Demise of Herring in Prince William Sound Still a Mystery
Twenty-five years after the Exxon Valdez oil spill, and millions of dollars in research, marine scientists still have no conclusions about the relationship between that environmental disaster and the demise of Pacific herring in Prince William Sound.
What we do know is that the Exxon Valdez oil tanker struck Bligh Reef in Prince William Sound shortly after midnight on March 24, 1989, spilling 260,000 to 750,000 barrels of thick, toxic crude oil, creating one of the most devastating human caused environmental disasters on record.
Then in subsequent storms and currents, the oil spread over 1,300 miles, fouling the shoreline, resulting in the deaths of vast numbers of wildlife, including sea otters, herring and birds.
Some of that crude oil is still not cleaned up, and while some species have recovered, herring have not. A once lucrative commercial fishery, the herring, which also provided nutrition for seabirds, salmon and marine mammals ranging from sea otters to whales, is still listed as “not recovering.”
What is not clear is the direct relationship between the Exxon Valdez oil spill and the demise of the herring fishery in Prince William Sound, but marine conservation scientist Rick Steiner of Anchorage says that without doubt the oil spill had a significant effect on the Prince William Sound herring population, and it is almost certainly one of the reasons for the crash in 1993.
“Most of the 1989-year class, that was spawned as oil washed ashore, was killed,” Steiner noted, in comments Sept. 10. “And, most of the adults were exposed to varying levels of toxic oil. The Viral Hemorrhagic Septicemia, Ichthyophonus, and Viral Erythrocytic Necrosis outbreaks were likely caused, at least in part, by suppressed immune systems in adult herring due to acute oil exposure, making them more vulnerable to such diseases and parasites.”
Still, marine ecosystems are complex, and many variables go into the herring equation – ocean conditions, zooplankton, stress induced by capture for the herring pound fishery, predation, and so forth, he said. “There are almost certainly multiple causes in the herring crash, but without doubt, the oil spill is one of them,” he said.
Steiner points to the April 2013 final report on the Prince William Sound herring survey program written by Scott Pegau of Cordova’s Prince William Sound Science Center, a document that concludes that “there is no consensus on the cause of the herring collapse in 1993 or the factors that have led to the low recruitment levels over the past 20 years.”
The survey program was funded by the Exxon Valdez Oil Spill Trustee Council. The goal was to develop an integrated research program to identify potential bottlenecks to recovery.
Pegau noted in the final report that there appears to be agreement that Prince William Sound herring stocks are not likely to recover without multiple large recruitment events, and that large recruitment events can occur from a small adult spawning biomass.
“A single large recruitment event may be able to increase the adult population to a level where future large recruitment events occur,” Pegau wrote in his conclusions of the study. “The rapid increase in adults may cause new spawning grounds to be used and therefore increase the possibility of retention of larvae leading to strong recruitment.”
Pegau also observed that there is some evidence that change in recruitment is related to zooplankton levels, but also noted that researchers’ ability to identify the conditions that lead to a successful recruitment event have been hampered by the fact that during all of the herring observation periods there had not been a large recruitment event.
Steiner has been recognized by the British national newspaper, The Guardian, as one of the world’s leading marine conservation scientists, and one of the most respected and outspoken academics on the oil industry’s environmental record. At the time of the oil spill disaster he was a marine conservation professor with the University of Alaska, stationed in Cordova.
As a university marine advisor for the Prince William Sound region of Alaska from 1983 to 1997, he provided leadership in response to the Exxon Valdez oil spill, proposed and helped establish the regional citizens advisory councils, the Prince William Sound Science Center, and the billion dollar legal settlement between Exxon and the government, with which much of the coastline of the oil spill region was protected. He has also worked on oil issues in Pakistan, China, Russia, Lebanon, Nigeria, Shetland, central Asia and the Gulf of Mexico.
Today he conducts the Oasis Earth project, a global consultancy working with non-government organizations, governments, industry and civil society to speed the transition to an environmentally sustainable society.
