Rivers and Fish, Not Rivers Versus Fish

By Thomas E. Bigford, Policy Director

Water is the penultimate habitat. Without water, even the most tempting submerged wood, overhanging bank, or vegetation bed will provide no safe harbor for the fish and aquatic resources we cherish. But water is not limitless. Based on a casual skim of the literature, it seems that water, and therefore fish, is often included in debate about fire suppression, interbasin transfers, drought, meteorological anomalies, industrial uses, agricultural practices, and much more. Sorry to share bad news, but there may be two
more freshwater issues to concern us all—increasing salinity and shifting hydrology. Let me explain, just in case you are running low on issues to debate around the drinking fountain.

First, salt. I have wondered about “chloride loading” for 40 years, mostly because those ephemeral pyramids of rock salt created each fall by transportation crews would eventually be spread on winter roads where I grew up in the Northeast and Midwest. In both regions, it is common to see roadway signs saying something akin to “Caution—Reduced Salt Treatment to Protect Watershed.” With my head buried in the salt, and thinking that dilution is the solution to water pollution, I mistakenly thought the threat remained safely over the horizon. My attention was piqued this spring when a report by Dugan et al. (2017) showed long-term chloride trends going up based on an analysis of 371 North American lakes. Though not shocked or even surprised, I focused on two points—lakes with adjacent impervious surfaces fared worse and the aquatic life threshold criterion for chronic chloride exposure (230 mg/L) will be exceeded within 50 years in many of those lakes. As Dugan et al. (2017) summarized, those trends are not good news for water quality, aquatic ecosystems, fish, or fishing. Now we need to get more serious about salt as bad for our blood pressure and the aquatic environment.

There are several approaches for groups such as AFS to engage on chloride. We could address the cause (impervious surfaces), focus on the environmental impact (more road runoff adding salt to freshwater systems and depressing water quality), or target the secondary implications (reduced fishing opportunities or benefits). We could request additional research (the merits of liquid brine solution as road pretreatment when wintry weather conditions are forecast, for example) or encourage greater awareness from managers (when seeking to limit runoff or to address certain species or life stages). For now, I think we will add chloride to our list of water quality concerns and consider some focused attention at the AFS 2018 Annual Meeting in Atlantic City.

My second realization relates to glacial melting. Shugar et al. (2017) wrote about large-scale watershed changes prompted by increasing air temperatures. The authors found that a retreating or melting glacier enabled massive volumes of meltwater to flow from one river course to another and shifting the outflow from the Bering Sea southward into the Pacific Ocean. This event on the Slims River in Canada’s Yukon Territory was described as “river piracy,” a seemingly natural event most likely prompted by human-induced atmospheric warming. If the piracy persists, the waterway may morph from a river into a closed basin, with many implications for water chemistry and aquatic life.

The shifting Yukon waters suggest that even the largest watersheds are susceptible to the effects of climate change. This is an example of a “threshold response” where an ecological tipping point triggered a major change. Though that fragility is surprising, especially in the rugged Canadian north, basic ecology suggests that such changes in temperate climes are expected earlier than at the poles or equator.

Scarily, these two examples are probably not the only two emerging issues incubating on my cluttered desk. They might serve as sentinels for mindful awareness, appropriate scrutiny, and careful interpretation of trends and change. Wearing my AFS policy cap, I will place these two items in my voluminous tickler file. Someday I hope to have time to resolve some of those issues. For the short term, vigilance will probably suffice. We can learn lessons from observation, whether how we treat wintry roads or how major geographic features such as the Kaskawulsh Glacier affect watersheds and fish. Press on with care and eyes wide open.

Note: the opinions expressed herein are those of the author alone. Comments are invited at [email protected]


Dugan, H. D., S. L. Bartlett, S. M. Burke, J. P. Doubek, F. E. Krivak-Tetley, N. K. Skaff, J. C. Summers, K. J. Farrell, I. M. McCullough, A. M. Morales-Williams, D. C. Roberts, Z. Ouyang, F. Scordo, P. C. Hanson, and K. C. Weathers. 2017. Salting our freshwater lakes. Proceedings of the National Academy of Sciences 114(17):4453–4458.

Shugar, D. H., J. J. Clague, J. L. Best, C. Schoof, M. J. Willis, L. Copland, and G. H. Roe. 2017. River piracy and drainage basin reorganization led by climate-driven glacier retreat. Nature Geoscience 10:370–375.

Members click below for the September 2017 Fisheries magazine’s complete issue. Non-members, join here.

This content is for members only. Please login.