Spatial Patterns of Fish Communities in Lake Michigan Tributaries

Understanding spatial patterns in freshwater fish communities is critical for the successful management of natural resources as well as a vital component for understanding aquatic ecosystems. Spatial patterns of species similarity of freshwater fish assemblages can be affected by dispersal processes and environmental conditions. We hypothesized that as distance increased between study systems, species similarity would decrease. We sampled 15 drowned river mouths (DRMs) connected to Lake Michigan by conducting 10-minute electrofishing transects (n = 5-6 per DRM) parallel to the shoreline in each DRM to characterize littoral fish assemblages. At each transect, we also characterized environmental conditions (e.g., specific conductivity or number of houses/buildings along shoreline). We captured 3,080 individual fish representing 45 species across the 15 DRMs, with catch among DRMs ranging from 115 to 358 individuals per system and species richness ranging from 11 to 26 species per system. The most abundant species in the catch were yellow perch Perca flavescens (13.9%), pumpkinseed Lepomis gibbosus (10.9%), and bluegill Lepomis macrochirus (9.8%). We found a weak positive correlation between species similarity and distance between each pair of DRMs (R2 = 0.03), which did not support our hypothesis that species similarity would decrease with distance, even though we found evidence of spatial autocorrelation of environmental variables. A potential explanation for our findings is related to gear selectivity associated with boat electrofishing. We suggest that sampling fish with additional gear or approaches is necessary to more rigorously test for the spatial pattern of species similarity among DRMs

Environmental context and contaminant biotransport by Pacific salmon interact to mediate the bioaccumulation of contaminants by stream-resident fish

1. The extent to which environmental context mediates the uptake of biotransported contaminants by stream-resident organisms is not understood. For example, there is no clear understanding of the extent to which contaminant type, instream characteristics, or resident fish identity interact to influence the uptake of contaminants deposited by Pacific salmon (Oncorhynchus spp.) during their spawning runs. 2. To address this uncertainty, we sampled four stream-resident fish species from 13 watersheds of the Laurentian Great Lakes in locations with and without salmon across a gradient of instream and watershed characteristics. We determined the polychlorinated biphenyl (PCB) and mercury (Hg) concentration along with the stable isotope ratio of C and N for each stream-resident fish. 3. We found that stream-resident fish PCB concentrations were 24-fold higher in reaches with salmon and were positively related to δ15N. In contrast, stream-resident fish Hg concentrations were similar or lower in reaches with salmon and either exhibited a negative or no relationship with δ15N. 4. Based upon AICc, stream-resident fish exhibited species-specific PCB concentrations that were positively related to salmon PCB flux. Hg burdens exhibited an interaction between fish length and salmon Hg flux – as salmon Hg inputs increased, Hg levels decreased with increasing resident fish length. We found no support for models that included the mediating influence of instream or watershed factors. Salmon eggs are enriched in PCBs but have very low Hg concentrations, so our results may be driven by the consumption of salmon eggs by stream-resident fish. 5. Synthesis and applications. Our results highlight that contaminants bioaccumulate differently depending on contaminant type, species identity, and the trophic pathway to contamination. Consequently, consideration of the recipient food web and route of exposure is critical to understanding the fate of biotransported contaminants in ecosystems. The transfer of contaminants by migratory organisms represents an understudied stressor in ecology. Effective management of biotransported contaminants will require the delineation of “hot-spots” of biotransport and implementation of best management practices in those watersheds that receive contaminants from spawning salmon

