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Fingerling grading

A guide by Lakeway Tilapia

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Tilapia Fingerling Grading

Three grades of tilapia fingerlings

Some tilapia are excellent for farming and production, some tilapia are perfect for aquaponics systems, and some tilapia are best suited for pond cleaning. To use a tilapia that is best used for one purpose, in a way that another would be better suited, will pay you back with poor results. For example, I would make a terrible athlete. You could put me on your ball team, but then you'd suffer the consequence of my poor performance and your poor choice. Here's a quick lineup of the tilapia ready to join your "team", along with a quick description for what each is best suited.

  • Fast Growth Rate - Also known as food grade. These predominantly male tilapia are the only grade suitable for farming and commercial production. Fast growth rate is required for commercial tilapia farming to be profitable, due to the size attained during their 240 day period of accelerated growth. Only about 30% of tilapia are considered to be fast growth rate.
  • Mixed Growth Rate - Also known as aquaponics grade, or medium growth rate. These are best suited for aquaponic systems and backyard tilapia farming when having the tilapia reach their harvest size at different times is preferred. This allows aquaponics growers to maintain a constant supply of nutrients for their plants, and allows backyard tilapia farmers to eat a few at a time, while the rest continue to grow. They are also preferred for home breeding due to a more even mix of males and females. They are a About 40% of tilapia fall into this growth rate.
  • Slow Growth Rate - Also known as pond grade, these are slow growing predominately female tilapia. They are well suited as pond cleaners, and in large quantities they will consume significant amounts of algae, and other nuisance vegetation. Because of their smaller size, they tend to ignore larger aquatic plants in favor of finer algae. They can take years to grow to a harvestable size, which also makes their filets far more gamey than their faster growing siblings. About 30% of tilapia are slow growing; about half of which are runts, that will never grow larger than six inches.

Note: There is an alarming number of slow growth rate hatchery rejects being given away by tilapia farms only to re-appear on the Internet being peddled as "tilapia fingerlings". Even worse, some of these sellers are breeding these slow growers, helping to further propagate the dominance of their undesirable traits. While most of these sellers market their fish on Ebay, there are no shortage of those who have nice looking websites. The only weapon you have against these people is your own intelligence. Chances are, if their website only contains places to spend your money, or they are on Ebay, you are not getting what you are paying for.

Understanding the 240 day accelerated growth period

For years, commercial tilapia farmers have trusted Lakeway Tilapia to deliver fingerlings with the fastest rates of growth. But why does it matter? Well, get ready to think like a commercial tilapia farmer and we'll show you.

As human beings, we are familiar with the relationship between puberty and accelerated growth. Our early teen years were spent out-growing our clothes on a nearly monthly basis. Tilapia have a similar period of accelerated growth, it just happens at a different time of their life. As a human, I started growing really fast around 13 years old, until I was about 16. Tilapia start growing very fast on day one, and continue to grow at a decreasingly accelerated rate until about day 240. After which, their rate of growth slows down considerably.

Note: We use the term 240 day accelerated growth period to help you understand what is happening physiologically with tilapia. It comes from a commercial tilapia farming term that refers to our food grade or fast growth rate tilapia as 240 day growers. If you've ever looked at a seed catalog, the days to harvest for every crop is listed; it's the same for tilapia. Farmers are dependent on this kind of information for their success. The important thing for you to remember is that all tilapia have this same period of accelerated growth, the difference is in the amount of weight that each will gain during this period.

So let's say that you are a commercial tilapia farmer, and you get a delivery of 10,000 fingerlings from Lakeway Tilapia. We send you fast growth rate fingerlings that are all 45 days old. You can already calculate the exact amount of food that you will need to get you fingerlings to harvest size, and you can even count 195 days ahead on your calendar, to get the exact harvest date. For you, there are no mysteries. You can arrange for processing months in advance, and even pre-sell your harvest before you receive your fingerlings. So why not just keep them longer if they aren't fast growth rate? Good Question.

