Increased urbanization paired with stagnant or decreasing fishing license sales has bolstered the importance of community fishing programs. Community fisheries require fish introductions, have highly variable chemical and physical characteristics, and are situated in urban settings with non-traditional fishers that can prefer unique species. Community ponds also often receive high angling pressure and exploitation that can hinder the establishment of sustainable populations. We evaluated angler exploitation and its effects as well as biotic (i.e., stocking density, predator relative abundance) and abiotic (i.e., water temperature, pond size, pond depth) factors affecting survival of stocked adult Yellow Perch Perca flavescens in community ponds. We tagged 580 adult Yellow Perch (>= 150 mm) and stocked them into four community ponds at 74 or 148 fish/ha in September 2018. We collected two years of fishery dependent (angler tag reporting) and independent recapture data to estimate angler exploitation and survival of Yellow Perch using a joint live-recapture and dead-recovery model. We estimated anglers harvested 44% (95% CI +/- 6%) of stocked Yellow Perch across the four ponds in two years, with the majority (81%) coming from one pond. Additionally, anglers harvested 66% of captured Yellow Perch and harvest probability increased with fish size. Seasonal exploitation ranged from 0% to 37% and was more prevalent in cold water seasons. Yellow Perch survival was negatively related to harvest ( beta = -0.14; 95% CI = -0.17 to -0.10) and a quadratic effect of water temperature (temperature: beta = 0.28; 95% CI = 0.02 - 0.53; temperature 2 : beta = 0.01; 95% CI = - 0.01 - 0.01). Yellow Perch survival was not related to stocking density or pond characteristics. After two years, cumulative survival in three ponds ranged from 0.83 to 0.87 whereas survival in one pond with high exploitation was 0.22. Our results suggest Yellow Perch can be successfully introduced in community fisheries, but populations may not be sustainable when harvest is high. Thus, management strategies to mitigate excessive harvest or multiple put-and-take stockings may be necessary to maintain Yellow Perch populations in community fishing programs.

Habitat introductions are often implemented in aquatic systems to meet fishery management goals. Conifer trees have been used to augment spawning habitat for Yellow Perch Perca flavescens to support and suspend their unique egg skeins above the lake bottom in hopes of increasing reproduction and recruitment; however, little is known about the influence of tree characteristics on the reproductive success of Yellow Perch. Our objective was to evaluate the effects of tree complexity on the skein deposition and survival rates of Yellow Perch. In February 2020, 30 eastern red cedar Juniperus virginiana trees were manipulated to one of five complexities (from 1 = least complex [all branches removed] to 5 = most complex [all branches retained]; n = 6 per complexity) and placed on the ice. After ice-off and tree submersion, we conducted snorkeling surveys every 2 d from March 31 to May 5, 2020, and recorded the number and viability of the skeins. We observed 35 Yellow Perch egg skeins. Yellow Perch preferred to deposit their egg skeins on tree complexities 4 and 5, whereas deposition on tree complexities 1, 2, and 3 was random. The nest survival models estimated that skeins that were deposited on tree complexities 1, 2, and 5 had a 27-d survival estimate of 0.07 (95% CI = 0.06 to 0.08) that was lower (beta = -1.29; 95% CI = -2.32 to -0.27) than that for skeins that were deposited on complexities 3 and 4, with a survival estimate of 0.48 (95% CI = 0.43 to 0.52). Our results indicate that Yellow Perch prefer to deposit their egg skeins on intermediate cedar tree complexities that resulted in increased skein deposition and survival. Given our results, once introduced trees have deteriorated below an intermediate complexity, managers should consider supplemental introductions of more complex trees that benefit the reproduction of Yellow Perch.