Spatial Patterns of Fish Communities in Lake Michigan Drowned River Mouths

Understanding spatial patterns in freshwater fish communities is critical for the successful management of natural resources as well as a vital component for understanding aquatic ecosystems. Spatial patterns of species similarity of freshwater fish assemblages can be affected by dispersal processes and environmental conditions. We hypothesized that as distance increased between study systems, species similarity would decrease. We sampled 15 drowned river mouths (DRMs) connected to Lake Michigan by conducting 10‐minute electrofishing transects (n = 5‐6 per DRM) parallel to the shoreline in each DRM to characterize littoral fish assemblages. At each transect, we also characterized environmental conditions (e.g., specific conductivity or number of houses/buildings along shoreline). We captured 3,080 individual fish representing 45 species across the 15 DRMs, with catch among DRMs ranging from 115 to 358 individuals per system and species richness ranging from 11 to 26 species per system. We found a weak positive correlation between species similarity and distance between each pair of DRMs (R2 = 0.03), which did not support our hypothesis that species similarity would decrease with distance, even though we found evidence of spatial autocorrelation between distance and environmental variables. A potential explanation for our findings is related to gear selectivity associated with boat electrofishing. We suggest that sampling fish with additional gear or approaches is necessary to more rigorously test for the spatial pattern of species similarity among DRMs

Influence of Interacting Stressors on Native Brook Trout in a Western Pennsylvania Watershed

Freshwater species have declined throughout their native ranges in part due to habitat fragmentation and invasive species. Information is often lacking, however, about how interactions between these stressors affect certain aspects of native populations. Brook trout (Salvelinus fontinalis) are a prime example of a species in decline due to human-related stressors, two of which are fragmentation from abandoned mine drainage (AMD) and competition with non-native brown trout (Salmo trutta). In an ongoing, multi-year study, we are assessing the abundance, behavior, and genetic structure of brook and brown trout in a western Pennsylvania watershed fragmented by AMD and scheduled for remediation in 2018. From past surveys, we predicted that AMD was acting as a chemical barrier to brown trout invasion into a tributary dominated by brook trout. This watershed represents a common situation in Pennsylvania—brook trout populations are simultaneously fragmented, yet “protected” from brown trout invasion by AMD, but remediation could permit brown trout invasion upstream. However, preliminary results show brown trout invasion has already begun prior to any remediation. We predict that as water quality improves after remediation, brown trout invasion upstream will accelerate, increasing interspecific competition with the resident brook trout. This trade-off between isolation and invasion presents a significant management challenge, and our study will highlight the need to be mindful of potentially negative outcomes stemming from AMD remediation efforts to the imperiled brook trout

Assessment of Road Culverts as Passage Barriers to Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta) in Pennsylvania Headwaters

Road culverts can pose as barriers to migratory fish and other aquatic organisms, which can lead to small isolated populations. To categorize the degree to which culverts prevent fish movement, watershed managers use physical measurements to classify culverts as “green” if they are passable, “red” if they are impassable, or “gray” if passability cannot be determined. The Little Bear Creek watershed, a small subwatershed within Loyalsock Creek, contains several road culverts that fell within the “gray” category. It is unknown to us whether or not the culverts falling within this category are indeed barriers to migratory fish, especially trout. To measure how passable these culverts are, we tagged 486 brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) with passive integrated transponder (PIT) tags throughout the Little Bear watershed, particularly upstream and downstream of the three “gray” culverts. Antenna arrays were constructed on the upstream side and downstream side of each culvert, as well as a control site lacking anthropogenic barriers to trout movement. In addition to tracking whether or not the culverts are passable, the arrays will reveal the exact time of movements through culverts. This will allow us to test for correlations with stream flow, water temperature, and other stream conditions that may influence trout movements. By “ground-truthing” culvert assessment methods, we anticipate our study will ultimately help watershed managers better prioritize culverts for removal or replacement

Assessment of Brook Trout Passage Through Ambiguous Culvert Barriers in Pennsylvania Headwater Streams

Habitat fragmentation driven by human activity is a common threat to aquatic organisms. Road culverts in particular can isolate fish populations and reduce genetic diversity by preventing access to upstream spawning habitat. The prioritization process for removing culverts and restoring connectivity includes an assessment of passibility. Culverts often receive scores that categorize them as partial barriers, known as “Reduced AOP” culverts, however detailed assessment of passibility on gray culverts is lacking. To fill this research gap, we used stationary PIT-tag readers to investigate brook trout passage through two No AOP culverts, one Reduced AOP culvert, and a reference stream lacking a culvert for 16 months in Little Bear Creek of Lycoming Co., PA. Results indicate significant differences in upstream movement rates among culvert sites. The rate of upstream passage was five times greater through the metal corrugated culvert than the reference stream. In contrast, relatively little upstream movement occurred through the two box culverts (up to 13 times less passage than the reference), indicating drastic passage differences in culverts receiving similar passibility scores. Our study implies that more nuanced culvert classifications may be needed to accurately reflect fish passage

