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Article

Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams

by
Eric J. Gates
1,† and
Peter C. Smiley, Jr.
2,*
1
School of Environment and Natural Resources, The Ohio State University, Columbus, OH 43210, USA
2
USDA Agricultural Research Service, Columbus, OH 43210, USA
*
Author to whom correspondence should be addressed.
†
This work was part of the undergraduate honors thesis of Eric J. Gates.
Fishes 2024, 9(8), 296; https://doi.org/10.3390/fishes9080296
Submission received: 7 May 2024 / Revised: 1 July 2024 / Accepted: 18 July 2024 / Published: 27 July 2024
(This article belongs to the Section Biology and Ecology)
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Abstract

:
Instream wood is important for fish in headwater streams because it promotes the development of pool habitat and provides cover from predators during periods of low flow. The benefits of large instream wood (length > 1 m and diameter > 0.1 m) have been extensively documented, but little is known about the influence of small instream wood (length ≤ 1 m or diameter ≤ 0.1 m) on fish communities and hydraulic conditions (i.e., water depth, water velocity, wetted width, discharge, pool area) in channelized agricultural headwater streams in North America and Europe. Understanding the influence of small instream wood will provide information that can guide the development of novel management strategies for fishes within these degraded streams. We conducted a two-part field experiment in the summer of 2011 in channelized agricultural headwater streams in central Ohio, consisting of an initial instream wood survey to document the amounts and types of instream wood found in these streams, and then conducted a before–after–control–impact experiment where we sampled fishes and hydraulic variables before and after the addition of small instream wood to pools. The instream wood survey documented that instream wood density ranged from 0 to 0.29 pieces/m2, small simple pieces were the most frequently occurring type of instream wood, and parallel was the most frequently occurring instream wood orientation. The amount of instream wood was greater (p < 0.05) in the treatment pools than the control pools after the small instream wood addition. No differences (p > 0.450) in fish community structure or hydraulic variables occurred between control and treatment pools before or after the addition of small instream wood. Our results suggest the addition of large instream wood might be needed to elicit a fish community response, and it is possible to add instream wood to channelized agricultural headwater streams without impeding the downstream water flow.
Keywords:
instream wood; fish community; hydraulic conditions; stream habitat management
Key Contribution: A field experiment was conducted to investigate the effect of adding small instream wood on fishes and hydraulic conditions in channelized agricultural headwater streams. Adding small simple instream wood pieces at a density of 1 piece/m2 did not influence fish community structure or hydraulic variables within pools in channelized agricultural headwater streams.

1. Introduction

Instream wood is an important resource for fishes and other aquatic animals because it contributes substantially to the physical dynamics and ecological relationships within streams and rivers [1], particularly in historically forested landscapes. Large instream wood influences stream hydraulic conditions (i.e., water depth, water velocity, etc.) and geomorphology by redirecting water flow, which creates heterogeneous and complex patches of pool and riffle habitat suitable for different fish species. Instream wood provides fishes with important cover from terrestrial predators and piscivores, shelter from strong water currents, spawning substrates, and feeding sites [2,3]. Instream wood also controls erosion and sediment loading by stabilizing stream banks [4,5]. Nutrient dynamics and cycling are influenced by instream wood through its ability to trap and accumulate detritus, plant matter, and other pieces of instream wood and provide an important source of energy, particularly in headwater streams that rely on allochthonous energy inputs from the riparian zone [6,7]. Many aquatic macroinvertebrates that are an important food resource for fishes rely on instream wood for reproduction, refuge, and foraging [8,9,10].
The benefits provided by instream wood to native fishes are the result of those fishes evolving and adapting to large amounts of instream wood that was once common in streams of the Midwestern United States prior to European settlement [11,12]. Common pathways of instream wood recruitment into headwater streams include falling trees and branches directly into the stream channel, beaver activity, and major disturbances within the watershed, such as landslides, debris flows, flooding, and logging activity [3,13,14]. Following settlement and westward expansion, the landscape of the Midwestern United States was permanently changed as forests were removed for agriculture, and wood was removed from rivers and streams because it impeded navigation and was considered unaesthetic [1,15]. Channelization involving the creation of new tributaries and the straightening and enlargement of existing streams was conducted to remove wetlands and drain hydric soils to increase agricultural productivity [16,17]. Headwater streams were often targeted because their small size made them easier to manipulate. Thus, channelized agricultural headwater streams (i.e., agricultural drainage ditches) have become common within agricultural watersheds of the Midwestern United States as a result of the widespread use of agricultural drainage and channelization practices [17].
Management of channelized agricultural headwater streams involves periodic dredging, removal of woody vegetation within the riparian zones, and removal of instream wood and other cover types that might reduce drainage capacity. The removal of instream wood and other cover types leads to reduced habitat diversity that has a negative impact on fishes [17]. Results from studies evaluating fish–habitat relationships within channelized agricultural headwater streams highlight the importance of instream habitat for fishes within these degraded streams [17,18,19]. Additionally, habitat destruction is a leading cause of extirpation and extinction of fish species worldwide [20]. Habitat degradation continues in these streams because farmers and stream managers remain unaware or ambivalent to the harmful impacts of channelization and instream wood removal on fish communities. Although channelized agricultural headwater streams are managed primarily to drain water from agricultural cropland, they are capable of serving as fish habitats [17,21]. Thus, there is a need for multiple-use management strategies for these degraded streams that can improve their ability to serve as fish habitats and provide agricultural drainage and other ecosystem services [17,22].
Instream wood addition is a common stream restoration practice in the United States [23,24]. However, within the United States, the research focus involving instream wood has been on large instream wood in the Pacific Northwest region, where salmon conservation and restoration are a priority issue for stream restoration [1,12,23,25]. As such, there exists a need to better understand the effects of instream wood in small headwater streams because the dynamics of instream wood recruitment, distribution, and movement differs between small headwater streams and large rivers [1]. Additionally, there is much less information on instream wood and its role in agricultural streams and rivers that lack or contain less instream wood than forested streams [25]. Only a limited amount of information on the influence of adding large instream wood (length > 1 m and diameter > 0.1 m) on fishes [2,26,27] and hydraulic conditions [2,28,29] in channelized agricultural headwater streams in the Midwestern United States is available. We also identified a limited number of studies [30,31,32,33,34] documenting the influence of adding small instream wood (length ≤ 1 m or diameter ≤ 0.1 m) on fishes. However, none of these studies were conducted in channelized agricultural headwater streams in the Midwestern United States, and none evaluated the influence of small instream wood on hydraulic conditions. The practice of adding small instream wood to channelized agricultural headwater streams has the potential to be adopted by the agricultural community because it does not require taking agricultural land out of production, it does not require heavy equipment to install, and it would intuitively be perceived as less of a drainage hindrance. We conducted a two-part field experiment in the summer of 2011 in channelized agricultural headwater streams in central Ohio, consisting of an initial instream wood survey and a manipulative field experiment to document the effects of adding small instream wood on fishes and hydraulic conditions (i.e., water depth, water velocity, wetted width, pool surface area, discharge). We hypothesized that adding small instream wood to channelized agricultural headwater streams would provide more cover that would benefit fish communities without influencing hydraulic conditions.

