Brown Trout Redd Locations in the Northernmost Section of Spearfish Creek in Spearfish, South Dakota, USA ()
1. Introduction
Brown trout (Salmo trutta) were introduced into the Black Hills of South Dakota, the USA in 1890 and quickly became naturalized [1]. With self-sustaining populations in nearly all 1287 km of streams in the Black Hills with the suitable habitat, they are an extremely important recreational fish species [2] [3] [4]. Black Hills brown trout populations are maintained entirely by natural reproduction; no hatchery stocking of brown trout occurs [3].
Brown trout typically spawn in the northern hemisphere during the fall [5] [6]. Spawning in the Black Hills typically begins in mid-October and continues until the middle of November [7] [8] [9]. Similar to other salmonids, female brown trout make gravel pit nests called redds for egg deposition [10]. The location of redds within a stream is based on stream morphology, substrates, and water velocity [11], with higher water velocities flowing over course substrates at shallower water depths preferred [5] [9] [12]. The number of redds in a stream section has been used to monitor trout populations [13] [14] [15] [16] [17], particularly in response to changes in water flow and temperature [18].
The city of Spearfish in the northern Black Hills contains a section of Spearfish Creek with an abundant brown trout population [19]. Future creek flows may be impacted by the growing human population of Spearfish, and the entire northern Black Hills [20]. Changes in Spearfish Creek flows and temperatures may also be impacted by future agricultural and commercial demands, such as changes in discharge from the D. C. Booth Historic National Fish Hatchery [21] [22]. Thus, information is needed on the current status of brown trout reproduction to create a baseline for comparison in the future as environmental conditions change.
Martling et al. [9] described redd numbers in a southern reach of Spearfish Creek in the city of Spearfish. However, no information on redd locations or numbers in Spearfish Creek exists beyond the relatively small section that Martling et al. [9] sampled. Thus, the objective of this study was to survey redds in a reach of Spearfish Creek on the northern edge of Spearfish. With the information from this study and other similar studies, management staff can begin to glean where habitat projects should occur and where money can be spent to improve overall spawning and recruitment to improve angler satisfaction even further.
2. Methods and Materials
2.1. Study Area
Spearfish Creek is located in the northern Black Hills, Lawrence County, South Dakota, USA. The creek has an upper section that begins at the headwaters and flows northward downstream through Spearfish Canyon. This upper section ends towards the bottom of the canyon where most of the water enters an aqueduct. After the aqueduct intake, the creek is dry for most of the year. Water re-enters the creek channel after its discharge from the hydroelectric plant, resulting in continuous flows of the creek through the city of Spearfish. This lower section eventually discharges into the Redwater River. Spearfish Creek at the city of Spearfish flows ranged from 1.38 m3/s to 2.16 m3/s during the duration of this study [23].
This study occurred in a 1.67 km long mainstem reach of Spearfish Creek within the city of Spearfish (Figure 1). The study site was bordered upstream by
![]()
Figure 1. Location of Spearfish Creek and the creek reach surveyed.
the Jorgensen Park walking path bridge (44˚30'21.19"N, −103˚51'59.05"W) and downstream by the bridge at Highway 14 (44˚31'4.73"N, −103˚51'56.68"W). The distance from the hydroelectric plant (44˚28'4.73"N, −103˚51'56.68"W) to the start of the survey site is approximately 3.86 km. Martling et al. [9] surveyed trout redds in a section of Spearfish Creek in short reach beginning at the hydroelectric plant. The study site of the current study was approximately 2.92 km from the end of the Martling et al. [9] survey location (44˚29'2.47"N, −103˚51'44.06"W) (Figure 2). The study reach was divided into five similarly-sized sections (Figure 3).
Land use in the study area varied. In the survey reach, the riparian area furthest upstream was a developed city park. Immediately downstream, the creek flows through an area of residential housing (Figure 4). The final part of the survey area was primarily undeveloped park land and a small area of commercial development (Figure 5).
Calcite precipitate characterizes the substrate of Spearfish Creek [19]. The creek has a wide variety of substrate sizes and in-stream habitats [9]. While Spearfish Creek contains naturalized populations of brown trout, rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), the fish population in the creek section in this study consisted almost exclusively of brown trout [24].
![]()
Figure 2. Location and distances of survey site, Marling et al. [9] study site, and hydropower plant.
![]()
Figure 3. Study area divided into five sections (section 5 is the furthest upstream).
![]()
Figure 4. Photo of residential section of Spearfish Creek.
![]()
Figure 5. Photo of undeveloped park land of Spearfish Creek.
2.2. Redd Identification and Location
Redd sampling began on October 13, 2020. Observations occurred approximately weekly until the construction of new redds and observations of spawning fish had ceased, as described by Gallagher et al. [25]. Each weekly survey lasted approximately two to three hours, depending on the number of redds observed. The final sampling date was November 17, 2020. Redd identification followed the techniques described previously [7] [8] [9] [25]. However, because redds varied greatly in size, and creek conditions varied from week-to-week, a redd was loosely defined as the presence of a clear pit and overturned substrate that formed a mound and/or a clear tail (Figure 6) [26]. Redd locations were recorded using TerraSync on the Trimble Geo7X Global Position System (Sunnyvale, California, USA). Every redd observed each week was marked, even if it was a repeat of prior weeks.
Ambient air temperatures were obtained for each of the sampling dates from a commercial website (https://www.wunderground.com/history/daily/us/sd/spearfish). The amount of daylight for each date was also recorded (https://sunrise-sunset.org/us/spearfish-sd/2020/11).
![]()
Figure 6. Photo of brown trout in study area on a typical redd.
