Geology topics

Hadley I. A. Boehm

Publications and source records attributed to Hadley I. A. Boehm.

4 recordsLinked to original sources

USGS2024

Evaluating effectiveness of restoration to address current stressors to riverine fish

River restoration programmes with the goal of conserving and rehabilitating inland fishes have a multi-decadal history, but evaluation and synthesis of past restoration actions have been limited by a lack of monitoring and reporting. Given that calls for both monitoring and systematic reviews of restoration have increased, we were interested in the influence that restoration has had on improving conditions for riverine fishes resulting from long-standing and increasingly prominent stressors. Our objectives were to (1) identify which stressors were targeted in river restoration efforts, (2) determine the proportion of published studies that articulate restoration goals and develop comparative monitoring designs for assessing the effects of restoration on fishes, and (3) conduct a meta-analysis to synthesise fish responses to restoration projects. We assessed restoration effectiveness for increasing fish density and richness from peer-reviewed papers published over the past decade using a global systematic review and meta-analysis. We found that restoration actions addressed major stressors primarily by improving in-stream habitat (37%), increasing in-stream longitudinal connectivity (26%) and increasing lateral floodplain connections (9%). Although 81% of studies had comparative monitoring designs (i.e., before/after and control/impact) and stated restoration goals, only 40% of those studies reported sufficient data to be included in the meta-analysis. Projects which increased in-stream connectivity had the largest positive effect size on fish density and richness compared to in-stream habitat improvements and increasing floodplain connections. Time since restoration and restoration size (i.e., geographical footprint) were not strong predictors of fish response effect sizes. Restoration effectiveness was highly variable among project types. Authors of studies included in the meta-analysis often identified spatial or temporal scale of monitoring, overriding catchment conditions, and recolonisation potential as sources of variability and effectiveness in restoration outcomes. Systematic reporting of these and other covariates may help guide processes in restoration evaluation and provide valuable research insights. Despite increased emphasis on monitoring, incomplete data reporting limited the number of studies that could be included for quantitative meta-analysis. Persistent emphasis on setting specific criteria (e.g., measurable outcomes of fish response) for restoration goals, project monitoring, data reporting, information sharing and collaborative projects is likely to continue to improve understanding of restoration effectiveness transferable to future endeavours. Our results can be used to support river restoration practitioners with evidence-based information to evaluate the cost–benefit ratio of competing restoration priorities, and inform restoration planning and implementation for riverine fish.

Freshwater Biology↗

USGS2022

Special section overview: Effects of ecosystem change on North American percid populations.

Walleye Sander vitreus , Sauger S. canadensis , and Yellow Perch Perca flavescens (referred to as percids herein) are collectively among the most culturally and ecologically important fish species in North America. As ecosystems change in response to environmental drivers, such as climate change, nutrient loading, and invasive species, there is a need to understand how percid populations respond to these changes. To address this need, a symposium was held during the 81st Annual Midwest Fish and Wildlife Conference to bring fishery scientists and managers together to describe and discuss percid population responses to ecosystem change. Prevailing symposium themes included the challenge of identifying mechanisms responsible for population-level changes, developing strategies to adaptively manage for resilient fisheries, and consideration of scale, context, and methods when interpreting variable results. Given the uncertainty of how ecosystem changes affect percid populations, participants emphasized the importance of communicating uncertainties to stakeholders, implementing data-driven management strategies, setting realistic goals, and revising management actions in an adaptive framework. There was universal agreement on both the challenge and necessity of facilitating constructive engagement among stakeholders in cooperative decision making. Symposium participants identified knowledge gaps and discussed future efforts to build on our current understanding of percid populations, including continuation of long-term monitoring, improved standardization of evaluation metrics, implementing adaptive management experiments to identify causal relationships, development of more robust analytical methods, use of historical data sources, and refining techniques to realistically convey management options to stakeholders.

North American Journal of Fisheries Management↗

USGS2021

Recruitment bottlenecks for age-0 walleye in northern Wisconsin lakes

Some northern Wisconsin lakes have shown declines in catches of age-0 Walleye Sander vitreus in standardized fall electrofishing sampling, suggesting that recruitment bottlenecks are occurring in the first several months of life. In 2016 and 2017, we sampled six lakes with declining trends in natural Walleye recruitment (D-NR lakes) and seven lakes with a history of sustained natural recruitment (S-NR lakes) to determine if timing of potential recruitment bottlenecks for age-0 Walleye were consistent among D-NR lakes and if abiotic and biotic metrics differed between D-NR and S-NR lakes. We also examined diets of larval Walleye to assess prey items that may be important to early growth and survival and to determine if occurrence of piscivory was related to larval Walleye total length. Differential patterns in the presence and absence of age-0 Walleye at different life history stages in the first 6 months of life suggested that recruitment bottlenecks in D-NR lakes were consistently occurring before mid-July (five of six lakes). Mean Secchi depth, surface conductivity, abundance of larval Yellow Perch Perca flavescens , and most metrics of zooplankton abundance and mean size were similar between D-NR and S-NR lakes. Log 10 transformed number of adult Walleye per hectare was lower and adult mean total length was higher in D-NR lakes. Across all lakes, diets of larval Walleye consisted of zooplankton and larval fish and the occurrence of piscivory was higher than reported in previous studies and was positively related to total length of larval Walleye. Causes of recruitment bottlenecks in D-NR lakes remain unclear, making it difficult to identify management actions that might be implemented to circumvent these bottlenecks. However, our results indicate that future research should focus on the period between egg deposition and mid-July.

Wisconsin↗

USGS2020

Indexing age-0 Walleye abundance in northern Wisconsin lakes Before fall

Age-0 Walleye Sander vitreus recruitment is often indexed using fall electrofishing surveys. However, collecting fish before fall may provide timely information regarding stocking decisions and factors influencing recruitment. We evaluated sampling methods for age-0 Walleye in northern Wisconsin lakes that could be used to assess recruitment in spring and summer. Initial assessments on two lakes indicated surface tows of ichthyoplankton nets at night during May-early June and 0.64-cm micromesh gill nets set in July provided highest catches of age-0 Walleye among the methods we evaluated. Additional sampling on 13 lakes over two years indicated catch-per-effort (CPE) of age-0 Walleye using these two methods did not correlate with age-0 CPE in fall electrofishing. However, presence or absence of age-0 Walleye in micromesh gill nets was 92% accurate in predicting whether age-0 CPE in fall electrofishing was ≥ 15 fish/h, the threshold above which eventual recruitment to the fishery is expected to occur. Micromesh gill netting may provide a useful tool for allocating fingerling Walleye that are stocked in fall, a resource that is often limited due to space and forage constraints associated with propagation. Additionally, our sampling protocol may help to identify timing of potential recruitment bottlenecks occurring in some lakes.

Wisconsin↗