dissolved oxygen Other parameters such as pH, temperature,
and salinity and alkalinity are also important but they don’t have to be measured
on as frequently a basis The most important being the oxygen, you can take any of these measurements from
several methods You can do it from meters, such as this
one, or you can use a kit Or you could farm it out to a lab The best way, if you have a lot of samples,
and you have a lot of fish involved is to put the expense into it and get a good
quality meter such as this one The meter itself is simply an electronic
probe method where you’re able to set your ranges by inserting the probe down in the water,
agitating the probe to allow the water to flow across a membrane on the end of the probe, you can get an oxygen reading At the same time, you wanna check
the oxygen inside a cage to see if there’s any difference between
what the fish are consuming in the cage versus what’s outside of the cage I’m getting an oxygen reading of
about 8 parts per million here on the surface That’s how quickly that was taken
care of To check the pH, you use your test kit,
you use your test tubes you use a little box that has a
colorimetric wheel in it It gives the different values of pH in a wide range You use the sample little test tube vials that are marked for a pre-measured volume Put water in there up to that level pH effects fish growth and health You need a major your pH every
2 to 3 days or a minimum of once a week To the sample volume of water
the pH indicator solution is added Mix it, and hold it up to the sunlight See, there’s obviously a color difference Turning the wheel, match the color to get
an idea of what the pH level is You will need to keep accurate
records of your measurements to determine if there are significant
changes in water quality As ponds warm up in spring and summer,
fish growth accelerates So does the growth of other organisms which often brings with it
oxygen depletion problems and fouling Algal plants can take over a pond,
especially filamentous algae They can also take over cages together with molluscs, such as mussels
or bryozoans in freshwater Overgrowth can reduce water circulation, thus
leading to further oxygen depletion It is essential that you keep cages clean
by regular scrubbing If you don’t, there is a great likelihood of fish mortalities because of deteriorating water quality The key to production is staying on top
of what is happening in your pond Record-keeping is crucial It will help with management in that it provides
a picture of trends in your pond It will allow you to anticipate and predict and then take the necessary steps to fix any problem that arises It will also show you where your profit is going Fish culture is animal culture A chicken farmer can tell you that you can’t come and visit your chicken house every week or so
and expect to find your chickens alive A dairy farmer will tell you, that if you’re not
milking your cows on a daily basis that you’re going to run into problems Fish farming is the same way, especially cage culture because the fish don’t have any
access to food unless you give it to them They can’t get into areas of the pond
where the water quality may be better So the whole key to management is those
first three letters in it And that’s m-a-n, man While some factors are out of your control the onset of unexpected bacterial
or viral disease, for example many factors depend on your control Having adequate and nutritious feed,
ensuring you don’t overload your cages monitoring water quality,
supplying aeration when necessary keeping cages and net pens clean In addition, you will need to be
concerned with proper handling packaging and marketing Problems will arise — disease,
water quality declines, fish mortalities You’re going to lose fish There’s no question about that,
you’re going to have problems But it is how you manage
around such problems it is how you plan for contingencies
that will help determine whether you can take a crop from
fingerling through to market size It is management and planning that will determine whether you get
a return on your investment and are a successful fish farmer [music]

Jean Kelley



  1. Dragon Yang Posted on February 22, 2014 at 6:03 am

    thanks for sharing.

  2. Mowi Canada West Posted on October 1, 2014 at 10:32 pm

    Throwback to aquaculture finding its roots in the 1980s. Thanks for the trip down memory lane!

  3. TheAquaman1979 Posted on November 19, 2014 at 8:09 am

    Great information I'm smarter for it.thanks 🙂

  4. landorabe Posted on December 6, 2014 at 5:32 pm

    i'd rather used natural organic feeding for their first 2 months,for example like putiing chicken manure 2 weeks bef.putting fingerlings in the pond and of course i have to culture  azolla as their food and also a little bit of organic feeds assuming azolla isnt enough as their food….if i follow this instruction giving feeds i think its hard to gain profit….

  5. I'll do it Posted on January 23, 2015 at 9:11 am

    that maryland fish market closed last year, it was where i got my fish. 🙁

  6. Dire Moon Posted on January 26, 2015 at 12:54 am

    Thanks for posting. A lot of good information. Helped with me with a collage assignment.

  7. Hieu Quang Trinh Posted on September 8, 2015 at 7:03 pm

    your clip is very useful. we done copper alloy mesh in Vietnam, I hope we can share experience together about that:

  8. Lunji Posted on January 3, 2016 at 3:28 pm

    ive been taught to cut zip ties right at the clip. people have told me this is because that shits sharp as fuck and like a deranged psycho is always waiting to cut you. telecom industry.

  9. JW Update Posted on November 24, 2016 at 12:22 am

    thanks for sharing…

  10. Robert DeLay Posted on July 26, 2017 at 12:41 am

    Just a heads up from a Maryland tech who does a lot of work under water. White nylon zip ties are good for about four months under water. You need to use black poly so they don't break down over time. Hope things went well this video is three years old.

  11. Kamal Ashmawi Posted on August 19, 2017 at 12:20 am

    well explained, thank you

  12. 253 Arifideology Posted on October 24, 2017 at 5:51 pm

    Clear explained. However I just think I use better way to cultivate my fish than this one. I documents my cultivation way on my channel then just go to watch it and lets learn together

  13. Abdul Raouf Posted on July 1, 2018 at 1:30 am


  14. Seraph Gomes Posted on April 14, 2019 at 3:57 pm

    Well explained…

  15. Christine Huang Posted on January 3, 2020 at 6:15 am

    Very nice video, I also made videos for fish cage system in a more modern technic, welcome to my channel~