By far the greatest feature of my office at the University of Alaska Southeast is its lovely view of Auke Creek as it empties into Auke Bay. I almost feel guilty that I need only look out my office window to see whales, seals, sea lions, ducks, dippers, bald eagles, kingfishers, and a plethora of other creatures in their quotidian activities. Almost. I put in lots of dark winter days and soggy autumns to earn this view.
However, Auke Creek is not just another pretty Alaska stream. Aside from being a wonderfully convenient field site for university courses and student projects, it is also home to a fish weir that has been used for decades to count all juvenile and adult salmonids (salmon and close relatives such as trout and char) that migrate between the stream and the Pacific Ocean -- a procession that has occurred since time immemorial as the local Tlingit remind us. The data collected at the Auke Creek weir reveal that its salmon, trout, and char are changing their migration timing in important ways that would not be immediately obvious to relative newcomers to Alaska, such as myself.
Analyses conducted by my graduate student, Ryan Kovach, in collaboration with researchers at the University of Alaska and the National Oceanic and Atmospheric Administration, who operate the Auke Creek weir, reveal that Auke Creek is warming and most of its salmon migrations or "runs" are occurring earlier than in the past. Eleven of 14 salmonid life stages examined show earlier migrations now than when data were first collected four decades ago. In the extreme, the adult coho salmon run is now 17 days earlier than when data were first collected in the 1970s. Our modeling results show that stream temperatures and flows have had significant impacts on salmon run-timing since then.
Other important results of these analyses are that most of these runs are occurring over a smaller window of time, and that, collectively, spawning salmon can be counted migrating past the weir about only 55 days a year. In the 1970s, salmon migrated past the weir on the way to spawn over a longer 79- day period. Their availability has decreased for those of us, humans and non-humans, who live along Auke Creek's banks and look forward to an annual salmon harvest.
All of this change is a bit alarming because salmon are such an important source of marine-derived energy and nutrients for terrestrial and freshwater ecosystems. Many humans and non-humans make use of these fish. Salmon are also an economic engine for coastal communities along the North Pacific Rim that have held salmon as central to their identities for eons. It is important that we pay attention to these shifts in migration timing and adjust our management accordingly.
However, there is good news. Despite these concerning shifts in migration timing and the shrinking window over which they can be counted at the weir, Auke Creek salmon have not decreased in abundance. They remain just as abundant as they were decades ago. In other words, they appear to be resilient to the environmental changes that have occurred in the last few decades. Will they remain resilient in the future? It is anyone's guess. Unfortunately, we do not know how widespread the trends in salmon migration are beyond Auke Creek, because there are few, if any, other places along the North Pacific Rim where there are such detailed, long-term data on wild juvenile and adult salmon runs. Our failures to maintain healthy stocks of Atlantic salmon in Europe and the Eastern US, as well as Pacific salmon in the lower 48 states, do not instill great confidence that we can keep them bountiful up here in Alaska.
Meanwhile, it's the time of year salmon make their way home again to spawn and time for me to turn my gaze and thoughts out my office window to contemplate what we can do to ensure their future -- and many future returns -- long after this marvelous view has passed onto someone else.