COVID-19 Pandemic Effects on Angler Effort and a Brown Trout Population in a Driftless Area Stream in Southeast Minnesota

The global COVID-19 pandemic resulted in variable social and governmental responses and uncertain environmental effects (Ciotti et al. 2020; Cooke et al. 2021). In the United States, most state governments enacted stay-at-home orders (of various durations), banned social gatherings or enacted other restrictions. In response, many citizens were perceived to engage in outdoor activities to satisfy needs for recreation and physical and mental wellness (Beery et al. 2021; Taff et al. 2021). Environmental impacts may have been even more variable ranging from a perception of improved ecological functioning from decreased human activity to increased environmental harm from reduced environmental regulation, more illegal activity, and increased use of limited natural resources (Cooke et al. 2021; Raza et al. 2023). Because of the rapid onset, spread and rareness of the pandemic, many early scientific publications and reports were limited to assessments of expert opinion of what the ramifications might be. Many publications concluded by noting the need for better quantified data as the pandemic progressed and suggested post-pandemic studies would ultimately be needed. Because more people will likely experience similar pandemics in the future (Marani et al. 2021; Penn 2021), the need to better understand and document the impacts of the COVID-19 global pandemic is essential.

Recreational angling is a popular outdoor activity enjoyed by millions of people in the United States and Canada that was subjected to a variety of evolving governmental regulations during COVID-19 with uncertain effects on fisheries resources (Cooke et al. 2021; Midway et al. 2021). Initial public-health responses in March and April 2020 coincided with traditional spring angling seasons. Most governments (92%) chose not to change the opening of their fishing season, but several enacted other measures to either promote outdoor angling or discourage associated social interactions (Paradis et al. 2021). For example, to promote more angling opportunities, some jurisdictions temporarily waived license requirements whereas others discouraged interactions by cancelling tournaments, closing parks, and restricting license sales for, nonresidents (Paradis et al. 2021). As with other early pandemic literature, fisheries-related publications consisted mostly of predicted effects on fisheries resources. Opinions included equivocal uncertainty on whether the pandemic would result in increasing or decreasing fishing pressure and harvest (Stokes et al. 2020; Cooke et al. 2021). Reduced pressure and harvest may result from stay-at-home orders, restrictions on nonresident license sales or more general fears of COVID-19 transmission. Alternatively, fishing pressure and harvest could increase, especially if lockdowns persisted and anglers sought to improve physical and mental wellness or food resources. Subsequent effects of these contrasting changes in human behavior on fish populations was even less certain and all such publications highlighted the critical need for quantitative data to rigorously assess the pandemic’s effects. With pandemic-related restrictions continuing in some states and provinces through 2021 and into 2022, such quantitative studies are only now beginning to be summarized, analyzed, and appear in the scientific literature. These studies have included pandemic effects on angler behavior (e.g., Midway et al. 2021), compliance with regulations (e.g., Ban et al. 2022), and exploitation rates (Bunt and Jacobson 2022).

There are many methods to quantify angler pressure and harvest, however most such methods were restricted during the pandemic (Cooke et al. 2021; Tracy et al. 2021). Common methods include indirect approaches such as mail surveys or angling license sales and more direct methods of creel surveys (Jones and Pollack 2013; Knuth et al. 2013). Most indirect methods could be enacted and still follow social-distancing restrictions with preliminary data suggesting an increase in angler participation. For example, Cooke et al. (2021) noted that fishing license sales appeared to have increased in many jurisdictions in 2020 but also noted that many routine creel surveys had been suspended making precise estimates of angler participation and pressure difficult to obtain.

