Navigation Links
When fish farms are built along the coast, where does the waste go?
Date:2/15/2009

If you are a fish eater, it's likely that the salmon you had for dinner was not caught in the wild, but was instead grown in a mesh cage submerged in the open water of oceans or bays. Fish farming, a relatively inexpensive way to provide cheap protein to a growing world population, now supplies, by some estimates, 30 percent of the fish consumed by humans.

Two hundred and twenty species of finfish and shellfish are now grown in farms.

Intuitively, it seems a good ideathe more fish grown in pens, the fewer need be taken from wild stocks in the sea. But marine aquaculture can have some nasty side effects, especially when the pens are set near sensitive coastal environments. All those fish penned up together consume massive amounts of commercial feed, some of which drifts off uneaten in the currents. And the crowded fish, naturally, defecate and urinate by the tens of thousands, creating yet another unpleasant waste stream.

The wastes can carry disease, causing damage directly. Or the phosphate and nitrates in the mix may feed an algae bloom that sucks the oxygen from the water, leaving it uninhabitable, a phenomenon long associated with fertilizer runoff.

It has been widely assumed that the effluent from pens would be benignly diluted by the sea if the pens were kept a reasonable distance from shore, said Jeffrey Koseff, a professor of civil and environmental engineering and co-director of Stanford's Woods Institute for the Environment. But early results from a new Stanford computer simulation based on sophisticated fluid dynamics show that the icky stuff from the pens will travel farther, and in higher concentrations, than had been generally assumed, Koseff said.

"What we've basically debunked is the old adage that 'The solution to pollution is dilution,' " he said. "It's a lot more complicated."

The computer modeling (with new Stanford software that goes by the acronym SUNTANS) was conducted by Oliver Fringer, an assistant professor of civil and environmental engineering. He created a virtual coastal marine area resembling California's Monterey Bay.

Previous software, he said, has not been up to the task of accurately predicting where the unhealthy effluent from fish pens will end up, and should probably not be used by state or federal regulators when they approve locations for fish farms.

Existing software is typically derived from models that attempt to describe the drift of effluent from sewage outfall pipes, even though the substances and situations are different from fish farms. (Sewage outflow, for example, is often warmer than the ocean water.)

The fine details of modeling the flow of dissolved fish poop from a submerged cage are not as simple as they may seem. The design of the cage itself can affect the outcome. How much of the current flows through the cage, and how much goes around? Does the moving water swirl into eddies at the edges of the pen? Even the effects of the rotation of the earth on the waste plume comes into play.

The fish farmer would prefer that currents flush out his pens frequently, but as those currents take out the garbage they might unfortunately deliver it to a mangrove ecosystem or a public beach. On the other hand, insufficient flow through the pen can create a "dead zone" on the ocean floor as the fecal matter and uneaten food pile up beneath the fish.

Fringer is designing his software so that it can be used to asses any sitePuget Sound, perhapswhere sufficient digital mapping of the area already exists. SUNTANS comes just in time, said Stanford oceans expert Rosamond Naylor, as federal and local officials begin spelling the details of new health and environmental regulations for fish pens.

Also participating in the research was former postdoctoral researcher Subhas Karan Venayagamoorthy, now at Colorado State University.


'/>"/>

Contact: Dan Stober, Stanford News Service
dstober@stanford.edu
650-721-6965
Stanford University
Source:Eurekalert

Related biology news :

1. The power of multiples: Connecting wind farms can make a more reliable - and cheaper - power source
2. Fish farms drive wild salmon populations toward extinction
3. Turning freshwater farm ponds into crab farms
4. A win-win: U-pick pumpkin farms recycle urban leaves
5. Tilting at wind farms
6. Built-in exercise monitor predicts fitness
7. A built-in strategy for transgene containment
8. New grants will support research in the sustainable built environment
9. Adaptation to parasites drive African fishes along different evolutionary paths
10. Unfavorable ocean conditions likely cause of low 2007 salmon returns along West Coast
11. Underwater microscope helps prevent shellfish poisoning along Gulf Coast of Texas
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/2/2016)... Calif. , Feb. 2, 2016  Based ... market, Frost & Sullivan recognizes US-based Intelligent Retinal ... Frost & Sullivan Award for New Product Innovation. ... in North America , is ... the rapidly growing diabetic retinopathy market. The IRIS ...
(Date:1/28/2016)... Jan. 28, 2016 Synaptics (NASDAQ: SYNA ), a ... its second quarter ended December 31, 2015. ... of fiscal 2016 increased 2 percent compared to the comparable quarter ... of fiscal 2016 was $35.0 million, or $0.93 per diluted share. ... income for the first quarter of fiscal 2016 grew 9 percent ...
(Date:1/22/2016)... DUBLIN , January 22, 2016 ... has announced the addition of the  ... to their offering. --> ... of the  "Global Behavioral Biometric Market ... --> Research and Markets ( http://www.researchandmarkets.com/research/4lmf2s/global_behavioral ...
Breaking Biology News(10 mins):
(Date:2/4/2016)... China , Feb. 4, 2016 Beike ... and various medical institutions attended a ceremony in late ... integrative, personalized cell therapy in 2016. ... "Shenzhen Clinical Translation Platform for Personalized Cell Therapy" was ... Regional Cell Production Center, both subsidiaries of Beike Biotechnology ...
(Date:2/4/2016)... and MENLO PARK, Calif. , Feb. 4, ... and the "Company"), a biopharmaceutical company focused on the development ... will present at the 18 th Annual BIO ... at 10:00 a.m. EST in New York, NY ... and CEO, will provide an update on the ongoing clinical ...
(Date:2/4/2016)... Feb. 4, 2016 ContraVir Pharmaceuticals, Inc. (NASDAQ: ... development and commercialization of targeted antiviral therapies, announced today ... Conference 2016, to be held February 8-9, 2016, at ... 2016 Disruptive Growth & Healthcare Conference, taking place in ... 2016. James Sapirstein , Chief Executive Officer ...
(Date:2/4/2016)... BEIJING , Feb. 4, 2016 Sinovac ... ), a leading provider of biopharmaceutical products in ... committee of its board of directors received on February ... 3, 2016, from a consortium comprised of PKU V-Ming ... Sinobioway Biomedicine Co., Ltd., CICC Qianhai Development ( ...
Breaking Biology Technology: