Saturday, December 11, 2010
The Geoduck is a species native to the Pacific Northwest. It is a very unusual animal – a large saltwater clam with a siphon that can reach over three feet in length and weigh up to fifteen pounds. “Geoduck” is a Lushootseed word that means “dig deep”. The Geoduck is an important part of coastal Native American aquaculture. It is also considered by some to be an aphrodisiac.
Geoducks are now harvested commercially and eaten all over the world. Bivalves are beneficial to our coasts, but we must ensure that the tides are clean and that we do not exploit the coasts when we grow Geoducks commercially. We can learn a lot from how the Native Americans fished, which was low-impact and environmentally friendly. This can be a challenge today though because our population has grown to over 300 million people in just a few hundred years. The Geoduck is a fascinating animal. Besides its interesting shape, it is one of the longest lived animals on Earth. The Geoduck can live over 150 years! Scientists believe this is because the animal has limited wear and tear on the body. Female Geoducks are also able to produce over a billion babies! The Geoduck is a truly unique animal and we should feel lucky that we share a home with it in our Puget Sound.
Thursday, December 9, 2010
Global demand for fish is rising at a rate our ocean is incapable to support. Aquaculture is here to fill that gap. The industry provides nearly half of all the fish we consume, and it is going to spread to more areas and provide more fish for the days to come.
The downside is that fish farming itself is unsustainable. Fish farming makes fish feed out of smaller fish or fish oil and feed them to bigger caged fish. To raise a pound of farm raised fish, it sometimes takes several pounds of wild fish. Fish farming is adding pressure to the ocean rather easing it. Then there are the escaped fish. Fish escape is unpreventable and can turn into invasive species, devastating nearby habitat. It raises more concern that genetically modified salmon may soon be approved for farming. An alternate argument is that we are consuming more carnivorous fish not because of our increasing population but of our increasing wealth. Unless we can invent some vegetable feed for carnivorous fish, we need to eat more herbivore fish like Tilapia and Striped Bass.
One fact is for sure though: we need aquaculture, but only one that is sustainable and would leave behind usable water bodies for us.
Wednesday, December 8, 2010
According to a new study, wild salmon populations living near salmon farms have lower rates of abundance and survival than wild populations unexposed to the farms. Study authors Ford and Myers looked at five different salmonid species – pink, chum, coho, and Atlantic salmon, as well as sea trout. They studied populations of these fish living in Ireland, Wales, and Scotland, as well as Canadian populations in Newfoundland, New Brunswick, and British Columbia. They defined a wild salmon population as “exposed” if at least one fish farm discharged water into wild spawning grounds, or into a bay downstream from spawning grounds (where juvenile fish had a high likelihood of swimming by fish farms). In almost all cases, having a fish farm upstream dramatically reduced the chances that wild fish would return to their natal spawning grounds. In many cases the rate of return was less than 50%.
Some of the causes of this might be pollution or spread of parasites from the fish farms, or problematic interbreeding of escaped farmed fish with wild fish. Ford and Myers’ study shows that salmon farms have strong negative effects on nearby wild populations. Further research may show what factors cause these effects.
-Ford, J., and Myers, R. (2008) A global assessment of salmon aquaculture impacts on wild salmonids. PLoS Biology 6(2): e33. doi:10.1371/journal.pbio.0060033
-Gross, L. (2008) Can Farmed and Wild Salmon Coexist? PLoS Biol 6(2): e46. doi:10.1371/journal.pbio.0060046
Posted by: Anne Accettullo
Tuesday, December 7, 2010
|Tuesday, 07 December 2010 12:11|
HUGHES Pumps have claimed that their range of Aquaculture Net Cleaning Systems provide the first truly reliable way of removing marine growth from aquaculture nets in situ, giving exceptional levels of reliability, maximum productivity with very low levels of maintenance.