2. Materials and Methods

Our field study was conducted in the summer of 2011 and consisted of two parts, with an instream wood survey and a manipulative field experiment (Figure 1). The first part consisted of conducting an initial survey of instream wood in six channelized agricultural headwater streams in central Ohio to identify the most common type of instream wood and the amounts of instream wood occurring in these streams. The results of this instream wood survey guided our selection of what type of instream wood (i.e., small simple instream wood pieces) and the amounts of instream wood that should be added in the second part of this study. Specifically, the second part consisted of a manipulative field experiment that used a before–after–control–impact sampling design. We sampled fishes and hydraulic variables (i.e., water depth, water velocity, wetted width, pool surface area, discharge) in control and treatment pools within four streams for two weeks before adding small instream wood into the treatment pools. After this initial sampling was completed, we added and maintained small instream wood within the four treatment pools for 28 days, and during this time, no sampling occurred. Finally, at the conclusion of this treatment period, we again sampled fishes and hydraulic variables within the control and treatment pools for two weeks.
Our study was conducted in six channelized agricultural headwater streams (channelized streams) of the Upper Big Walnut Creek watershed in central Ohio, USA (Figure 2). The six study streams are headwater streams with an average watershed size of 5.1 km2 (range 1.2 to 9.7 km2). Land use adjacent to the sites consisted of row-crop agriculture of corn or soybean. Channelized streams exhibit the straightened, trapezoidal channel shape typical of agricultural drainage ditches in the region and contain narrow riparian zones composed mostly of herbaceous vegetation.

2.1. Instream Wood Survey Methods

We surveyed instream wood in six channelized streams to determine what types of instream wood and the amounts of instream wood that naturally occur in these streams. Specifically, this instream wood survey was conducted to help us select what type of instream wood and how much instream wood to add as part of our experiment. We established one 200 m long site in each stream and conducted one instream wood survey in each site under baseflow conditions between 16 June 2011 and 24 June 2011. We systematically searched for instream wood within the wetted width of each 200 m long site. We recognized 14 types of small and large instream wood (Table 1). All individual pieces with lengths > 0.4 m length and diameter > 0.02 m and all accumulations and overhanging vegetation found in the water of each 200 m long site were counted and measured at each site. All found individual pieces were stationary, and the orientation of each piece relative to stream flow (e.g., parallel, diagonal, or perpendicular) was also recorded. The diameter was measured at both ends of each individual piece with a vernier caliper, and the length within water was measured with a tape measure. We also enumerated and determined the surface area in the water of accumulations, root wads, and overhanging woody vegetation. We obtained one measurement of length and one measurement of width at the widest point of accumulations, root wads, and overhanging woody vegetation so that their surface area calculations would represent a square or rectangle capable of containing the entire accumulation, root wad, or overhanging woody vegetation. We used a tape measure and measured wet width at transects located every 25 m in each 200 m long site to calculate the wetted surface area of each site, as needed for calculations of instream wood density and the percent instream wood.
We calculated abundance (number of all instream wood/200 m stream length), density (number of all instream wood/m2), instream wood richness (number of types of instream wood), percent small instream wood (number of all small instream wood types/number all instream wood types), percent large instream wood (number of all large instream wood types/number of all instream wood types), and the number of each type of instream wood found and the observed orientation of all instream wood types found.

