Is Climate Change Killing Our Fish?

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 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.

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.

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.)

A question, sir - in your experience, do curves such as the chart you offer normally have such a smooth transition to stability - or do they have significant fluctuations?

I'm thinking that most predator-prey models are more chaotic.

A second half-baked thought - maybe we're prey from the perspective of a bacterium or virus.

But that argument then is once removed from the problem of fish decline. Carbon dioxide might cause climate change, but climate change then that would be killing the fish.

Even if carbon dioxide is responsible, one would need to show first that the climate has in fact changed, and then that the change impacted the ocean to kill the fish.

The article didn’t mention anything about carbon dioxide. Maybe it’s causing the problem, maybe it’s not. I think that’s pretty hard to prove.

First of all one has to show what’s killing the fish. If it is linked to some change in the ocean then that’s something I can sink my teeth into. That is something we should be able to see.

I think the article’s weakness is that specific links have not been clearly identified even at that ocean level; maybe that’s why it was posed as a question. But at least it is something to look for. I wish I could say an answer would help bring the fish back, but I’m not hopeful about that.

You're right. Dams aren't the problem. There hasn't been a dam built in the PNW since the forties, yet the highest runs have all be after that. Salmon are running in record levels that haven't been seen in decades.

In the Pacific NW the whole issue is about "wild" salmon which is, pardon the pun, a "red herring". If there were no hatcheries, the actual population and the resulting gene pool of salmon would actually be smaller, not larger. There is a HUGE amount of junk science in the papers of the PNW about salmon.

If you want to talk about the salmon issues in the PNW, one need look no farther than the indian tribes, and the Boldt decision of the 70's. But I digress....

Out here in the Pacific NW the PC newspapers are blaming "favorable ocean conditions" for the record salmon runs. But they nearly always finish up each article with a demand for more regulation and/or removal of dams.

How could "ocean conditions" be so favorable in the Pacific and yet no so in the Atlantic? Color me unconvinced....

The chart is simply to show the difference in a 19th century world and our present 21st century one.

Whatever changes we make now will be small perturbations in a field as large as that.

It is true that human population is rising fast. While I don't totally buy the geometric curve in the example... there is no denying that technology in the last century has resulted in more people surviving childhood and more people reproducing.... and therefore more people...

I'm not convinced, however, that this means that we're locked into some starvation model. Technology also means that food-production efficiency has *also* grown by at least the same curve in the model. Humans are capable of producing food now at rates that are orders of magnitude beyond the growth in population. The U.S. alone could produce enough food, if we had to, to feed the whole population of the world. Food production capacity in third-world countries (where most of the population growth is) will do nothing but improve in coming decades.

I think the problem is, and what the article seems to point out, that changes in the ocean can impact different types of fish in different ways. A change that's good for salmon might be bad for some other kinds of fish. Salmon are much different then codfish.

OK... fine.

Since when have "ocean conditions" ever remained absolutely static? Never. Not over a zillion years.

It's like the "global climate change" crowd. They crow that climate is changing. Well, yes, of course it is. When has global climate ever remained static for any (however short) amount of time? Never. That last ice age we had is still ending. When it finishes ending... what happens then?

AMEN! The outrageous regulations preventing US seafood farming are criminal!!! The mostly pristine waters of the Oregon Coast could provide large amounts of jobs to families and towns devastated by the destruction of the timber industry.

Roger that. Seafood farming could be the answer to a host of issues. Good stewardship and good science could simply put an end to these issues.

It could also easily feed the world. Too bad that's not something liberals are truly interested in.

That's right. The work done in California discussed in the article points out that conditions are not static. Sardines give way to anchovy when the water temperature changes. Even short-term temperature changes, like El nino, can affect what fish will live and what fish will die. But a short-term cycle probably didn't kill the codfish because they have been fishing that area for 400 years and have never seen such a decline before.

The article points out the overfishing is not enough to explain the decline; something else is involved.

I always though it was overfishing myself. But nobody's been fishing there for over ten years and still the fish are not coming back. Something's wrong. Who cares if the change is natural or manmade. First of all you have to show what's killing the fish.

The article points out that some pretty big changes are taking place in the ocean, not what's causing those changes.

Ten years? Since when is that a biologically or geologically relevant time period?

There are now massive herds of buffalo running the plains of the American west. How long did that take to recover? Somewhat longer than ten years, methinks.

In California sardines go from boom to bust in less then ten years. Fish are not Buffalo. It takes many years for a buffolo to grow, and they have few offspring. Fish lay millions of eggs and they grow faster. Although I don't know how fast codfish grow, I think thier life-cycle probably shorter then buffalo. Also, the article said that scientist expected the fish to start coming back within two years. I would give them a little credit . . . It's now been 12 years.

Here on the New Jersey coast our local paper publishes a fishing column. Recently the writer spoke with party boat skippers who said that though whiting are scarce, cod are increasing on the inshore wrecks.

Striped bass are abundant as well. The fish seem to have natural cycles; bass were scarce 10-15 years ago but whiting were common.

When stocks of a particular fish are low, blame tends to be placed upon the recreational fisherman. But the commercial guys are in it for a living, and adjust to fish for whatever is profitable at the time.

It would be great if that is true. But from what I can tell, farther out in the ocean -- along the Grand Banks and such where most of the fish live -- fish have still not comeback. Maybe there some scientific surveys somewhere that show a something different, but I haven't seen any.

If somebody knows of any perhaps they might share it with us.

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