FACTORS INFLUENCING LARGEMOUTH BASS RECRUITMENT: IMPLICATIONS FOR THE ILLINOIS MANAGEMENT AND STOCKING PROGRAM Annual Progress Report July 1, 2007 to June 30, 2008

During the past segment, all activities outlined in the annual work plan were accomplished and within the specified budget. The goal of this study is to develop management strategies that maximize growth, recruitment, and harvest of largemouth bass Micropterus salmoides in Illinois impoundments. Largemouth bass are frequently stocked in many Illinois impoundments to compensate for variable recruitment. Even so, the long-term contribution of stocked fish to recruitment and harvest of natural bass populations is unknown and we are addressing these questions. Because stocking is only one of several management options for this species, it is critical that additional information on factors limiting recruitment processes be identified. In addition, information on the importance of rearing technique, size of stocked fish, forage base, cover, resident predators, physical-chemical conditions, and stocking stress in determining largemouth bass stocking success is needed to optimize use of hatchery produced fish. There was no new activity in Job 101.1 as final recommendations were presented in previous reports. In Job 101.2 we are assessing stocking strategies for largemouth bass. Supplemental stocking is a widely used management tool for increasing the standing stock of an existing population. We evaluated four sizes of stocked fish (50, 100, 150, and 200 mm) that were stocked in four lakes. Survival of stocked largemouth bass fingerlings to adult size was relatively low and ranged from 0 to 2.7 stocked fish per hour of electrofishing during the fall of 2007 and spring of 2008. Scales were collected from each adult stocked fish and will be aged in order to determine which year each fish was stocked and what size it was at stocking. We did not observe any stocked largemouth bass remaining in Woods Lake in 2007 or 2008, however there were stocked fish collected in Lake Charleston, Mingo and Homer. We observed very few stocked largemouth bass remaining and will conclude our sampling for long-term survival with this segment. Data from this segment were combined with previous segments in order to assess differences in growth and survival with varying stocking size. Despite initial differences in size and catch per unit effort (CPUE), all stocked bass were found in similar relative abundances and at similar mean size from the first summer after stocking throughout the following seasons. Cost analysis showed that growing bass to 150 or 200 mm increased the overall cost of producing and stocking largemouth bass without increasing survival. As a result, we recommend stocking four inch bass because small fingerlings do not survive well and no differences in long-term survival exist between medium, large, and advanced fingerlings. In this segment we also continued to evaluate long-term survival and growth of intensively and extensively reared stocked fish. Thus far, no differences in survival have been observed between intensively and extensively reared fish in any of the three study reservoirs. However, the relative survival of intensively and extensively reared largemouth bass did vary between lakes. We are no longer collecting significant numbers of stocked fish in any of the three lakes stocked with intensive and extensively reared fish and sampling was concluded in this segment. Scales were collected from adult fish in electrofishing samples and were aged during this segment by two independent readers. These age data will be used to assign a rearing type to each stocked fish that was collected and will be used to evaluate the long-term survival differences of the fish reared vifrom these different techniques in the next segment. Based on our results thus far, the usefulness of supplemental stocking as a management strategy will vary by individual lake. We initiated a new stocking experiment in this segment to examine the relative advantages of point and dispersed stocking of largemouth bass. We stocked four lakes by both stocking at the boat ramp and stocking into habitat at locations around the lake. We observed very low survival to the first fall for stocked fish regardless of stocking strategy. Future stockings will be needed to assess differences in survival and growth. In this segment, we also evaluated the long-term contribution of four-inch stocked largemouth bass from three annual stockings in 15 reservoirs. Stocked largemouth bass were marked with fin clips and sampled for five years. Contribution of stocked fish to the population was highest for young of year (21%) and juvenile bass (17%), but decreased dramatically in adult fish (5%). Catch per unit effort (CPUE) from electrofishing samples was also low for adults resulting in small contributions to the population. Our results suggest limited contribution of stocked fish to adult largemouth bass populations and the size of stocked fish in the first fall following stocking is related to higher CPUE of adult fish. Substantial mortality exists between the age-1 and adult ages of stocked largemouth bass which differs from wild fish that experience low mortality following the first fall. Additional research regarding the importance of predator and prey populations, habitat, and abiotic factors are needed to determine lake characteristics most favorable for stocking largemouth bass. The objective of Job 101.3 is to evaluate