Although changes in fishing license sales and mail surveys can be informative, they can also be misleading, as they typically represent angler use for a spatially-broad area (e.g., state or province) and not how much time an angler spent fishing a specific lake or stream. Even more problematic, having a license per se, does not provide any information on how much time an angler actually fished. For example, a licensed angler might fish one day or 100 days. Also, some angler groups, including youth, elderly, veterans or the disabled, may be exempt from needing a license. Many states also offer free fishing time periods (e.g., take a kid fishing weekend) and during the pandemic some states temporarily waived the need for a license entirely (Paradis et al. 2021). Mail surveys can address the first two issues but still suffer from the last issue (i.e., not everyone needs a license) because the sample pool is almost always license holders. Traditional creel surveys alleviate most of these issues but are costly, labor intensive, and subject to their own biases. As creel surveys were suspended during the pandemic, digital time-lapse trail cameras might offer an alternative method to assess angler use, pressure and demographics and still comply with social distancing rules. Digital trail cameras have become more common in the past decade with several studies examining their efficacy (e.g., Stahr and Knudsen 2018; Hartill et al. 2020; Ban et al. 2022).

Minnesota is a state with abundant angling opportunities that implemented pandemic restrictions, observed an increase in license sales, but also canceled planned creel surveys. With over 5,000 fishable lakes and >29,000 km of rivers and streams, Minnesota routinely supports angling opportunities for over 1 million anglers (Burkett and Winkler 2018; MNDNR 2023). Although trout angling opportunities are less widespread than those for walleye, bass, and panfish, Minnesota supports regionally important trout fisheries, including on the north shore of Lake Superior and in southeast Minnesota. Southeast Minnesota cold-water streams are part of the broader Driftless Area stream trout fishery that includes portions of southwest Wisconsin, northeast Iowa, and northwest Illinois that collectively generate over $700 million to local economies (Anderson 2016). In response to the escalating pandemic, Minnesota declared a state of emergency on March 13, 2020, followed by closings of schools, daycares, sit-down restaurants, and nonessential retail stores, and finally a stay-at-home order was enacted on March 27. The stay-at-home order included exemptions, such as for those seeking medical care and shopping for food, but also allowed residents to leave their homes for outdoor activities, including angling. These restrictions coincided with the spring-summer stream-trout angling season in southeast Minnesota, which began with a catch-and-release season from January 1 to April 17, a harvest season from April 18 to September 14, and catch-and-release from September 15 to October 15. Angler use of this stream-trout fishery has been routinely assessed with periodic creel surveys, with recent surveys in 2005 (Snook and Dieterman 2006) and 2013 (Dieterman and Snook 2015). These surveys and others (e.g., Anderson 2016) have traditionally identified April, May, and June, key months during the onset of the pandemic, as months that have also had peak angling activity (Snook and Dieterman 2006; Anderson 2016). Another creel survey was scheduled to begin in April 2020 but was initially canceled because of the pandemic with a later decision to postpone until July 1, 2020.

Escalating pandemic concerns during March and April 2020 created many challenges and uncertainty. State fisheries staff were informed on March 25 that a stay-at-home order was going into effect on March 27 with no known timetable for return to normal operations. To gauge how creel estimates might be influenced if the creel survey schedule was modified (e.g., postponed) and, more broadly, to assess the pandemic effect on angler pressure, a decision was quickly made to deploy trail cameras at two angling sites with long-term fish population data. Unfortunately, one trail camera malfunctioned shortly after deployment, reducing data collection to only one site. Although data were limited to this one site, it has been widely acknowledged that the pandemic presented unprecedented challenges and disruptions to routine environmental assessments (Cooke et al. 2021; Tracy et al. 2021) emphasizing the importance of collecting pandemic-related data. Thus, objectives of this study were to 1) compile and review angling license sales before, during and after the pandemic, 2) quantify angler pressure and demographics during the 2020 pandemic and compare with data collected post-pandemic (in 2021 and 2022) and with angler license sales, 3) examine temporal changes in trout abundance to determine any pandemic-related effects resulting from changes in angler pressure, and 4) use trail camera data to better inform the relative influence of different temporal strata (day type, time of day) on future creel survey designs to assess stream-trout fisheries in the Driftless Area.

