Shop Products
Houzz Logo Print
digit_gw

fish farming - missing the boat?

digit
16 years ago

I know we have some pond gardeners here and a comment by David about his life-experiences got me thinking about something. Does David still have fish?? Also, there was that recent trip to Costco and a box of breaded fish fillets . . . .

My sunshed sits nearly empty each Summer. Oh, there have been a row or 2 of basil in there but that's mostly to take advantage of the growing space and the fact that we can put things that can really take the heat directly in front of the plastic south wall. In the Fall, a few potted herbs migrate in and take up residence. The intent there is only to protect them from severe freezing. They aren't growing and I'm not even putting them out in the sunnier and more exposed area where the plants would be more difficult to protect from the cold. Until the furnace is turned on in March, the sunshed has more-or-less sat idle for 9 months!

The package of fillets from Costco was tilapia. I've had tilapia before - baked. Struggled a bit with the bones and . . . I'm not hugely fond of fish. The breaded fillets were much like ocean perch and tasted great!

Could I raise tilapia in my sunshed thru the Summer and into the Fall? Would it make any sense for me to even head off down this route to explore information? Taking an hour or so, I found precious little on the 'net, anyway. I don't even know where one would buy 25 or so fingerlings.

I've had beautiful gold fish before - in the house, in a tank. And, once had quite a few gorgeous bettas, so fish keeping isn't entirely unknown. But, fish farming . . . ??

Here's a little something I came across from a missionary group who send folks off to help people in tropical areas with tilapia farming. You should know that they sell set-ups for home fish farming. Part of their water filtration system using plants is somewhat familiar to me, also. I have seen and used similar systems to grow plants in commercial greenhouses.

Am I missing the boat on fish farming? Or, just out to sea?

digitS'

Here is a link that might be useful: Aquaculture & Hydroponics

Comments (25)

  • david52 Zone 6
    16 years ago
    last modified: 9 years ago

    Steve, you might just want to put down that thought and slowly..... walk...... away. :)

    So happens I spent 25 years raising tilapia, which is now one of the most widely farmed fish in the world. I was the one of the guys that made all the beginning mistakes and figured out the odds and ends, what works and what doesn't, and so ended up designing, building, and managing all kinds of hatcheries and farms. I even got to that exalted stage of "Consultant" where outfits would actually pay me to pontificate and bore the socks of anyone who makes the mistake of asking. .....including closed recycling systems that incorporate hydroponics. It's a lot of fun and not that expensive if you improvise.

    A couple years ago, I stumbled across a forum similar to this one, with the usual set of fanatics arguing away. I'll see if I can find it again, - but thats the place to start. There is a lot of mis-information and some serious snake-oil out there as well.

    I don't do it now, sort of turned that page in life, although we keep an aquarium. We had two aquariums but one cracked this last winter, and my daughter used the clear marbles that were the filter bed to create a mini "Christo and Jeanne-Claude" display across the gravel driveway; hundreds of small glowing prisms in the sun.

    I'll see what I can find later,

  • david52 Zone 6
    16 years ago
    last modified: 9 years ago

    Ok, I'd start off with the course down in St Croix, don't forget the sunscreen and your swimming trunks -

    http://rps.uvi.edu/AES/Aquaculture/UVIShortCourse.html

    Click on the 'registration and course fee' to get a better idea.

    And these guys will sell you your own set up;

    Here is a link that might be useful: Such a deal.

  • david52 Zone 6
    16 years ago
    last modified: 9 years ago

    Steve, here's a pretty good forum on the subject

    Here is a link that might be useful: here's a forum

  • digit
    Original Author
    15 years ago
    last modified: 9 years ago

    Thank you, David.

    Tilapia are cichlid fish like some of those at the pet shop but how different than those are the ones used for food?

    I enjoyed searching thru the forum and will spend a little more time there. However, unless I missed a Yank, they are all Australians. Some have put interesting photo's and descriptions up for others to learn from - I especially liked what is pretty much a self-watering outdoor garden with a small pond. Michelle could set that up as an alternative but her poultry would probably start running fishing derbies!