the survival and reproductive success of stocked largemouth bass to resident populations. To determine the contribution of stocked fish to a population, fingerlings were produced at the Little Grassy Fish Hatchery with the MDH B2B2 allele as a genetic tag. These genetically tagged fingerling were then stocked into six study lakes. Once these fish reached sexual maturity, it is possible to assess their reproductive success and recruitment to the population by comparing the pre-stocking MDH B2 allele frequencies with the post-stocking MDH B2 allele frequencies. Young-of-the-year produced in 2007 were collected from each of the six study lakes and their allele frequencies determined for the MDH B2 allele. Although it is still early to fully evaluate the effects of stocking, five of the six lakes do show an increase in the MDH B2 allele. Stocking contribution appears to be high in small lakes, but relatively low in larger ones. Further yearly sampling is needed to fully evaluate the long-term impacts of stocked fingerlings in these populations and to fully assess the costs and benefits of largemouth bass stocking programs. In Job 101.4, we assessed which abiotic and biotic factors are associated with variation in recruitment of largemouth bass to age 1. We used the results from previous segments to construct lake-specific regression models of largemouth bass recruitment and then tested their accuracy with data from this segment (2007 year class). In general, differences among lakes in mean recruitment were related to survival of young-of-the-year (YOY) to fall, implying that year class strength differences are set prior to winter. For each individual lake, reproductive output (i.e., spawning stock abundance, peak YOY density) or abundance of larval and juvenile bluegill sunfish were included in models predicting recruitment strength. Lakes where bluegill abundance was not included in recruitment models had very productive bluegill populations; therefore, recruitment in these systems was not limited by prey fish abundance. These models generally over- viiestimated abundance of age 1 recruits in the 2007 year class, but were accurate at predicting if a lake would have either below or above average year class strength. For all year classes examined, YOY largemouth bass exhibited a negative relationship between abundance and growth. Future work involving improvement of habitat availability (i.e., aquatic vegetation) may improve growth rates by increasing the number of YOY individuals that can be sustained by the environment. We also began to evaluate the influence of vegetation and woody habitat on young-of-year largemouth bass and other fish. We sampled 6 enclosures on Lincoln Trail, 3 with vegetation, and 3 without. We observed greater average densities of largemouth bass, bluegill, and all other fish in the vegetated enclosures compared to the non-vegetated enclosures. These differences however were small and we plan to continue this work in Lincoln Trail and expand to additional lakes. We also expanded our analysis of the influence of vegetation and woody debris to largemouth bass recruitment. Lakes were mapped for composition and abundance of vegetation and woody habitat. We observed no direct correlations with vegetation and woody habitat with young-of-year largemouth bass abundance in the fall. In future segments, we will expand these analyses to incorporate additional years of data and evaluate the interaction between vegetation and woody habitat.In this segment, we also identified 13 lakes to include in a multi lake experiment examining the effects of manipulating vegetation on largemouth bass populations. We have identified two low vegetation lakes where we will increase aquatic vegetation. In spring of 2008, we began planting vegetation in fish enclosures in Lake Paradise. Five species of vegetation were planted in varying size and array of enclosures. We will evaluate the different types of enclosures and vegetation species in order to assess the vegetation planting as well as make management recommendations on planting techniques. In fall of 2006 through spring of 2007, Dolan Lake was drawn down and rotenone was applied to reduce carp and gizzard shad abundance and expose the seed banks in an attempt to increase vegetation and sportsfish production. These lakes are being monitored for changes in the fish community. We also began monitoring three high vegetation lakes where we will decrease vegetation levels (Airport Pond, Kakusha Lake, and Stillwater Lake). An additional 8 lakes will be treated as control lakes where no vegetation management will occur. The control lakes vary in vegetative cover from low to high and will be coupled with experimental lakes. We began monitoring these lakes before vegetation treatments to evaluate the effects on largemouth bass recruitment and the fish community. These studies will allow us to make recommendations on vegetation management in order to increase largemouth bass recruitment in Illinois reservoirs. We also began monitoring dam escapement of largemouth bass during high water events. We have observed largemouth bass moving over the dam at Forbes and Ridge Lake. This project is in the initial phase and we will continue to evaluate fish passage during high and low flows to evaluate if escapement can effect largemouth bass recruitment. There is potential for angling to have a large influence on largemouth bass populations. In particular, competitive tournament fishing for black