MIT tests self-propelled cage for fish farming
September 3, 2008(PhysOrg.com) -- A self-propelling underwater cage developed and recently tested by an MIT researcher could not only cut costs for offshore ocean-based fish farms but also aid the movement of such operations into the high seas, avoiding the user conflicts and compromised water quality of coastal zones.
Fish farms account for more than half of the seafood produced globally; 40 percent of the seafood consumed in the United States is farmed in other countries and imported. However, very little of that comes from ocean-based farms.
In conventional offshore fish farming, cages are routinely repositioned to control disease. Stout towboats haul the enormous cages to another site, and both the cage size and typical propulsive inefficiency of boats make such movements very energy-intensive events.
Cliff Goudey, director of MIT Sea Grant's Offshore Aquaculture Engineering Center, is exploring a different approach to moving the cages. By placing large, slow-turning propellers directly on a cage, Goudey frees it from the normal constraints of a boat. His system uses a pair of eight-foot diameter, electrically powered propellers, with 6.2-horsepower underwater motors. The motors are powered through tethers to the surface attached to a diesel generator and a pair of motor controllers mounted on a small boat.
Recently he tested the approach at Snapperfarm Inc., an offshore fish farm in Culebra, Puerto Rico, that grows cobia in submerged cages. By fixing a pair of the propellers to the mid-depth of a 62-foot diameter Aquapod® fish cage in a horizontal line 9 feet apart, Goudey maneuvered the cage as well as any boat-based system.
"These tests demonstrate that the concept of mobile cage operations is technically feasible," Goudey says.
The project is funded by NOAA's Marine Aquaculture Program, aimed at demonstrating the technology needed to raise fish in the vast portions of the oceans that are too deep for conventional anchored fish cages. By operating while submerged and in predictable ocean currents, mobile fish farms need only a modest means of positioning to stay within planned trajectories.
Although the recent tests are promising, Goudey notes that "the economic feasibility [of offshore mobile fish farming] remains an open question, as only a very large-scale operation" could be viable.
However, "the utility of cage self-propulsion extends well beyond the futuristic application of ocean-going aquaculture," he continues.
For example, besides the use of self-propulsion for routine cage movements, the propellers have additional utility. Often, the limiting factor in cage stocking density is dissolved oxygen levels due to fish metabolism during slack water. The propellers provide a ready opportunity to supplement water flow through the cage during those brief events, thereby allowing larger crops of fish.
All involved in the testing were impressed with the performance of the propellers. Steve Page, CEO of Ocean Farm Technologies, developer of the Aquapod, says, "My opinion of the [propellers] is very high. I want to consider using them to help with future installations. There is also a growing demand for self-propelled harvest pens that may be a great market for this technology."
Brian O'Hanlon, founder of Snapperfarm, says, "I was incredibly impressed with the power and efficiency of the [propellers] and Cliff's ability to steer the cage. I see this technology having a broad range of applications in mariculture and other marine industries. This futuristic concept of farming the high seas just came one step closer to reality."
With the technical feasibility proven, Goudey is turning his attention to assessing the system's economic viability, both as a tool for routine cage movements in offshore fish farming and in a business strategy involving mobile cages associated with specific routes in concert with predictable ocean currents or tidal gyres. This future work will involve the collaboration of ocean modelers and aquaculture business people.
Provided by MIT
-
Engineers build first sub-10-nm carbon nanotube transistor
Feb 01, 2012 |
4.9 / 5 (33) |
30
-
Something old, something new: Evolution and the structural divergence of duplicate genes
Jan 31, 2012 |
4.6 / 5 (7) |
1
-
The hidden nanoworld of ice crystals: Revealing the dynamic behavior of quasi-liquid layers
Jan 30, 2012 |
5 / 5 (4) |
1
-
Stock market network reveals investor clustering
Jan 27, 2012 |
3.9 / 5 (23) |
8
-
Of microchemistry and molecules: Electronic microfluidic device synthesizes biocompatible probes
Jan 26, 2012 |
5 / 5 (2) |
0
-
How to calculate total compressibility in liquid porous solid system
6 hours ago
-
Need help reading 3-D
Feb 11, 2012
-
A way to send and receive wireless data
Feb 11, 2012
-
Calling function with no input argument
Feb 10, 2012
-
Force free body diagram problem on gym equipment
Feb 10, 2012
-
Empirical data regarding shower heads and water
Feb 10, 2012
- More from Physics Forums - General Engineering
More news stories
Google might launch Drive for cloud storage soon
(PhysOrg.com) -- Google's next big move, according to the Wall Street Journal, is a cloud storage service called Drive. Hardly first to the plate, Google is simply catching up to introducing its cloud reposi ...
Iran blocks email, restricts net access: reports
Iran has further restricted access to the Internet and blocked popular email services for the past few days, in a move a top lawmaker said could "cost the regime dearly," media reports said on Sunday.
7 hours ago |
5 / 5 (2) |
3
Love a click away in Indonesia's Twitter Republic
He was a geeky kid from Yogyakarta, she a glamorous city girl in Jakarta. In a country with one of the world's most vibrant social networking scenes they fell in love on Twitter.
15 hours ago |
4 / 5 (1) |
0
Walney offshore wind farm is world's biggest (for now)
(PhysOrg.com) -- The Walney wind farm on the Irish Sea--characterized by high tides, waves and windy weather--officially opened this week. The farm is treated in the press as a very big deal as the Walney ...
Navy to begin tests on electromagnetic railgun prototype launcher
The Office of Naval Research (ONR)'s Electromagnetic (EM) Railgun program will take an important step forward in the coming weeks when the first industry railgun prototype launcher is tested at a facility ...
Feb 06, 2012 |
4.5 / 5 (19) |
95
|
Scientists discover molecular secrets of 2,000-year-old Chinese herbal remedy
For roughly two thousand years, Chinese herbalists have treated Malaria using a root extract, commonly known as Chang Shan, from a type of hydrangea that grows in Tibet and Nepal. More recent studies suggest that halofuginone, ...
New method to examine batteries -- MRI from the inside
There is an ever-increasing need for advanced batteries for portable electronics, such as phones, cameras, and music players, but also to power electric vehicles and to facilitate the distribution and storage of energy derived ...
A mitosis mystery solved: How chromosomes align perfectly in a dividing cell
Although the process of mitotic cell division has been studied intensely for more than 50 years, Whitehead Institute researchers have only now solved the mystery of how cells correctly align their chromosomes during symmetric ...
Lab study raises questions over nano-particle impact
Tests involving chickens have raised questions about the impact on health from engineered nano-particles, the ultra-fine grains commonly used in drugs and processed foods, scientists said on Sunday.
Overeating may double risk of memory loss
New research suggests that consuming between 2,100 and 6,000 calories per day may double the risk of memory loss, or mild cognitive impairment (MCI), among people age 70 and older. The study was released today and will be ...
Starve a virus, feed a cure? Findings show how some cells protect themselves against HIV
A protein that protects some of our immune cells from the most common and virulent form of HIV works by starving the virus of the molecular building blocks that it needs to replicate, according to research published online ...