PAES W.A.T.E.R. Center Oxygen Supply | Fish Swimming in Two Directions | Raises & Harvests Next Cohort of Fish | Tilapia Sampling in System D
PAES W.A.T.E.R. Center Oxygen Supply
April 18, 2017
Recirculating Aquaculture Systems (RAS) require either aeration or oxygenation to support the fish population. At higher fish densities and higher feed rates, there is a greater oxygen demand for the system, and aeration, with the use of air only, cannot provide the quantity of oxygen required to maintain dissolved oxygen (D.O.) concentration. In these cases, supplemental oxygen must be provided. In PAES W.A.T.E.R. Center, we have created an oxygen supply system for the entire building. Three sources of oxygen are used: (1.) electrically powered oxygen generator, (2.) high-pressure oxygen cylinders, and (3.) liquid oxygen storage cylinders, or ‘dewars’. These three oxygen sources are connected and managed to assure an uninterrupted oxygen supply to the building and our systems. Oxygen is injected into saturators that dissolve oxygen in the water supplied to the fish tanks, and oxygen is also available to maintain the D.O. concentration in the event of electrical power outages, or during sampling and harvesting activities. With high fish density and high feed rates that these systems experience, in the event of an interruption of the oxygen supply, D.O. levels can decline rapidly enough for fish to begin to die within 20 minutes. Take a look at our Live Video Camera at http://paeswater.com/live-events.html, and note the small tubes around the perimeter of the tank to supply backup oxygen to diffusers in the tank.
Fish Swimming in Two Directions
April 13, 2017
In PAES W.A.T.E.R. Center, while the water is very clear in Tank E1 (due to withholding of feed for purging and harvest), notice the swimming patterns of the fish. On our Live Video Camera at http://paeswater.com/live-events.html, you see fish swimming in two directions. Looking down on the tank, there is a current being created by the incoming water in a clockwise direction. This current is common in well-designed RAS and helps to move solid waste to the center of the tank, where it can be removed at the drain. The upper layer of fish is swimming with the current (clockwise), while the group of fish nearer the bottom is swimming against the current (counter- or anti-clockwise). Fish behavior of swimming against the current is natural behavior, orienting themselves upstream so that they can benefit from any food being moved toward them by currents and flow. In Tank E1, fish swimming with the current are resting, expending less energy, as are those fish gathered near the center of the tank where the current is slower. If you watch for a while, you will notice fish changing direction, moving from one layer to the other.
PAES W.A.T.E.R. Team Raises & Harvests Next Cohort of Fish!
April 7, 2017
On Friday, April 7, our PAES W.A.T.E.R. team harvested and sold about 250 pounds of live Hybrid Striped Bass (HSB). These fish had been purged in preparation for sale and live transport. Purging fish is a common practice in aquaculture in which feed is withheld for a period of time before moving fish, to allow the fish to empty their digestive systems, improve their flavor, and create less waste during live transport. An additional 600 pounds of HSB were moved from Tank E1 to begin the purging process for upcoming sales. Average size of the fish was 726 grams each, or about 1.6 pounds. These fish came to us in August 2016, and are on day 247 of this growout trial. Tank E1 is the main tank of our coolwater demonstration system, and is visible on our Live Video Camera at: http://paeswater.com/live-events.html.
Tilapia Sampling in System D
November 16, 2016
Check out some photos from our Tilapia sampling at PAES W.A.T.E.R. on November 15, 2016. The tilapia in System D weigh on average 720 grams (1.59 pounds). They have reached their target weight and are ready for harvest. We will update everyone on when the harvest is going to happen!
Please view more information for System D:
D1 = 2,798 fish @ 721 g (1.59 lbs) = 2,017 kg (4,437 lbs)
D2 = 1,015 fish @ 676 g (1.49 lbs) = 686 kg (1,509 lbs)
Green text is average weight of fish in each tank. Blue text is the total biomass is each tank.
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