Seasonal sampling dynamics of smallmouth bass ( Micropterus dolomieu ) in northeastern South Dakota

Since their introduction in the 1970s, Silver Carp Hypophthalmichthys molitrix have spread throughout the Mississippi River basin. Management of any species relies on an accurate understanding of population characteristics and dynamics. However, Silver Carp seasonal sampling variation is unknown. Sampling during periods of peak catch rates would facilitate Silver Carp assessment and management, improving monitoring and removal techniques. The objective of this study was to evaluate adult Silver Carp seasonal sampling variation with boat electroshocking and trammel nets. Silver Carp were collected monthly (April–October) during 2014 and 2015 from four locations in the Des Moines River, Iowa. Trammel nets rarely captured Silver Carp (mean ± SE = 4.9 ± 1.6 fish/net; 60% of fish were captured in 6.3% of net sets) and therefore were not included in analyses. Electroshocking catch rates (CPUEs) exhibited a bimodal distribution, with peak CPUEs generally occurring in May, June, and September and lower catch rates observed during July and August. Catch rates were positively related to river discharge at upstream sites but not at downstream sites. Silver Carp size structure was similar among months and sites except at Cliffland, where fish were smaller during August and October compared to earlier in the year. Finally, Silver Carp condition peaked during April and May and decreased throughout the year except at Keokuk, where peaks were observed during both May and August. Although spatiotemporal variability was substantial, these results suggest that sampling of Silver Carp via electroshocking in May–June and September–October generally produces higher catch rates compared to July–August sampling and generates a more representative size structure. Using site‐specific knowledge, monitoring and surveillance programs could more effectively sample during these periods of high vulnerability and densities in order to manage the spread and impacts of Silver Carp at statewide and regionwide scales. Received December 7, 2016; accepted May 11, 2017Published online June 30, 2017

Section: Methodsmentioning

confidence: 61%

mentioning

confidence: 99%

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confidence: 99%

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Intra‐Annual Variability of Silver Carp Populations in the Des Moines River, USA

Sullivan

Camacho

Weber

et al. 2017

“…Smallmouth Bass sampling and diets.-Smallmouth Bass were sampled from Pickerel and Clear lakes every 7-10 d during May-September using boat electrofishing conducted at night. Littoral transects with rocky substrate were randomly selected at the onset of sampling and were fixed for the study duration at each lake based on the recommendations of Bacula et al (2011). Specifically, six 10-min transects were sampled using a boat electrofisher equipped with a Smith-Root 7.5 GPP pulsator unit (Smith-Root, Vancouver, Washington).…”

Section: Methodsmentioning

confidence: 99%

Influence of Smallmouth Bass Predation on Recruitment of Age‐0 Yellow Perch in South Dakota Glacial Lakes

Dembkowski

Willis

Blackwell³

et al. 2015

We estimated the influence of predation by Smallmouth Bass Micropterus dolomieu on recruitment of age‐0 Yellow Perch Perca flavescens in two northeastern South Dakota glacial lakes. We estimated a likely range in consumption of age‐0 Yellow Perch using Smallmouth Bass diet information from two time periods when age‐0 Yellow Perch constituted high (2008) and low (2012 and 2013) proportions of Smallmouth Bass diets, and bass population size estimates as inputs in a bioenergetics model. The proportion of age‐0 Yellow Perch consumed by the Smallmouth Bass populations was determined by comparing estimates of consumption with estimates of age‐0 perch production. During 2008, age‐0 Yellow Perch constituted between 0% and 42% of Smallmouth Bass diets by weight, whereas during 2012 and 2013, age‐0 perch constituted between 0% and 20% of bass diets by weight. Across both lakes and time periods, production of age‐0 Yellow Perch ranged from 0.32 to 1.78 kg·ha−1·week−1. Estimates of Smallmouth Bass consumption measured during the same intervals ranged from 0.06 to 0.33 kg·ha−1·week−1, equating to consumption of between 1% and 34% of the available Yellow Perch biomass. Given current conditions relative to Smallmouth Bass abundance and consumption dynamics and production of age‐0 Yellow Perch, it does not appear that Smallmouth Bass predation acts as a singular factor limiting recruitment of age‐0 Yellow Perch in our study lakes. However, future research and management initiatives should recognize that the long‐term impact of Smallmouth Bass predation is not static and will likely fluctuate depending on environmental (e.g., temperature) and biotic (e.g., trends in macrophyte abundance, predator and prey population structure and abundance, and predatory fish assemblage dynamics) characteristics. Received December 19, 2014; accepted April 20, 2015

“…; Bacula et al. ), but routinely data are collected and analyzed for a multitude of other species and may represent the only information available for those nontarget species (Wuellner et al. ; Ellender et al.…”

Section: Discussionmentioning

confidence: 99%

Spatial and Temporal Variability in a Large‐Reservoir Fish Assessment and Application of a Stratified Random Sampling Approach

Schall

Schoenebeck

Koupal

2019

Sampling is often standardized with regard to time and space to monitor population characteristics. Effective sampling of large reservoirs can be complicated by the inherit bias of habitat variability along the reservoir gradient. Our objective was to assess spatial and seasonal distribution patterns of target and nontarget fish species in a large reservoir to identify potential sources of bias. A multitude of fish community and habitat characteristics were measured during seasonal (spring, summer, and fall) gill‐net surveys in 2015 and 2016 at Lake McConaughy, Nebraska. Spatial assessments along the longitudinal gradient (up‐reservoir to down‐reservoir) and between opposing shorelines were made for fish metrics from the seven most common species, and associations between species‐specific relative abundance and habitat data were examined. Spatial differences in relative abundance and size structure occurred for nearly all species, with the greatest spatial variability occurring between the upper and lower reservoir zones, but few strong correlations were observed between species‐specific relative abundances and habitat data. Seasonal differences occurred in relative abundance and size structure for most species, and size structure was lowest in the fall for most species. To reduce the impact of spatial variability, we determined the minimum required sampling effort to achieve precise estimates of mean catch per net‐night using two resampling strategies, with 16 or fewer gill‐net sets required for five of seven species and 14 or fewer required if a stratified random approach is utilized. This research quantifies the extent of spatial and temporal variability in standardized sampling on a large reservoir and provides novel insight for managers of similar systems considering a stratified random approach to reduce sampling effort while maintaining desired levels of precision.