Surveys and investigations for sportfish management in lakes and rivers in Illinois Annual Report July 1, 2018 through June 30, 2019 Surveys

Joseph J. Parkos III, David H. Wahl, Anthony P. Porreca, Thomas M. Detmer, Kyle Broadway

Research output: Book/Report/Conference proceedingTechnical report


Black Crappie, White Crappie, and Bluegill are some of the most widely harvested species of fish in Illinois lakes. The high harvest rates of these species make them particularly well suited for evaluating the potential of regulations for managing size structure. In general, regulation outcomes for various types of recreational fisheries have been variable and interpreting the causes for regulation success or failure has been hindered because most studies evaluating regulations were conducted over too short a period, lacked proper controls for comparison, and did not include creel data to document if there were changes in angler catch rates. In Study 101.1, we initiated data collection on 12 reservoirs chosen in consultation with Illinois Department of Natural Resources (IDNR) fisheries biologists to be part of an experimental assessment of crappie and Bluegill regulations. The sampling regime for water quality, prey resources, and fish assemblages was implemented in May 2018, with creel surveys conducted at six of the lakes (Evergreen Lake, Forbes Lake, Homer Lake, Lake Mattoon, Lincoln Trail Lake, and Sam Parr Lake). We chose to focus creel surveys on a subsample of lakes in the first year so as to collect a sufficient number of survey-days per lake to be able to properly characterize fishing pressure on these systems. Creel survey questionnaires are designed to assess fishing effort, harvest, factors influencing choice of lake, perceptions of bluegill and crappie quality, and level of angler experience. During this reporting period, creel clerks conducted 486 interviews over 15-17 sampling events per lake. Shore-angler visitation rate standardized by shoreline length available varied more among reservoirs than boat-angler visitation rates standardized to lake area. The majority of fishing effort at each reservoir was from anglers that had travelled less than 50 kilometers, with Evergreen Lake and Lake Mattoon having the highest frequency of observations of travel distances 200 kilometers or greater. Evergreen Lake, Forbes Lake, and Lake Mattoon had the highest percentage of total hours of angling effort directed solely at crappie species, while Lincoln Trail had the largest amount of effort specifically targeting Bluegill. The majority of motivations given for choosing to direct fishing effort at a particular reservoir fell into eight general categories: proximity to home or work, previous experience angling at that location, familiarity with the location or habit, pre-fishing for a tournament, camping facilities, the presence of particular fish taxa, the aesthetics or environmental quality of the location, and recommendations of other individuals or groups. When site visits were motivated by the presence of a specific kind of fish, Bluegill and crappie were the most common taxa of interest. Both overall catch rate (catch per hour of fishing effort) and harvest rate (standardized to reservoir area) of Bluegill were highest in Forbes Lake, Lincoln Trail, and Lake Mattoon, with highest total catch and harvest rates for crappie in Evergreen Lake, Forbes Lake, and Lake Mattoon. Most harvested crappie were below the “quality” size classification (200 – 249 mm TL), with similar numbers harvested in the “quality” size class among reservoirs, and harvested crappie in “preferred” (250 – 299 mm TL) and “memorable” (300 – 379 mm TL) size classes only observed in Lake Mattoon. Bluegill sizes harvested were more variable among reservoirs than crappie, with low numbers of “quality”-sized fish (150 – 199 mm TL) and no “memorable” category (250 – 299 mm TL) Bluegill harvested in Homer Lake and Sam Parr Lake, and varying numbers of Bluegill in these size categories harvested in the remaining reservoirs. The relative frequency of anglers that perceived the quality of crappie size structure to be less than acceptable was 22% - 25% of respondents across all crappie study lakes, except Lake Mattoon where there was a larger proportion of anglers that rated crappie size structure at that location favorably. Compared to crappie, angler ratings of Bluegill size structure were more variable among study 6 lakes, with Lincoln Trail and Lake Mattoon having the most favorable angler ratings of Bluegill size structure, while the remaining Bluegill populations had from 33% - 46% of respondents rating size structure as less than acceptable. Biological data collected during this reporting period included fishery-independent assessments of fish size structure, reproductive output, and prey availability. Based on fyke-net surveys, reservoirs were quite variable in number of quality-sized individuals present, especially Bluegill and White Crappie. The number of preferred- and