The Revealing Otolith
Heard at the Tillamook Bay Watershed Council, October 25, 2016:
“Therein lies the story.”
The biologist, Dr. Daniel Bottoms, speaks about the salmon in the river he’d studied for ten years, how they lived, and how their habitat changed after dikes were removed and estuaries are regaining their primordial way of life.
Research is showing that the assumed cycles of life and old assumptions grew more complex.
Much is revealed in the otolith, a bone found in the sensory organs, the “ears” of salmon. It grows every day. A new layer of bone is added, much like a tree ring. In each day, there is the record of the nutrients consumed, growth, the salinity of the water.
Scientists analyze the rings and measure the amounts of strontium, a telltale sign of salt water.
He talks of estuaries and restoration efforts, man trying to undo what has been done in the last one hundred and fifty years, hoping to bring back the number of salmon, strengthening species and the various runs in a particular river and estuarine system. Estuaries provide a varied mix of salt and fresh water, nutrients, and food populations.
Oregon has twenty estuaries, ranging from a few miles to 148 miles on the mighty Columbia, from the ocean to the head of tidal influence. Within those systems, a wide spectrum of salinity, and complex “detrital based food webs”.
What is learned is that within a species, within a particular run of salmon on a particular river, there are up to six varieties of life histories. There is diversity in numbers and adaptability. Resilience is directly related to habitat, the more diverse the better. Both genetics and environment are major players in their lives.
In the Salmon River estuary, north of Lincoln City, Oregon, various marshes have been restored over a 30 year period. In restored areas, salmon tend to spend more time, and life histories become more diverse. Food becomes more plentiful and diverse.
Depending on the environment, salmon can shift their life behaviors, thus ensuring their survival and their success.
In the Salmon River estuary, 70% of the Chinook population has significantly benefitted from estuary restoration, but only 30% of the coho have significantly benefitted.
Old hypotheses have been revised, and there are more questions to be answered. All of the research reveals more of the complexity of the life of salmon and more questions.
Tillamook Bay is now undergoing significant estuary restoration, with 528 acres undiked and tide gates and other barriers removed. This is the largest estuary restoration project in Oregon. We aren’t sure what this will mean to salmon in this watershed but the changes are significant.
Pathways to Resilience: Sustaining Salmon Ecosystems in a Changing World, Bottom, et al, Editors, (Oregon State University Sea Grant, 2011)