Will Fishing Cool Down as Oceans Heat Up?by Kate Ramsayer, Columbian staff writer
Statesman Journal, March 29, 2006
North Coast fishers tackle consequences of climate change
Last summer, the northerly winds that blow down the Oregon Coast were two months late.
The upwelling of cold, nutrient-rich water usually churned by the winds didn't happen in May. There was no corresponding burst of microscopic plant growth, and so there was little food for plankton, for small fish, for bigger fish, for birds and marine mammals.
When the winds did come, they were stronger and more persistent than usual. This kicked off a chain of events that left patches of water off the Oregon Coast depleted of oxygen, suffocating creatures like crab that couldn't escape this dead zone.
Is this what the future holds for the Pacific Northwest's coastal ocean?
Scientists don't know for sure, but some say that last summer's events are consistent with what to expect from climate change: extreme and unanticipated ocean conditions.
The Earth is warming, and computer models predict that it will keep doing so. The Pacific Northwest will heat up by 2.7 degrees Fahrenheit through 2030 and by 5.4 degrees Fahrenheit through 2050, according to a consensus statement that regional scientists drafted for Oregon's governor in 2004.
"One thing that's been documented to already be happening is that global temperatures are rising, and that's surface temperatures of both the ocean and over land. And it's happening most everywhere," said Nate Mantua, a research scientist with the University of Washington and its Climate Impacts Group.
"If you look along our coast, it's clear that there's a warming trend from Alaska all the way down to the equator."
Scientists can't be certain what effect global warming will have in the oceans in the coming decades. However, if it does cause the oceans to warm, changes are in store for this ecosystem.
"Warm water temperatures allow a whole different community of animals to be in the nearshore ocean," Mantua said. Currently, the waters off Oregon and Washington have sub-Arctic characteristics that nurture creatures like herring, krill, anchovies, salmon and rockfish, notes Mantua. But warmer oceans mean less productivity, attracting a new crop of sub-tropical animals.
"These fish come in and they are predators. They're looking to eat what's available and compete with things like salmon and rockfish, and also eat the juvenile salmon and rockfish," he said. As a potential benefit, warmer waters could bring valuable fisheries like albacore and sardines.
Diverting the fishery
The change in temperature could also divert one of the North Coast's most valuable fisheries, however.
"When the oceans warm, the whiting migration starts earlier," said Bill Peterson, a Newport-based oceanographer with the National Oceanic and Atmospheric Administration.
Pacific whiting, or hake, usually spawn off the coast of Southern California and swim north in the summer to feed, he said. But not only does warmer water cause the fish to head north earlier, it also takes them further north to the waters off Canada, Peterson said. This could pose problems for American fishermen.
In addition, when whiting arrive in the Pacific Northwest earlier, some scientists believe they're a big predator on other fish, including juvenile salmon.
"It's an idea that people are looking at, that perhaps if hake come earlier and eat other fish, they could have a big impact," Peterson said. Warm water also brings whiting up on the continental shelf where the salmon are, he said.
The salmon themselves "definitely don't like the warm ocean," he said. He's investigating one possible reason for this involving copepods, which are zooplankton at the bottom of the food chain.
Cold-water copepods hibernate in the winter, so store up fat. This makes them a nutritious meal for smaller fish like anchovies and smelt, who then become a nutritious meal for young salmon.
"Salmon really have to achieve a certain level of fat to survive their first winter," Peterson said. "They can achieve that fat if the whole food chain is producing fat."
But warm-water copepods don't store fat. So the anchovies and smelt are leaner, and the salmon don't consume as many calories.
Peterson thinks that this could be a way to demonstrate directly how climate can affect fish, and is conducting studies to examine the idea.
Taking the temperature
Fishermen recognize that different fish swim in different temperature water Ð that's why most boats have temperature sensors on board, said Al Pazar, a fisherman from Newport. Salmon prefer waters that are about 54 Fahrenheit, he said. If the water's warmer, the salmon are "sluggish" and "moody;" if it's colder, they move to the temperatures they prefer.
When a strong El Ni–o event in 1983 brought warm waters north, "we noticed a huge amount of tropical species, species that you normally wouldn't see north of Santa Barbara," he said. And some of them, like pelicans, appear to have stayed, he added.
But the warmer waters of that year might have also had a benefit, Pazar said. Crabs take four years to reach a harvestable size, and in 1987, Washington crabbers had a record season.
"You could conclude that the warm El Ni–o water, with no supporting data, enhanced the survival of the crab," Pazar said, stressing that it's an observed link, not a direct cause-and-effect relationship. "It certainly didn't hurt them."
Processors keeping watch
Change in a fisherman's catch ripples up to the fish processors as well.
"I'm concerned about how and when the fisheries are going to change," said Steve Fick, owner of Fishhawk Fisheries.
If global warming creates more El Ni–o periods, it means less productivity in the oceans, which leave salmon "long and skinny and malnourished," he said. The salmon fisheries, which used to occur as far south as San Diego, could be focused further north.
And there could be other, seemingly distant events impacting local fisheries, he said. If the number of polar bears decreases because of melting ice, it could cause a rise in seal populations, "and how's that going to affect the fish populations?" he said. "All these things, they're certainly going to be challenging in putting the pieces of the puzzle together."
But not everyone is too concerned about the fluctuations or the possibility of warming oceans.