3. Results
A total of 146 redds were observed over the six-week study period. Redds were first observed on October 13 and redd construction ceased after November 17. Peak spawning activity was observed on November 3, when 52 new redds were observed (Table 1). Brown trout were the only fish species visually observed in the study area. During the fifth week of the study, redds started to deteriorate rapidly making it more difficult to observe those redds previously recorded. Redd construction varied considerably throughout the study area (Figures 7-11). A few creek sections in the study area had relatively high redd concentrations (Figures 12-14). Mean daily ambient air temperature varied greatly during the study, with temperatures dropping to −10˚C in one week of the study (Table 2). A sizable number of redds were observed under the Highway 14 bridge at the north end (section 1) of the study site (Figure 15).
4. Discussion
4.1. Redd Timing
The timing of redd construction in this study from October 13 to November 17 was similar to that reported elsewhere in the Black Hills. Martling et al. [9] observed the first redds in Spearfish Creek upstream from the current study site on October 15, with the final redds observed on November 12. Ketelsen et al. [7] reported that brown trout in Rapid Creek and Box Elder Creek began on October 14 and continued until November 5. Blaine et al. [8] observed the first brown trout redds in Crow Creek on October 17, with the final redds appearing on November 21. These spawning dates observed in this study are also within the range of dates reported elsewhere in the United States [5] [6] and Canada [27]. However, spawning of brown trout in the Black Hills is earlier than that reported for brown trout in their native range [28] [29], likely due to differences in latitude, photoperiod, altitude, and water temperatures [18] [26] [30] [31].
![]()
Table 1. The number of redds observed by week and cumulatively from a section of Spearfish Creek in the city of Spearfish, South Dakota, USA during the fall of 2020.
![]()
Table 2. Ambient air temperature and daylight length on the days of sampling redds from a section of Spearfish Creek in the city of Spearfish, South Dakota, USA during the fall of 2020.
![]()
Figure 7. Weekly redd locations and numbers (as denoted by blue dots) in section 1 of Spearfish Creek study stretch.
![]()
Figure 8. Weekly redd locations and numbers (as denoted by blue dots) in section 2 of Spearfish Creek study stretch.
![]()
Figure 9. Weekly redd locations and numbers (as denoted by blue dots) in section 3 of Spearfish Creek study stretch.
![]()
Figure 10. Weekly redd locations and numbers (as denoted by blue dots) in section 4 of Spearfish Creek study stretch.
![]()
Figure 11. Weekly redd locations and numbers (as denoted by blue dots) in section 5 of Spearfish Creek study stretch.
![]()
Figure 12. Weekly additions of redds in one concentrated area in section 2.
![]()
Figure 13. Weekly additions of redds in one concentrated area in section 4.
![]()
Figure 14. Weekly additions of redds in one concentrated area in section 4.
![]()
Figure 15. Photo of redds under highway 14 bridge.
4.2. Redd Density
At 91 redds/km, the redd density observed in this study is similar to the 84 redds/km reported by Martling et al. [9] for an upstream section of Spearfish Creek. In other streams in the Black Hills, redd densities of 106 redds/km, 43 redds/km, and approximately 5 redds/km were reported for Rapid Creek, Box Elder Creek, and Crow Creek, respectively [7] [8]. In locations outside of the Black Hills, redd densities of 73 redds/km were reported in Scotland [32], 36 redds/km in Spain [33], and 10 redds/km in Canada [27]. Spearfish Creek may have high redd densities because of the high-water quality, good spawning substrate, and lack of sedimentation, as opposed to the lower densities of redds observed in the more heavily-sedimented Crow Creek and Box Elder Creek [7] [8] [9] [34].
4.3. Superimposition
Redd superimposition, when a female trout uses a previously excavated redd, was observed in this study [35] [36] [37]. Martling et al. [9] did not report redd superimposition in a more upstream location on Spearfish Creek but stated that redds were in very close proximity to one another. Redd superimposition has only been reported in the Black Hills where both brown trout and brook trout coexist at relatively high numbers [8]. Only intra-specific superimposition occurred in this study, however. Brook trout are only rarely observed in the section of Spearfish Creek in Spearfish, and only brown trout were observed spawning. Superimposition of salmonid redds has been observed in other locations outside of the Black Hills and may be due to brown trout altered creek substrates, homing behavior, or other non-habitat related reasons [33] [37] [38].
4.4. Limitations
Because this study was conducted for only one spawning season on one specific 1.6 km reach of Spearfish Creek, the results may not be applicable to other reaches of Spearfish Creek or other reaches of the 1287 km of streams in the Black Hills [2]. The relative inexperience of the redd observer may have also impacted the results [25]. Just because a redd is observed does not necessarily mean that eggs were deposited or that reproduction was successful. However, despite these limitations, the similarity of the results of this study to those reported for an upstream location of Spearfish Creek [9] provides some assurance that the results are valid.
4.5. Implications
Salmonid populations can be estimated using redd counts [13] [14] [15] [16] [17] [39]. Redd surveys are also much less expensive than using stream electrofishing for population monitoring [13] [14] [15] [16] [17]. Thus, the use of brown trout redd surveys could be a feasible alternative to electrofishing Spearfish Creek on a regular basis as is currently done. In addition, because redd monitoring can assess environmental changes [18], this initial study can be used as a baseline for comparison to future changes in this specific section of Spearfish Creek due to urbanization [26] [30] [31] [40].
4.6. Conclusion
This study showed that redds in this section of Spearfish Creek are being made from mid-October through mid-November, which is consistent with Martling et al. [9]. With continuation of these studies throughout the Black Hills, future habitat projects can be created to potentially improve spawning habitat for salmonid fish, and increase angler satisfaction.
Acknowledgements
We would like to thank Shaylee Martling, Nathan Huysman, and Jeff Stevens for their assistance with this study.