    We'll leave the trip to the Virgin Islands aside for a moment but the "deal" doesn't seem too much of one. The one I linked to is even worse, I think. I've got a couple of heavy plastic tubs - certainly, I didn't pay thousands of $$'s for them.

    The only high tech item is the water pump and that runs between $40 and $50 even from these very high-priced sources. An aereation pump can be found with my old aquaria and I doubt if I'd need to use the heater because the greenhouse is definitely on the HOT side thru the Summer even while fully vented. Water would probably never fall below 75 until late September.

    I checked with the public library and they have a book by Gene Logsdon published by Rodale in 1978!! Thirty years ago, did we even know how to spell tilapia?

    After I came home and checked with worldcat.org, I discovered that a local library has another book, "Freshwater aquaculture: a handbook for small scale fish culture in North America" by William O McLarney. I've asked to borrow it. Copyright is 1998 so there's a little more expectation on my part that this could be information one could act upon.

    I think you may need to climb back "in the boat" and write something for folks like me. There must be people everywhere in this temperate nation with greenhouses that sit idle well over half the year. If tilapia needs 76F+ water, I don't see why I can't supply it for months and months.(Maybe not todaaaay since it won't reach 50°F outdoors) And, if they are eating essentially chicken food, well, I've got that by the bagful anyway.

    They've got a 1.5 to 1 pound feed conversion rate!?! Could that mean that I'd feed 75 cents worth of chicken feed and harvest a 1 pound++ fish in 5 months?

    I can see setting up a PVC pipe filtering system with something like malabar spinach. That veggie gets a good start in my plastic tunnel thru June and continues growing well after the plastic comes off with the advent of hot weather. I bet it would "love" fish water.

    digitS' reaching for the fishin' rod

  • david52 Zone 6
    15 years ago
    last modified: 9 years ago

    Steve, as you already figured out, the biggest expense is that big water tank and a pump, of which there are lots of options out there. The rest of it can be pieced together with bits and pieces of PVC pipe, and there are all sorts of tricks for filtration and so on. The other thing is a good concrete slab to put it all on, because these things are heavy once they're full of water.

    Yikes, I hadn't realized that was an Australian forum, I'll look around and see if I can find something more local.....

    Tilapia are one of the genus of African cichlids, which is an amazing field one can easily get lost in. Linked is a site specifically about Lake Malawi, but there are completely different but related species in the other African Great Rift lakes. Lake Tanganyika has another few hundred species. That place is amazing, with water so clear, you look over the side and see fish swimming along the bottom, 60 feet down.

  • windwhipped
    15 years ago
    last modified: 9 years ago

    Interesting topic. Since we have an expert here, and an eager investigator, may I chime in with a completely uninformed question? Awile ago I read that farm-raised salmon had dioxin in them and should be avoided. Since then I have tried to stick with wild salmon; so my question is 1)is that true? 2) why would that be, is it what they are being fed? 3) would that be the same for other farm-raised species like tilapia (which I buy all the time, tortilla crusted, by the way)? I guess that is more than one question, but if either of you find the answers in your information gathering, I'd love to hear it.

    Meanwhile, good luck with this new endeavor, Steve.

  • david52 Zone 6
    15 years ago
    last modified: 9 years ago

    windwhipped, a discussion of farmed fish, or any animal for that matter, contaminated with industrial chemicals accumulated from their feed / environment, sorta opens up a Pandora's box. Basically, there is very, very, little testing going on, and the same holds true for wild fish, wild animals, and so on. The more they test, the more they find. Enter politics, special interests, and wild-arse manipulated media reporting, and it rapidly gets absurd. Stuff like tuna are considered by the FDA as *safe* with a mercury level 10x higher than what the EPA says is *safe* in the fish out of the local river, which has warning signs all over the place about pregnant women and so on not eating the bass, trout, and salmon.

    What I gleaned, form a quick google re dioxin and related nasties and farmed salmon, is that yea, they have more, but unless you're snarfing it more than 20X a month, *they* say you're safe. It also looks like the industry realizes they have a problem, so they're reducing the level quickly, at least in Europe and Canada. Elsewhere, I have no idea. I, personally, would eat farmed salmon a couple times a month, but if I can find wild salmon, I'd pick that first as well.

