Melissa R. Wuellner

Physical structures, constructed from either natural or artificial materials, are added to aquatic systems to provide habitat for fish. Attraction to new structures is well documented, but few studies have compared attraction on added structures to existing or bare areas in multiple reservoirs or species. Thus, the objective of this study was to compare species richness and diversity and abundances of target taxa over newly added structures constructed of different materials to those over nearest existing available habitat and an open site with no apparent habitat structures within three reservoirs where sampling was conducted across seasons and years. Cedar brush piles and Georgia cube complexes were placed in into three reservoirs in October 2020. Existing physical habitats and areas devoid of any physical structure were also selected near added structures. Sampling was conducted in spring, summer, and fall 2021 and 2022 using boat‐mounted electrofishing. Richness and diversity were generally higher over existing or added structure than over open habitat. However, none of our target taxa showed consistent association to a single habitat type between reservoirs, and seasonal differences in habitat use were common. Our results point towards the need to understand the inherent factors, such as existing habitat availability, the recipient fish community, and abiotic factors on the outcomes of adding physical habitat structure in reservoirs. Continuous monitoring over multiple years beyond the timeframe of this research is recommended to provide information on the longevity of benefits to fishes and to decide when habitat structures may need to be replaced.

Recreational fishing provides sociological and economic benefits, and fish populations are managed by state agencies to meet angler expectations. One of the most popular species in Midwest reservoirs are walleye (Sander vitreus), and most of these fisheries have established restrictions on the number and sizes of fish harvested. Regulations are set based on population structure and dynamics and management goals, but often agencies have incomplete information needed to establish regulations. Predictive models can provide insight on population responses and inform managers of the tradeoffs between angler restrictions and population sustainability. Lake McConaughy, Nebraska, supports a popular walleye fishery. Despite annual stockings of age-0 walleye since 1991, annual standard surveys conducted by the Nebraska Game and Parks Commission has shown that the relative abundance of adults has generally declined since the 1990s. Current harvest regulations allow harvest of four walleye, all of which must be at least 38 cm long but only one ≥ 56 cm, but population responses to other possible regulations used in Nebraska and elsewhere to manage walleye are unknown. The objectives of this study were to: 1) model various population outcomes for walleye in Lake McConaughy under different minimum length and bag limits; and 2) compare the proportion of individuals reaching 56 cm under different natural and fishing mortality rates. Models were informed by previous creel interviews and annual standard surveys of walleye by the Nebraska Game and Parks Commission and were constructed in Fisheries Analysis and Modeling Simulator (FAMS). Overall, the population was more sensitive to changes in minimum length limits than bag limits, likely due to rapid growth in body length. Additionally, fishing mortality was a greater limitation to recruitment of fishes to 56 cm than natural mortality. Overall, our approach and results can be informative for state agencies throughout the Midwest in setting the appropriate harvest regulations needed to reach management goals.

Rising global food demand necessitates improved crop yields. Biostimulants offer a potential solution to meet these demands. Among them, antioxidants have shown potential to improve yield, nutritional quality, and resilience to climate change. However, large-scale production of many antioxidants is challenging. Here, we investigate Coenzyme M (CoM), a small, achiral antioxidant from archaea, as a potential biostimulant, investigating its effects on growth and physiology. CoM significantly increased shoot mass and root length of the model plant, Arabidopsis thaliana, in a concentration-dependent manner. Sulfur-containing CoM supplementation restored growth under sulfur-limited conditions in Arabidopsis, whereas similar recovery was not observed for other macronutrient deficiencies, consistent with it being metabolized. In tobacco, CoM increased photosynthetic light capture capacity, consistent with observed growth improvements. Interestingly, this effect was independent of carbon capture rates. Furthermore, CoM promoted early-stage shoot growth in various crops species, including tobacco, basil, cannabis, and soybean. Our results suggest CoM is a promising, scalable biostimulant with potential to modify photosynthesis and enhance crop productivity.

Rising global food demand necessitates improved crop yields. Biostimulants offer a potential solution to meet these demands. Among them, antioxidants have shown potential to improve yield, nutritional quality and resilience to climate change. However, large-scale production of many antioxidants is challenging. Here, we investigate Coenzyme M (CoM), a small, achiral antioxidant from archaea, as a potential biostimulant, investigating its effects on growth and physiology. CoM significantly increased biomass of the model plant Arabidopsis thaliana in a concentration-dependent manner consistent with it being metabolized. In tobacco, CoM increased photosynthetic light capture capacity, consistent with observed growth improvements. Interestingly, this effect was independent of carbon capture rates. Furthermore, CoM promoted early-stage shoot growth in various crops species, including tobacco, basil, cannabis, and soybean. Our results suggest CoM is a promising, scalable biostimulant with potential to modify photosynthesis and enhance crop productivity. Key Points: Antioxidant application improves plant growth but is typically too expensive to use widely. Coenzyme M is a small, easily made antioxidant of Archaeal origin. Applied exogenously, Coenzyme M conditionally increases plant biomass. Coenzyme M represents an antioxidant with potential to be a widely used biostimulant.

Fish stocking continues to be an important and often‐used tool in fisheries management. Mortality of fish may be high in the first few days after stocking due to predation and a lack of appropriate food and habitat. The objective of this study was to develop a conceptual model that may identify stocking locations that can help improve the survival of stocked fish. We identified three factors—predator risk, zooplankton (food) availability and measures of habitat that could be important to the survival of stocked Walleye (Sander vitreus) and White Bass (Morone chrysops) fingerlings in Lake McConaughy, Nebraska. The spatial distribution of these factors was used to create a predictive surface to identify those stocking locations hypothesised to lead to higher survival. Final stocking maps identified the best 12.8% and 13.9% of the predicted area of Lake McConaughy for stocking Walleye and White Bass, respectively. Both maps predicted that the best locations were along the south‐central shoreline of Lake McConaughy. The maps for both species were interestingly similar. These results are likely due to the similarities in predators consuming the stocked species and the zooplankton consumed by fingerlings of both species. Habitat availability may be less important, or other aspects of habitat may need to be considered. Identifying the best locations for stocking based on predation risk and the availability of food and habitat could increase the survival of stocked fishes and help managers reach population objectives.