To understand changes in angler license sales during the pandemic, data gathered annually by the Minnesota Department of Natural Resources was compiled and plotted for selected pre- to post-pandemic years (2017 to 2022) and then simple percentage change among the years 2020, 2021, and 2022 was calculated. Anglers fishing for trout in southeast Minnesota are required to purchase one of several angling license options (e.g., individual, married couple, combination hunting and angling) and a trout stamp. All anglers aged 16–89 are required to purchase an angling license but trout stamps are only required for anglers aged 18 to 64. Also, trout stamps are not required for trout anglers fishing with either a 24- or 72-hour license. Temporal changes for total license sales, for both resident and nonresidents combined, and trout stamps was also examined. Minnesota did not temporarily waive any fishing license requirements during the pandemic but did maintain two free fishing weekends; for mothers (May 9–10) and residents taking kids fishing, June 5–7, 2020. Similar free fishing weekends have been present every year since at least 2017.

Angler use and pressure data were collected at one of the primary angling areas on Garvin Brook (UTM: Easting-596074, Northing-4873793), a stream site considered representative of the cold-water trout stream resource in southeast Minnesota and with a long-term fish monitoring station. Garvin Brook is a 17.2 km designated trout stream, but most anglers fish the upper 8.0 km, because it is designated as class 1A trout water and flows through easily accessible state forest land and a county park. Class 1A trout waters are defined by good water conditions (e.g., adequate water temperature) with high natural reproduction and adequate density, such that stocking is not needed. For safety reasons, most anglers access this upper 8.0 km area at one of four designated parking areas located along a U.S. highway. Per considerations in Hartill et al. (2020), I selected one parking area where a majority of anglers fish (personal observation) because the parking area has a gate that funnels anglers to the stream, making it an ideal place to stage a trail camera. More broadly, in past angler surveys, Garvin Brook ranked between the 15^th and 25^th percentiles for both percentage of all anglers stating they fish this stream and total estimated angler days across all 123 southeast Minnesota trout streams (Vlaming and Fulton 2003; Schroeder 2014). Thus, Garvin Brook is considered a popular stream to fish but not one of the top 20 most popular streams, nor one of the 75% of streams considered less desirable in southeast Minnesota. The goal of this study was not to obtain a total census of all anglers fishing Garvin Brook during the pandemic but rather to capture a representative sample of how much more angler activity and pressure was expended during the pandemic, and Garvin Brook should be considered an ideal representative of other trout streams in southeast Minnesota.

The Garvin Brook study site was also selected because fish populations are monitored annually as part of the southeast Minnesota long-term stream monitoring program (Dieterman et al. 2020). These annual fish data simultaneously allowed an examination of effects of potential changes in angler pressure on fish populations. Garvin Brook is managed primarily for Brown Trout Salmo trutta, and harvest of larger trout is prohibited by a 305–406 mm total length (TL) protected slot limit. Harvest of other sizes is allowed but with a bag limit of five fish daily and only one trout can be larger than 406 mm TL. Fish populations are assessed annually in late September with a tow-barge electrofishing unit.

To quantify recreational angling pressure, a trail camera was deployed at the Garvin Brook site. Trail cameras have become a common and cost-effective tool to assess angler use with their efficacy tested for several aquatic systems (e.g., Stahr and Knudsen 2018) and found to be especially effective for small limited-access streams similar to Garvin Brook (Hining and Rash 2016). One trail camera (Stealth Cam® Model STC-G45NGX: 22 megapixels, 30 m range) was placed within 8 m of, and facing, the entrance gate, but with a view of most of the parking area. The trail camera was programmed for motion capture and to record a photo of the parking area every 30 min between the hours of 5:00 AM and 11:00 PM. Fishing hours for stream trout in Minnesota are from one hour before sunrise to 11:00 PM. The camera was monitored about every two weeks with batteries and data storage cards changed monthly.