    Back to tilapia. It's all imported, and now, most of it is from China. That country has a millennia long tradition of sustainable agriculture and aquaculture, and this species was right up their technical expertise alley, so to speak. My attached link shows the gargantuan gains in imports from there , shoving out other countries. As something I know about, I dunno how they can raise a fish, fillet it, freeze it, package it, and send it across the Pacific, distribute it frozen here in SW Colorado for cheaper than I could raise it in my back yard. Thats gummit subsidies and wierd world trade stuff.

    Anywho, and I wish to tread lightly here, yet get my point across. China is now not known for its environmental ethics, above all in water quality. The whole sustainable agriculture thing is going down the tubes rather quickly as they move into massive pesticide, herbicide, and fertilizer use. Check out this month's National Geographic for an idea for water quality issues, it's is really sad. I now refuse, categorically, to buy any fish product farmed/raised in China, and thats a lot, if not most, of what's available here. Because we have gotten so amazingly sick from some of this stuff - rashes that last weeks, and so on. Tilapia will eat and grow big eating all kinds of food stuffs, and live in some of the most amazingly extreme environments around the world, toxic to most other fish. Their ability to withstand normally lethal conditions might be a reason for their increased popularity in that country.

    I'm pretty sure, but not positive, that the prepared fillets, the ones with the coatings and stuff already to fry, are from South / Central America. They raise their fish in far better conditions and with far better feed than they do in China.

    I've asked the local guys at the Safeway where the tilapia is coming from, and it sure varies. So it might be worth your while to ask. If its from China, I'd pass. Look for frozen Alaska cod fillets. Thats the best thing I've seen available for years now.

    The biggest tilapia I ever raised was 8 kg, or 17 lbs, and took just shy of 3 years. Size of a sofa cushion.

  • windwhipped
    15 years ago
    last modified: 9 years ago

    Thanks, David, very informative if not very reassuring. But pretty much as I expected. Sadly, so much of our food supply seems open to contamination these days. I checked the tilapia I have in the refrigerator right now - distributed by some company in Massachusetts, but who knows where it originated. Start farming, Steve, and send some fresh home-grown my way. (And now I'll butt out of your discussion.)

  • digit
    Original Author
    15 years ago
    last modified: 9 years ago

    I'm happy you "butted in," WW! We don't get enuf correspondence from WY!

    Also, your comment points to a strong reason to do all this food production some of us are engaged in. Not even necessarily contamination but "questionable" food industry practices.

    I find some of the livestock feed ingredients, APPALLING!! Good goobly goop! I'm as frugal as most anyone but some of these things going into our laying hens and cattle would be better used as organic fertilizer! Or at least, would do more for my peace of mind and appetite.

    Of course, there's also a certain JOY to be gained from "production." Just surrounding ourselves with life is fun.

    I've long known the productive potential of greenhouses. They aren't 100% efficient of course. I am very reluctant to elevate my energy consumption by kicking that furnace on any earlier than March. And then, use just "plays out" in May when solar energy is just getting a good start.

    That feed conversion ratio I find enormously encouraging. Beef cattle require more than 8 lbs of feed to gain 1 lb of weight. Some of us are trying to limit our beef consumption because of that simple fact. Can we really afford the environmental, political, and economic costs of using so much grain to produce an animal protein?

    Laying hens may need a better quality feed than cattle but it only takes about 2.5 lbs of feed to produce 1 lb of eggs. Gardeners can probably lower that ratio by 30% without half trying.

    Tilapia have a very low "maintenance" requirement. This fish lives in very warm water and, like with all fish, suspension in H2O lowers the food energy needed for life. Further, the ability to stay healthy and grow on a plant-based diet, is a huge step up from some farmed fish.