Trophic dynamics and conceptual niche spaces of top piscivores were assessed using stable isotope analysis following the introduction of hybrid striped bassMorone saxatilis(Walbaum) xMorone chrysops(Rafinesque) into an established reservoir fishery devoid of gizzard shad,Dorosoma cepedianum(Lasueur). Hybrid striped bass were initially stocked into Three Mile Lake, Iowa as an attempt to biologically control pervasive yellow bass,Morone mississippiensisJordan & Eigenmann, populations. From the analyses, it concluded that hybrid striped bass predominately targeted prey fish located in the littoral habitats of the reservoir and did not selectively consume yellow bass as intended. Bayesian isotope mixing models described the diets of hybrid striped bass to include a variety of prey fish, predominantly consisting of young bluegillLepomis macrochirusand yellow bass. Food resource overlap among hybrid striped bass, largemouth bass,Micropterus salmoidesLacepede, and walleye,Sander vitreus(Mitchill), appeared substantial based on the isotopic niche overlap model. Results from this case study, in conjunction with the hindsight that yellow bass populations became prolific even with stockings of hybrid striped bass, suggest that their use to control yellow bass populations may not be a viable management strategy in southern Iowa.

Gantzer PA, Preece EP, Nine B, Morris J. 2019. Decreased oxygenation demand following hypolimnetic oxygenation operation. Lake Reserv Manage. XX:XX-XX. We analyzed long-term oxygenation dynamics in 3 waterbodies: Spring Hollow Reservoir (SHR) and Carvins Cove Reservoir (CCR), which are water supply reservoirs, and North Twin Lake (NTL), a natural lake. Bubble plume line diffuser hypolimnetic oxygenation system (HOS) operation was for 13, 10, and 7 yr for SHR, CCR, and NTL, respectively. Water column profiles were measured in all 3 waterbodies. Additionally, remotely deployed sensors were used to monitor dissolved oxygen (DO) in NTL year-round, specifically to capture winter conditions during ice cover. Hypolimnetic oxygen demand (HOD) was observed to decrease after several years of HOS operation in all 3 waterbodies. Annual HOD decreased more for HOS operated year-round compared to recovery-based operation where HOS was started after DO decreased below 5.0 mg/L. Additionally, HOD throughout the summer stratified period was lower following maintenance of higher DO during spring prior to onset of stratification. An analogous result was observed during winter ice cover relative to DO conditions following fall turnover. Prior work showed increased HOD during HOS operation compared to pre-HOS. The increased HOD during HOS operation was termed diffuser-induced oxygen demand and implied the HOS was inducing oxygen demand. However, the current work shows HOS operation is not actually inducing oxygen demand; rather, it is addressing the existing oxygen demand already in the sediments. Our data suggest that a HOS is an effective tool to maintain hypolimnion DO in stratified lakes and reservoirs. When operated year-round or before DO decreases, HOS can decrease HOD and reduce overall long-term operational costs.

The role of restricted feeding on the growth and feed efficiency (FE) of juvenile walleye, Sander vitreus, was investigated through two experiments. In the summer/fall experiment, 7.44-g walleye were fed on one of the three schedules for 84days: control (daily satiation feeding at 6% BWday(-1)), D2 (2days of feed deprivation, then fed at 12% BWday(-1) for 7days, repeated throughout the study) and SS80 (subsatiation feeding involving 2weeks of maintenance ration, then fed at 80% of the control group's feeding level). Juvenile walleye growth rates were significantly higher in the SS80 than in the control group, however, their growth rates in the D2 group were no different than in the control. Mean FE of the SS80 group (0.49), significantly exceeded those of the control (0.36) and D2 (0.28) groups. In contrast with the summer/fall experiment, no differences in growth rate were detected among the control, SS80 and D2 groups in the subsequent 84-d spring experiment, where the juvenile walleye (97.45g) were substantially larger, and their mean FE values were generally lower, with less distinction observed among the groups. Our findings indicate potential to increase growth and FE of juvenile walleye in advance of fall, by applying restrict-feed schedules.