2.2. Small Instream Wood Addition Experiment Methods

2.2.1. Experimental Design

Our manipulative field experiment was conducted in four channelized streams (Figure 2) that were selected because they were low-gradient warmwater streams that possessed similar watershed sizes, narrow herbaceous riparian habitats, and sparse canopy cover (Table 2). Our instream wood survey results indicated these four sites exhibited low instream wood densities (≤0.03 pieces/m2), low instream wood richness (≤5), and lacked large accumulations (Table 3).
In July 2011, we established one site in each of the four channelized streams (Figure 2). The location of the site within each channelized stream was dependent on the location of pool habitat. We chose pools as the microhabitat type to experimentally manipulate because they serve as refugia for fishes during the summer. We felt increasing instream wood amounts within pools would be more likely to benefit fishes than increasing instream wood amounts within shallower microhabitats that would be more likely to dry up during our study. Each site consisted of one pair of adjacent 3 m long pools that initially contained no naturally occurring instream wood. The downstream pool was assigned as the treatment pool, and the upstream pool was assigned as the control pool at each site. We assigned the downstream pools of each pair as the treatment pool to ensure that our instream wood additions would not influence the control pools. The mean distance between the control and treatment pools within each stream was 25 m (range 7 to 49 m). Transects were established at the downstream (T0), middle (T1.5), and upstream (T3) ends of each pool for measurements of hydraulic variables.
Our experimental design was a replicated before–after–control–treatment (BACI) design, in which fish and hydraulic variables within all four sites were sampled weekly for two weeks during the first sampling period (before small wood addition) when both the treatment and control pools lacked instream wood. After the completion of the first sampling period, we added small instream wood to the treatment pools in each site. Small instream wood was not added to the control pools. We then conducted weekly checks within the treatment pools to ensure the established instream wood densities were maintained for a period of 28 days. No fish sampling or measurements of hydraulic variables occurred during this treatment period. At the end of the treatment period, we began the second sampling period (after small wood addition) where we sampled fish and hydraulic variables weekly for two weeks within four treatment pools that contained the added small instream wood and four control pools that lacked small instream wood.

2.2.2. Before Small Wood Addition Fish and Hydraulic Condition Sampling Methods

The first sampling period before the addition of small instream wood within the treatment pools began on 14 July 2011 and was completed on 21 July 2011 when all pools within each site lacked instream wood. We set block nets at the upstream and downstream boundaries of the treatment and control pools to prevent fishes from entering or leaving the pools. After block nets were set, a visual inspection was conducted to confirm that no instream wood had migrated into either the treatment or the control pool. Fishes were collected first from the treatment pool and then the upstream control pool. Fishes were collected with a backpack electrofisher (100 V, 60 Hz) using a two-pass depletion method. One person operated the backpack electrofisher while another captured stunned fishes with a dip net. After completing the first pass, we waited five minutes before conducting the second pass. All captured fishes were identified, enumerated, and their total lengths measured before being released. Fish data were used to calculate fish abundance (number of captures), species richness (number of species), percent sunfishes (number of sunfishes/number of all fishes captured), percent minnows (number of minnows/number of all fishes captured), mean fish length, and Shannon Diversity Index [35] for each pool during each sampling week.
We measured hydraulic variables after fish sampling was completed and the block nets were removed from both pools within a stream. Beginning at the downstream transect (T0) of the treatment pool and working in an upstream direction, wetted width was measured at each transect and used to identify four equidistant points along each transect where we measured water depth and water velocity with an electromagnetic flow meter and top setting wading rod. We used the hydraulic variables data to calculate mean water velocity, mean water depth, mean wetted width, pool area, and mean discharge for each pool during each sampling week. Mean water depth and mean water velocity were calculated for each pool by averaging the 12 water depth and water velocity data points from each pool. Mean wetted width was calculated for each pool by averaging the wetted width of the three transects in each pool. Mean discharge was calculated for each pool by first calculating instantaneous discharge at each transect and obtaining the average discharge of the three transects in each pool. Pool area was calculated by multiplying pool length (3 m) by the mean wetted width of the three transects.

