Fish & Fisheries

Bristol Bay Blog, Part 1: Understanding Remote, Wild Waters

May 1, 2013

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The author caught fish on nearly every cast, including this nice Arctic char, fishing in the Bristol Bay watershed. And he wasn't even there for the main event--the sockeye salmon run. Photo: Jennifer Miller
The author caught fish on nearly every cast, including this nice Arctic char, fishing in the Bristol Bay watershed. And he wasn't even there for the main event--the sockeye salmon run. Photo: Jennifer Miller

No fishing hyperbole: We caught something every other cast. At least.

Huge king salmon spawned in the river, but these were not the fish we were seeking. It was the fish following the king salmon. A host of species lined up downstream as the kings spawned, picking off eggs as they drifted past. We cast little beads that imitated the eggs and bam! Fish on!

Maybe it was a grayling or a large rainbow trout or a char. It didn’t matter: it was the greatest fishing of my life.

That was my first afternoon in the Bristol Bay watershed. The ensuing days there seemed like a parade of wonders: volcanic mountaintops, bears roaming lakeshores, hooking silver salmon in the rain, more rainbow trout and grayling and char.

Here’s the thing: We weren’t even there for the main event—the largest sockeye salmon runs on earth that taken together produce more sockeye salmon than the rest of the world. Combined.

Just last evening, we baked one of our Bristol Bay silver salmon fillets, and the memories came rushing back—memories of one of my finest adventures in a life filled with the pursuit of outdoor experiences around the globe.

And so I understand well the passion, the emotion, people feel for this place, especially when a gigantic mine is proposed right in the midst of it.

The Bristol Bay watershed is located in southwestern Alaska, a mind-bogglingly wild expanse of rivers and streams that covers 58,000 square miles. It has always been best known for its salmon population and the subsistence, commercial and recreational fisheries it supports.

Lately, though, Bristol Bay has received even broader attention, with the proposed mine most commonly known as the Pebble Mine. As it happens, Bristol Bay also sits atop the largest copper and gold deposit on earth. By most estimates, Pebble Mine would be the largest copper mine in North America and one of the largest in the world.

Bringing the Data

Bristol Bay has an incredibly complex hydrology--which demands complex computer modeling tools to adequately predict threats. Photo: Clark James Mishler/TNC
Bristol Bay has an incredibly complex hydrology–which demands complex computer modeling tools to adequately predict threats. Photo: Clark James Mishler/TNC

The proposed mine has predictably drawn intense controversy. But there is one notable problem as people argue about the possible impacts of the mine: a distinct lack of data.

“Alaska is a remote state and Bristol Bay is a remote part of this state,” says Dave Albert, director of conservation science for The Nature Conservancy’s Alaska program. “We didn’t have good data on the water quality, the salmon or the subsistence values of the watershed. Without data, things become pretty polarized.”

One of the Conservancy’s strengths is bringing data to complex conservation issues. “We aren’t against mining,” says Albert. “We also didn’t want to wade into the politics of the issue. That was not our expertise. But we could provide solid baseline data. There was no reason to wait for that.”

In addition to gathering baseline data, The Nature Conservancy in Alaska commissioned a preliminary ecological risk assessment to better understand the  potential risks to salmon posed by large-scaling mining in this area.

An ecological risk assessment takes baseline conditions—for salmon, hydrology and other factors—and models the risks posed by potential mining activity.

Flying over Bristol Bay, you see a tangle of rivers, streams and wetlands. The movement of freshwater shapes this place, and shapes the life histories of salmon and other wildlife. Modeling this hydrology would appear a daunting task.

“The system is so dynamic and complex,” says Albert. “Glaciers carved out this landscape and deposited layers of gravels, sands and silts as they retreated. Because of this layering, water from one watershed might flow underground into an entirely different stream system. ”

To map and model such a complex system requires an equally complex tool. Enter the MIKE SHE, an integrated hydrological model; it accounts for both surface water and groundwater. The model simulates water flow of the entire hydrological cycle: from the time precipitation hits the ground until the river flows to the sea. (Contributor Dayna Gross described a different application for this tool, on Idaho’s Silver Creek, in a recent blog).

The model incorporates climate, soil infiltration, the effects of vegetation and sub-surface hydrology, among other factors—to a complete picture of how water behaves. It allows researchers to predict the effects of proposed activities (such as stream restoration or a large mine) over an entire river system.

“The MIKE SHE revolutionizes freshwater modeling the way Geographic Information Systems revolutionized mapping twenty years ago,” says Albert.

Geographic Information Systems (GIS) made two-dimensional mapping tools widely available, and today the technology can be easily used by anyone via programs like Google Maps. The MIKE SHE takes this a step further: it includes sub-surface geometry and hydrology (making it three dimensional) as well as the complex ways in which surface water and groundwater flow through the system over time (which in essence adds a fourth dimension).

“This tool is just so cool,” says Albert. “It is a technology that allows us to better understand the complexity of water in the real world.”

Using this modeling and other studies, researchers developed solid baseline data for the region. What did they find?

The answer to that begins and ends with salmon, the drivers of this ecosystem – in ways that most people never imagined. Join us as tomorrow’s blog examines the full complexity of the salmon at Bristol Bay.

You can't discuss Bristol Bay without discussing salmon--the subject of tomorrow's blog. Photo: Clark James Mishler/TNC
You can’t discuss Bristol Bay without discussing salmon–the subject of tomorrow’s blog. Photo: Clark James Mishler/TNC
Matt Miller

Matt Miller is a senior science writer for the Conservancy. He writes features and blogs about the conservation research being conducted by the Conservancy’s 550 scientists. He has served on the national board of directors of the Outdoor Writers Association of America, and has published widely on conservation, nature and outdoor sports. More from Matt

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