A Brook Trout restoration project was initiated on Rinehart Brook, a tributary to the Black River within Hacklebarney State Park in 2017. Prior to the project, non-native Brown Trout had become the dominant trout species, with the native Brook Trout residing in small numbers. The objectives of this study were: to determine if multiple depletion electrofishing could be an efficient manner to remove Brown Trout, to monitor potential rebound effects of the Brook and Brown Trout populations, to determine if natural boulder waterfalls prevent Brown Trout from recolonization, and ultimately restore Brook Trout. The following bullets are highlights from this five-year study:
- 19 single pass removals of Brown Trout via backpack electrofishing were conducted along Rinehart Brook from 2017 through 2021.
- A total of 1,533 Brown Trout were removed from Rinehart Brook (1,255 in 2017, 65 in 2018, 118 in 2019, 87 in 2020, and 8 in 2021).
- A total of 1,215 Brown Trout were removed from the 1.1-mile core study area upstream of the upper waterfall (1,110 in 2017, 19 in 2018, 83 in 2019, 3 in 2020, and 1 in 2021).
- In 2017, to determine if a series of natural waterfalls on Rinehart Brook would prevent Brown Trout from recolonizing upstream, 1,048 Brown Trout captured from Rinehart Brook were fin-clipped and relocated to several locations along the Black River.
- 46 of these fin-clipped fish were subsequently captured upstream of the waterfalls (43 in 2018, 3 in 2019, 0 in 2020, and 0 in 2021), indicating the waterfalls are not a barrier to the upstream movement of Brown Trout.
- The maximum number of Brook Trout captured on any given complete pass was 65 in 2017, 147 in 2018, 841 in 2019, 1,169 in 2020, and 1,316 in 2021.
Capture and removal of Brown Trout were accomplished via multiple electrofishing passes from August 2017 through October 2021. Approximately two miles of Rinehart Brook and approximately 0.5 miles of an unnamed tributary were initially electrofished. Rinehart Brook was divided into multiple sections that could be electrofished either consecutively or at different times. Starting downstream and moving upstream; Section 1: mouth of the Black River and ended at the uppermost waterfall, which at one time was considered a potential barrier to fish movement (see photo). Section 2: from the waterfall upstream to the beginning of the standardized 150-m stretch (surveyed for several years as part of a study that aims to better understand the relationship of temperature with various measures of wild trout populations); Section 3: standardized 150-m stretch (so that it could be compared with trout numbers from previous surveys); Section 4: above standardized electrofishing section upstream to a small dam upstream of Hacklebarney Road. The core study area is designated as sections two through four. A fifth section continued upstream to Old Farmers Road. An unnamed tributary (Rinehart Brook)(trib.)(Fairmont) converges with Rinehart Brook just upstream of Hacklebarney Road. This tributary was also electrofished and only Brook Trout were found.
During 2017, a total of seven passes were completed. This was broken down into 29 surveys for removal and 1 to mark fish below the potential barrier. In 2018, a total of four passes were completed, totaling 19 surveys. Five passes were conducted in 2019, totaling 21 surveys. The tables below describe the numbers of both Brook and Brown Trout that were captured in each section for 2017 -2019, followed by the percentage of all trout that were Brook Trout.
The first pass through the core study area revealed a total of 725 Brown Trout and only 58 Brook Trout (7.3% Brook Trout). All Brown Trout were removed, and all other species were returned where they were captured. Subsequent passes resulted in fewer Brown Trout and relatively stable numbers of Brook Trout. By the seventh pass, only 9 Brown and 60 Brook Trout were encountered (87.0% Brook Trout). Seventy-seven Brook Trout (and no Brown Trout) were collected on the first pass in the tributary. Passes four through seven resulted in the capture of 79 additional Brown Trout that were euthanized.
Questions remained regarding the ability of trout to traverse a series of waterfalls/plunge pools near the stream’s confluence with the Black River. To test this, adipose fins were removed from 1,048 Brown Trout collected in 2017 and were transplanted below the falls in both Rinehart Brook and the Black River. All Brown Trout were examined during subsequent removal efforts, to determine if any marked Brown Trout are found upstream of the falls. As of the final survey of 2017 on October 3, many marked Brown Trout were found below and between the series of falls, however none had been re-captured above the falls as of the final electrofishing survey.
Additional surveys resumed in 2018, continuing to remove Brown Trout not previously captured and to monitor the Brook Trout population. Unfortunately, 43 clipped Brown Trout were found upstream of the waterfalls, demonstrating recolonization. Those fish, in addition to 74 Browns that were not initially captured were euthanized. A total of four electrofishing passes took place in 2018, with the final pass on October 4, when no Brown Trout were found upstream of the upper falls for the first time in this study. In the best interest of the resident Brook Trout, all Brown Trout (152) captured in Rinehart Brook during 2018 were euthanized. A final removal was conducted from the confluence to the upper falls on October 18, with only six Brown Trout found.
After one year, Brook Trout benefited from the removal of Brown Trout, as the total number has more than doubled. The average number of Brook Trout captured on any given complete pass in 2017 was 55 (max. 65 / min. 38). This average increased to 120 (max.147 / min. 111) in 2018. More impressive was the total number of Brook Trout older than young-of-the-year (YOY) increased from a maximum of five (low of 2) to a maximum of 43 (low of 26). The lack of Brown Trout upstream of the upper falls and the increase in older than YOY Brook Trout give great reasons for optimism for 2019 and beyond. During the third year of the study (2019) five passes took place, removing 83 unclipped Brown Trout from the core study area and three clipped Brown Trout were found upstream of the upper falls. The largest number of Brook Trout collected in 2019 (841) was almost 13 times greater than the initial largest number (67) in 2017. The fewest number of Brook Trout in 2019 was 748 and the average was 797.
In addition to the increase in total numbers of Brook Trout over time, the size distributional changes are noteworthy. Age I or older found in 2017 was only 5, whereas they increased to 43 (2018) and 52 (2019) in subsequent years. The largest Brook Trout captured in 2018 was 8.7”, whereas 24 Brook Trout were found in 2019 that were greater than or equal to 8.4”.
Sampling in 2020 and 2021 was reduced, not only due to the pandemic, but also because it was less necessary due to the decreased number of Brown Trout in the system. Brown Trout removals took place in the fall of 2020 and the summer and fall of 2021, producing only 3 Brown Trout in 2020 and 1 in 2021. As for the Brook Trout, numbers continue to climb, with 1,169 in the fall of 2020 and 1,316 in the summer of 2021 and 1,048 encountered in the fall of 2021.
This study is ongoing. Subsequent electrofishing surveys will occur in 2022 and beyond to remove Brown Trout until the waterfalls are constructed and to monitor the existing Brook Trout population. Enhancement of the natural waterfalls is being considered to prevent Brown Trout recolonization from the Black River into Rinehart Brook.
This study has demonstrated that removal of Brown Trout by electrofishing is a feasible tool to use in the conservation of native Brook Trout. Other means of removal, such as the use of a piscicide, result in the loss of all fish present. Therefore, electrofishing is a preferred method to restore native fish populations when other natives are present. Additional Brook Trout restoration projects utilizing backpack electrofishing are likely to occur in other New Jersey streams in the near future.
|Year 1 (2017)||Year 2 (2018)||Year 3 (2019)||Year 4 (2020)||Year 5 (2021)|