Objective Acoustic telemetry is a tool commonly used to better understand the fates of fish following a stocking event. Until recently, predation on stocked fish could only be inferred by observing and identifying abrupt changes in tag detection histories. Recently, a novel predation transmitter has provided better insight into how predation affects poststocking survival. The main objective of this study was to use these transmitters to estimate predation rates on stocked juvenile Chinook Salmon Oncorhynchus tshawytscha in a landlocked system (Lake Oahe, South Dakota). Our secondary objectives were to determine how quickly predation was occurring, the time of day of predation events, and if there were differences in size between predated and nonpredated fish. Methods In 2021 and 2022, we surgically implanted Innovasea V5D 180-kHz transmitters in 110 juvenile Chinook Salmon. These tagged Chinook Salmon were stocked at two locations on Lake Oahe along with a large cohort of untagged individuals. The tagged Chinook Salmon were passively tracked using an array of Innovasea VR2W 180-kHz acoustic receivers. Result Across the two study years, we observed a mean predation rate (±SE) of 32.9 ± 6% on the tagged Chinook Salmon. Predation on the tagged Chinook Salmon occurred relatively quickly, with a mean time to predation of 86.7 ± 10.8 h. Additionally, 70% of the observed predation occurred during the daytime. Interestingly, results indicated that total length did not differ between fish that were preyed upon or and those that were, but there was a difference in total weight between the two groups. Conclusion Our results provide insight into recruitment bottlenecks within this population and offer information to other researchers regarding the advantages and limitations of this novel technology. Understanding how to mitigate predation could help to guide future stocking strategies to ensure a better return on investment for costly stocking programs.

Objective: Track cohort survival, individual growth, and PIT tag retention, as well as relative growth rate, from fall to the following spring for age-0 Muskellunge Esox masquinongy held in an extensive culture pond. Methods: A total of 806 age-0 Muskellunge were provided a 12-mm PIT tag in October 2021 and placed into a 0.1-ha pond. Individual total length (mm) was recorded for each fish. When the pond was drained in March 2022, an assessment of survival and PIT tag retention was calculated for the cohort, as well as assessment of mean individual growth and relative growth rate. Result: Muskellunge experienced high survival (91.9%) but low individual mean growth (21.7 ± 0.2 mm [mean ± SE]). The mean length of surviving Muskellunge (267.8 ± 0.9 mm) was significantly greater than nonsurviving Muskellunge (251.4 ± 3.1 mm). However, smaller surviving Muskellunge did exhibit slightly improved growth compared to individuals that were initially longer. Conclusion: The results provide an expectation for overwinter survival and growth in an extensive culture pond. This can assist managers in developing expectations on the numbers and length of Muskellunge that will be available to stock the following spring, which has largely been unreported previously.

Understanding and predicting recruitment, longstanding goals in fisheries science and ecology, are complicated by variation in the importance of environmental drivers coupled with the dynamic nature of individual ecosystems. Developing an understanding of recruitment from well-monitored stocks offers an opportunity to overcome these complexities. We used a systematic literature review, a survey, and a workshop attended by professionals with expertise in recruitment of Walleye Sander vitreus to identify common environmental drivers of Walleye recruitment and additional sources of variation (i.e., context dependencies) among populations. The importance of individual environmental drivers, as well as the direction of their influence, differed as a function of geographic region, lake surface area, and Walleye life stage. The literature suggested abiotic conditions (e.g., temperature) during the first year of life were influential in determining recruitment. Professional opinion noted the importance of biotic factors, with prey availability and predation risk having the most consistent relationships with recruitment. We synthesized this information to propose a conceptual model that illustrates the suite of characteristics that shape Walleye recruitment over large spatial and temporal scales. Our findings emphasize the importance of first-year growth and system-specific contextual factors, which can alter the relative importance of the environmental drivers of recruitment.

Habitats may become unavailable to fish in reservoirs at different water elevations. Coves are particularly vulnerable to habitat loss, as these peripheral zones may become isolated from the main reservoir. Quantifying habitat loss at different water elevation reductions and estimating the cost of replacing specific types of habitat or maintaining a target percentage of total habitat cover can help fisheries managers to plan for habitat restoration projects in reservoirs. We used side-scan sonar to estimate areas of rock, tree, and brush habitat in one cove within Harlan County Reservoir, Nebraska, and used quotes for materials, placement, and personnel from recent habitat restoration projects to estimate replacement and maintenance costs. Materials included riprap rock, cedar trees, and those needed to construct Georgia cubes. Overall, rock, brush, and trees covered a total of 2% of the cove at conservation pool. Rock habitat covered 10 times more area than brush and 100 times more area than trees. All habitats became unavailable when water elevation decreased by 3.5–4.0 m. The cost to replace each habitat type increased as water elevation decreased, and the total cost to replace all habitat at 3.5 m of elevation loss was US$390,000. The cost to maintain the original area of habitat available in the cove (2% of the total cove area) increased for each type of habitat but only until water elevation decreased by 2.5 m. At this point, the total cost to maintain similar habitat coverage was $219,000. Climatic variability may lead to greater oscillations of water elevations in reservoirs, making the vertical distribution of available habitat even more relevant to management planning. The findings of this study serve as an example for how managers can identify the vertical distribution of available habitats and estimate costs for habitat restorations.