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Dave Drewiske column: Annual field census of trout populations

A trout being measured on the Kinnickinnic River during a recent Wisconsin Department of Natural Resources survey. Photo courtesy of David Drewiske1 / 2
Kinnickinnic River Land Trust Executive Director Dave Drewiske recently accompanied WDNR fisheries biologists on a survey of sections of the Kinnickinnic River. Using the data collected, biologists are able to estimate the number of trout per mile of stream, species present, age structure and annual survival rates. Photo courtesy of Dave Drewiske2 / 2

While on our tour of the Aldi Site (in River Falls), I mentioned how interesting it was to accompany the Wisconsin DNR Fish Management crew on their annual field census of the trout populations in area streams.

WDNR Fisheries Biologists Kasey Siebert and Heath Beineke are continuing to survey specific sections of each stream following criteria set by renowned Fishery Biologist Marty Engel over 25 years ago. Using this data, the biologists are able to estimate the number of trout per mile of stream, species present (brook or brown trout), age structure and annual survival rates. From this data, resource management decisions are made as to bag limits, size limits, season length and where hatchery stocking is needed. Fortunately, land management practices and plentiful ground water supplies have supported a sustainable, naturally reproducing trout population in the Kinnickinnic River. No stocking of hatchery raised fish has occurred in the Kinni since 1974.

The crew tows small barges containing a generator that produces low voltage current in the water sufficient to stun and collect fish long enough to collect census data. The crews walk shoulder-to-shoulder up the stream using electrode wands to locate fish beneath rocks, logs and undercut banks. Trout have excellent camouflage, so it is simply amazing to see how many fish come to the surface in locations where a casual observer can rarely see a fish. I now believe the estimates of 3,000, 5,000 even 9,000 fish per mile in area streams that we see in WDNR reports. The fish are stunned, netted and measured, then released unharmed. Waterproof waders protect the crew from being shocked, however if a volunteer ventures too close to the generator with breathable waders or bare skin, they are quickly reminded to keep their distance.

Of the hundreds of fish we collected, it is evident just how rare fish 16 inches or longer are in our streams. So, if you catch one that size or longer, take a picture and carefully release it. That fish will help produce future generations of trout in our streams if it is not hanging on your wall. On the other hand, don't be afraid to keep a smaller trout (less than 12 inches in the Kinni). Populations are high in this age group of fish, so you will not harm the resource. Trout are a delicious, sustainable, organic and gluten free product of our cold, clean stream.

Weather conditions at key times of year play a huge role in survival of trout. Both brown and brook trout lay their eggs in the late fall on gravel bars in areas with good spring water flow. Spawning most often occurs in upper reaches of our rivers and their tributaries. Flooding or extreme cold can have a devastating effect on the young trout when they hatch in February or March. Spring water maintains a constant temperature year around, so when those newly hatched trout emerge, the springs offer them warmer water than water exposed to air temperatures. The extreme cold we experienced in the winter of 2013-14 hurt the survival rate of young trout. Since then, we've had very good survival rates in recent years, which lead to harvest limits of 5 fish, 12 inches or less per day.

Volunteers assisting these WDNR Fish management crew mostly are members of our local KIAP-TU-WISH Trout Unlimited chapter. Members of this dedicated group also help with stream habitat restoration and improvement, long-term watershed management studies, Trout in the Classroom programs in area schools, Learn to Fish seminars and conservation fund raising. All these efforts will help ensure trout for future generations.

Trout fishing will improve as we move into the Fall. There are only a couple of weeks left in the 2018 season. Get out there and enjoy our river.

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