2.2.3. Small Instream Wood Addition and Treatment Period

We collected small simple pieces (length = 1 m; diameter = 0.3 to 0.6 m) of instream wood from other headwater streams within the Upper Big Walnut Creek watershed. The collected instream wood pieces were submerged in a tub filled with water to maintain water saturation and neutral buoyancy. Four to six small instream wood pieces were added to the treatment pool in each site on 25 July 2011 (Figure 3). We did not anchor the added pieces to the stream bottom because we wanted to evaluate the effects of small instream wood as it would occur naturally (i.e., unanchored). We also did not anchor the added pieces to the stream bottom because we were concerned that water flow around the anchor points might create scouring as a result of the anchor, not the instream wood piece itself. All small instream wood pieces were placed parallel or diagonal to stream flow because these two orientations occurred most frequently in the initial instream wood survey (see Results below). The number of wood pieces added differed slightly across pools because of variations in pool sizes among streams. We also wanted to ensure that each treatment pool received enough wood pieces to achieve an instream wood density of 1 piece/m2 of treatment pool area (Figure 3). Colored zip ties were wrapped around each piece of small instream wood to enable us to distinguish it from naturally occurring instream wood that could migrate into the treatment pool as the study progressed. We chose to add small simple pieces of instream wood because it was the most frequently occurring instream wood type found during our initial instream wood survey (see Results below). We established a density of 1 piece/m2 because results from our instream wood survey indicated that this density represents an increase of 50-times the mean instream wood density found within the four streams selected for this experiment (see Results below).
After the small instream wood addition, a 28-day treatment period from 25 July 2011 to 21 August 2011 was established and during this time periodno sampling occurred. Weekly checks were conducted at each site to ensure added instream wood did not migrate out of the treatment pool. Any added pieces of small instream wood that migrated out of the treatment pool were found and returned to the treatment pool from which it originated. If the piece could not be found, then it was replaced to maintain instream wood density in the treatment pools.

2.2.4. After Small Wood Addition Fish and Hydraulic Condition Sampling Methods

The second sampling period was nine days long (22 August 2011 to 30 August 2011). During this time, the four treatment pools contained small instream wood, and the four control pools lacked instream wood. Fishes and hydraulic variables were sampled on 22 August 2011 and then again on 30 August 2011 in each pool using the fish and hydraulic condition sampling procedures, as previously described in Section 2.2.2 above. During this time, we also continued to maintain the experimental instream wood densities within each of the four treatment pools.

2.2.5. Statistical Analysis

We used the Kolmogorov–Smirnov test and the Levene Median Test to determine if the response variables met the assumptions of normality and equal variance. Response variables that did not meet the assumptions were either log10(x + 1) transformed (fish abundance, species richness, wood density, wood volume, mean discharge) or arcsine square root transformed (percent sunfishes) before analysis. We used a blocked two-factor analysis of variance (ANOVA) coupled with the Tukey multiple comparison test to determine if adding small instream wood influenced the amount of small instream wood, fishes, and hydraulic variables. The blocked two-factor ANOVA was performed using the Proc GLM procedure within SAS for Windows version 8 [36] with individual streams serving as the block and pool type and time (i.e., before and after small wood addition) as independent factors. We were specifically interested in the interaction effect between pool type and time. We focused on the interaction effect because our experimental design was a replicated BACI design. This experimental design was specifically developed to enable one to document the impact of an anthropogenic or natural disturbance event by determining if the differences between the control and treatment sites (i.e., pools, streams, experimental units) change before and after the disturbance [37]. Therefore, only the interaction effects within the ANOVA results will provide us with the needed information to determine whether the trend in the amount of instream wood (wood density, wood volume), fish community structure (fish abundance, species richness, percent sunfishes, percent minnows, mean fish length, Shannon Diversity Index), and hydraulic variables (mean water velocity, mean depth, meant wetted width, mean discharge, mean pool area) between control and treatment pools changed after the small instream wood addition. All statistical tests were conducted with a significance level of p < 0.05.

3. Results

3.1. Instream Wood Survey Results

Instream wood abundance ranged from 0 to 188 pieces, and instream wood density ranged from 0 to 0.29 pieces/m2 (Table 3). Instream wood richness ranged from 0 to 9. Three of the five streams containing instream wood exhibited a greater proportion of small instream wood than large instream wood (Table 3). Small simple pieces were the instream wood type that occurred most frequently, and small bark, large branching pieces, and large artificial pieces occurred the most infrequently (Table 3). Notably, the two streams with the greatest instream wood abundance, density, and richness contained five or more large accumulations (Table 3). We also noted that, in streams containing instream wood, the parallel orientation occurred most frequently, followed in frequency of occurrence by diagonal and perpendicular orientations (Table 3).

3.2. Small Instream Wood Addition Experiment Results

Of the 21 pieces of small wood added during the experiment, only 1 piece was lost and replaced. We documented several other occurrences of migration of individual pieces of instream wood out of the treatment pools, but all pieces were found and returned to their respective treatment pool. The interaction effect of pool type and time was significant for both instream wood density (F = 85.48, df = 3, p < 0.0001) and volume (F = 62.05, df = 3, p < 0.0001) and indicated that the trends in these response variables between pool types differed before and after the small instream wood addition. Specifically, mean instream wood density and volume did not differ (p > 0.05) between the control and treatment pools before the small instream wood addition and mean instream wood density, and volume was greater (p < 0.05) in the treatment pools than the control pools after the small instream wood addition (Figure 4).
Overall, we captured 660 fishes from all control and treatment pools (Table 4). We captured 209 fishes during the first sampling period, when all pools lacked instream wood, and 451 fishes were captured during the second sampling period when treatment pools contained small instream wood and the control pools did not (Table 4). The most common fish species captured were fathead minnow (Pimephales promelas), creek chub (Semotilus atromaculatus), bluegill (Lepomis macrochirus), Johnny darter (Etheostoma nigrum), and orangethroat darter (Etheostoma spectabile) (Table 4). The interaction effect of pool type and time was not significant (p > 0.425) for the six fish community response variables (Table 5) and indicated that the trends in these response variables between the treatment and control pools did not differ before and after the small instream wood addition.
Not including the storm event one day prior to the instream wood addition on 25 July 2011 (EJG personal observation), there were no major precipitation events during the experiment, and pools gradually reduced in size as the study progressed through the summer. Between the first and second sampling periods, mean water depth (0.18 m to 0.17 m), mean wetted width (1.82 m to 1.76 m), mean discharge (0.001 m3/s to 0.000 m3/s), and mean pool area (5.46 m2 to 5.28 m2) decreased in all pools, which was expected because our study was conducted during a season that exhibits warm air temperatures and limited rainfall (i.e., summer). Despite the drying conditions, all pools retained water during the experiment. The interaction effect of pool type and time was not significant (p > 0.825) for the five hydraulic variables (Table 6) and indicated that the trends in these response variables between the treatment and control pools did not differ before and after the small instream wood addition.