memorable-size crappie was relatively low in all lakes expect Lake Mattoon. Very few preferred-size Bluegill were present in the study reservoirs, except in Lincoln Trail. No memorable- or trophy-category Bluegill were captured during fyke-net surveys. The amount of reproductive productivity (i.e., larval fish density) by Bluegill and crappie varied considerably among reservoirs. Density and relative abundance of Dipterans, an important prey resource for Bluegill and crappie, varied between sampling periods (June and August) and among reservoirs. Future reports will include analyses of zooplankton densities and otolith-based estimates of growth and mortality rates. Creel surveys, environmental measurements, and population assessments are planned to encompass three years prior to the implementation of experimental regulations. These data will be used to characterize the environmental conditions and angler behaviors that may influence the efficacy of harvest regulations. As we approach the treatment phase of this project, we will discuss with IDNR biologists the options for experimental regulations and use our analyses of baseline conditions in the study reservoirs to guide assignment of populations to treatments and controls. In Job 102.1 we continued to evaluate artificial and natural habitat structure additions for improving sportfish populations. A pond experiment was conducted during fall 2018 at the Sam Parr Biological Station to evaluate how fishes and other food web processes respond to clumped and uniformly spaced habitat additions. Each pond was assigned a single habitat spatial arrangement (n = 5 ponds/treatment). The uniform habitat arrangement consisted of six Safe Haven™ structures manufactured by the Mossback Fish Habitat Company spaced 5 m apart and the clumped arrangement consisted of six structures placed directly adjacent to each other without overlapping limbs. Ponds were allowed to condition for one month prior to fish introduction. Each pond received 400 age-0 bluegill sunfish and three largemouth bass. Benthic macroinvertebrate and zooplankton sampling began after fish introduction to characterize changes in invertebrate communities through time and between treatments. After two months, each pond was drained and surviving bluegill sunfish and largemouth bass were enumerated, weighed, and measured to determine differences (if any) in growth and survival between habitat spatial arrangements. Largemouth bass growth did not differ between habitat arrangements. Mean (standard error) growth of largemouth bass in the clumped arrangement was 0.26 (0.05) mm d-1 and mean growth rate in the uniform arrangement was 0.37 (0.04) mm d-1. Survival of bluegill sunfish varied considerably between ponds (range = 35 – 175 individuals recovered pond-1) but did not differ between the two habitat arrangements. Bluegill growth did not differ between habitat arrangements. Mean (standard error) growth in the clumped arrangement was 0.71 (0.04) mm d-1 and mean growth was 0.67 (0.03) mm d-1 in the uniform spatial arrangement. Macroinvertebrate and zooplankton samples are currently being processed in the laboratory and the results will be included in future reports. As part of a collaborative effort with the Illinois Department of Natural Resources and Army Corps of Engineers, the Kaskaskia Biological Station is evaluating the efficacy of artificial habitat structure additions in Lake Shelbyville. A field experiment was initiated during fall 2017 in which six reservoir coves of similar size, depth, shoreline morphometry, and existing 7 submerged habitat were identified as candidate areas for habitat manipulation. Pre-habitat conditions within all coves were sampled for fish, benthic macroinvertebrates, and zooplankton during August 2017. During October 2017, three coves received PVC cube fish attractors, while three coves remained un-manipulated to serve as control coves. All coves were sampled for fish, benthic macroinvertebrates, and zooplankton post habitat addition during fall 2017, spring 2018, fall 2018, and spring 2019. Fish sampling in littoral habitats within coves was conducted by DC boat electrofishing. Because standard boat electrofishing is not effective for collecting fish at depth, fish using artificial structures were sampled with deep water AC boat electrofishing. Prey resources within treatment and control coves were collected during May and October 2018. Zooplankton and benthic macroinvertebrates were sampled at three sites adjacent to cubes in each cove. No difference in relative abundance of fish in littoral habitats of treatment and control coves has been observed post habitat enhancement. However, more fish were collected on average in treatment coves than control coves with deep water AC electrofishing during the four sampling periods post habitat enhancement. Data from deep water electrofishing continue to indicate structure-oriented sport fishes are more abundant near added habitats. Taxonomic diversity and density