In science, Steiner said, there is a theorem called “Occam’s Razor,” which is that among competing hypotheses to explain an observation, the one with the fewest assumptions should be selected. “Essentially saying that, when in doubt, the simplest hypothesis is usually the most accurate. Or,” said Steiner, “as they say in the south, “if it quacks, it’s a duck.
“The simple explanation for the decline of Prince William Sound herring, the hypothesis with the fewest assumptions, is the Exxon Valdez oil spill.
“Nowhere else in Alaska has the herring population crashed as it has in the Sound, and nowhere else in Alaska has had 40,000 tons of a toxic chemical (crude oil) dumped into it, right at the time of herring spawning.”
While it has become fashionable in the marine research community to assert that there was no baseline data on the herring fishery in Prince William Sound prior to the oil spill, that is simply untrue, he said. Herring has been assessed and managed by government agencies for many decades prior to the spill, and they had a pretty good idea of herring population dynamics in Prince William Sound prior to the spill, he said.
Meanwhile, studies related to the demise of and hope of rebuilding the Pacific herring stocks in Prince William Sound continue, with marine biologists at Alaska Department of Fish and Game, the Prince William Sound Science Center, and others.
“There are no conclusions,” said Rich Brenner, a research biologist with ADF&G at Cordova. “That is the nature of scientific consensus. We build information toward conclusions. That is the way it is.
“You think of science as building a glass house and people throw objects at it, and when those objects no longer break the glass, then you have reached scientific consensus,” he said.
Brenner also points to several studies on the herring fishery, published from 2007 to 2011 in scientific journals, which came up with different hypotheses.
One study published by the Ecological Society of America in 2008 noted effects of competition and predation by juvenile hatchery pink salmon on herring juveniles, poor nutrition in the winter, ocean temperatures in the winter, viral hemorrhagic septicemia virus and the pathogen Ichtyophonus hoferi, and suggested that it may well be difficult to simultaneously increase production of pink salmon and maintain a viable Pacific herring fishery.
The ADF&G studies include acoustic and aerial surveys, said Brenner, whose role is to facilitate a variety of studies, including current herring biomass trends. He also works with other agencies, including the National Oceanic and Atmospheric Administration and the US Geological Survey, on studies into physiology and disease related to herring.
ADF&G keeps in contact with researchers with the Prince William Sound Science Center, who may be on the Sound at the same time, doing acoustic surveys, he said.
“We have been fairly focused on adult herring and adult spawning biomass. We are looking at prosecuting a fishery, and they are focused on juveniles.”
So the research continues, with many questions still to be answered.
Did the initial absence of zooplankton from the herring diet weaken their resistance to disease, ability to reproduce or defend themselves against predators?
Did the oil spill somehow inhibit the ability of the herring to fight off viruses and predators determined to have them for lunch?
Has there been too much competition with pink salmon from hatcheries in the area for the same food?
How do changing temperatures and other environmental conditions, or fishery management and harvests play into this picture?
Meanwhile, Steiner recently resubmitted a proposal he made to the Exxon Valdez Oil Spill Trustees Council in 2002, proposing a herring permit buyback initiative as a restoration effort.
When he first submitted that proposal to the council in 2002, many permit holders were in support of the idea, Steiner said.
The money could then be used to buy individual fishing quota or other salmon permits, thus giving the former herring fishermen an opportunity to turn an inactive herring permit into some real fishing time.
And, said Steiner, this would clearly be best for the marine ecosystem, leaving all the herring in the water for the many predators that rely on them.
Unlike other fishery buyback, or capacity reduction/rationalization programs, programs based on economic efficiency rationale, the Prince William Sound herring fishery buyback for spill restoration purposes would have to be applied on an all-or-nothing basis, he said.
Participation would have to be mandatory, not optional, and to accomplish this, permit holders should be compensated at higher than current market value for their permits, he said.