Idaho Fish and Game biologist Joe Kozfkay came to the January 9th meeting of the Ted Trueblood Chapter of Trout Unlimited with an update on the South Fork Boise River fishery, showing the 2012 trout population appears stable or increasing depending on fish size.
As manager of the Southwest Idaho Region’s fisheries Kozfkay came loaded with data and historical information in his Powerpoint slide show. And he explored many facets of this river resource we all cherish. Over the next few posts we will break down the information. This update looks at the overall population densities for the latest samping efforts.
Like any good drama, the results were held until towards the end of the presentation, but it was well worth the wait as the nearly four dozen in attendance were able to see the results of the October 2012 population sampling effort. This 2012 edition adds to the library of data consistently collected every three years beginning in 1994.
Added to the past survey efforts the results show a stable or ever to slightly increasing number of rainbow trout ten inches or larger on a fish per kilometer basis (trout/km). A more pronounced increase can been seen with numbers of trout/km for rainbow trout five inches or larger.
South Fork Boise River Rainbow Trout population data 1994 - 2013
The trout/km metric for rainbows five inches or longer is the highest it has been since the 1994 sampling effort. While the actual numbers were not presented it appears from the chart that the population increase is on the order of 40 percent. Nearly all of the increase came in the component of fish measuring between five and ten inches in length.
Fish ten inches and longer appear to have increased, but the trout/km number is probably trivial and probably falls within the confidence interval, or sampling error. This conjures up visions of Election 2012 as Nate Silver or Chuck Todd would pore over the latest presidential election polls from a state like Ohio where the numbers would move one percent in one direction or the other for one or both of the candidates. Their wise counsel was that such changes within a margin of error are too small to derive much if any meaning. The rainbows 10 inches or larger appear to show an increasing number on the trout/km measure from 2006 – 2012, but the slope of the line is so flat as to not constitute much of a trend.
What to make of the trout/km for rainbows five inches and larger? Clearly the jump in numbers is large enough to be outside the margin of error. The numbers portend what one hopes is good news in the coming years as those rainbows between five and ten inches continue to grow and their higher densities provide a terrific fishery. This is tantalizing information, enough to make a fly angler’s mouth water with anticipation.
Usually the response to good news in a sampling effort like this (or a public opinion poll during a political campaign) is to read much into the results. To start measuring the drapes in the Oval Office, or in our case to sit down in front of the vise and tie a few Pink Alberts. Keep in mind when a politician is presented with an adverse poll they respond, “the only poll that counts is the one on election day.” For anglers of the South Fork our poll that counts comes on the day we are fishing the river.
But for now, in the dead of winter, the most one can do is anticipate the 2013 fishing and beyond. So some time at the vise or with your favorite trout book and a glass of single malt or rye seems a good use of time.