of zooplankton varied by season but was not influenced by habitat additions. Season, however, was a major driver of the density of zooplankton with higher abundances of all groups in the spring. Data processing of benthic macroinvertebrates is underway and will be presented in future segments. We have continued sampling to determine the effects of a whole-reservoir habitat manipulation that was conducted on Walnut Point Lake by the Illinois Department of Natural Resources. Fisheries and Forestry Specialists added over 1,500 trees along the shoreline of this 52-acre reservoir during January 2018, resulting in approximately 13 times more littoral coarse woody habitat compared to pre-habitat enhancement conditions. Sampling of Walnut Point Lake started in April 2018 and the reservoir will continue to be sampled at one-month intervals April through October of each year of the study. As of July 2019, a total of 11 sampling events have been conducted. Each monthly sampling event consisted of collection of water for nutrients and other water quality parameters, zooplankton, and larval fish. Benthic macroinvertebrates were sampled during June and August 2018 using D-nets and both petite Ponar dredges and stovepipe samplers to provide a comparison between these sampling gears. A DC electrofishing survey was conducted during fall 2018. Walnut Point will continue to be sampled monthly through October of each year. In future segments, these data will be compared with pre-habitat enhancement data collected over the last 5 years to monitor changes in this reservoir attributable to habitat enhancement. Data collected on Walnut Point Lake will also be compared to Lincoln Trail Lake, which is a reservoir of similar size, fishing pressure, fish assemblage and is under an identical sampling regime. As of July 2019, all larval fish, macroinvertebrates, and water quality samples collected during 2018 have been processed in the laboratory. Macroinvertebrate samples indicate differences in community assemblage between June and August and between Walnut Point and Lincoln Trail lakes, but no differences between the petite Ponar and the stovepipe samplers, suggesting no bias between sampling methods. Zooplankton sample processing from 2018 and 2019, along with data analysis of all other samples is underway and will be reported in future segments. Research on mid-sized warm-water rivers is limited in part because of sampling difficulties associated with highly irregular hydrological conditions characterized by extreme fluctuations in water levels and flow regimes. Consequently, the role of habitat in structuring sportfish populations in mid-sized rivers is not well understood compared to larger rivers and 8 small streams. In mid-sized rivers, which are generally defined as 5th to 7th order streams, there currently is no standardized method for evaluating fish-habitat associations in Illinois. To guide management strategies and habitat restoration efforts, research is needed to develop fish and habitat sampling procedures that allow assessments of habitat value for sportfish in mid-sized rivers. In Job 102.2, we completed analyses of habitat in the Kaskaskia and Embarras Rivers at multiple spatial scales using side-scan sonar mapping, habitat transects, and microhabitat-targeted sampling. We conducted habitat and fish sampling of the Embarras and Kaskaskia Rivers during early summer months from 2016 to 2018. Three reaches in both rivers were sampled over a three-year time period to incorporate longitudinal and annual variation in fish assemblage and habitat conditions. Landscape-level habitat conditions were assessed across each reach using the transect method and side-scan sonar imagery. Electrofishing was conducted in each segment at the reach scale with 15-minute transects and at the micro scale in sites with homogeneous habitat. Physical habitat features at the landscape level of each river was relatively similar, characterized by flow velocities of less than 1 m/second, mean depths less than 3 meters, and substrates composed primarily of sand, cobble, and gravel. In total, 2,717 fish were captured from the 15-minute and microhabitat electrofishing sampling over the duration of the study representing 64 different species. Fish community structure varied temporally in the Embarras River and along the upstream-downstream longitudinal gradient in both the Embarras and Kaskaskia rivers. Coarse woody habitat was highly important in structuring mid-size river fish communities both temporally and longitudinally and was positively related to 15-minute electrofishing catch rates (fish·hr-1) of sport fishes. Catch rates were also influenced by the degree of complexity of the coarse woody habitat sampled, where habitats with greater complexity had greater fish abundance than less complex habitats. Catch rates of all species combined did not differ between 15-minute and microhabitat electrofishing methods, although greater catch rates of sportfish species was observed with