"I'm not so sure that if it is happening, if it's going to affect us in our lifetime and if it is, if it's necessarily going to be all bad," said Brad Pettinger, administrator of the Oregon Trawl Commission. The trawl industry fishes for whiting, shrimp and groundfish off the Oregon Coast.
"People don't even know what those implications in the oceans are going to be," he said. "We just don't know Ð it's a very dynamic system." While there has been warmer water in recent years, the trawl fleet had a robust winter, and more young groundfish are showing up in the fishery, he said.
Tough to predict
While the vast majority of scientists agree that the Earth is warming, in part because of human influences, the complexities of the ocean make it difficult to predict how warming will influence this ecosystem in the future.
"Although scientists have made huge progress with models that capture the large-scale dynamics of some of the changes that are already happening, and others that might, we still don't have the ability to zoom in on the Pacific Ocean off the coast of Washington and Oregon and say with any precision exactly what is going to happen, and I don't think we should pretend otherwise," said Jane Lubchenco, a marine ecologist with Oregon State University.
Models are one way scientists study the ocean. Researchers put large amounts of data into a computer program, which predicts both what should have happened in the past and what could happen in the future.
"We don't have a perfect model of the system, but we have some pretty good ones," Lubchenco said.
In addition, although the researchers can't set up an experiment to replicate all the workings and variables of the Pacific Ocean to test hypotheses, they are observing ocean conditions to measure changes.
"All we can do is just document what we see," said Peterson, the NOAA oceanographer. "If we're starting to see a pattern of maybe a warmer ocean year after year, then we can say this is getting pretty scary." Although three or four years might not make a pattern, if something happens for a decade or so, scientists would take note.
"You start to see patterns develop, then make predictions, and I can almost guarantee once you make a prediction, it will be proven wrong next week."
Still, researchers have come up with a number of scenarios for the Pacific Northwest coastal ocean as the earth warms.
Already, scientists have seen warmer temperatures in the waters closest to the ocean's surface, said Mantua. This increase makes it harder for the upwelling winds to push those top layers away and allow the deep, cold, nutrient-rich water to come to the surface and kick off the summertime burst of productivity.
However, this decrease in productivity could be negated by the winds, Mantua said. Some scientists theorize that because the oceans can absorb much more heat than land masses, the differences in temperature over land and sea could generate stronger upwelling winds along the coast. These stronger winds could alternatively stir up even more cold water on the coast, and more productivity.
"The changes in the winds along the coast can lead to enormous changes in ocean temperatures," Mantua said.
As temperatures rise, warm pools of water can create high or low pressure systems in the oceans, which could influence wind and current patterns, said Ronald Neilson, a bioclimatologist with the U.S. Forest Service and Oregon State University.
"These persistent pools of warm or cold water out in the oceans can push these jet streams around," he said.
For example, last winter, "there was a monster high-pressure system that was just sitting off our coast and blocking the jet stream," Neilson said. While Oregon was unusually dry, the wet weather was pushed down to Southern California and even went into the desert of the Southwest, he said. "It was a highly unusual pattern."
Scientists can't say for certain that this was caused by one particular factor, such as global warming, he said.
"For any given event, you can't say for certain that the event is specifically a result of climate change," he said. "All you can say is that it's really unusual weather. And even this year, it's really unusual weather. But attributing it to some specific mechanism is always going to be a difficult prospect."
The wandering jet stream is in effect this year as well, Neilson said. While the high pressure system was off Oregon last year, this year it moved further south, aiming the polar fronts and a subtropical jet stream right at the Northwest.
"Those two sources of moisture are converging in the same jet stream path, pointed at us right now," he said, which is why this winter was warm and wet and stormy.
What causes the shifts?
Other observations of unusual ocean events have scientists investigating what could be causing these shifts.
"What we've been seeing off our coasts is most definitely more extreme and more bizarre events," said OSU's Lubchenco. "Those anomalies are completely consistent with many of the predictions about what we will see as the climate continues to change."
Lubchenco cites two examples that scientists are trying to understand. Last summer, the winds that cause an upwelling of cold, nutrient-rich water to the top layers of water off Oregon's coast were two months late. This upwelling usually fuels the growth of microscopic plants, which become food for plankton, who are food for fish larvae.
"There's no food for baby fish. It sort of percolates all the way up the food web," she said. Seabirds starved, fishermen had lower catches and marine mammals became emaciated. When the winds did come, they were strong and constant, and the system was "kicked into hyperdrive."
One result of this is a "dead zone," a second example of bizarre events. A dead zone is an area of water depleted of oxygen, suffocating the critters that live there. These events have happened off central Oregon recently in 2002, 2004 and 2005, and evidence is pointing to changes in ocean and atmospheric currents as the culprit.
"There are a lot of researchers working madly to figure out what was causing this," Lubchenco said. While they can't say for certain that it is due to global warming, the models examining a warming world predict more extreme events and a "number of surprises."
Some scientists compare global warming's effects to shaving dice, said Mantua. As you keep shaving them, the outcome is going to increasingly be biased in one direction. As the atmosphere continues to warm, even though there are many other factors influencing weather and climate, ocean conditions are going to change.
"We're already in the midst of a period of global warming, it's already happening. And the kind of changes that people have witnessed are likely to be foreshadowing what the future looks like," Mantua said.
"If you're trying to make a forecast, I'd say that the dice are getting loaded every year for a warmer and warmer future."
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