bass has grown rapidly in the United States over the past several years. Previous work has shown high levels of mortality associated with these tournaments in other parts of the United States. viiiIn Job 101.5, we continued monitoring largemouth bass spawning activities at Lincoln Trail Lake. Largemouth bass appeared to prefer cobble, pebble and gravel nesting substrates. Spawning date for young-of-year largemouth bass surviving to the fall was disproportionately skewed towards nests from later in the spawning season in most years. Nesting frequency was also compared to existing water quality parameters. Frequency of new nests was directly related to water temperature. Spawning activity decreased when temperature decreased and no spawning was observed at temperatures under 50o F. Total number of nests was not related with the number of recruits. However, adult standing stock was related to the total number of recruits indicating a stock recruitment driven system. We continued to monitor largemouth bass tournaments in order to assess if reproductively active males are being preferentially caught. Data from three of the four lakes examined suggests that this may be the case during both spring tournaments and the post-spawning period. Information provided by tournament angler surveys suggests that the culling and release of smaller males for larger females is minimal and not skewing sex ratio estimates. Additional research to determine the implications of angling bass from the nest on the overall bass population and year class strength are needed. We continue to determine sex and ages of largemouth bass in lakes with varying fishing exploitation. We will examine how angling activities influence sex specific characteristics such as growth, longevity, and age of maturity. Using this data, we will be able to make predictions about how angling will affect recruitment of largemouth bass. In this segment, we also began to monitor largemouth bass tournaments at Bloomington and Evergreen Lakes in order to assess tournament related mortality and stress related physiology at different times of year. Livewell simulation experiments were also initiated to assess the influence of water temperature and dissolved oxygen on fish exposed to tournament conditions. In addition, pond experiments were implemented to evaluate how holding cages can influence mortality and stress response estimates in the tournament experiments. Results from these experiments will be used to assess the potential impacts of tournament fishing on largemouth bass populations and used to make management recommendations regarding tournament procedures. In Job 101.5, we also conducted a controlled pond experiment at the Aquatic Research Facility in Champaign, IL to assess the effects of angling on largemouth bass recruitment. We tested the effect of brood reduction on young-of-the-year recruitment, and found that predation on largemouth bass nests during catch and release angling events did reduce the number and biomass of YOY surviving later in the first year of life. We will repeat this experiment in 2008 to increase experimental replication so that statistically significant trends may be detected if present. We also conducted a field experiment on Ridge Lake, holding largemouth bass angling tournaments during the spawning season – the first time Ridge has been open to angling during the spawning season since at least 1996. We detected slightly lower than average YOY densities in fall sampling for 2007, indicating that angling during the spawning season and concomitant brood predation may be influencing YOY recruitment later in the first year of life. Data collection and analysis on Ridge Lake will continue in future segments to further explore the relationship between angling and recruitment in a more natural system, while pond experiments will continue to allow for controlled examination of specific, angling-related mechanisms influencing recruitment. ixIn Job 101.6, a portion of Clinton Lake that was closed to fishing was sampled to determine the effects of a refuge on largemouth bass populations. Electrofishing samples yielded a higher abundance of adult largemouth bass in the refuge than in the main lake. Some increase in the number of largemouth bass has also been observed throughout the lake. Sampling will continue at Clinton Lake to monitor largemouth bass populations for changes resulting from the refuge. We also began sampling Otter Lake as an additional location to evaluate refuges. Electrofishing and seine samples were initiated in two proposed refuge sites as well as three control sites. We plan to implement the refuge after several years of monitoring pre refuge conditions in the lake. We also began assessing potential study design and lakes for monitoring effects of harvest regulations on largemouth bass populations. Initial lakes were selected to compare the effects of regulations on largemouth bass populations. INHS study lakes have regulations from standard 14and 15-inch length limits to varying slot limits. We will employ FAS data in future segments to supplement the initial study lakes used in this analysis. We will be specifically targeting assessments of how size limit regulations may influence angler decisions to choose between harvest and release, and how those cumulative decisions may alter population size structure over time. These data can then be used to guide future discussions about various management experiments that might be implemented.