4. Discussion

4.1. Fish Community Responses

Our results do not support our hypothesis that adding small instream wood at a density of 1 piece/m2 would influence fishes in pools in channelized streams. Others [30,33] observed mixed fish community responses to the experimental addition of small instream wood bundles. Fourteen days after the addition of small wood bundles in the shallow sand-bottom littoral zone of a large floodplain river in Texas, fish abundance and species richness were reduced in locations with small wood bundles than reference locations without small wood bundles [30]. These results were attributed to the lack of sunfishes (Centrarchidae), darters (Percidae), and catfishes (Ictaluridae) that are often associated with instream wood within the experimental reach and the lack of large instream wood near the experimental reach [30]. Conversely, fish species richness and evenness were greater in reaches containing dense bundles of small instream wood than reference reaches lacking these small wood bundles in a channelized and incised third order sand-bed stream in Mississippi [33]. Additionally, darters (Percidae) and madtom catfishes (Noturus spp.) exhibited the strongest increases to the addition of the small wood bundles [33]. These positive fish responses and localized changes in fish distribution were attributed to the complex cover provided by the small wood bundles and localized increases in the diversity of water depths and water velocities in the locations where the small wood bundles were installed [33]. In light of these findings from the southeastern United States, we suspect that the lack of a fish community response we observed is a result of both the fish species composition within our experimental streams and the manner in which the small instream wood was added. Thus, 66% of all fish captures during our study were minnows (Cyprinidae), and only 33% of all fishes captured were sunfishes, darters, and catfishes. Thus, the dominance of minnows within our experimental pools may have hindered us from detecting an effect of adding small instream wood. Additionally, our small instream wood addition consisted of adding individual pieces of small wood placed haphazardly within each of the treatment pools. In contrast, both studies from the southeastern United States [30,33] used small wood and constructed instream wood bundles that were anchored to the stream bottom. Thus, these bundles, although constructed from small wood, are likely more accurately classified as instream wood accumulations and would be expected to influence the fish communities differently than separate individual pieces of small wood. Specifically, interstitial spaces provided by instream wood bundles and accumulations may provide better refugia from predators and have a greater impact on hydraulic conditions than small simple pieces of instream wood [3].
In channelized streams in the Midwestern United States, fish communities have been observed to respond positively to instream wood additions [2,26,27]. Angermeier and Karr [2] conducted a split stream experiment and found that species richness, abundance, and the abundance of large fish were greater on the side containing instream wood compared to the side lacking instream wood in a channelized stream in Illinois. Angermeier and Karr [2] also conducted a multiple reach experiment in the same stream, in which wood structures were added at different densities to treatment reaches and found that fish abundance was generally greater in the shallower treatment reaches than the deeper control reaches lacking instream wood. However, they noted that the effect of instream wood was often dependent on species and age class. Gatz [26] increased overhead cover in a headwater stream in central Ohio by placing floating wood structures in treatment reaches that resulted in greater abundances of bluntnose minnow (Pimephales notatus), creek chub, and longear sunfish (Lepomis megalotis). Hrodey and Sutton [27] added half log structures to three channelized streams in Indiana and observed greater abundance and species richness in reaches with half logs, but the frequency of positive fish responses to half log structures was dependent on the amount of pre-existing instream cover and adjacent riparian conditions. Positive fish responses to half log structures occurred more frequently in reaches lacking or having minimal amounts of instream cover and riparian zones dominated by row crops [27].
Initially, we thought our results differed from the other Midwestern United States studies [2,26,27] because the amount of instream wood we added was less than that added in other studies. The other studies did not use instream wood density as an indicator of the amount of instream wood added. Therefore, to facilitate comparisons, we calculated the percent of pool or reach area covered by instream wood in our experiment and those of Angermeier and Karr [2], Gatz [26], and Hrodey and Sutton [27]. In our experiment, the treatment pools exhibited 3.9% instream wood coverage in treatment pools. In contrast, treatment reaches in Angermeier and Karr [2] multiple reach experiment exhibited an instream wood coverage of 1% to 3%, treatment reaches in Hrodey and Sutton [27] contained 1.7% instream wood coverage, and the treatment reaches in Gatz [26] exhibited 3 to 4% instream wood coverage. Thus, we conclude that our results differ from other Midwestern United States studies because we added small instream wood pieces rather than large instream wood structures. Large and complex types of instream wood produce localized changes in flow that fish may use as refuge from stream current [4]. Furthermore, large and more complex instream wood structures may support more individuals because they provide overhead cover for predator protection [2,26] and increased macroinvertebrate foraging area [8].
In addition to providing a high-quality habitat, large and complex instream wood types remain effective longer because they are more resistant to environmental degradation. Of the 108 half log structures installed by Hrodey and Sutton [27], 106 were still functional after two years. By the end of our field experiment, the added pieces of small instream wood had become covered with a thick layer of silt that may have reduced their effectiveness as a fish habitat. Although we did not observe a significant loss of added small instream wood pieces during our experiment, their small size and resulting high probability of downstream migration may reduce their ability to serve as fish habitats over longer time periods [38].

