We’re talking about salmon. What were you thinking?
Some neat sciency stuff was published yesterday. That is, researchers at the University of Washington have discovered that salmon stocks have been highly variable for centuries - long before the start of commercial fishing. And these variations are not just year to year, but can stretch out for decades. Heck, one particular cycle was found to last 200 years!
But how can we know the abundance of salmon without written record, you ask? Read on, we reply.
Yesterday’s U of W release stated that the researchers examined sediment cores collected
from 20 sockeye salmon nursery lakes in southwestern Alaska. The scientists focused in on something that salmon accumulate in the ocean and leave behind in lake sediments when they die: nitrogen. When there was a lot of this specific nitrogen in the sediments, it meant returning runs during that time period were abundant; when there was little, runs had declined.
Interestingly, most of the lakes examined showed declines in the kind of nitrogen the scientists were tracking beginning around 1900, once commercial fisheries had developed. However, earlier fluctuations also showed that natural processes had at times reduced salmon densities as much as recent commercial fisheries.
The researchers state that climate change is not the only reason for long-term changes in salmon abundance. “Changes in food webs, diseases or other factors might be involved; however, at present, there are no clear explanations for the factors that cause the long-term variability observed in this study,” they conclude.
Sadly, we’ve heard that doomsdayers, finger pointers and professional activists are not taking this news well (sarcasm if you didn’t catch it). After all, it’s going to be pretty tough to raise money to protest against this nasty culprit affecting ‘their’ sacred salmon - Mother Earth.