Light in lakes and forage habitat

Figure 1.  Capture probabilities for Siscowet Lake Trout at different light intensities

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Recently, we have been investigating how fish habitat changes with daily and seasonal light changes.  With the help of Bryan Matthias, a post-doc at UMD, we have created a light model for Lake Superior that predicts changes in Siscowet Lake Trout foraging habitat on an hourly, daily and seasonal time scale.

Figure 2. A photon of light's path through water

Using Siscowet prey capture data from Keyler et al. (2015), we are able to determine the light intensity associated with 50% prey capture during foraging trials (Fig. 1).  We can then calculate the depth within Superior associated with this light intensity throughout the day and seasons using the model.  

Figure 3.  Changes in solar altitude and angle with seasons

Our model accounts for reflection at the lake's surface, refraction by water, and attenuation within the water (Fig. 2).  Due to the angle and altitude of the sun associated with different seasons (Fig. 3), light penetrates deeper in the summer compared to the winter season. Siscowet forage habitat is therefore greater in the summer, than in the winter (Fig. 4).  

Additionally, we are working on calculating the daily light changes within Lake Superior as well as how light penetration, and respective siscowet forage habitat, will change with climate warming. 

Figure 4.  Solar maximum siscowet habitat depths for cross-section of Lake Superior (right) and associated geographical distribution (left) for spring, summer, fall and winter (from top) within the Western Arm of Lake Superior. 

Publication Link: https://link.springer.com/article/10.1007/s10750-019-3888-9

Undergraduate Research

Sarah Muellner and Julia Narow are seniors at UMD who just finished their UROP (undergraduate research opportunity program) projects.  Each helped with my research while conducting small studies of their own which they presented today at the UROP poster fair.

Sarah Muellner

Sarah's poster on juvenile walleye foraging

Sarah helped with the walleye foraging study looking at how water clarity and light intensity affect juvenile walleye.  This study will be completed within the next year.  Sarah is interested in fishes, particularity cichlids. She may have the opportunity to see some first hand during her next 2 years near Lake Malawi while working for the Peace Corp in Africa.

Julia's poster on treatment of barotrauma

Julia Narow

Julia has helped with the Barotrauma work on Lake Superior working with the USGS and Owen Gorman.  Julia helped compare how fish that were treated for decompression after being trawled from the deep waters fared compared to fish that did not receive the treatment.  Julia is interested in marine mammals and has an internship this summer rehabilitating marine mammals in Sarasota, FL.

Best of luck to you both and thank you for your help.

DNR proposal acceptance

Just got word that our walleye foraging study has been approved by the SPA and we have funding for our fall study.

Our initial goal is to determine the effects of water temperature, water clarity and light intensity on young of the year walleye foraging. Due to increasing water clarities from invasives like dreissenid mussels, it is thought that the thermal-optical habitat needed to produce strong walleye year classes is on the decline.  Our study aims to tease out the habitat requirements needed for successful foraging.

Link to Brule River Sportsments Club page

Thank you to the Brule River Sportsmens Club. I greatly appreciate the 2016 scholarship award and am happy to be recognized by a group that works to protect and improve a river that means a great deal to me.  

Over the years, I have spent a lot of time on the Brule and it has become a mental refuge for me after stressful days in the lab.  I look forward to working with the members of the club in the future on a personal level and collaborating efforts with our own UMD AFS student subunit.

Read more below about the efforts of the Brule River Sportsmen Club or visit the link to their page above.

Right: A large brown caught on the Brule river with good friend and former grad student, Kirk Olson.

UW Trout Lake Station and Escanaba Research Station

This spring and summer I've been living at the University of Wisconsin, Madison's Trout Lake Station and working at the Wisconsin DNR Escanaba Research Station.

Trout Lake Station is operated by the Center for Limnology at UW Madison and located in northern Wisconsin. Graduate and undergraduate students spend their summers at Trout Lake conducting graduate work and individual research studies.

The station was established in 1925 as a place to study the lakes of Northern WI. Edward Birge and Chancey Juday, considered the founders of limnology, founded the station as a hub to determine the shared characteristics of northern lakes.

Escanaba research station

I started at the Escanaba research station in early May working for Dr. Gregory Sass.  The Esacanaba station has the longest continuous creel survey within the United States which began in 1946.  I've been involved in assessing the five research lakes associated with the station including Escanaba, Nebish, Palette, Spruce and Mystery and helping with the creel.

Escanaba lake at dawn

Each spring and fall, the fish communities are assessed on these lakes using various gear types including fyke nets, gill nets and electrofishing.  In July, we will start the cisco survey on the lakes via gill nets.

Jamie and Austin prep of plankton samples

We also conduct limnology studies on the 5 research lakes biweekly.  Limno includes phytoplankton sampling via wisconsin plankton nets, chlorophyll a readings to assess productivity, dissolved oxygen/temp profiles and secchi readings.

Checking fyke net on Sandford experimental lake

Another long term study being conducted on Sanford lake is looking at the effects of the addition of course woody debris (CWD).  This spring, the fish community was assessed pre-CWD addition.  The lake will be reassessed every five years to look at how fish populations change.

Dissolved oxygen and temperature profile readings

Additionally, Dr. Sass, Dr. Hrabik and I have written a grant for the WI DNR to fund a study on the effects of water quality, light intensity and temperature on walleye foraging.  This study currently has three objectives: 1) Determine foraging characteristics of adult walleye including reaction distance, angle of attack, and foraging success for ecologically relevant light intensities, temperatures, and water clarities, 2) determine effect of these variables on foraging success for young of year (YOY) walleye, and 3) assess YOY walleye predator avoidance of Large Mouth Bass under these variables. Currently, the status of the grant is pending.




Lastly, I have been analyzing creel surveys to look at angler demographics.  Specifically, we are interested in whether there are harvest rate differences for angler sex, age, travel distance and seeing how these change over time.

Above photos show taking Chlorophyl a readings (left) elctrofishing on Nebish lake (middle) and collecting phytoplankton (right)

This week I also presented some of the research we've been doing at UMD for the weekly Trout Lake seminar.  Research topics covered included siscowet vision and foraging, lake trout vision, walleye vision and the proposed walleye foraging study.

49.5" Musky caught in fyke net on Escanaba lake

Big thanks to IAGLR

Water Action Week

Click HERE for link to MN water action week

This week I was able to meet with Larry Pogemiller, John Downing and Chancellor Black to discuss the importance of Lake Superior research.  Larry Pogemiller is the Commissioner of the Minnesota Office of Higher Education appointed by Governor Dayton and came to discuss fishy topics as part of the Governor's Water Action Week.

Discussing invasive species with Larry Pogemiller

Chancellor Black, Larry Pogemiller and John Downing 

This April 17 – 23, 2016, is to be Water Action Week in Minnesota. Throughout the week, Governor Dayton will visit school classrooms, water treatment facilities, research institutions, and farms to encourage Minnesotans to learn more about the challenges facing Minnesota’s waters, and empower every individual to take actions in their own lives to be part of the solution.

This was a great opportunity to showcase the freshwater research, outreach and education at the University of Minnesota and talk about the research being done with John Downing, the MN Sea Grant director, and Chancellor Black from UMD.

Photos courtesy of Sharon Moen, MN Sea Grant