4.2. Hydraulic Variable Responses

Our results support the hypothesis that adding small instream wood at a density of 1 piece/m2 would not influence hydraulic conditions in pools within channelized streams. Our results are consistent with other studies [2,28,29] that examined the influence of large instream wood on hydraulic conditions in channelized streams. During the split stream experiment of Angermeier and Karr [2], water velocity slightly increased on the side lacking instream wood compared to the side with instream wood. Water depth and water velocity did vary between reaches with and without instream wood during the multiple reach experiment, but differences were not consistent and were attributed to the discharge regime rather than the addition of instream wood [2]. Ehrman and Lamberti [28] found that water velocity decreased in reaches that contained a channel spanning wood accumulation compared to reaches with wood accumulations only at the stream edge or reaches with no wood at all in an Indiana headwater stream. Additionally, Ehrman and Lamberti [28] observed that discharge and water depth did not differ between reach types. Lester and Wright [29] did not observe differences in water velocity and discharge between treatment and control reaches following an instream wood addition in agricultural streams in Australia. The degree to which instream wood influences hydraulic conditions is dependent on several factors, including size, structure, orientation relative to stream flow, and location within the water column [29,38,39,40,41]. Our field-based hydraulic condition results combined with those of others [2,28,29] suggest that instream wood types (i.e., small single pieces, large individual pieces of instream wood, large non-channel blocking wood accumulations, etc.) that do not create impoundments within agricultural streams may not significantly reduce the hydraulic capacity of these streams. Future research needs to document the effect of adding instream wood types that do not create impoundments on hydraulic capacity of agricultural headwater streams.

5. Conclusions

Our results, coupled with those from sand-bottom streams and rivers in the Southeastern United States [30,33], indicate that warmwater (>20 °C) fish community responses to the addition of small instream wood will depend on the fish species composition within the streams receiving the small wood additions and the way in which small instream wood is added (i.e., as individual pieces or as bundles). Our results coupled with those of other studies from the Midwestern United States [2,26,27,28,29] highlight the greater value of large instream wood for fishes and that it is possible to add instream wood without significantly influencing hydraulic conditions within agricultural streams. Furthermore, our results and others from the Midwestern United States suggest that adding instream wood is a practice that could be incorporated as part of a multiple-use management strategy for channelized streams intended to improve the ability of channelized streams to serve as fish habitats and to ensure it continues to provide the drainage needed for agriculture. Adding a variety of instream wood sizes and types (i.e., large simple pieces, wood accumulations, overhanging woody vegetation, etc.) that do not span the entire channel would provide needed instream cover for fishes without impeding the drainage capacity of channelized streams. Alternatively, allowing the woody vegetation to develop within the riparian zones adjacent to these streams would contribute to inputs of wood into the stream and serve as a passive management strategy for increasing the amount of instream wood. This passive management strategy would not require maintenance, is cost-effective, and can at least partially restore stream dynamics to which the native fish community is adapted.
Our results and others [2,26,27,28,29] also suggest there may be a threshold loading at which instream wood can be added that will benefit fish communities without influencing hydraulic conditions. Engineering equations are available that provide predictions on how instream wood removal and addition can influence stream hydraulic conditions [39,40,42], but equations capable of predicting both fish and hydraulic condition responses to changes in instream wood loadings are lacking. Future research needs to quantify the relationships among instream wood, hydraulic conditions, and fishes to identify the threshold of instream wood loading for channelized streams in the Midwestern United States. Identifying threshold values of instream wood loading and the development of methods for determining these values would assist with restoring fish diversity in streams that have been negatively impacted by agriculture [39].

Author Contributions

E.J.G. and P.C.S.J. conceptualized this study, developed the experimental design and sampling protocol, wrote the manuscript, and were responsible for review and editing of the manuscript. E.J.G. conducted the field work and conducted the statistical analyses. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported in part by the Barneby Family Scholarship and URS-College of NRE Scholarship to E.J.G. and by the USDA Conservation Effects Assessment Project.

Institutional Review Board Statement

This research followed Ohio State University Institutional Laboratory Animal Care and Use Committee (Protocol # 2002 A0133; 2008-A0161-R1) and USDA-ARS animal care protocols for the handling and live release of feral fishes. Additionally, fishes were collected using collecting permit (Permit #14-78) issued to Peter C. Smiley Jr. provided by Ohio Department of Natural Resources.

Data Availability Statement

Data are contained within the article.

