Posted on 03/19/2004 4:42:58 PM PST by tgarr
IN JULY 1992, the Canadian Government closed the Grand Banks, waters off of Newfoundland, and most of the Gulf of St. Lawrence to groundfishing. By the time this moratorium came into effect populations of goundfish, like sole, mackerel, and cod -- fish that live in the Ocean's bottom layer -- had already suffered a catastrophic decline. Most observers pointed to overfishing and damage to habitat by commercial dragnets, as the primary culprits. But by the end of the moratorium, in 1994, it had become clear that the collapse was more serious than at first thought, and that the declines in fish could not be explained by overfishing alone.
The North Atlantic groundfish industry was not the first to suffer from such sudden and severe declines fish populations. Another notable example is the demise of the Pacific sardine industry centered at Monterey, California, which went from 250,000 tons in 1942 to less than 20,000 tons six years later. The sardine population seemed poised to rebound after canneries were closed -- a catch of 100,000 tons was registered in 1958 -- but before long populations collapsed once more, and have never regained their former levels. Scientists in California searching for clues to help explain the demise now hypothesize that fluxuations in ocean temperature may have played a role. Could a similar explantion be applied to declines in the North Atlantic?
The East Coast Cod Industry
The Pacific sardine industry, even in its heyday, was small compared to the giant North Atlantic fishing industry that drew trawlers from around the world to the shores off New England, Nova Scotia, and Newfoundland. By 1968, draws of Northern Cod (Gadus morhua) taken in the waters off Canada’s east coast stood at 800,000 tons. Less than ten years later, however, sudden declines in fish populations had lowered the yield to below 300,000 tons. And other groundfish, various species of hake, were also showing signs of decline.
Concern led both Canada and the United States to pass legislation in 1976 extending national jurisdictions over living marine resources to 200 nautical miles, and foreign fishing fleets were banned from coastal areas. Without foreign trawlers, the take of Northern Cod quickly dropped to 140,000 tons by 1978.
Elated at having the fishing grounds all to themselves, investments in the Canadian fishing industry began to soar. By the mid 1980s catches had increased to 250,000 tons. It was around that time that inshore fisherman and scientists began to note declines in fish populations.
The Canadian government, although acknowledging the dwindling stocks, put off action until 1992. By then the estimated biomass for Northern Cod was at the lowest level ever recorded -- just 1 percent of the level 35 years earlier. For the first time in 400 years fishing of Northern Cod ceased in Newfoundland, over 40,000 people lost their jobs, communities were devastated, and a billion dollars in federal assistance expended to pad the economic impact.
Fish Populations Continue to Decline
Despite the moratorium, however, populations of groundfish in the Atlantic did not rebound as expected. Much to the chagrin and anger, of tens of thousands who have been put out of work, the two year moratorium first announced by Fisheries and Oceans Minister John Crosbie in 1992, was extended again and again. Now two years have turned to twelve, and still there is no sign that cod stocks are recovering.
Scientists have been frantically searching to explain the decline, but explanations have been difficult to pin down. Depensation -- reduced survival or egg production caused by increased predation or reduced likelihood of finding a mate when spawning populations fall below a critical level -- has been put forward as one possible reason for the failure of fish populations to recover, but some view this an unsatisfactory answer, and it has been a difficult theory to prove.
But a new twist is beginning to emerge in the debate over possible causes linked to the collapse, or for its continued demise. Scientists are beginning to take seriously the consideration that climate and fluctuations in marine ecosystems could be a possible culprit.
Michael Heath, a biologist at the Scottish Fisheries Research Services' Marine Laboratory in Aberdeen, and UK chair of the international project Global Ocean Ecosystem Dynamics (GLOBEC), said at a recent meeting of the Royal Society in London that "marine ecosystems, particularly in the northern Atlantic, are much more vulnerable to natural fluctuations than previously realized."
This statement follows scientists' warnings that global warming could, in effect, "turn off the Gulf Stream," causing temperatures in Northwestern Europe to plummet. And that this could happen rapidly, over the course of decades, rather than centuries as some might have figured. Moreover, scientists from the Woods Hole Oceanographic Institution have describe recent changes in Atlantic as "the largest and most dramatic oceanic change ever measured in the era of modern instruments." -- Giving impetus to the suggestion that we could already be in the midst of such an upheaval.
Changes in ocean temperature and currents have broad implications for fish populations. Variation in salinity, cooling of surface waters caused by melting ice in the Arctic, alterations in circulation patterns, could impact fish populations directly, by changing their immediate surroundings, or indirectly, by causing changes in planktonic rich feeding grounds in areas like the Grand Banks, where warm and cold ocean currents collide over broad sections of continental shelf.
Species may, for example, be poorly adapted deal with even small changes in temperature. Or they may face stiff competition or predation, from invading species. Changes in bottom layer temperature could impact bottom feeding groundfish in many ways not yet understood.
Changes Linked to Environment
Scientists from the Monteray Aquarium, in California, have been wrestling with the problem of depressed sardine populations for many years. One group of researchers began drawing on historical surveys and increasingly detailed geophysical data to piece together a seemingly simple, yet somewhat surprising, theory that the depressed sardine populations were a result of environmental pressure; not overfishing as previously thought. They suggest that cycles between sardine and anchoveta occur in relation to decadal shifts in weather and water patterns in the Pacific Ocean.
Their results, published in the 10 January 2003 issue of Science, show that during periods of warmth sardines predominate, and during cold shifts anchoveta have the advantage. Thus, a complex interplay between nutrients, food supplies, and predation exists that shifts throughout the Pacific Ocean in relation to these cycles -- cycles we have more commonly come to associate with La Niña (characterized by unusually cold ocean temperatures in the equatorial Pacific) and El Niño (characterized by warm temperatures.)
[Continued . . . ]
WHO CARES!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
As you can see, the population worldwide has increased from just about 2B in 1942 to 5.8B today; in order to support an increase of this magnitude an organic source of food must have been sacrificed or multiplied along with it.
While I'm not saying that this pressure accounts for the changes we see now, what I am suggesting is that it is a bit late to start saving string.
We do not know the impact that the amount of people we are creating now is going to have. It does throw things out of whack. Mother nature is fighting back though. Fertility rates are dropping rapidly in the first world. Everything tends to balance itself out.
There actually was an article about this poster on FR a few days ago - they have detected a decrease in deep-sea oxygen levels. I did a bit of Googling to check out the premises and learned something new, although I should have figured this out from other sources - cold water holds more dissolved oxygen than warm water, which is the opposite of how dissolution normally works.
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