the microhabitat electrofishing method. Side-scan imagery techniques is an inexpensive, non-labor intensive, and accurate method available to fisheries managers to inventory riverine habitat across large areas, particularly for the purposes of quantifying the amount of coarse woody habitat by identifying laydowns and large woody debris. Due to sampling difficulties associated with highly irregular hydrological conditions, sampling regimes in mid-sized rivers should occur during standardized hydrological conditions (i.e., water level and flow regime) to minimize variation in catch efficiency between sampling events. Sportfish-targeted surveys in mid-size rivers would also benefit from the inclusion of microhabitat sampling. An equal distribution of sampling based on channel position and the presence or absence of coarse woody habitat is recommended as this provides an effective and holistic approach to characterizing fish-habitat association based on the availability of particular habitats. Future habitat enhancement efforts in mid-size rivers should consider adding structurally complex woody habitats, such as felling of large trees from river banks, as this presents the most feasible option considering labor time, costs, longevity of the structure, and benefits to fisheries. Additionally, we recommend assessing the current densities of woody habitat in river reaches, easily done using side-scan imagery, proposed for habitat additions and then developing target densities for habitat additions based on relative abundances of fish targeted and other management objectives. The development of effective management plans typically requires information on the demographics of the managed species. Study 103.1 was an assessment of a novel, image-based method for rapidly aging fish in a non-lethal and non-invasive manner. Analyses incorporating multiple morphometric characteristics derived from images and total length measurements 9 indicated that ageing accuracy ranged from 54 to 97% depending on taxa and lake origin evaluated. Total length was the most important predictor variable for four of the five evaluations, with caudal peduncle width the most important predictor variable in the remaining evaluation. Eye diameter was one of the least important predictor variables in all analyses. Accuracy was greater than 90% for all taxa and lake evaluations, except White Crappie from Lake Mattoon, where age was misidentified for 25% of the sample. The strong influence of total length on all models and high misclassification rate in the only taxa and lake combination where there were numerous individuals greater than age-4 indicates that although this technique provides intriguing results and novel technologies and approaches should continue to be considered, the use of morphometrics derived from images is not currently worth vigorous pursuit and investment. In Job 104.1, we have continued to evaluate sampling efficiency of Smith Root and ETS electrofishing control units as part of a field experiment that will run through October 2019. To control for variation in shoreline habitat sampled, fish assemblages, and specific conductivity that may be encountered across different lakes, we have conducted all sampling in Lake Shelbyville, IL. Three electrofishing treatments are being evaluated in the experiment. The first treatment uses a Smith Root Type VI electrofisher with its DC voltage selection set to 177 DC V, which based on previously collected data, is closest to the voltage output of the standardized MBS unit within Lake Shelbyville (~ 180 V). The second treatment uses a Type VI electrofisher with its voltage output selection set to 354 DC V, representing a higher power setting that may be used with this control box. The third treatment consists of electrofishing with an ETS MBS electrofisher set to a power goal (e.g., 3000 W) based on temperature and conductivity of the local environment. Three 15-minute electrofishing transects are conducted with each treatment at three fixed sites that are sampled monthly from May through October of each year using the same boat (cathode), 6500W generator, and anode array. The driving style, driver, and single dipnetter have been kept consistent for each treatment. As of July 2019, we have completed nine months of sampling (81 transects). Data collected to this point indicate that mean catch per unit effort (fish hr-1) is consistently greater across sampling months within the standardized electrofishing control box treatment (i.e., MBS electrofisher configured using a power goal based on water temperature and conductivity) and 354V Type VI control box treatment compared to the 177V Type VI treatment. Full analyses of catch data will be completed and reported after completion of the field experiment.
Original languageEnglish (US)
PublisherIllinois Natural History Survey
StatePublished - Sep 2019

Publication series

NameINHS Technical Report 2019 (07)


  • INHS


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