    My problem with tilapia in the greenhouse looks to be more of a problem with the uncommon nature of this enterprise in the US. My only choice at the moment appears to be purchasing these fish by the tens of thousands! Maybe I just need to make inquiries.

    digitS'

  • windwhipped
    15 years ago
    last modified: 9 years ago

    It may be old age or too many bad fish, but it only now occurred to me that I recently read an article on tilapia farming. As you know, we here in WY are always on the forefront of new and environmentally concerned industries (ok, you can read sarcasm there), and in that vein apparently the women's prison in Lusk has begun a tilapia farming operation.

    I would link you to the article here, but I am ashamed to say I have never bothered to figure out how to link from this forum. But if you google "Lusk womens prison fish farming" the first thing up will be the article from the Star-Tribune. It does talk about them taking delivery on 7500 of the little devils, but also gives the name of the expert on fish farming who is helping them. Perhaps if you decide you really want to pursue this, you could contact him and ask about sources for small farmers, or if they would be willing to resell a small number for your start-up.

  • digit
    Original Author
    15 years ago
    last modified: 9 years ago

    WW, I'm thinking of a captive audience on both sides of the glass goldfish bowl . . .

    The article is interesting from a number of standpoints. I googled the, what was he, assistant warden who had experience fish farming but didn't find anything.

    The University of Arizona site that David posted took me to a supplier in New Mexico. This may be the same outfit the prison used and they halved their normal shipment to accommodate the Wyoming State Penal System.

    The fish went off to "finishing school" in North Dakota - of all places. But, I'd just read something about ND tilapia farming. An odd location for a fish that may not survive Florida winters outdoors.

    I may have had an idea for acquiring these critters. The Asian markets in Seattle sell LIVE tilapia! They'll clean them right there on the spot for you but that would defeat my purpose.

    If David's biggest tilapia was 17 lbs and 3 years of age, perhaps, a one-pounder would grow to 3 lbs in 5 months and $1.50 in feed. I'm just wondering. Of course, after I pay for a 600 mile round trip to carry a dozen fish home . . .

    U of A directed me to a 4 page pdf on "Tank Culture of Tilapia." The protein level of their feed is higher than I expected but their space requirement is smaller. U of A also has nutrition info. I'd need to look carefully at the vitamin content of something like "meat builder" for broilers to be sure that the fish would get sufficient levels.

    This may be too much of an undertaking to put in place by next month, I'm thinking. I've been getting busier & busier . . .

    d'S'

  • digit
    Original Author
    15 years ago
    last modified: 9 years ago

    DW picked up some frozen tilapia for me this morning. The "Trident" tilapia fillets from Costco are a "product of the USA."

    d'S'

  • digit
    Original Author
    15 years ago
    last modified: 9 years ago

    DW picked up some frozen tilapia for me this morning. The "Trident" tilapia fillets from Costco are a "product of the USA" it says on the box.

    d'S'

  • stansharpman
    14 years ago
    last modified: 9 years ago

    I raise tilapia in Kansas. It costs me about $1 a pound to grow most years.

  • david52 Zone 6
    14 years ago
    last modified: 9 years ago

    Hi Stan! Care to share your experiences?

  • markmahlum
    14 years ago
    last modified: 9 years ago

    I have recently been growing with hydroponics and the aquaculture concept looked quite interesting. I found a few informative, although basic videos concerning the topic on You Tube. One fish they raised in Australia was white perch.

    Mark

  • digit
    Original Author
    14 years ago
    last modified: 9 years ago

    It will probably surprise no one that I did not act on this idea, 2 years ago. But, I'm still buying and eating tilapia on a regular basis.

    Traditionally, farmers care for livestock during the winter and turn them out to pasture in the spring. The farmers then move on to the growing of field crops. I have this essentially backwards with the idea of using the greenhouse thru the summer and early fall for fish farming.

    It still makes sense to me but the long days of the growing season may just not be long enuf for me to have much time for this. Maybe if I start with babies in an indoor tank about Christmas . . .

    I'm also very interested in what you are up to, Stan. I may even be able to get the local pet shop guy interested, also.

    Steve

  • stansharpman
    14 years ago
    last modified: 9 years ago

    Hi David. I'll describe how I do things pretty basically, and then if you have any questions fire away.

