Does anyone have an idea what might be causing the brownish fish color and the better growth in the sump tank? Share Tweet. Views: The size difference could be food competition.
In tilapia, the more aggressive fish eat a lot more than the more passive fish. So a single fish could grow three times as fast as another, depending on how aggressively they compete for food.
That's actually an advantage if you want a high stocking density and continual harvest. Therefore, the Mozambique tilapia and some mossambicusderived red tilapia are preferred for saltwater culture. Some lines of the Mozambique tilapia reportedly have spawned in full strength seawater, but its reproductive performance begins to decline at salinities above 10 to 15 ppt.
The Blue and Nile tilapias can reproduce in salinities up to 10 to 15 ppt, but perform better at salinities below 5 ppt. Fry numbers decline substantially at 10 ppt salinity. The intolerance of tilapia to low temperatures is a serious constraint for commercial culture in temperate regions. The lower lethal temperature for most species is 50 to 52 o F for a few days, but the Blue tilapia tolerates temperatures to about 48 o F.
Tilapia generally stop feeding when water temperature falls below 63 o F. Disease-induced mortality after handling seriously constrains sampling, harvest and transport below 65 o F. Reproduction is best at water temperatures higher than 80 o F and does not occur below 68 o F. In subtropical regions with a cool season, the number of fry produced will decrease when daily water temperature averages less than 75 o F. Optimal water temperature for tilapia growth is about 85 to 88 o F.
Growth at this optimal temperature is typically three times greater than at 72 o F. Tilapia survive routine dawn dissolved oxygen DO concentrations of less than 0. In research studies Nile tilapia grew better when aerators were used to prevent morning DO concentrations from falling below 0. Growth was not further improved if additional aeration kept DO concentrations above 2. Metabolism, growth and, possibly, disease resistance are depressed when DO falls below this level for prolonged periods.
In general, tilapia can survive in pH ranging from 5 to 10 but do best in a pH range of 6 to 9. The first mortalities from prolonged exposure may begin at concentrations as low as 0. Un-ionised ammonia begins to depress food consumption at concentrations as low as 0. Nitrite is toxic to many fish because it makes the haemoglobin less capable of transporting oxygen; chloride ions reduce the toxicity. Tilapia are more tolerant of nitrite than many cultured freshwater fish.
Tilapia are more resistant to viral, bacterial and parasitic diseases than other commonly cultured fish, especially at optimum temperatures for growth. Lymphocystis, columnaris, whirling disease, and hemorrhagic septicemia may cause high mortality, but these problems occur most frequently at water temperatures below 68 o F.
Ich, caused by the protozoan Ichthyopthirius multifiliis , can cause serious losses of fry and juveniles in intensive recirculating systems. External protozoans such as Trichodina and Epistylis also may reach epidemic densities on stressed fry in intensive culture. In recent years the bacterial infection Steptococcus inae has caused heavy losses, primarily in recirculating and intensive flow-through systems.
Under good growth conditions, 1-gram fish are cultured in nursery ponds to 1 to 2 ounces 20 to 40 grams in 5 to 8 weeks and then restocked into grow-out ponds. To produce 1-pound to gram fish, common practice is to stock 6, to 8, males per acre in static water ponds with aeration or 20, to 28, males per acre where 20 percent daily water exchange is economically practical. After 6 months of feeding with good quality feeds, such ponds can produce 5, to 7, pounds per acre and 18, to 20, pounds per acre, respectively.
If grow-out cycles are longer than 5 to 6 months in an attempt to produce a more marketable size fillet there is a risk that offspring from reproduction of the few females that were unintentionally included in the all-male culture will have time to reach sexual maturity and overpopulate the pond. Consequently, a farmer who wishes to produce fish yielding 5-ounce fillets a 2-pound fish is often forced to add a second grow-out phase so females and fingerlings can be eliminated from the grow-out ponds, or to stock a predaceous fish with the males.
Dressout percentage on tilapia is relatively low compared to species such as trout and catfish. Tilapia generally have a dressout of 51 to 53 percent of live weight for whole-dressed fish head-off and 32 to 35 percent for fillets pin bones along the lateral line removed. For additional information about tilapia culture see SRAC publications , and Tilapias are native only to Africa; many states in the US consider them exotics or non-indigenous species and have restricted their transport and culture.
Tilapia are a good fish for warm water aquaculture. They are easily spawned, use a wide variety of natural foods as well as artificial feeds, tolerate poor water quality, and grow rapidly at warm temperatures.