The role of offering a commercial pelleted diet has been characterized as both an expensive organic fertilizer and as a selected food item for larval hybrid striped bass (palmetto), Morone saxatilisxMorone chrysops, culture operations. In this study, we examined the effects of providing a commercial diet on fish production and zooplankton dynamics during phase I culture in plastic-lined ponds. We also sought to estimate relative dietary contribution of a commercial fish feed relative to natural pond biota using stable isotope tissue analysis. Palmetto bass were stocked into six 0.04-ha plastic-lined ponds at a rate of 125,000/ha. During the 31-d culture period, ponds were fertilized with alfalfa pellets at a rate of 112kg/ha/wk. At 14d post-stock (dps), Silver Cup Trout Fry diet was offered at a rate of 13.6kg/ha/d and fertilization was discontinued in three ponds. Although mean final fish length was significantly greater within the fed treatment, no other production parameters were found to be different (P<0.1). Following feed application, copepod concentrations within the fed ponds were greater in magnitude by 24dps. Through stable isotope tissue analysis, we found a significant enrichment in both C-13 and (15) of fish, zooplankton, and Chironomidae larvae within the fed ponds (P<0.10). Using a three-source mixing model, the mean (+/- SE) percent composition of feed in the fish's isotopic signature increased from 5% +/- 2 to 20% +/- 6 within 16d. Although fish production was not greatly affected through the addition of a commercial fish feed, enriched C-13 and (15) of fish tissue indicate that palmetto bass fingerlings increasingly utilized the prepared diets over time. However, based on the isotopic values of fish and potential food sources, it can be estimated that natural pond biota likely accounted for up to 80% of nutrient assimilation in the hybrid striped bass.

This biomechanical study assessed integrated function of the proximal radioulnar joint (PRUJ), interosseous ligament (IOL), and distal radioulnar joint (DRUJ). Tekscan™ pressure sensors were inserted into the DRUJ and PRUJ of 15 cadaveric specimens. MicroStrain(®) sensors were mounted onto the IOL on nine of these specimens. A customized biomechanical jig was used to apply axial loads and take measurements through pronosupination. The PRUJ, IOL, and DRUJ were shown to function as an integrated osseoligamentous system distributing applied load. The PRUJ has transmitted pressure profiles similar to those of the DRUJ. Different IOL components support loading at different stages of pronosupination. The IOL is lax during pronation. Mid-IOL tension peaks in the midrange of forearm rotation; distal-IOL tension peaks in supination. Axial loading consistently increases IOL strain in a non-linear fashion. There are clinical implications of this work: disease or surgical modification of any of these structures may compromise normal biomechanics and function.

Chairperson: Joseph E. Morris, Iowa State University Industry Advisory Council Liaison: Harry Westers, Rives Junction, Michigan Funding Request: $95,000 Duration: 2 Years (September 1, 1999 August 31, 2001) Objectives: 1. Strengthen linkages between North Central Regional Aquaculture Center (NCRAC) Research and Extension Work Groups. 2. Enhance the NCRAC extension network for aquaculture information transfer. 3. Provide in-service training for Cooperative Extension Service (CES), Sea Grant Advisory Service, and other landowner assistance personnel. 4. Develop and implement aquaculture educational programs and materials for the North Central Region (NCR). Proposed Budgets:

This study used six 0.04 ha plastic-lined ponds to compare the effects of a fertilization regime using a one-time initial application of an organic fertilizer (alfalfa pellets) with the current regime of weekly applications of organic fertilizers on the abundance and distribution of aquatic invertebrates and walleye, Sander vitreus, fingerling production. Walleye, 3-4 days post hatch, were stocked on 1 May 2002 and harvested on 6-7 June 2002. Throughout the growing season, a ratio of 7:1 total nitrate-nitrogen to total phosphorus was maintained in all ponds regardless of the treatment. Once fry were stocked, ponds in Treatment #1 were fertilized weekly with organic fertilizer (alfalfa pellets; 112 kg ha-1 week-1) for a total of 795 kg ha-1 pond-1. Ponds in Treatment #2 only received an initial application of alfalfa pellets (112 kg ha-1). Ponds in Treatment #1 had significantly higher ammonia and nitrate levels as well as higher chironomid larvae but not zooplankton compared with the other treatment. At harvest, walleye in the Treatment #1 ponds were significantly longer and heavier; however, the survival and relative weight were not significantly different. These results suggest that weekly applications of organics are important for the benthic food base and growth of fingerling walleye reared in plastic-lined ponds.