    It takes about 6 months to grow a tilapia to a little over a pound, which is a good harvest size. High quality stock is very important when it comes to growth rates, and there is a lot more lousy stock than good stock available out there to the backyard crowd. I prefer Nile tilapia, particularly I prefer White Brook strain White Niles. Mozambique tilapia and hybrids involving them grow way too slow and their food conversion rate is terrible. Blue tilapia have a little better cold tolerance by a couple degrees, but they grow slower than Niles. Ultimately, it is about getting the biggest fish you can within a 5-7 month growing window (in my area, zone 5), and Niles beat Blues by a long shot in this regard. Good Niles that is. I like the White Brook strain because they are the fastest growers I've had (I've grown a LOT of different strains), and they are a white color with pinkish fins. They look more like a saltwater fish than a freshwater one, and this makes them very attractive to the customers I sell my surplus to. I sell my surplus fish to local customers at $5-7 per pound live weight. I sell fillets at $9-10 per pound. Most buyers prefer live or whole on ice, which is fine by me because it's less work for me!

    Mainly I grow them in 8'x2' stock tanks. They are about 640 gallons. I can grow about 300-350 pounds of tilapia per season in each one of these tanks, and I usually run 5 at a time. Filtration is extremely important if you do the recirculating route, which is how I do it... combined with a little bit of aquaponics too. Other methods are flow through using a pond, lake or well water as the water source or cage raising in a pond, creek, river or lake.

    I feed a specially formulated high protein diet for tilapia from Premium Fish Food Co that is rich in vitamins C, D and E until they get to 5 inches. It costs about $2.50 a pound, but it gives the tilapia a HUGE headstart in growth and disease resistance. It's money well spent. Once at 5 inches, I switch them over to catfish food at about 25 cents a pound and continue feeding this, supplemented with duckweed, black soldier fly larvae, worms, bugs, soy meal, shredded alfalfa and alfalfa pellets. I also grow them in greenwater (algae water) if the tank is not being used in my aquaponics setup. Tilapia are fairly decent filter feeders and they are omnivores but prefer plants and algae as they get older/bigger, so algae water is yet another food source for FREE.

    Before I process the fish, I purge them for 4 full days. I place them in a tank of crystal clear water with lots of aeration and withhold food for the entire time. This gets rid of any "off" or "fishy" flavor.

    Processing equipment is important to address also. Now, considering that I have to clean nearly a ton of fish in the fall every year, I can't stress enough how important a high quality electric fillet knife is! I like the American Angler Saltwater version (saltwater version is just a heavier duty knife than their freshwater one) and the Rapala brand knives (just don't get the cordless version... it's nice and I have one for "fishing trips" but battery life isn't long enough for this kind of job). Don't even bother trying to fillet this volume of fish with an old-fashioned fillet knife. You'll be miserable! I bathe the fillets in a salt brine for about 10 minutes before packing. I use a vacuum sealer for packing. I pack 6 fillets to a pouch usually. I also take it one step further. I flash freeze them using a cooler of dry ice. Once I seal them in the vac pouch I throw them in the cooler of dry ice.

    Links and resources:
    - White Brook Tilapia Farm - www.tilapiasource.com
    - Premium Fish Food Co. - www.premiumfishfood.com
    - American Angler Saltwater Knife - www.americananglerusa.com/products/saltwater/31300.php
    - Rapala Electric Knives - www.rapala.com/products/knives/electric_knives/

  • david52 Zone 6
    14 years ago
    last modified: 9 years ago

    Hi Stan - it sounds like you know what you're doing.

    So some questions - do you have any problem with those White Brook Tilapia reproducing in your tanks? Curious because thats often a problem, and I see they sell a mixed lot of males and females, the males growing considerably faster. Do you find the same?

    What temperature range is the water in your tanks, and do you need to do any supplementary heating or cooling? Reason I ask is that over 5-6 months, getting the water up to 75-80º might add a significant amount of weight, and you might accomplish that by some hillbilly engineering.

