HFF Monitors New Winter Fishing Seasons

Thursday, February 11, 2016 - 6:15pm


James Chandler

HFF Monitors New Winter Fishing Seasons


          Prior to moving to Ashton and beginning work on an angler use survey for the Henry’s Fork Foundation I had never been fishing in the winter.  Honestly, the thought never even crossed my mind. 

            Fishing in the winter has opened up a whole new series of challenges for me as a fly fisherman.  I love it.  Landing a fish in January was extraordinarily satisfying and rewarding because it meant overcoming not only the usual challenges of fly fishing but also those of fishing with gloves and dealing with mostly frozen line guides.  Let’s just say my casting wasn’t the best it has ever been.  Although the fishing has been good, the real treat has been the opportunity to observe the river in a relatively undisturbed state. 

Survey Objectives

         As of January 1, 2016, Idaho Fish and Game has opened up two new sections of the Henry’s Fork to winter fishing: the section from Vernon Bridge upstream to Ashton Dam and the section from the southern boundary of Harriman State Park downstream to Riverside Campground. The winter seasons in both sections of river allow catch-and-release fishing only. Of course, the Harriman-to-Riverside section is catch-and-release all year. In the Ashton-to-Vernon reach, once the general season opens on May 28, regulations revert to the two-fish limit that now applies to the entire river from Riverside Campground to the South Fork Snake River confluence. For complete 2016 fishing regulations go to: http://fishandgame.idaho.gov/public/fish/rules/upperSnake.pdf

            Because some anglers expressed concern over the potential effect that additional winter angling might have on fish populations, HFF jumped at the chance to monitor these new winter seasons. In cooperation with Idaho Fish and Game, we are conducting an angler use survey to gain an idea of how these portions of river are being used now that they are accessible.  The objectives of the survey are twofold.  First, we are working to estimate angler effort through angler counts.  Angler effort is measured in angler hours.  For example, if one fisherman spends one hour on the river then we record one angler hour.  If two fishermen spend 30 minutes on the river then this would also count as one angler hour.  Second, we are gathering information on catch-and-release rates based on angler observations and interviews.  We measure this in fish caught per hour fished.  For example, if I interview a fisherman at the end of his or her trip and they tell me that they fished for two hours and caught four fish in that time we would be able to say that they caught fish at a rate of two fish per hour.


            To accurately reflect the efforts of fishermen without introducing bias to the study we implemented a stratified random sampling design for the study.  This means that the study time, January through May, was broken into four strata.  The first is January 16 to February 12 and represents the mid-winter portion of the season.  The second is from February 13 to April 1, which represents the late winter and early spring portion of the season.  The third is from April 2 to April 29, accounting for the spring season.  The fourth is from April 30 to May 27, which will describe the late spring season.  Within each stratum we divided days into two subgroups: weekdays and weekends/holidays. For example, we would expect that more people would be fishing on the weekends than during the week; therefore we group these times separately. Also, we expect more people to fish during the month of May than during January. Accordingly, we allocated more sampling effort on weekends than weekdays and more effort later in the spring that during the winter. This allows us to concentrate survey time in proportion to expected angler effort. 

         The final step in setting up the study is to randomly draw sampling days and time blocks within each stratum and subgroup.  By doing this, there is an equal chance that any given sampling date falls on a snowy, windy day as it would on a clear, sunny day. Within each randomly selected sample day, we randomly select a three-hour time block in which to count and observed anglers. Again, the random selection provides equal probability of selecting any given time during the day, avoiding bias.

            I begin each sampling block by first getting a simple count of the number of fishermen that are on the river.  In the Ashton reach, I drive from Ashton Dam to Vernon Bridge, stopping to get out and observe the river at certain points so that I can have a visual of each section of the river on this stretch.  After completing the count, the next thing I do is observe anglers that are there to see if they catch anything.  Finally, if possible, I will interview anglers to see how long they fished for, what species of fish they caught and the number of fish caught.  I also record access method (wade vs. float) and terminal gear type (e.g., fly vs. lure). Similar procedures are applied in the Pinehaven reach. At the end of the survey time I complete a second count along the full stretch of the sample area. The data collected is then extrapolated to describe angler activity in a time period over the subgroup in each stratum.


          To date, I have conducted formal surveys on three different days at Pinehaven and six days in the Ashton-Vernon reach. Additionally, I have spent unofficial time on the river.  I have logged several hours fishing below Ashton Dam and spent one day determining how accessible the Pinehaven section is by taking a snowmobile out onto Wood Rd 16.  It is not easy to access the river at this point in time up there, which why, so far, I have observed no anglers at Pinehaven and no evidence (e.g., tracks in the snow) that anyone has fished there so far this winter. In fact, during this first portion of the survey the river here has been either covered with ice or full of large ice blocks, further inhibiting any possibility of fishing.

         In the Ashton-Vernon section of the river I have observed anglers and spoken with them, confirming that they have caught fish.  For the first stratum of the survey we have recorded angler-hours and catch rates for both weekday and weekend/holiday sub groups. 

         To calculate the angler-hours we averaged the number of angler hours per hour fished and multiplied that number by the total number of possible fishing hours during the entirety of the sampling period, in this case from January 16 to February 12.  For example, for the two weekdays that I surveyed the Ashton-Vernon site January 18 and February 9, I observed two anglers over four counts, which equates to 0.5 angler-hours per hour fished.  This number is multiplied by the total number of possible fishing hours for weekdays, 163, to get a total of 81.5 anger-hours for the first sample stratum.  When we do the math for the weekend, we get 1.25 angler-hours per hour.  Multiplied by the total number of possible fishable hours for the stratum, 65 hours, we get a total of 81.25 angler-hours.  We can calculate total effort by adding the angler-hours from weekdays and the weekend/holiday hours.  Total effort equals 162.75 angler-hours in a total of 228 fishable hours.

          To calculate catch rates we utilize information obtained from interviews and divide the number of fish caught by the total hours fished.  For Ashton-Vernon I conducted five interviews totaling 8 fish caught in 9.5 hours for an overall catch rate of 0.84 fish per hour.  Specific catch rates were 0.53 Rainbow Trout per hour, 0.11 Brown Trout per hour and 0.21 Mountain Whitefish per hour. 

          By combining our angler-hour data and catch-rate information we can estimate total catch.  Overall, 137 fish were caught and released from January 16 to February 12.  We calculated this by multiplying total effort by catch rate.  162.75 x 0.84 = 137.  Of these 137 fish, 86 were Rainbow Trout, 17 were Brown Trout, and 34 were Mountain Whitefish.

            As the days begin to warm and more people are likely to be out fishing, the number of sample periods will increase both during the week and on weekends/holidays.  Thus far it has been both fun and educational spending this time on the river.  I have been able to speak with a few anglers who have braved the elements to be on the water.  In conversations with them I have learned about various places to fish and what sort of flies and techniques are working this time of the year.  There is camaraderie about this sport that is contagious and welcoming.  As a newcomer to the area and one whose experience is fairly limited to smaller mountain streams, it is wonderful to have people share their fishing experience with me.  It makes me all the more excited to get out and fish the Henry’s Fork and continue to gather information that will be utilized to protect and conserve this watershed. 


Photography by James Chandler Photography