Anglers were identified by users with a fishing pole and pressure was quantified based on photos from either motion capture or from the 30-min time lapse feature. For most anglers, the motion capture feature was triggered every time a person or group walked through the gate, and the total number of minutes between photos of the same person/group entering and exiting was recorded. For groups of more than one angler, the times for the first person in the group to enter and for the last group member to exit the area were recorded. In practice, most groups passed through the gate at the same time, but occasionally one group member took extra time before entering or exiting. Time spent at the site for a few angler groups could not be quantified from motion capture showing the exact time of entrance or exit. Instead, time spent fishing was estimated from time-lapse photos taken every 30 minutes. In almost all cases these were photos showing the presence of an angler associated with a vehicle in one photo but not in the preceding or following 30-minute photo, indicating that the angler had entered or left the parking area. The vehicle was still observed in each 30-minute photo but at some point the vehicle was gone and the angler did not trigger the motion capture. To calculate time present, I used the 15-minute interval between photos showing presence and absence of the vehicle, as the missing enter or exit time. Motion capture and time lapse photos were sufficient to measure time present for 703 of 743 parties observed in the study area (95%) over the three years. For the remaining 40 parties, 23 were a picture of just a vehicle with no person associated with it. Consequently, it was impossible to determine if the party was angling or not, so I ignored these parties from all calculations. The number of instances of these unknown activities was eight in 2020, eight in 2021, and seven in 2022. The final 17 parties consisted of single photos of an angler (no vehicle) either entering or exiting the study are, but with no corresponding photo to delineate total time present. These anglers may have parked a vehicle outside of the parking area or had been dropped off, with the angler exiting at a different location. For these 17 parties (eight in 2020, seven in 2021 and two in 2022), mean angler trip length within the corresponding month and weekday/weekend-holiday strata was used for analysis. The trail camera stopped working for 12 days from August 28 to September 9 in 2020, the peak pandemic year, so all recreational use estimates for 2020 were minimum values. Estimates were not calculated for these missing days. As angler use and pressure data were essentially census data, all comparisons among time periods were based on summarized data with no statistical testing.

To better understand which anglers might have been affected by the pandemic, data for three demographic categories were also compiled from trail camera photos: gear type (fly fishing, spin fishing or could not determine), sex and age. Ages were assigned into young (ages 0–19), middle age (20–59), and older (60+). Chi-square goodness of fit tests were used to determine significant differences in demographic variables between the peak pandemic year of 2020 and each of the subsequent two study years.

To assess potential pandemic effects on Brown Trout populations, annual abundance data from 2017 to 2022 were plotted and examined. Brown Trout populations are assessed annually in late September with a two-pass population estimate and data summarized as the number of Brown Trout per kilometer (± 95% C.I.) for age-0 recruits, all age-1+ adults and adults > 305 mm TL (see Dieterman et al. 2020 for more details on sampling protocols and population estimation methods). Data were plotted and visually examined for differences based on population estimates and confidence intervals.

To better inform future creel survey designs, the number of anglers present at the study site was calculated for various temporal strata used in previous creel surveys of the southeast Minnesota stream-trout fishery. Those creel surveys assumed equal probabilities between AM/PM and weekday/weekend-holiday strata and among two-hour time blocks across a full day because angler effort in each of these strata was unknown. Thus, data from trail cameras running every hour of the day were also used to calculate the proportion of anglers fishing each of the AM/PM, weekday/weekend-holiday, and each two-hour time block (0600–2100 hrs) strata. Chi-square goodness of fit tests were used to determine if the proportion of anglers in AM/PM and weekday/weekend-holiday strata differed significantly from a 0.50/0.50 ratio of sampling probabilities and from equal proportions (0.125) among the eight two-hour time blocks.

Sales of angling licenses and trout stamps increased substantially during 2020, the peak year of the pandemic and declined in subsequent years (Figure 1). In the three years prior to the pandemic, an annual average of about 1.31 million angling licenses and 107,000 trout stamps were sold. In the first year of the pandemic (2020), angling license sales increased by 8.9% from those sold in 2019, and 25.6% for trout stamps, suggesting increased angling pressure on fish populations. One year after the pandemic (2021), sales of both licenses and trout stamps declined by about 4% and in 2022 were about 11% lower than during the 2020 peak pandemic year (Table 1).