The company says: “Aquaculture producers are only too aware that marine growth build up reduces the tidal flow of oxygen rich seawater through nets, limiting fish growth and increasing the possibility of disease. In severe cases the weight and additional drag of marine growth can damage nets, leading to a breakdown of the cage allowing predators in and fish to escape.
“These revolutionary Aquaculture Net Cleaning Systems combine Hughes’ range of high pressure pump sets that bring a level of engineering and performance not seen before in the net cleaning market, with the unique range of Terminator net cleaners.
“Traditional in-situ net cleaning systems are inherently inefficient, because the pumped high-pressure seawater is split between the net cleaning process and holding the cleaning discs in position, which can cut the high-pressure seawater available for net cleaning by around 50%. The Hughes Pumps range of Aquaculture Net Cleaning Systems allow the net cleaning system’s cleaning discs to be held against the net using only a small amount of the high-pressure seawater pumped to the cleaning heads.
“The Hughes package, that combines the HPS2200 pump set and Terminator 9 disc net cleaner, has become the pump of choice among net cleaning contractors. This package is available in two versions; a conventional stand alone pumpset fitted with an acoustic canopy that is generally used from a workboat deck, and a marine engine driven version designed to be installed below deck, that uses seawater to cool the engine, making for a very compact installation.”
Monday, December 6, 2010
Overfishing at such a high level demonstrates one of the principles we learned about in class, Gifford Pinchot’s concept of nature as a resource. (In contrast to John Muir’s concept of nature as a place that should ideally stay wilderness.) However, Pinchot said that the resource should be managed so as to sustain production at a reasonable level. He would not agree with resources being depleted unsustainably. The latter is what is going on with the world’s fisheries.
I think that there are only a few solutions to overfishing. The most obvious one is to let fish stocks recover by drastically reducing our catch of the most overfished species. Another is to rely more on farmed fish. Or we could start eating more of certain species that people have not fished very much before. But any permanent fix probably will have to include the first idea of reducing catch. With a growing population, especially one being advised by health associations to eat more fish, this will be difficult.
|People protesting overfishing in Kenya|
Source: Swartz W, Sala E, Tracey S, Watson R, Pauly D (2010) The spatial expansion and ecological footprint of fisheries (1950 to present). PLoS ONE 5(12)
Posted by: Anne Accettullo
Example of a trophic pyramid for marine organisms. (Source: ScienceLearn.org, <http://www.sciencelearn.org.nz/Contexts/Life-in-the-Sea/Science-Ideas-and-Concepts/Marine-food-webs>)
- According to a team of scientists led by Trevor Branch of the University of Washington, the most used method of measuring the health of ocean ecosystems and fisheries yields accurate results only half the time.
- Science originally published the measurement method in 1998, which is based on the trends of fish at various trophic levels. The paper that was published said that based on catch data over 40 years, trophic level averages were falling. This led the researchers to believe that humans were taking a top-bottom approach to fishing; in other words, they thought humans were overfishing species at higher trophic levels first and then moving to lower trophic levels as the stocks became depleted.
- Now, new analyses have been developed that integrate and assess other factors besides average trophic levels of catches; these other factors include populations, catch data, and which species of fish live in the particular ecosystem being studied.
- With the new data, catches of species at higher trophic levels have actually increased rather than decreased (a decrease what would have been expected from fishing down the food web).
- The older measure of the health of fisheries ecosystems only works if there is top-down fishing rather than bottom-up fishing. For example, the assessment fails in Thailand because the fisheries in that area went after low-trophic level organisms like shrimp first and then moved to catching higher-level species later. The measure thus concluded that Thailand fisheries were healthy when in actuality the ecosystems were being overfished.
- Because we are catching more of everything in general, average trophic levels are not a good sole indicator of the health of an ecosystem, which is why the 1998 method of measurement fails half of the time.
"Scientists question indicator of fisheries health, evidence for 'fishing down food webs'". 17 Nov 2010. PhysOrg.com. <http://www.physorg.com/news/2010-11-scientists-indicator-fisheries-health-evidence.html>.
-- Erika Najarro