Understanding the trophic ecology of closely-related species is important for providing insight on inter-specific competition and resource partitioning. Although catostomids often dominate fish assemblages in lotic systems, little research has been conducted on their ecology. This study was developed to provide information on the trophic ecology of catostomids in several Iowa rivers. Food habits, diet overlap, and gill raker morphology were examined for highfin carpsucker Carpiodes velifer, quillback C. cyprinus, river carpsucker C. carpio, golden redhorse Moxostoma erythrurum, shorthead redhorse M. macrolepidotum, silver redhorse M. anisurum, and northern hogsucker Hypentelium nigricans sampled from four Iowa rivers (2009). Diet overlap among all species was calculated with Morista's index (C). Food habit niche width was quantified with Levin's index (B) and similarity in gill raker morphology was compared with analysis of covariance. Values from Morista's index suggested significant overlap in the diets of highfin carpsucker and river carpsucker (C = 0.81), quillback and river carpsucker (C = 0.66), and shorthead redhorse and silver redhorse (C = 0.67). Levin's index indicated that golden redhorse (B = 0.32), quillback (B = 0.53), and river carpsucker (B = 0.41) had the most generalized feeding strategies as their food niche widths were substantially wider than the other species. Gill raker length and spacing were positively correlated with the standard length of the fish for all species (gill raker length: r(2) = 0.67-0.88, P <= 0.01; gill raker spacing: r(2) = 0.63-0.73, P <= 0.01). Slopes of regression of gill raker length and spacing to standard lengths were significantly (P <= 0.05) different among species, indicating that rates of change in gill raker morphology with body length varied among species. Differences in gill raker morphology likely allow catostomids to partition resources and reduce competitive interactions.

In 2004, research was conducted to compare chironomid larvae populations and their use by channel catfish (Ictalurus punctatus) fingerlings in two different culture systems. Over a 4-month culture period, chironomid larvae densities in plastic-lined ponds were significantly less than those in earthen ponds. The consumption of chironomid larvae by channel catfish fingerlings was related to chironomid abundance in earthen ponds. The significance of these findings is the possible relationship among pond type, initial consumption of commercial diets and subsequent survival rates of fingerling channel catfish.

Twelve 0.26-m(3), shallow, plastic pools at an Iowa fish culture facility were used as mesocosms to determine the mode (airborne versus water supply) and rate of colonization by benthic chironomid larvae without the predation pressure of fingerling walleyes Sander vitreus. Chironomid larvae have particular importance in the culture of walleye fingerlings. Concurrent with walleye hatchery operations in nearby plastic-lined production ponds, pools were filled and then fertilized using the same protocols as the production ponds. A 2 x 2 factorial experimental design was used that included screened (1,000-mu m mesh over the top of the pools) and nonscreened pools and filtered (75-mu m-mesh sock) and nonfiltered water in the pools. Chironomid larvae were sampled twice during the 5-week culture season with Hester-Dendy samplers. At the end of the walleye culture season, there were no significant differences in chironomid density between filtered (108 larvae/m(2)) and nonfiltered (657 larvae/m(2)) pools, but nonscreened pools (592 larvae/m(2)) had larger densities of chironomid larvae than screened pools (174 larvae/m(2)). These results suggest that airborne movement and egg deposition by chironomid adults, rather than transfer of organisms from the water supply reservoir to the culture facility, constitute the primary method of chironomid colonization in plastic-lined ponds.