After the 240 day period of accelerated growth, the amount of food that is converted into weight gain drops considerably. So a tilapia that previously converted one pound of food into 16 ounces of weight gained in its first 240 days, might take another year, and several more pounds of food, just to gain just a few more ounces. The economics just aren't there. This is why most commercial tilapia farmers harvest soon after 240 days, with an average weight of around 20 ounces for pure strain Blue and Nile species.

For the new tilapia farmer who shops by price only and falls prey to the lower cost of unsorted fingerlings, the results will be much different. The 240 day accelerated growth period is still in play, but the rate at which each tilapia will grow during that period is completely unknown. Some will naturally be fast growing, however without any reliable feeding statistics for the entire group the potential of the fast growers will never be unlocked. Of course, there will be a bunch of slow growers too. They will munch away at the food budget, eating about the same portions as everyone else, but never paying the farmer back in harvestable filets. Most of their fingerlings will not grow to a minimally harvestable size before their internal clocks set their growth rate to a crawl.

The true cost of tilapia fingerlings

A harvest size tilapia is about 45% edible. So a 20 ounce tilapia will yield two 4.5 ounce portions. Tilapia sells for $4.99 per pound in our local grocery store, so I'll use that amount for my calculations. This puts the grocery store price of our two 4.5 ounce filets at $2.81. It costs about .80 cents worth of commercial tilapia feed, and a few more pennies for electricity and maintenance, I'll go with five cents, to raise our 20 ounce tilapia. It started out as a food grade, fast growth rate fingerling, that cost us $1.40 from the hatchery. So the final cost of our tilapia dinner is $2.25. That's a dollar less per pound than our grocery store price for fresher, cleaner and healthier tilapia.

Now let's try to save some money by starting out with random unsorted fingerlings that cost us .80 cents each. Instead of all of them growing to 20 ounces in 240 days, only 30% of our fish grew to a harvestable size. Another 30% have barely grown to 8 ounces, and the remaining 40% are a mix of fish between 8 and 16 ounces each. During the first 240 days, each fish still cost us .85 cents plus the .80 cents that we paid for each one. But now only 30% are at an acceptable size. So our effective cost for this "first" harvest is $5.50 per fish. There will be a second harvest several months later when the middle 40% have grown a bit more, but this will incur even more rearing and feeding costs. The cost per fish for this second harvest is much less at only .85 cents each. There probably won't be a third harvest because the 30% that remain are growing so slowly that they could take years to raise.

So comparing this to our first example, our two 4.5 ounce filets now cost us an average of $3.18 instead of $2.25. Stated another way the cost is $5.64 per pound versus $4.99 per pound. The .60 cents per fingerling saved up front, now winds up costing us .66 cents more as well as several months of lost productivity while we wait for the slower growing fish in our ponds.

The true cost of tilapia fingerlings can't be reconciled until after the filets have been processed. The investment of feeding, heating, and maintenance; as well as the cost of employees, or the time value of the owner/operator, is far greater than the difference in the initial price paid.

Important note: For those commercially minded people who are asking "Where's the profit?", please bear in mind that commercial farms buy several thousand tilapia fingerlings at a time for an effective price of between .11 cents and .45 cents each. They also buy tilapia feed by the ton at a significant discount.

Grading tilapia fingerlings

This is an aspect of the farming that you can really get yourself involved with if you wanted. There are research papers available on the Internet, and you can even subscribe to the Journal of Applied Aquaculture, if you want to feed your inner egghead. Luckily for you, by virtue of the fact that we are an operating hatchery, we stay on top of this sort of stuff, so we'll give you the highlights.

Before tilapia fry can be graded, their largest siblings, about 5%, must grow out of their fry stage into fingerlings. We already have a page about fry and fingerling development, so there's no sense in repeating it here. There are however, a few procedures that must be followed prior to grading in order to keep the results accurate. The main ones are:

  • The entire brood must be kept together, in the same container, and not mixed with the offspring of other breeding females.
  • The brood must be fed the proper type and amount of food.
  • The brood must be kept in perfect water conditions: pH of 8.0, temperature of 85 degrees, etc.
  • The brood must get 18 hours of light every day set on a timer.