At least one angler was present at the Garvin Brook study site on 84% of days in 2020, 66% in 2021, and 69% in 2022. Angler presence was reduced in June 2021 (anglers present only 43% of days), likely because of a prolonged heat wave from June 3 to June 11 (MNDNR 2021), when anglers were only present on two of these nine days. Over 900 anglers spent over 1,500 hours fishing across the three years (Table 2). Total number of parties, anglers, and hours spent fishing were higher in the peak pandemic year of 2020 than in subsequent years. Following the pandemic peak of 370 anglers fishing for 602.8 hours in 2020, the number of anglers present declined by 29% in 2021 and by 22% in 2022. Similarly, total angler-hours declined by 23% between 2020 and 2021 and by 16% between 2020 and 2022 (Table 1). Higher angler pressure during the pandemic was mostly because of consistently higher pressure during the months of July, August, September, and October (Table 2).

Several angler demographics differed significantly between the peak pandemic year of 2020 and subsequent years, suggesting which demographic groups most used recreational angling as a safe outdoor activity (Table 3). There were significantly more anglers younger than 20 years old fishing during the pandemic and about 12% of all parties in 2020 had at least one child that appeared to be younger than age 10. There was also a significantly higher proportion of female anglers during 2020 (9%) than in 2021 (5%). However, this proportional difference did not extend into 2022, making it difficult to conclude the pandemic influenced the number of female anglers present. Similarly, the proportion of anglers using spinning gear was also significantly higher during 2020 than in 2021 but not in 2022. In addition, for 5%–11% of angling parties, depending on year, it was difficult to identify whether the fishing rod observed was a fly rod or a spinning rod, further obfuscating significant differences in gear types used.

Adult Brown Trout abundance varied across study years, declined slightly during the peak pandemic year of 2020, but rebounded with no lingering effects (Figure 2; Table S1 Supplemental Material). Pre-pandemic (2017–2019), Brown Trout abundance averaged 671 adults/km, but in 2020, abundance (542 ± 58/km) was 24% lower than in 2019 (710 ± 54/km). However, adult abundance in 2020 was not different from abundance in 2017 (554 ± 36/km) as confidence intervals overlapped. This suggests that the 2020 pandemic decline was not outside of normal variation for this population. Conversely, age-0 Brown Trout abundance increased by more than 2000% between 2019 and 2020. Consequently, adult abundance rebounded in 2021 with the highest estimate (1,838 ± 101/km) in any of the study years and remained high in 2022, likely influenced, in part, by the large 2020 year-class. There were no discernable temporal patterns in abundance of larger Brown Trout (≥ 305 mm TL) that appeared related to higher angling pressure in 2020.

The proportion of anglers fishing AM/PM and weekday/weekend-holiday strata differed significantly from previously assumed equal 0.50/0.50 sampling proportions. Proportions differed significantly for each year independently and for all years combined with disproportionately higher numbers of anglers fishing the PM (69% overall) and weekday (61% overall) strata (Table 4). Similarly, the proportion of anglers present at the Garvin Brook site differed significantly from assumed equal proportions (0.125) among the eight two-hour time periods for each year (2020 χ² = 199.91, df = 7, P < 0.001; 2021 χ² = 181.52, df = 7, P < 0.001; 2022 χ² = 129.03, df = 7, P < 0.001) and for all years combined (χ² = 479.37, df = 7, P < 0.001; Figure 3). There were disproportionally more anglers present between the hours of 10:00 AM and 7:00 PM when proportions ranged from 0.15-0.17 for each two-hour period and 83% of all anglers were present. Conversely, there were disproportionally fewer anglers present before 10:00 AM and after 8:00 PM with proportions being 0.03 for 6:00–7:59 AM, 0.08 for 8:00–9:59 AM, and 0.06 for 8:00–9:59 PM.

This study represents the first, and perhaps only, quantitative data assessing the effect of the COVID-19 pandemic on angler use and pressure and fish populations for a stream-trout fishery in the Driftless Area. These data verify that angler use was higher during the pandemic than in subsequent years; they contrast slightly with other indirect methods to estimate angler pressure, identify why these differences might exist, and suggest no long-term harm to these stream-trout fisheries. The results should also help inform future creel surveys to obtain more robust estimates and indicate shifting angler behaviors.

