SELECTIVE BREEDING OF JADE PERCH AND SILVER PERCH -
Although we follow a similar process for silver perch, on this page we only focus on jade perch.
We have been breeding our jade perch every year for almost 30 years.
|The fish on the left were selected from a harvest of 60,000 fry the size of those on the right.|
From the very beginning we noticed that sometimes a few fish were much bigger than the rest of the fingerlings harvested from the pond. We call these fish "shooters" and keep them for future breeders.
Originally we collected our breeders from the wild, from the Barcoo River, under special government permit. We collected wild fish for about five years until we were able to access breeders from our customers in Australia, who grow our fry to table size. (The fish we produced from wild brood fish we call F1, first generation from wild.) We were/are able to access their fish at first harvest and select the biggest of the crop to use as breeders. We used their fish with the shooters we had grown on for breeding. This was working very well for years. However, we were alerted by our customers in Asian countries to issues regarding slow growing, deformities, and disease outbreaks experienced in fish thay had been buying from hatcheries in Asia. These were not our fry, but fry produced from shipments we had sent years earlier. Those hatcheries had been breeding from those fish for several generations. After making enquiries with scientists here in Australia, the consensus was that qualities the wild fish have were being lost after several generations of breeding from such a small gene pool. This is usually referred to as "inbreeding".
Wild jade perch, (scortum barcoo) come from an area in Australia that has very little rainfall. The red area in the map below is the Lake Eyre Basin. The only place in the world where wild jade perch occur. The fish we produced from wild brood fish we call F1. True F1 fry or fingerlings can only be supplied from Australia, because only Australian hatcheries have access to wild fish under special permit. Conditions on this special permit forbid the sale of fish collected from the wild. We are not even permitted to give them away. They can only be taken directly from the wild to the licenced hatchery named on the permit. Guaranteed F1 fry are available to order. Prices here
Often this area only has rain once a year, sometimes several even years without any rain or water flows. The rivers in this area dry up to just a few water holes. When there are water flows the water conditions can change in a few hours. Temperature, turbidity, PH, oxygen levels etc, change very quickly. Food which was scarce during the dry can explode, becoming abundant. In effect a real famine to feast situation occurs. The fish that live in these areas have adapted survival strategies that help them thrive in these hostile conditions. Very high water temperatures can be experienced in summer, and relatively low temperatures during winter. Food is in short supply. Dissolved oxygen can be very low. Water can become clearer between rainfall or water flow events. During water flows the water is extremely turbid. If you put your finger into the water you literally can't see the end of your finger.
Most fish species would die, either directly from the poor water quality during dry periods, or the sudden changes in water quality, or from disease as a result of prolonged stress.
During the famine phase, jade perch have evolved to survive. This makes them ideal for aquaculture. They survive poor water quality, lack of quality food, and have great disease resistance. All perfect qualities for aquaculture. They also grow extra quickly during the "feast" conditions. It is during the "feast" conditions that they need to grow fast so they can reproduce. Their growth during the "feast" time is quite remarkable. Again, a very desirable aquaculture quality. By the way, these conditions generally occur in the warmer months. They have the ability to compete with several other species that also share their environment. One unusual example of how other fish have developed survival strategies is a catfish that lives in the same water as the jade perch. There are several catfish that are native to these waters, one of them I call the eye eater. It will pluck the eyes from any fish nearby. I conclude this is a survival strategy that has evolved because a fish without eyes can't eat your food.
What happens during the "feast" time. Local heavy rainfall or water flows from hundreds of kilometers away flood the dry river bed and surrounding areas. This results in an explosion of phytoplankton which provides food to support an equally significant explosion of zooplankton. This is the bottom end of the food chain that will support higher life forms such as shrimp, aquatic insects, and so on. The larger items of the food chain are what the jade perch thrive on and grow extra fast. Then they can breed, while the water is flowing. When the eggs of the fish hatch, they need the bottom end of the food chain, the phytoplankton and the zooplankton.
Wild fish go through harsh summer and winter periods, long dry times, and "feast" times. In aquaculture they are usually always in "feast" times. It appears that, over several generations they lose the ability to resist disease, and the fast growing qualities that they needed in the wild. They no longer need to survive like they did in the wild. Those good genes get lost. That's why we introduce a wild fish to our line bred fish to our gene pool, to keep those desired aquaculture qualities.
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