What are the main features of GMT^®

GMT^® was first developed in the Philippines, the World's third largest producer of tilapia. A series of on-farm trials of the first release of GMT^® was conducted in the Philippines, including all major types of culture system ranging from extensively managed earthen ponds through to intensive, tank based farms. The GMT^® proved to have excellent properties for aquaculture, producing, cost effectively, significant increases in yield of uniformly sized fish and controlling reproduction in all the culture systems (Figure 1). YY males proved to be as viable and fertile as normal males.

Fishgen, with its associates, is the only organisation that has been able to produce YY males in large numbers and they are now being used commercially to mass-produce high yielding GMT^® in a number of countries. GMT^® produces higher yields, through a combination of enhanced survival and faster growth rates, in all the farms on which it has been tested. These higher yields were accompanied by better food conversion ratios and greater size uniformity, factors that also contributed to the improved profitability of culturing GMT^® compared to other available stocks. GMT^® have shown similar increases in performance in intensive culture systems in other countries. 

We are often asked about the performance of GMT^® with questions such as "will it grow to 600g in 9 months?" or "how big does it grow?". These question are very difficult to answer as growth rate and performance are, of course, determined by a combination of factors including genetic quality of stock and the type and intensity of the production system. We do not, for this reason, give figures on production of GMT^® in our publicity material. What we do say is that, based on our research and on feedback from clients, GMT^® will outperform comparable mixed sex or hormonally sex-reversed fish in the same system. However, we can give some typical results as follows: · 

We have also seen older GMT^® weighing over 5kg so clearly the fish does have the capacity to grow to a large size. GMT^® has fillet yields in the region of 36-39%.

Figure 1. Summary of comparative harvest characteristics from GMT^® and controls (either mixed sex tilapia - MST or hormonally sex reversed male tilapia - SRT) from 18 completed on-farm trials in a range of Philippine tilapia production systems. Values represent percentage difference of GMT^® compared to the two types of control fish. 

Figure 2. Photographs showing a typical harvest of GMT^® (left) compared to mixed sexed tilapia (right) resulting under identical culture practices in pond trials in the Philippines. In the mixed sex culture (MST) note the irregular size of the stocked fish and the presence of fingerlings.