FRIDAY, FEBRUARY 5, 2010 UPWELLING AND UPWELLERS
If you want to grow a large volume of oysters you need to buy a bunch of seed and at $25/1000 a million oysters gets expensive. So this would be the first reason to have your own upweller. An upweller allows you to purchase seed directly from a hatchery at a much smaller size and price. Right now 1-2mm seed from a hatchery will run you anywhere from $7-9/1000 based on strains and genetic characteristics (triploid/diploid). Picture with penny shows 2mm seed.
Some hatcheries will even go a little cheaper by selling it to you a bit smaller say .5mm, this gets a little tricky for some because .5mm is SUPER SMALL!! This stuff acts like dust once it gets dry and will blow away.
What is upwelling and why does it work?
You can upwell or downwell; one moves water up, one moves water down...the diagram explains it better.
When you are trying to set spat on micro-culch (tiny pieces of oyster shell) to get single oysters a method known as downwelling is used and is most frequently a closed system (recirculating water). Once the spat are set upwelling is used and it can be an open or closed system but the methods we will refer to are all open systems or flow through. Upwelling brings a constant supply of nutrient rich water past your animals. All they need to do is open up and feed, which they do constantly as long as the food is in the water. This method produces hearty oysters in short order that continue to feed at a rapid pace when placed out on the farm. When running large quantities of oysters we recommend a combination of two systems, bucket upwellers for handling the small 1-2mm seed from the hatchery and larger floating upwellers for 1/4"and up. We upwell to a size that will seive off a 1/2" screen then it goes out to the farm. So if upwelling is so fast why not run the oysters up to a larger size? The answer is efficiency. There is a sweet spot between size and volume and once you start to get past the 3/4" size oysters you begin to run out of space rapidly and can run into ugly anoxic situations especially as the water heats with summer temperatures. Its doable but you will need more upwelling units or silo space.
Since our spat comes so small we use a bucket upwelling system first.
The two pictures above show the tank upweller that we build and sell. We do our own fiber glass work and the tank upweller can be purchased assembled ready to go, as a kit, or just the tank with or without holes.
Prepping to make a new tank mold
As you can see in the picture its a series of buckets (in this case literal 5 gal buckets) that have mesh in the bottom and hold the seed. The buckets are in 4'x10' tanks. Water is pumped into the tank from a submersible pump (low pressure high flow) which fills the tank and the only way for the water to escape is to pass up through the buckets, taking the algae rich water passed the young oysters. The water is then sent back into the bay. Bucket upwelling is a simple principle that can be applied to any size tank, container, or bucket. This method is great for handling small seed but in order to get speed and volume it is essential to move to a floating upweller system.
We recommend and offer our 27" version of the floating upweller system. 27" is the size of the silos in this unit. We can produce custom size silos, as we do our own glass.
Upweller float with doors ready to deploy
A floating upweller operates on the same upwelling principle as explained above but on a larger scale. In this case a fan pump removes water from a trough, the trough is filled back up by water flowing up and through 8 individual silos and the seed sits on mesh in the silos. The system sits in an 8 'x 20' floating dock and can handle 1 million animals/ per unit with ease.
A deployed upweller with doors up.
We run upwards of 10 million seed through our system in a nursery season and use three tank upwellers and four floating upwellers.
We use this many units so we can take large quantities of seed from the hatchery all at one time (4-6 million at a whack). If you can space out your seed purchases you can get away with fewer units.
Original method for rafting and tying up four units
Improved setup on pilings with rollers
Improved method with pilings installed so dock can move with the tide and waves and stay close to the pier. Also, note that we do not use doors, over the years we found them to be a hassle. Bins on dock are for water to adjust float height as it will vary based on salinity and load.
Bonuses to floating upwellers...
- cheap to run
- high rates of growth
- high animal capacities They are inexpensive to run because you are moving the water laterally so gravity and equilibrium take care of the rest of the work. We offer all of this equipment completely assembled, in kit form, or by individual components. Want the tank and get your own buckets or just all of the glass and you'll get the other hardware, we can do that as well.
8'x 20' FLOATING UPWELLER KIT
Kits include everything pictured above including the hardware and instructions so you can build the frame below (you purchase the wood, nails etc on your own).
Kits can also come with no floats or just with the glass with or without holes.
Also see the quicktube to sort oyster