Higher angler use observed in this study helps address the uncertainty of how the COVID-19 pandemic affected outdoor recreation and adds to the growing number of studies reporting similar increased outdoor participation. Some early studies suggested that stay-at-home orders and fear of COVID-19 transmission might result in less outdoor participation, whereas others thought participation could be higher to satisfy physical and mental wellness (e.g., Rice et al. 2020; Beery et al. 2021). This study observed the highest number of angling parties, people, and pressure (total hours) during 2020 followed by declines, supporting other recent studies that have showed, in most instances, outdoor participation was higher during the pandemic than in other years (e.g., Midway et al. 2021; Hansen et al. 2023).

Because of pandemic-related suspensions of traditional creel surveys, managers may have been compelled to rely on changes in license sales to infer changes in angler effort and exploitation (Cooke et al. 2021; Tracy et al. 2021). Data in this study helped assess this inference and suggest caution in this interpretation. For example, in Minnesota, trout stamp sales declined by 11% between 2020 and 2022. Conversely, total anglers and angler-hours at the Garvin Brook site declined by 22% and 16%, respectively. Stated differently, although there were 12% more trout stamps sold during the height of the pandemic in 2020 relative to 2022, the number of anglers fishing Garvin Brook was 28% higher and total angler pressure (angler-hours) was about 19% higher. Other metrics in this study, such as angling license sales and changes between 2020 and 2021 were similar and suggest actual angler pressure was much higher during the pandemic than could be inferred by simple changes in fishing license and trout stamp sales.

Higher angler pressure can be partly explained by demographic differences between 2020 and the two subsequent years. One of the most consistent differences in angler demographics was a higher number and proportion of young anglers (< 20 years old) fishing in 2020, with several that appeared to be younger than 10 years old (personal observation) fishing with one or both parents. Consequently, most of these youngest anglers would not be represented by either angling licenses or trout stamps, as they were not required to purchase them. Such anglers also would not be represented in most indirect survey methods such as mail or electronic surveys because such surveys are usually limited to a survey pool of licensed anglers (e.g., Vlaming and Fulton 2003; Midway et al. 2021).

This study was also able to simultaneously assess changes in angler pressure and an associated sportfish population and documented no long-term pandemic impact on this trout fishery, despite a substantial increase in angling pressure. Lack of a long-term impact could be because of the high productivity of Driftless Area streams which are some of the most productive in the world (Kwak and Waters 1997). If increased angler pressure in 2020 resulted in higher harvest or even high hooking mortality, high trout production could have buffered the stream trout population from such increased mortality (Waters 1992). Adult Brown Trout abundance declined slightly from 2019 to 2020 but rebounded substantially in 2021, likely because of the abundant 2020 age-0 year class. Alternatively, there is a strong catch-and-release ethic among trout anglers fishing southeast Minnesota streams, as over 70% of anglers typically release most, or all, of the trout they catch (Vlaming and Fulton 2003; Schroeder 2014), which can lead to reduced harvest mortality. Finally, the 305-406 mm TL protected slot limit could have protected the population too; however, only a small proportion of trout in the Garvin Brook population exceeded 305 mm. In addition, in a broader assessment, Dieterman et al. (2020) found no changes in trout abundance between streams with and without the protected slot limit examined before and after it was implemented. Definitively identifying the specific reason for little change in the trout population was beyond the scope of this study, especially because harvest was not measured, but regardless of reason, these data suggest that this trout population was resistant to pandemic-influenced changes in angler pressure. Other researchers have also noted that, although several studies are being published that have documented increased angler pressure during the pandemic with perceived consequences to fish stocks, few actually documented those consequences (Bunt and Jacobson 2022), in part, because many fish sampling and monitoring programs were discontinued or modified during the pandemic (Cooke et al. 2021; Tracy et al. 2021). Thus, this study contributes important novel information on how the pandemic effected recreationally important fish stocks.