All of these steps and more ensure that each individual tilapia will grow at it's own maximum rate and will be easy to compare to the others when they are graded. When the time comes to grade the tilapia, here's the process in a nutshell:

  • Put the entire brood on the sorting table. Which is basically a big white plastic table with a thin layer of water that contains channels and holes.
  • Estimate the total number of fingerlings and fry on the table.
  • Using a plastic wand, move the largest 30% of the tilapia down a channel and into the appropriate hole where they are deposited into a container of water. This includes both fingerlings and large fry.
  • Get a new container and repeat the process for the smallest 30% of the brood.
  • Finally, put the remaining fish into a third container.

Now you have three containers of fingerlings, all from the same brood, and you have successfully graded your tilapia.

Important point: Do not confuse this level of visual length grading with width grading. Proponents of width grading use grader boxes or panels to trap wider fish, while allowing slimmer fish pass through. This method does not consider the age of the tilapia or if they are from the same brood. An older pond grade will get stuck on the same side as a younger food grade tilapia. Some old time hatcheries, resistant to modern methods and changes in tilapia farming economics, have been touting this method as a way to confuse the issue of grading altogether. Grading by visual top down length, as outlined above, is the only way to determine food grade from the other grades.

All of this grading and sorting is primarily done to satisfy the requirements of our hatchery customers, however it is also of tremendous benefit to the tilapia themselves. Even with our rapid growth, predominantly-male hybrid fingerlings, some individuals will still grow faster or slower than the rest. This is mostly due to natural genetics, but competition for food amongst the larger individuals, further exacerbates the situation for the smaller tilapia. By grading the fingerlings according to size, we actually give the smaller tilapia a much better chance of growing at their own maximum rate, albeit a slower rate than their larger siblings. Most will eventually get to a harvestable size; it will just take them a bit longer to get there. We know of at least one published article that recommends to hatchery managers that they destroy the slowest growing fingerlings, but this inhumane practice against these otherwise perfectly healthy tilapia is unforgivable. Slow growing tilapia make great pond cleaners, and can even be utilized in micro aquaponics systems, where the focus is more on vegetable growing and not so much on tilapia farming.

There is also some bad information on the Internet (no surprises there) which incorrectly blames the fact that female tilapia grow slower than males, on another unrelated fact that females do not eat while carrying eggs and fry in their mouths. This is a prefect example of someone incorrectly connecting the dots, and then presenting their best guess as an authoritative fact over the Internet. So let's put this one to rest. It has been researched and published that female tilapia, even when isolated from males with no possibility of spawning, do in fact tend to grow slower on average than males. This is due to a genetic trait that is more common in female tilapia.

Thinking point: This is also why using sex reversal hormones in an effort to increase growth rates doesn't work.

It would be accurate to say that we do all of this sorting in our hatchery as a quality control measure, intended to provide the most reliable and consistent product to our tilapia farming customers. It is also important for all tilapia farmers to understand that there are minor genetic differences in each tilapia, that can cause every individual to grow at a slightly different rate within their own grade. While we do quite a bit in our hatchery to group the faster and slower growing fingerlings and fry together, they are not clones of each other. Later on, during grow-out, there will be more opportunities to sort the tilapia. As in all living creatures, including humans, every tilapia is slightly different. Their growth rate can also change based their own internal genetic mechanisms, and environmental conditions.

On the tilapia farm, grading by rate of growth can give the tilapia farmer a serious economic advantage over the competition. The sizes of the tilapia during grow-out will vary slightly as they mature, and individual feeding requirements will become more and more difficult to meet. This will suppress the growth rate of the smaller tilapia, due to renewed competition for food amongst the largest individuals. Grading allows for a "precision" approach to tilapia feeding that can result in a significant savings of costly tilapia food. The decision of how often to grade, or even whether or not to grade at all, rests with the tilapia farmer. For some farmers, further grading might be impractical, or competition from other tilapia farms might not be an issue.