Jade Perch Info
The members area has detailed information about jade perch, including growing and disease management. click here
It all starts with the eggs hatching. In this YouTube video you can see the larvae breaking out of the egg shells.
YOUTUBE HERE https://www.youtube.com/watch?v=uu39J-Sq_bs
SEE jadeperchman on YouTube
The marketing name, "JADE perch" was chosen because of the distinctive greenish, (JADE) colour displayed by the fish as the light catches the dorasl area scales. The name was chosen by the worlds FIRST 3 pioneer growers of Australian JADE perch while sitting around the kitchen table of the, then president for the Aquaculture Association of Queensland Inc., Bruce Sambell. (The JADE PERCH MAN.) The common, local name, was Barcoo Grunter, which does not sound as pleasant as JADE perch.
They eat very well and have a firmer, slightly flaky flesh than Silver Perch. They grow extremely fast and are highly suited for aquaculture in areas with a moderate sub tropical to tropical climate. They are also proving to be a good species for recirculating aquaculture systems. (RAS) (Unlike silver perch which are very difficult to grow beyond a few hundred grams in a RAS.) The fish come from a very hostile environment. Fish in Australian rivers must be able to cope well with the “feast and famine” nature of many of the river systems in Australia. These rivers can be dry for months, even years. Large water holes are the surviving refuge for many species of Australian native fishes, especially JADE perch. The fish in these water holes predate on each other for survival. After flooding the natural food supply for these fish is abundant. This glut of food is a contrast in the extreme compared to a drought situation where the fish will find getting a feed very difficult. Also during the cooler water temperatures experienced in winter (usually the dry season) the fish are less active and probably rarely feed. The stored fat will be used to help the fish survive in these situations. In aquaculture, fish are grown in an artificial environment such as a commercial fish pond or a RAS. They are in fact being kept in a “feast” situation. The fish grow rapidly and store fat as quick as they can, to be ready for the “famine”, which never comes in a controled aquaculture situation.
This fish sure has a great place in commercial aquaculture !
Purging or "finishing"
Some people can detect a taste that they describe as “off flavour”. Freshwater fish are often referred to as having a weedy, muddy or off-flavour. There are 3 chemicals responsible for these tastes. The weedy taste is usually caused by the algae present in ponds where the fish were raised, as is the muddy flavour caused by turbid water in pond raised fish. None of these are harlmfull, just not pleasent to the tast. Obviously this is very undesirable. The chemicals that cause these off flavours are concentrated in the skin and fat of the fish.
The remedy is simple. If the fish are held in very clean water for a few days these flavours can be removed. Generally the purging, or finishing time is 7 days, sometimes longer. It is recommended that before fish are sent to market that the grower taste test 2 or 3 fish from each batch. If there are no “off flavours” present, the product can be said to be “finished,” or market ready. When properly purged of these off flavours, these fish have excellent table qualities. The flesh is white, slightly flaky, and has a delicate, melt in the mouth texture. A tip when cooking, is to cook a little longer that you might many "sea" or salt water fish. The longer you cook them the firmer and drier the flesh will become. As a freshwater fish, the fillet is a lot more moist than salt water fish. If not cooked for long enough, the fillet can be a little "mushy" in texture. Too soft, and too moist. Another tip... The chemicals that cause these off flavours are concentrated in the skin and fat of the fish. A skin off fillet will always tast the best.
Some people believe the purging of the fish in salted water makes the flesh taste better. This is not scientificly supported. There is no actual change in the texture, or flavour of the fish due to the salt content of the purging water. Although the salt in the purging water is of great benifit to the fish, (I have always said salt is the asprin of aquaculture, and should always be used when handling fresh water fish. In fact if a professional grower, or hatchery operater did not use salt, he makes things difficult for himself, and his fish.) it actually has no biological effect on the flesh. The salt content of the fishes body, including the mussel tissue will always be the same through the fishes ability to *osmoregulate the salt in its body. There are exceptions such as barramundi, but jade and silver perch undergo NO changes when kept in high levels of salt. Too little, or too much salt will stress the fish. When handeling live fish, such as harvesting, the fish become stressed, and lose salt to their "freshwater" environment. A little salt added to their water is extreamly helpful. I recomend 2 to 5 parts per thousand, (ppt). That's 2 to 5 grams per liter. A salt content of 10ppt will result in stock losses for jade and silver perch. At levels above 10ppm the fish experience difficulties balancing the salt levels in their bodies. No matter how much salt you add to the water, the fish will try to regulate the salt content of their bodies. This is known as osmoregulation. Osmoregulation is the regulation of a cells fluids. It keeps the mussel tissue of the fish from becoming to dry or becoming to fluid. It regulates the salt content and what waste to get rid of and what to keep) The salt in the purging water does help the fish to purge their gut, and helps with parasite management. It is also a mild antiseptic. It also acts as a mild anaethetic keeping the fish calmer. For greater detail on the use of salt and other chemicals to manage and treat disease go to the members area. click here for more
The amount of fish that can be produced in a pond is greatly dependant on aeration, and water temperature. The higher the temperature the lower the oxygen. Put simply, this is because less oxygen can be dissolved in water at higher temperatures. The fishes demand for oxygen is also increased as the temperature of the pond increases. The higher the temperature the greater the metabolic rate of the fish. From the farmers point of view, they grow faster, BUT, generally for every ten degrees that the temperature increases, the fishes metabolic rate doubles. Therefor without aeration less fish can be produced in the same area. Since Australia JADE perch grow twice as fast as Queensland Silver Perch at higher temperatures, they require more aeration. As a rough guide a one acre pond with one 2hp paddle wheel will grow about 5-6 ton of Australian JADE perch. Some produces believe that this size pond is not well suited to two paddle wheels. If a 1.25 acre pond is used two paddle wheels can be used to best advantage to raise 6-7 ton of fish.
How big do they get?
We actually don't know the answer to this question just yet. In their natural environment, they don't get anywhere near as big as the one in these pictures. The fish in these pictures weighs 3.2 kilo. This is an aquacultured fish. (Note the "plate friendly" shape.) They just don't get this big in the wild. Is this probably because they don't get a chance to live long enough, or the conditions are not good enough, not enough food and too cold in winter? Another consideration is improved genetics. For many years the breeders have been selected for their fast growing qualities. The slow growers are never used as breeders. This will be having an influence on the potential size of the off-spring. It will be a few more years before we have the answers to these questions.
For detailed information about growing jade perch, and their health management (Disease management.) go to the members area of this web site.
Below left the Gut of a wild JADE perch with all organs visible and NO fat. RIGHT an aquacultured JADE perch which has been fed on a diet perhaps a little too rich. No organs are visible through the fat.
*Keeping the osmotic pressure, the salt in their cells, in freshwater fish is a constant battle and will result is serious stress to the fish if not managed by the grower, or hatchery operator. Fresh water fish constantly face two kinds of problems, they gain water passively through their skin due to osmotic gradient, and continually lose body salts to the surrounding water of much lower salt content. Osmoregulation in fresh water fish is affected by pumping out excess of water from their bodies. The salt loss through the excretion of water is made good by salt absorbing gills, skin and various parts of the alimentary canal.