These data also suggest shifting angler patterns that should be accounted for in future creel survey designs for stream trout fisheries in the Driftless Area. Early creel surveys of southeast Minnesota streams either ensured more clerk effort on weekends/holidays and at dawn and dusk because of the perception that anglers were more active during these times (e.g., Kuehn and Schumacher 1957; Hayes 1990) or else simply used equal sampling probabilities among all strata because of an absence of information to better adjust clerk effort (e.g., Dieterman and Snook 2015). This study documented higher angler effort on weekdays (58–61% of anglers) and in the PM time periods (68–71%). Further, most anglers fished during midday hours. Such changing angler patterns could be because of an aging, retired clientele that has been documented in several outdoor pursuits including the stream trout fishery in southeast Minnesota (Dieterman and Snook 2015). The pandemic also altered work habits via factors such as, work-from-home orders or provided more free time in general (Howarth et al. 2021) and could explain shifting angling patterns too, but angler patterns observed during the pandemic peak in 2020 continued into subsequent years when such work-related restrictions were eased or removed entirely. Regardless of reason, these angling patterns appear to be present and continuing and should be used to help inform future angler creel survey designs, especially data from the two-hour time blocks (Figure 3) that have been used to extrapolate angler pressure and catch estimates in spatially extensive surveys (e.g., Dieterman and Snook 2015). Last, two-hour time block data may aid state agencies in helping anglers plan their fishing trips via publicizing these data on social media. For example, Driftless Area trout anglers commonly desire solitude as part of their angling experience (Schroeder 2014) and might use this information to choose when they want to fish to avoid other anglers, analogous to the “busiest times” figures often associated with restaurants and stores on internet searches.

Unfortunately, this study was limited to a single stream using a mechanical trail camera that can be subject to various problems (Hartill et al. 2020). As noted previously, I originally sought to collect data at two sites with long-term fish population monitoring, but one of our cameras stopped working and could not be replaced in a timely fashion. In addition, our remaining trail camera malfunctioned for 12 days in 2020, from August 28 to September 9, with erratic picture taking. Rather than attempt to estimate data for these 12 days, these data were omitted from analyses, so all 2020 estimates of angler use should be considered minimum estimates. Even missing these data, the 2020 peak pandemic year was still substantially different from 2021 and 2022 and thus, does not change the fundamental conclusions. By September 2020 additional cameras were purchased and the malfunctioning one was replaced. Lastly, Minnesota’s stay-at-home order began on March 27, 2020 and cameras were placed on March 25–26 with the intent to collect data during the early catch-and-release trout season. However, when this time frame was repeated in 2021, the trail camera at the Garvin Brook site was stolen sometime between late March and the beginning of the trout harvest season in mid-April. So again, rather than estimate missing 2021 data, all data collected during the early catch-and-release season from all study years was omitted to maintain consistency. Several authors have noted the chaotic nature of the early days of the pandemic and lamented how it might result in the loss of key information during an unprecedented time (Cooke et al. 2021; Tracy et al. 2021). Many pandemic related studies published recently have focused on larger-scale pandemic effects but have been mostly surveys of expert opinion (e.g., Stokes et al. 2020; Cooke et al. 2021) or of the recreational users (e.g., Smith et al. 2022). Fewer studies have been published of actual field data collected through the pandemic. As such, the present study will be an important contribution added to others to ultimately provide a more comprehensive quantitative assessment of the pandemic’s effects on fisheries resources. In summary, this study documented higher levels of angler use and pressure during the peak pandemic year than indicated by sales of angling licenses and trout stamps; but with no long-term effect on the Brown Trout fishery in a Driftless Area stream.

Please note: The Journal of Fish and Wildlife Management is not responsible for the content or functionality of any supplemental material. Queries should be directed to the corresponding author for the article.

Reference S1.Anderson D. 2016. Economic impact of recreational trout angling in the Driftless Area. Report to Driftless Area Restoration Effort. Trout Unlimited.