Acknowledgments

We thank E. Braig, R. Gillespie, L. Pintor, and S. Knight for providing helpful comments on an earlier draft of this manuscript. We also thank A. Rapp for her assistance in the field, K. Stillman for preparing data summaries for site characteristics, T. Wood for helping prepare the figures, and the landowners for granting us permission to sample the sites.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Graphic providing overview of the two components (instream wood survey, small instream wood addition experiment) of the field study conducted to document the effects of adding small instream wood on fishes and hydraulic conditions in pools within channelized agricultural headwater streams in central Ohio. The manuscript subsection for each component is identified within the graphic.
Figure 1. Graphic providing overview of the two components (instream wood survey, small instream wood addition experiment) of the field study conducted to document the effects of adding small instream wood on fishes and hydraulic conditions in pools within channelized agricultural headwater streams in central Ohio. The manuscript subsection for each component is identified within the graphic.
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Fishes 09 00296 g002
Figure 2. Location of sampling sites within six channelized agricultural headwater streams within the Upper Big Walnut Creek watershed. The inset map depicts the location of the Upper Big Walnut Creek watershed in Ohio, USA. Sites S1 to S4 were part of the instream wood survey and the small instream wood addition experiment. Sites S5 and S6 were only part of the instream wood survey.
Figure 2. Location of sampling sites within six channelized agricultural headwater streams within the Upper Big Walnut Creek watershed. The inset map depicts the location of the Upper Big Walnut Creek watershed in Ohio, USA. Sites S1 to S4 were part of the instream wood survey and the small instream wood addition experiment. Sites S5 and S6 were only part of the instream wood survey.
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Fishes 09 00296 g003
Figure 3. A depiction of the arrangement of added small simple pieces of instream wood (grey rectangles) in the treatment pools. Either six pieces (streams—S1, S4), five pieces (stream—S3), or four pieces (stream—S2) of small simple pieces were added within the treatment pools to increase the instream wood density to 1 piece/m2. No instream wood was added to the control pools. The figure is not drawn to scale. Sites S1 to S4 are depicted in Figure 2.
Figure 3. A depiction of the arrangement of added small simple pieces of instream wood (grey rectangles) in the treatment pools. Either six pieces (streams—S1, S4), five pieces (stream—S3), or four pieces (stream—S2) of small simple pieces were added within the treatment pools to increase the instream wood density to 1 piece/m2. No instream wood was added to the control pools. The figure is not drawn to scale. Sites S1 to S4 are depicted in Figure 2.
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Fishes 09 00296 g004
Figure 4. Differences in mean instream wood density (a) and volume (b) between the control and treatment pools before and after the small instream wood addition within channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011.
Figure 4. Differences in mean instream wood density (a) and volume (b) between the control and treatment pools before and after the small instream wood addition within channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011.
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Table 1. Types of instream wood recognized during instream wood surveys of six channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011.
Table 1. Types of instream wood recognized during instream wood surveys of six channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011.
Instream Wood TypeSmall 1Large 1
Simple—single piece lacking branches or branches with one branch < 10 cm longSmall simpleLarge simple
Branching—Single piece with minimum of 1 branch ≥ 10 cm longSmall branchingLarge branching
Overhanging vegetation—wood vegetation branches breaking the water surfaceSmall overhanging vegetationLarge overhanging vegetation
Accumulation (e.g., wood jams)—aggregate of 2 or more individual pieces2Large accumulation
RootwadSmall rootwadLarge rootwad
Artificial—Non-natural instream wood (e.g., plywood)Small artificialLarge artificial
Bark—residual barkSmall bark2
1 Small instream wood defined as individual pieces with length > 0.4 m and ≤ 1.0 m or diameter > 2 cm and ≤0.1 m and overhanging vegetation and accumulations with an area ≤ 0.1 m2. Large instream wood consisted of individual pieces with length > 1.0 m and diameter > 0.1 m and overhanging vegetation and accumulations with an area > 0.1 m2. 2 Small accumulations and large bark did not occur in any of the sites.
Table 2. Watershed, geomorphological, and riparian habitat characteristics within the four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA that were selected as study sites for the 2011 instream wood addition experiment. Sites S1 to S4 are depicted in Figure 2.
Table 2. Watershed, geomorphological, and riparian habitat characteristics within the four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA that were selected as study sites for the 2011 instream wood addition experiment. Sites S1 to S4 are depicted in Figure 2.
Stream
S1S2S3S4
Watershed size (km2)1.164.444.503.78
Percent Agriculture95.160.975.875.1
Percent Residential3.925.721.318.5
Percent Forest/Shrub1.013.42.96.4
Slope (m/m)0.0030.0030.0010.003
Sinuosity (m/m)1.001.001.041.28
Cross-section area (m2)9.347.308.897.01