    When I did this commercially, we raised them in either fixed or floating cages. Cram them in around 250 per cubic yard and feed them a high-calorie supplement with 15% protein, they'd filter the algae in the water coming through the cages and get supplementary protein and all the vitamins and such.

    Dollar a piece for a 1/2 inch fingerling. Wow. Linked is an article about large scale fry production, I did all the stuff in Cote d'Ivoire, the Campbell, D. in the references. I used to have to deal with some taxonomical geeks - no matter what they call it, its all the same species of nile tilapia

  • digit
    Original Author
    14 years ago
    last modified: 9 years ago

    ". . . 8'x2' stock tanks. They are about 640 gallons. I can grow about 300-350 pounds of tilapia per season in each one of these tanks . . ."

    Wow, I could fit 2 of those under the bench in the greenhouse!

    That would be more meat (from any source) than this little household consumes in a year.

    Steve

  • stansharpman
    14 years ago
    last modified: 9 years ago

    David said "do you have any problem with those White Brook Tilapia reproducing in your tanks? Curious because thats often a problem, and I see they sell a mixed lot of males and females, the males growing considerably faster. Do you find the same?"

    A: If kept in high densities, spawning is extremely rare. The few that still manage to usually lose most of the fry to predation by the other adults in the tank. Another way to prevent spawning with mixed sex fish is to grow them in cages in the tanks. With larger mesh floors, they have nowhere to nest. If spawning is prevented or mostly prevented, the females will grow ALMOST as fast as the males, but they will still lag slightly. In my experience, even in lower density situations, these fish typically don't start spawning until 5 months of age, just a month shy of harvesting anyway. It is mostly a non-issue on a 6 month harvest cycle.

    David said "What temperature range is the water in your tanks, and do you need to do any supplementary heating or cooling? Reason I ask is that over 5-6 months, getting the water up to 75-80º might add a significant amount of weight, and you might accomplish that by some hillbilly engineering."

    A: I start fry out inside until they reach about 3 inches in plain old aquariums usually. I keep them at 80-84 degrees. 82 seems to be the sweet spot with them. Outside, my tanks will range from 72 in the spring to about 90 in the heat of summer, and then back down to about 68 in the late fall when I do my final harvesting for the year. I use a somewhat earth sheltered greenhouse for most of them, which helps to regulate temps a great deal. I usually overwinter about 500 fry minimum every year, but sometimes up to 1500 when I'm feeling up to it.

    David said "When I did this commercially, we raised them in either fixed or floating cages. Cram them in around 250 per cubic yard and feed them a high-calorie supplement with 15% protein, they'd filter the algae in the water coming through the cages and get supplementary protein and all the vitamins and such."

    A: As long as you start them out when young on a high protein diet, they will do good in such a situation. I have friends who simply stock them in their fishing ponds every year, and they don't even feed them. The fish simply browse on the diatoms, algae, vascular plant life and inverts already in the pond. They harvest some impressive fish in the fall when temperatures drop. The tilapia get lethargic and just hang out at the water surface making them easy to net up or cast net for them.

    David said "dollar a piece for a 1/2 inch fingerling. Wow. Linked is an article about large scale fry production, I did all the stuff in Cote d'Ivoire, the Campbell, D. in the references. I used to have to deal with some taxonomical geeks - no matter what they call it, its all the same species of nile tilapia"

    A: I buy some new stock just about every year to keep genetic diversity where it should be, but it doesn't require buying a ton of fish to do that (50 a year works fine). After I established my initial "colony" of fish, cost of stock has become largely irrelevant to my overall production costs. Sometimes I will buy a very large number of fish to stock (500+), and when I do that I buy at wholesale prices which are far less than what they ask for on small lots. Your last comment about "no matter what they call it, it's all the same species of nile tilapia" I'm unsure of what you mean. There are numerous strains within Oreochromis Niloticus that are VASTLY different. Recent studies have even shown that they carry different sex determinant markers (A good study from UMD is out there as well as one from Virginia Poly off the top of my head). This is generally indicative of distinctly separate evolution of various communities of fish (usually prolonged geographical separation), even if they are in the same species. In this case, one could quite easily argue that there are numerous subspecies of Niles (and other tilapia as well of course), and that many of them have quite different traits and requirements.

