The truth behind redd counts

The stream walks are over for this year, and the results are in: The bulls of Flathead Lake are hanging in there and are maybe on their way to a comeback. At least that was how the Flathead Basin redd count report came across to the Pacific Northwest public. Headlines proclaimed "Better Montana bull trout reproduction," "Tally holds steady," and "Bull trout numbers down but on the rebound."

With redd counts in the North and Middle Forks of the Flathead remaining so low-down 46 percent since 2000-how do the biologists of Fish, Wildlife and Parks Region 1 manage to put across such a positive message? Since these redd counts are used as major indicators of the strength of the threatened Flathead Lake bull trout population, it is important to examine this question in some detail. What do the recent redd counts imply for bull trout recovery efforts? Are they succeeding, failing miserably, or don't we know?

The report says there is some "good news" and some not-so-good news. The not-so-good news is that the redd counts for the Flathead Lake population remain low. According to the report, the "good news is that the current generation appears to be more abundant than the previous one." But is this what the redd count data really show? Let's take a look.

The report takes a bull trout "generation" to be about seven years long. So the abundance of this previous generation is indicated by the total number of redds found seven years ago in the North and Middle Forks. That 1997 count was 114 redds. The count for 2004 is 136 redds, an increase of 19 percent.

Looks pretty good, right? No, wrong.

An important fact about the Flathead Lake bull trout is that the North Fork bulls and the Middle Fork bulls are distinct populations. Bull trout reared in the North Fork return to the North Fork, and probably to the same rearing stream. The same goes for the Middle Fork bull trout. So when we pool the data for these two populations, we obliterate what could be important differences between the North and Middle fork fish. When we take a closer look at the data, here is what we see.

First, the North Fork. In 1997, the redd count there was 44. Now in 2004, the count is 89. That's an increase of 102 percent, and that does appear to be good news. Now for the Middle Fork. In 1997, the redd count there was 70. Today, in 2004, the count is 47, a drop of 33 percent. That appears to be not-so-good news. Furthermore, the current Middle Fork count is the second lowest for the entire 25-year record. That looks like bad news.

According to the report, however, generational increase is not the only good news; there is another reason for optimism, reflected in the headlines across Montana proclaiming, "Bull trout numbers down but on the rebound" (the Missoulian and the Billings Gazette). Where does this idea of a "rebound" come from?

The answer is that the report proposes a theory to explain why the low 2004 redd count was "just about what we expected," and why these counts might be expected to rise next year-the "rebound" idea. The basic idea seems plausible enough. The counts of the last two years are low, the explanation goes, because the first time spawners-the bulk of this and last year's spawning run-came from the redds of the previous generation, the redds of 1996 and 1997.

A look at these earlier redd counts shows them to be at the bottom of a trough; hence, the dip in the redd counts now and the expectation of higher counts in the future. In short, the theory is saying that an increase or decrease of redd counts in a given year is "largely the result of" the increase or decrease in the level of the redds of the previous generation.

While this "previous generation theory" sounds plausible, it faces a serious problem-25 years of data do not bear it out. To illustrate, let's see what would happen if the theory were used-and it was so used last year-to predict this year's redd counts. Since, as we have seen, it makes no biological sense to use the theory to predict the pooled North plus Middle forks count, let us make predictions for the 2004 counts in the two forks separately.

First, the Middle Fork. For the generation previous to 2003-the generation of 1996-the count was 31. It then rose to 70 in 1997, an increase of 126 percent. So the previous generation theory says we should expect the 2004 count to be higher than the 2003 count. But what do we find? The count actually dropped 32 percent in 2004.

The reverse holds for the North Fork. In this case, the count declined by 15 percent from 1996 to 1997, but increased by 46 percent from 2003 to 2004. In short, in each fork, the way the count changed from 2003 to 2004 was exactly the opposite of what the previous generation theory tells us to expect.

So what do the latest redd count data tell us about the Flathead Lake bull trout population? In the opinion of some fishery biologists, we are left with overall levels that place the security of these populations at risk. We have a possible rise in two streams in the North Fork, and a possible decline in Middle Fork numbers to near-record low levels. And finally, there is a very real possibility that must not be neglected-that despite implementation of the Flathead Lake co-management plan over the last four years, the lake trout population of Flathead Lake continues to obstruct the recovery of its native bull trout populations.

John Winnie Sr. is the conservation chair of the Flathead Valley Chapter of Trout Unlimited.