MYSTERIES OF TILAPIA SEX CHANGE

This article, while short in length, is substantial in its content for those who are serious about raising Tilapia and the most fish for their time and money.

3-inch-Tilapia2
A 3″ Tilapia but just give him enough to eat and watch out, he’ll grow like a weed!

This is the results I got from non-heat treated Nile Tilapia feeding floating Koi pellets twice daily with the fish being raised in algae-rich green water tanks.  From three (3”) inch fingerlings in August to eight (8”) inch males with the females being slightly smaller here at the end of December 2011.

There are always the midgets to cull as it would seem they are a different species altogether as they refuse to grow regardless of how much you feed them.  These I sell to the pet stores because they will never get big enough to be a problem for the typical aquarist.  It helps to offset the cost of the pellets even though I do feed them to the KOI also.

The tanks I used had flowing green water fed directly from and returned to the KOI pond and algae was allowed to grow on the sides of the tanks until you were no longer able to see inside the tanks.  The three (3”) inch fingerlings were then introduced and within less than three days they had reduced the algae growing on the glass to the point of almost a clean view.  They do love their algae.

When breeding your Tilapia you are always interested in producing more males than females because male Tilapia metabolic energy is directed toward growth while the female energy is directed toward reproduction and quick growth is what we are after.

TILAPIA
A good sized Tilapia ready for the dinner plate.

I have not had the chance to prove this theory as of yet, but offer up this analogy from the many articles I have read on the subject.

There are a number of ways to accomplish a higher production of male to female Tilapia however for this article those forms of conversion will be narrowed down to the simplest of all, heat treatment of Tilapia fry.

Heat as a means of triggering a particular sexual results in fish and reptiles is not new, however not a lot has been put into print about Tilapia and the results that can be expected.

The use of heat as a means of producing more males than females in Nile Tilapia can be done during the critical initial developmental period.  Exposure to an elevated temperature, as described below, for fry immediately after yolk sac absorption for a period of 10 to 12 days can increase the proportion of male to female ratio substantially.

In Nile Tilapia and possibly most Tilapia that temperature would be within a narrow range around 95°F (35°C) to 97°F (36°C) for said period of time then the thermostat should be set to a temperature range no lower than 80°F (27°C) and no higher than 85°F (29°C).

You will probably see your best results using a treatment of 97°F (36°C) as it appears to be the most optimal temperature for both sex reversal and survival of the fry.  At this temperature, you can hope to produce an approximate 89% ratio of males to females with the best fry survival rate at approximately 90% prior to culling.  At 99°F (37°C) there is little change in sex reversal however the fry survival rate will be reduced drastically.

These temperatures must be monitored constantly and you must stay within the range prescribed in order to obtain the optimum results as described above however as with nature, there is no guarantee of success.  Considering a survival rate of untreated fry after the malformed individuals have been culled being approximately 85%, you be the judge if it is worth the effort.

 

This article, while short in length, is substantial in its content for those who are serious about raising Tilapia and the most fish for their time and money.

Leave a Reply