Maximum channel depth (m)2.101.841.841.52
Mean riparian width (m)9.165.1139.1641.45
Mean percent canopy cover0.000.235.150.12
Mean riparian woody vegetation density (no./m2)0.000.380.100.02
Table 3. Instream wood characteristics in six channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Instream wood types defined in Table 1. Sites S1 to S6 are depicted in Figure 2.
Table 3. Instream wood characteristics in six channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Instream wood types defined in Table 1. Sites S1 to S6 are depicted in Figure 2.
Stream
S1S2S3S4S5S6
Abundance (no.)08101461188
Density (no./m2)0.000.030.030.030.130.29
Instream wood richness043589
% small instream wood0.0087.50100.0021.4340.9881.38
% large instream wood0.0012.500.0078.5759.0218.62
no. small simple pieces048113120
no. small branching pieces0200831
no. small overhanging vegetation010031
no. small rootwad001200
no. small artificial000011
no. small bark001000
no.large simple pieces000101
no. large branching pieces000001
no. large overhanging vegetation01022620
no. large rootwad000831
no. large accumulation0000512
no. large artificial000020
no. parallel orientation0861132112
no. diagonal orientation00321650
no. perpendicular orientation00111326
Table 4. Number of fish species captures within control and treatment pools before and after the small instream wood addition within four channelized agricultural headwater streams within the Upper Big Walnut Creek, Ohio, USA, 2011.
Table 4. Number of fish species captures within control and treatment pools before and after the small instream wood addition within four channelized agricultural headwater streams within the Upper Big Walnut Creek, Ohio, USA, 2011.
SpeciesBefore Small Wood AdditionAfter Small Wood Addition
Control PoolsTreatment PoolsControl PoolsTreatment Pools
Black bullhead Ameiurus melas0001
Bluegill Lepomis macrochirus11202025
Bluntnose minnow Pimephales notatus10274
Creek chub Semotilus atromaculatus68333229
Fathead minnow Pimephales promelas8110358
Green sunfish Lepomis cyanellus4368
Johnny darter Etheostoma nigrum632420
Largemouth bass Micropterus nigricans1014
Orangethroat darter Etheostoma spectabile111163
Pumpkinseed Lepomis gibbosus2000
Central stoneroller Campostoma anomalum20011
White sucker Catostomus commersonii2014
Table 5. Means (standard error) for fish community response variables within control and treatment pools before and after instream wood addition within four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Associated F values, degrees of freedom (df), and p values were derived from the interaction effect between pool type and time (before and after small wood addition) in the blocked two factor analysis of variance.
Table 5. Means (standard error) for fish community response variables within control and treatment pools before and after instream wood addition within four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Associated F values, degrees of freedom (df), and p values were derived from the interaction effect between pool type and time (before and after small wood addition) in the blocked two factor analysis of variance.
Response VariableBefore Small Wood AdditionAfter Small Wood AdditionFdfp
Control PoolsTreatment PoolsControl PoolsTreatment Pools
Abundance17.63 (3.78)8.50 (2.18)32.75 (15.53)23.63 (11.63)0.3430.795
Species richness3.38 (0.63)2.25 (0.37)3.63 (1.00)3.63 (1.12)0.8330.494
Percent sunfishes26.73 (16.02)36.77 (14.68)16.57 (8.50)38.45 (14.55)0.3730.775
Percent minnows62.43 (14.06)48.38 (14.63)56.11 (14.83)30.41 (11.62)0.2130.887
Mean length (cm)5.14 (0.63)4.71 (0.49)6.31 (1.14)6.31 (0.82)0.0830.971
Shannon Diversity Index0.73 (0.21)0.50 (0.15)0.94 (0.24)1.13 (0.17)0.9730.426
Table 6. Means (standard errors) of hydraulic variables from control and treatment pools before and after instream wood addition within four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Associated F values, degrees of freedom (df), and p values were derived from the interaction effect between pool type and time (before and after small wood addition) in the blocked two factor analysis of variance.
Table 6. Means (standard errors) of hydraulic variables from control and treatment pools before and after instream wood addition within four channelized agricultural headwater streams in the Upper Big Walnut Creek watershed, Ohio, USA, 2011. Associated F values, degrees of freedom (df), and p values were derived from the interaction effect between pool type and time (before and after small wood addition) in the blocked two factor analysis of variance.
Response VariableBefore Small Wood AdditionAfter Small Wood AdditionFdfp
Control PoolsTreatment PoolsControl PoolsTreatment Pools
Water velocity (m/s)−0.01 (0.01)0.00 (0.00)−0.02 (0.00)−0.02 (0.00)0.3030.828
Water depth (m)0.18 (0.01)0.19 (0.02)0.17 (0.01)0.17 (0.02)0.2130.890
Wetted width (m)1.86 (0.18)1.79 (0.14)1.81 (0.19)1.71 (0.19)0.0730.975
Pool discharge (m3/s)0.001 (0.000)0.001 (0.000)0.000 (0.000)0.000 (0.000)0.3030.825
Pool area (m2)5.57 (0.54)5.36 (0.43)5.44 (0.57)5.13 (0.56)0.0730.975
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Gates, E.J.; Smiley, P.C., Jr. Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams. Fishes 2024, 9, 296. https://doi.org/10.3390/fishes9080296

AMA Style

Gates EJ, Smiley PC Jr. Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams. Fishes. 2024; 9(8):296. https://doi.org/10.3390/fishes9080296

Chicago/Turabian Style

Gates, Eric J., and Peter C. Smiley, Jr. 2024. "Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams" Fishes 9, no. 8: 296. https://doi.org/10.3390/fishes9080296

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