Redfish Lake in the Stanley Basin in central Idaho is at the extreme end of the state's Columbia River salmon migration. The lake takes its name from the red color of the returning Sockeye salmon that once ended their journey home here beneath the Sawtooth Mountains. Visitors to the area in the first half of the twentieth century reported camping along the Salmon River near the lake and being able to hear the thousands of fish in the river making their way to spawn in the lake's gravel beds - like those pictured here in a contemporary picture from Alaska. Visitors to the Stanley Basin today do not hear this sound.
During the summer and fall of 1992 a single male sockeye found its way into the fish weir at the mouth of Redfish Lake. Named "Lonesome Larry," he became a symbol for salmon recovery efforts put in place beginning in the mid 1980s. You will begin to explore the success of these efforts in the activities below.
How far did Larry travel? His route home took him up the three major rivers of the Columbia Basin, a small creek, and into Redfish Lake. Open the map and measure the distance river-by-river from the Pacific Ocean to the spawning beds of Redfish Lake.
Larry's ancestors were not lonesome. Until the mid 20th century they came back to Redfish Lake by the thousands. Analysis of the graph and table below will help you paint a picture of the dramatic change that began in the 1950s:
1) Describe the type of pattern (linear, exponential, etc.) suggested by the scatter plot of the sockeye population returning to Redfish Lake from 1954 when this data was first collected until 1992, the year Lonesome Larry returned.
2) Transform the data so that the curve is "straightened" as best possible.
3) How well does the transformed data fit a straight line. Explain
4) Determine the equation of the line of best fit and transform it to model the original data.
5) Use your model to predict the number of returning sockeye for 1994 and 1995.
6) Adjust the Ending year above to 2016 and compare your predicted counts with the actual values.
7) Discuss conclusions you draw about (a) changes in the sockeye population in Redfish Lake and (b) the use of mathematical models as predictive tools.
8) Examine and analyze the trend in the sockeye population since 1992.
9) Read "Lonesome Larry's Legacy Lives" and write a brief summary of steps that have been taken to restore the Salmon River sockeye run.