These attributes, along with relatively low input costs, have made tilapia the most widely cultured freshwater fish in tropical and subtropical countries. Consumers like tilapias firm flesh and mild flavor, so markets have expanded rapidly in the US during the last 10 years, mostly based on foreign imports.
The reason for this seems to be rooted in temperaments between these two species. Wami tilapia tend to be more skiddish, whereas Blue tilapia can get so used to your hand that they let you "pet" them when the conditions are right. In fact, we regularly see Blue tilapia spawning at one end of a gallon aquarium, while we were working on the filtration at the other end, as if we weren't even there.
Of course, as any aquarist can tell you, every fish has its own unique "personality"; but generally speaking, the more harmonious the females and the more aggressive the male, the more reliable the spawning, and the more likely that the eggs will survive into fry.
At least as important as the readiness of the species to breed, and arguably even more important, is the purity of the species. Many people are confused about the scientific naming of hybrids.
For example, If you cross a male Nile, with a female Blue, scientifically speaking, the offspring should be called "blank" Nile Hybrid Tilapia, where the "blank" is any word that you choose. For example, Lakeway Nile Hybrid tilapia. Unfortunately, people don't do this.
Instead, they drop that inconvenient "hybrid" word, and just go with names like Lakeway Nile tilapia. Unfortunately there are huge problems with this practice when it comes to tilapia breeding. Improper naming causes confusion that leads to misidentification of tilapia, contamination of genetic lines, and unreliable rearing and harvesting parameters. This can result in catastrophic financial losses to tilapia farmers.
Now is a really good time for you to read our page on tilapia genetics. It will help you understand tilapia breeding colony species selection better than anything that we could re-write on this page. So seriously, go read it and come back. We'll hold your place on this page until you return. There are five species of pure strain tilapia common to tilapia breeding in the United States.
Blue tilapia are by far the easiest to manage for breeding purposes, as well as the most appropriate species for our overall average climate. Consider Nile a close second because what they lack due to their intolerance to cold water, they almost make up for with their ability to survive in poor water conditions, making them a good choice for the absentee tilapia farmer.
Mozambique would have to be the third pure strain species of choice, but only because Wami tilapia are incredibly finicky, and there's only very limited data on breeding Zilli tilapia. As far as cross breeding tilapia, the first and most famous hybrid is the Red tilapia. If you want more information on red tilapia, check out our tilapia myths page. A far superior cross that was developed in the late 50's, and brought to the United States in the late 70's, is a predominantly-male cross between specially culled strains of Wami and Mozambique.
Of course, it would take about 20 more years before tilapia farming took hold in the United States, so there was plenty of time to cull each species for the most desirable traits.
The results of these efforts are the Wami hybrids that we have today. Important Point: To cull a species simply means to take away undesirable traits from each subsequent generation by only breeding pairs with desirable traits. Genetic diversity and inbreeding is avoided by preventing spawning with previous generations. Done properly, it takes many years to bring a naturally occurring trait into dominance. Other hybrid crosses that get some mention on the Internet are "White Nile", which is a possible hybrid cross between a Blue female and a Nile male; and the Hawaiian gold, which is a possible line of Mozambique.
We say that these are "possible" because they appeared on the Internet a few years ago absent any scientific study or documentation, however the results are hypothetically possible. Neither of these tilapia are farmed to any measurable degree, regardless of what their re-sellers would have you believe. Is it possible that my male is not mature enough to fertilize the eggs yet? Tilapia females use mouth feel to determine if their eggs are properly fertilized.
Normally they will swallow any unfertilized eggs. However, the texture of the eggs in her mouth, and therefore the feel, can be masked by an out-of-range pH. In addition, the water temperature plays an important role in the incubation period of fertilized eggs. View active topics. My white tilapia turned dark gray. Moderator: editors. Posted: Tue Mar 11, am.
I recently set up a 55 gallon breeding tank and placed two of my smaller tilapia in it. The tilapia were very pale, almost white. I put a large flower pot in each end of the tank, facing away from one another. A few days later, I placed my largest tilapia in the tank. He was quiet for a day. I noticed that the water was in the 70's and put in a heater. The water temp is now in the lower 80's. The large tilapia I assume he's a male is now constantly badgering one of the smaller ones.
This tilapia has almost completely changed color. It is now gray with almost black striping. Is this stress? Is is something to do with mating? I noticed this sort of thing before myself. Not sure what causes it. I know the tilapia I have raised seemed to get more pigment as they matured. I have also noticed that bluegill, largemouth bass and channel catifsh all will be lighter almost white if they are in light colored muddy water.
On the flip side they become much darker in clearer or tannin stained black water like Florida in some spots. I would think it is some sort of a defense mechanism. I think it is quite normal.
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