  • david52 Zone 6
    14 years ago
    last modified: 9 years ago

    Hi Stan - I think you're right on the sub-species being so different, particularly when isolated populations are manipulated, and there are some natural and forced hybrids that have occurred and gotten in the mix as well. I've been out of this now for some time, and its great to hear of the advances in knowledge about the fish and the techniques used to raise them. I think if you saw a Tilapia straight out of the Nile river or Lake Victoria, it won't look a whole lot like what anyone here is raising.

    A bit of history: In Africa, the taxonomy on all these cichlids were done originally on physical differences - number of gill rakers, jaw bone shape, and all that. Picture a bunch of old duffers in the British, French, and Belgian Museums of Natural History writing incredibly boring papers based on something floating around in formaldehyde, and then get into fights about it. Finally, when they ran into a problem with bones and stuff being identical but a different coloration and breeding habits, they got into calling them different things by the way they breed. All of which is, thankfully, water long gone under the bridge. Now we look at genetic markers.

    To get into naturally isolated populations of T. nilotica over in Africa- over the eons, there were lakes here and there, rivers going this way and that, and then it changed again, all the while leaving isolated populations in lakes and rivers.

    In West Africa, we used the strain from the isolated population in the Bandama River. So these fish had adapted to surviving in little mud puddles when the river dried up in the dry season. If they were stressed, they'd breed when they were 2 months old and 3" long. Put a bunch in a pond and 4 months later, you have a pond full of 3" female brood fish and fry, however the males would growing very well until the pond got so over-crowded. So our big push was 1) how to control the breeding and 2) get an all-male population. Even in a cage with no breeding, males would generally reach market size, a bit over a lb, 2 months ahead of the females. And even between the males themselves and the females, there were significant differences in growth rates. So the job turned into pretty much daily sorting tens of thousands of fish by size, using lift nets and grills and all kinds of stuff, sorting out the faster growing individuals in the population. Of course we kept the fastest growing ones and used them for breeding stock. Even in a short 5 years of selection, we saw a dramatic difference.

    After a while, I moved to Lake Victoria, the headwaters of the Nile. A whole different fish. Looked the same, but they wouldn't breed until they were nearly a pound. Still, the males grew considerably faster and bigger.

    And today, you've dealing with a fish that doesn't have any of these issues. This is fun to talk to someone who's up to speed.

  • digit
    Original Author
    14 years ago
    last modified: 9 years ago

    Here are some photo's that David sent me. As I understand it, they show some of what he was up to, as a fish farmer.

    I hope they come out okay (they have traveled 1 or 2 miles from where they were taken :o):

    {{gwi:1195269}}

    {{gwi:1195270}}

    {{gwi:1195271}}

  • david52 Zone 6
    14 years ago
    last modified: 9 years ago

    Thanks, digit! These pics are scanned from slides taken in the early 80's and are a bit faded. This is one of the better tilapia farms I built, worked out the kinks, and managed for a few years.

    Top picture is from the spawning ponds out to the cages, 2nd picture shows the extent of the cages, and the last, one of the mesh grills we used to sort fish. Each cage was 6m x 12 m, or roughly 19 x 37 feet, and held 10,000 tilapia, at harvest weighing 2 metric tons, or 4,400 lbs. We'd harvest one or two a week. The bottom picture is one of the workers holding a sorting mesh up, we'd put this in the middle of a smaller nylon net cage, empty a big cage into the smaller one with an underwater opening, then gently lift one side of the nylon net to 'encourage' the smaller fish to swim through the mesh. We had all kinds of different mesh sizes depending on the fish that needed sorting.

    The cages are in a lagoon that changed water level about 6" a day, no matter what the season. The cages are built with scaffolding poles, and we'd hook up a water pump to one end and with the water gushing out the other, drop them vertically into the sand.

    I hope this will entice Stan to show us his set up.-)

  • stansharpman
    14 years ago
    last modified: 9 years ago

    Neat stuff David. Thanks for sharing!