Is Henry's Lake Overpopulated?

The Pendulum Swings

Through the mist rising slowly off the water, snow capped mountain tops materialized almost magically as the October sunrise burned through the fog.  For anyone that loves the outdoors as much as I do, the period of time between pre-dawn light and daybreak is an evanescent moment where anything is possible.  The thrill of the day before you fills the air, yet the world seems to be entirely still.  In this cold tranquility, all the focus of a surgeon is devoted to every cast.  Form, presentation, and stealth become paramount.  Inevitably, I will smack myself in the back of the head with my size 6 woolly bugger at least once in this small window of time alone.  I looked slowly across the lake, admiring the beauty around me while stripping in my fly line.  The only sound breaking the silence was the water dripping from my guides as I brought in my streamer.  Without warning, an aggressive Yellowstone Cutthroat trout smashed my fly.  When I set the hook, my line zipped up into the air from the water, breaking the surface tension and spraying water as it chased down my line towards the thrashing trout.  Very few places on Earth can hold embody the grandeur and wonder this world has to offer to a fisherman as Henry's Lake.

The fish that call these waters home grow freakishly fast, often developing a hump on their backs behind their head as their body weight outgrows their skeletal structure. Henry's Lake boasts a population of over 500,000 catchable trout, with the average trout caught by anglers measuring at 18".  With such a prized lake, it certainly grabbed my attention when I heard some concerning news about the declining size of the fish found here.  Recently, a video has been circulating by Tight Line Media detailing the status of the Henry's Lake fishery.  This lake has been the holy grail for trophy trout fisherman all over the country for twenty plus years, but several consecutive years of good water years have resulted in a population upswing - not in the number of fish surviving that are planted - but due to wild fish spawning.  Tributaries previously inaccessible to trout become viable again with a higher water table, resulting in miles of spawning grounds for wild fish.  Ultimately, biologists believe this is resulting in an overpopulation that is lowering the average size of the trout.

Chris Cutler with a beautiful cutbow caught on the fly last fall

After watching the video, I decided to ask around the local fishing community and see what other anglers had to say about the average size of fish in the lake.  The results could haven't have been more varied.  There were definitely the nay sayers that said the average size fish was "way down" and the F&G didn't care about maintaining the trophy quality of the lake.  From my own fishing experience I hadn't noticed any reduction in average size.  I decided to revisit the F&G website once again for some actual data to shed light on the argument.

Science has a way of polarizing sportsmen.  Either they find it fascinating and agree or vehemently disagree and point to faulty methods - swearing there must be some conspiracy afoot to discourage fishing and hunting.  I have never understood the latter, but I doubt there can be much argument for the data I found.  The following is a chart I drafted to illustrate the variation in average fish length taken by the hatchery during the spring spawning seasons from 2006 - 2010, the 2011 report is not yet available.  Looking back at 5 years of data I think we can draw some conclusions on what to expect and gain some perspective on what a change in size looks like.

The large variation in hybrid trout size is partially due to the relatively small number of cutbows that actually return to the hatchery every spring.  Since the fish are sterile, they should lack the spawning instinct and not behave as natural fish in that respect.  The success of sterilizing these fish while in infancy has fluctuated over the past 5 years from 98 - 100%, which means there are SOME fertile hybrids in the lake.  Sterilization has been increasingly successful, culminating in 2010 with only 2.9% of the total fish returning to the hatchery being hybrids.  The running 5 year total stands at 7.3%, and with a smaller sample group, greater variation can be expected to some degree.  The chart below details the exact numbers.

The Fish & Game also studied fish mortality with extended seasons and opening the lake to 24 hour fishing, and neither had measurable detrimental effects on fish mortality or trophy quality.  While we wait for the final data to be published detailing this year's spawning trout, I think it's safe to say Henry's is not in imminent danger of losing trophy status.  History teaches us that changes of great magnitude often take longer than 1 year in this fishery, so while size may be slightly down - it's unlikely that it should be of major concern to anglers.  With this fishery under close watch from biologists, a plan has already been enacted to combat the issue.

On an average year, 1.6 million trout are released in the lake, this year that will be lowered to 1.3 million, with Yellowstone Cutthroat trout seeing a 42% reduction in planted fish, while hybrid and brookie numbers won't change.  However; there is another interesting piece to this puzzle.  Amid concerns from anglers about the effect extending the ice fishing season until January 1st would have on the trophy population of hybrid trout - the Fish & Game decided to release 10,000 "super hybrids" with the annual planting this year.  These "super hybrids" have spent an extra year in captivity bulking up, and will be a  whopping 10 - 12" when released compared to the typical 3 - 4" fingerlings.  What does this mean to anglers?  These hybrids will clear the 20" mark easily within 3 years, reaching trophy proportions much quicker than run of the mill cutbows.  Survival rates should be higher among these trophy trout as well, resulting in a healthier class of upper-tier giants.

Back in the frigid waters of the lake that morning in October, I stood marveling the beauty of the trout I had in my hands.  Abundant food sources, careful management, and a remarkable marine environment combine to create a truly world class fishing experience.  I gently held the 18" cutthroat in my hands beneath the surface and watched it thrust water through its gills as it regained its strength.   In keeping with tradition, no matter how badly I want to have fresh trout that night - I loosened my grip on the fish's tail and slid it back in the waves.  The first fish of the day swam slowly towards the deep, then quickly darted out of sight.  While we may not always agree with the Department of Fish & Game, and some may question their motives behind certain decisions; it seems clear that they are very carefully monitoring the health of this outstanding fishery.  I applaud their continued efforts to maintain and improve the quality of fishing on Henry's Lake, and have complete faith that they have anglers' best interests at heart with the management of this remarkable resource.  I look forward to the day I set into one of those "super hybrids" on the fly.

As the Canadian brookies mature, more of these humped freaks will be showing up