The sound of recovery:Coral reef restoration success is detectable in the soundscape

Pantropical degradation of coral reefs is prompting considerable investment in their active restoration. However, current measures of restoration success are based largely on coral cover, which does not fully reflect ecosystem function or reef health. Soundscapes are an important aspect of reef health; loud and diverse soundscapes guide the recruitment of reef organisms, but this process is compromised when degradation denudes soundscapes. As such, acoustic recovery is a functionally important component of ecosystem recovery. Here, we use acoustic recordings taken at one of the world's largest coral reef restoration projects to test whether successful restoration of benthic and fish communities is accompanied by a restored soundscape. We analyse recordings taken simultaneously on healthy, degraded (extensive historic blast fishing) and restored reefs (restoration carried out for 1–3 years on previously degraded reefs). We compare soundscapes using manual counts of biotic sounds (phonic richness), and two commonly used computational analyses (acoustic complexity index [ACI] and sound-pressure level [SPL]). Healthy and restored reef soundscapes exhibited a similar diversity of biotic sounds (phonic richness), which was significantly higher than degraded reef soundscapes. This pattern was replicated in some automated analyses but not others; the ACI exhibited the same qualitative result as phonic richness in a low-frequency, but not a high-frequency bandwidth, and there was no significant difference between SPL values in either frequency bandwidth. Furthermore, the low-frequency ACI and phonic richness scores were only weakly correlated despite showing a qualitatively equivalent overall result, suggesting that these metrics are likely to be driven by different aspects of the reef soundscape. Synthesis and applications. These data show that coral restoration can lead to soundscape recovery, demonstrating the return of an important ecosystem function. They also suggest that passive acoustic monitoring (PAM) might provide functionally important measures of ecosystem-level recovery—but only some PAM metrics reflect ecological status, and those that did are likely to be driven by different communities of soniferous animals. Recording soundscapes represents a potentially valuable tool for evaluating restoration success across ecosystems, but caution must be exercised when choosing metrics and interpreting results

Congener Patterns of Persistent Organic Pollutants Establish the Extent of Contaminant Biotransport by Pacific Salmon in the Great Lakes

In the Great Lakes, introduced Pacific salmon (Oncorhynchus spp.) can transport persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), to new environments during their spawning migrations. To explore the nature and extent of POP biotransport by salmon, we compared 58 PCB and 6 PBDE congeners found in spawning salmon directly to those in resident stream fish. We hypothesized that stream fish exposed to salmon spawners would have congener patterns similar to those of salmon, the presumed contaminant source. Using permutational multivariate analysis of variance (PERMANOVA) and nonmetric multidimensional scaling (NMDS), we found that POP congener patterns of Pacific salmon varied among regions in the Great Lakes basin (i.e., Lake Huron, Lake Michigan, or Lake Superior), tissue type (whole fish or eggs), and contaminant type (PCB or PBDE). For stream-resident fish, POP congener pattern was influenced by the presence of salmon, location (i.e., Great Lakes Basin), and species identity (i.e., brook trout [Salvelinus fontinalis] or mottled sculpin [Cottus bairdii]). Similarity in congener patterns indicated that salmon are a source of POPs to brook trout in stream reaches receiving salmon spawners from Lake Michigan and Lake Huron but not from Lake Superior. Congener patterns of mottled sculpin differed from those of brook trout and salmon, suggesting that brook trout and mottled sculpin either use salmon tissue to differing degrees, acquire POPs from different dietary sources, or bioaccumulate or metabolize POPs differently. Overall, our analyses identified the important role of salmon in contaminant biotransport but also demonstrated that the extent of salmon-mediated POP transfer and uptake in Great Lakes tributaries is location- and species-specific

JAE_Gerig_Dryad_Data

JAE_Gerig_Dryad_Dat