Available: https://doi.org/10.3996/JFWM-24-027.S1 (338 KB PDF) and https://bloximages.chicago2.vip.townnews.com/lacrossetribune.com/content/tncms/assets/v3/editorial/7/e4/7e46cd72-74b0-5c00-b640-079c58168870/5923b87c76669.pdf.pdf

Reference S2. Burkett EM, Winkler RL. 2018. Recreational fishing in Minnesota: using an age-period-cohort approach to understand fishing participation. Michigan Technological University. Houghton, Michigan, USA.

Available: https://doi.org/10.3996/JFWM-24-027.S2 (26.9 MB PDF) and https://www.mtu.edu/greatlakes/fishery/state-level/pdf/minnesotaangler-demographics-2000-2016.pdf

Reference S3. Dieterman DJ, Snook VA. 2015. The 2013 summer stream trout fishery in southeast Minnesota: historical changes and influence of angling regulations and instream habitat enhancement projects. Special Publication 177, Minnesota Department of Natural Resources, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S3 (2.21 MB PDF) https://files.dnr.state.mn.us/publications/fisheries/special_reports/177.pdf

Reference S4.Hayes M. 1990. Evaluation of special regulations for a winter trout season on the Middle and South Branches of the Whitewater River. Completion report for Job 179, F-29-R(P)-9. Section of Fisheries, Minnesota Department of Natural Resources, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S4 (2.54 MB PDF)

Reference S5. Kuehn JH, Schumacher RE. 1957. Preliminary report on a two-year census on four southeastern Minnesota trout streams. Investigational Report 186, Minnesota Department of Conservation, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S5 (4.98 MB PDF)

Reference S6.Schroeder S. 2014. A study of trout angler participation and activities in southeastern Minnesota. Minnesota Cooperative Fish and Wildlife Research Unit, Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S6 (980 KB PDF)

Reference S7. Snook VA, Dieterman DJ. 2006. A roving creel survey of selected southeast Minnesota trout streams – 2005. Completion Report for Job 737, F-29-R(P)-25. Section of Fisheries, Minnesota Department of Natural Resources, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S7 (196 KB PDF) https://files.dnr.state.mn.us/areas/fisheries/lanesboro/Creel_Report_Final_7_25_06.pdf

Reference S8. Vlaming J, Fulton DC. 2003. Trout angling in southeastern Minnesota: a study of trout anglers. Interim report for Fisheries Division, Minnesota Department of Natural Resources. Minnesota Cooperative Fish and Wildlife Research Unit, University of Minnesota, St. Paul.

Available: https://doi.org/10.3996/JFWM-24-027.S8 (636 KB PDF)

Data S1. Microsoft Excel file of data and metadata from trail camera observations of recreational users at Garvin Brook, Winona County, Minnesota during the stream trout angling seasons in 2020, 2021 and 2022. Data include dates (month, day, year, day of week), time periods (AM/PM and weekday vs. weekend/holiday strata) and recreational activity of each user party observed. Data also include arrival and departure times, trip length (minutes), number of people in the party and total time spent at the site. For anglers, additional data include the angling gear used and an estimate of age and gender for each person.

Available: https://doi.org/10.3996/JFWM-24-027.S9 (93.2 KB XLSX)

Table S1. Annual Brown Trout Salmo trutta population estimates for Garvin Brook, Winona County, Minnesota, 2017-2022 to assess effects of increased angling pressure during the 2020 COVID-19 pandemic on this population. Population estimates include the number per kilometer ± 95% confidence intervals for age-0 recruits, all adults, and all adults >305 mm total length. Data were taken from annual Federal Aid in Sportfish Restoration (Dingell-Johnson) reports completed by Minnesota Department of Natural Resources, Fisheries Managers.

Available: https://doi.org/10.3996/JFWM-24-027.S10 (14.2 KB DOCX)

Avery Schnaser and Anne Kemper were critical in helping process and analyze the many digital photos collected during this study. Jeff Reed, Dale Logsdon, the Associate Editor and two anonymous reviewers provided helpful comments on earlier drafts of the manuscript. This study is a contribution of the Southeast Minnesota Long-Term Stream Monitoring Program with support provided by the Minnesota Department of Natural Resources, Section of Fisheries. The authors of this article have no conflicts of interest to declare.

Any use of trade, product, website, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.