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Study on salmon ear stones cited by EPA in Pebble draft EIS comments

Jason Ching
University of Washington

The EPA's 100-page comment on the Pebble Mine draft EIS cited a study focusing on the growth and development of young salmon in the Bristol Bay watershed.



On Monday, the Environmental Protection Agency released its formal comment on the draft Environmental Impact Statement for the proposed Pebble Mine.



The 100-page release pointed to a bevy of environmental studies that highlight potential harm to land, water and animals in the Bristol Bay region -- consequences that the EPA claims were not fully considered in the draft EIS from the Army Corps of Engineers.


One of those studies focused on the growth and development of young salmon in a region with the largest wild sockeye run in the world. 


One of the study’s co-authors, Daniel Schindler, said his findings show that the waters where young sockeye and Chinook salmon grow and develop can shift from year to year. Essentially, even rivers and streams that don’t serve as homes for young fish now, may do just that in the future.

“Certain parts of the habitat do well in some years,” Schindler said. “And other parts of the habitat do better in other years. So it's really the intact nature of the whole Nushagak watershed that produces such reliable returns to the fishery.”

Schindler and his colleagues at the University of Washington figured this out by analyzing tiny stones within the ear bones of salmon. The stone, which is called an otolith, accumulates layers as the fish grows and moves over the years, with each layer bearing a unique chemical signature based on its environment.

Researchers can take that stone, cut it open, and read it like rings of a tree -- using each layer as an indicator of where that salmon was during a particular year. Another author of the study, Sean Brennan, explains. 

“Using those signatures in the otolith,” Brennan said. “We can essentially map individual fish to a spot in the Nushagak to say that this fish originated here, then using the region of the otolith that was laid down while it was in fresh water, we can say these are all the different habitats that this individual fish used.”



Credit Sean Brennan / University of Washington
University of Washington
The otolith of a juvenile Chinook salmon captured in the upper Nushagak River. Otoliths grow similar to tree rings; this otolith has been sectioned in order to expose its concentric daily growth rings.

And when they did that, they found that the same fish occupied a variety of different habitats during its life. When young salmon are looking for somewhere they can eat, grow and hide from predators, they may turn to rivers and streams they haven’t occupied in the past. To have those options on the table, it’s important to keep rivers and streams in every part of the watershed clean and capable of hosting fish.

Critics of Pebble have pointed to its potential to harm waters near the proposed mine site. Those defending the project have countered, saying that even if the project does disrupt area waters, that harm would be contained to a select tributaries near the mine’s footprint. Pebble CEO Tom Collier has seen Schindler’s work and says there’s science that actually supports his side. 

“He was saying that it's sometime in the future,” Collier said. “These tributaries and how much salmon they have in them change over time. And we hadn't taken that into consideration and he's wrong about that. He claims that all we did was count salmon in the streams and that's not correct. We did a very detailed and elaborate study of habitat.”

Schindler says his research proves that even localized disruption to those rivers and streams could have an impact on the salmon fishery, and that it’s important to consider the long term.

Collier, though, believes that Schindler’s take on things is all wrong. Not only does he say that the science is on his side, but he also feels that Schindler may be using his studies to push an agenda.

“Schindler, I believe, has swung at the ball and entirely missed it. Schindler has been an opponent of this project for 10 years, 12 years, something like that. And I think he is continuing to oppose it on notwithstanding the fact that the data may not support his position.”

The latest comments from the EPA seem to agree with Schindler, saying his study should be reason enough to be concerned about any impact to the watershed. As for Schindler himself, he thinks the people putting together the draft Environmental Impact Statement willingly overlooked his findings.

“They are readily accessible by people who wrote that document,” Schindler said. “And they chose to ignore them. And they chose to ignore the concepts that emerged from those papers that tell us about what we should value in terms of a fish habitat in Bristol Bay.”

Now, the Army Corps will review the more than 94,000 comments it received on the draft EIS, including the hundred pages from the EPA. How those comments will influence the final Environmental Impact Statement, though, remains to be seen.

One of those studies focused on the growth and development of young salmon in a region with the largest wild sockeye run in the world.