Smallmouth Bass Micropterus Dolomieu Research Articles

Reproductive History and Nest Environment Are Correlated with Circulating Androgen and Glucocorticoid Concentrations in a Parental Care–Providing Teleost Fish

Using a long-term study population of wild smallmouth bass Micropterus dolomieu in a connected river-lake system, we investigated whether circulating glucocorticoid (cortisol) and androgen (testosterone) concentrations are influenced by reproductive investment and nesting environment in fish providing nest-guarding paternal care. For all individuals, we collected measures of reproductive history and the value of current parental care. We assessed nest environment and monitored individuals to quantify seasonal reproductive success. Finally, we measured circulating cortisol concentrations following a standardized stressor and circulating testosterone concentrations. Using general linear models, we found that poststress circulating cortisol concentrations were positively related to water temperature and were higher in fish nesting in the river than in the lake. Circulating testosterone concentrations were negatively related to water temperature and were higher in reproductively experienced fish. When considering the factors that influence reproductive success, we found that only parental size was positively related to current nest success. In summary, the results demonstrate that nesting environment is correlated with parental stress responses during parental care, while reproductive history and nesting environment are correlated with circulating androgen concentrations. Collectively, these results offer insight into the roles of both glucocorticoid and androgen steroid hormones during parental care in teleost fish.

Movement patterns of smallmouth and largemouth bass in and around a Lake Michigan harbor: The importance of water temperature

Smallmouth bass Micropterus dolomieu and largemouth bass M. salmoides in southwestern Lake Michigan use shallow, warm harbors for spawning during spring. After the reproductive period ends in early summer, catch rates from standardized sampling of smallmouth bass in harbors decrease. Fishes are presumed to use the main lake during summer but little is known about how black basses use main-lake habitat in Lake Michigan or mechanisms driving this transition. We tracked smallmouth bass (N=26) and largemouth bass (N=8) using radio and acoustic telemetry during 2005–2006 near North Point Marina, IL. A temperature difference persisted between inside and outside the harbor for much of May–October where harbor temperatures were generally warmer than those outside the harbor. Smallmouth bass responded to water temperature changes, inhabiting the harbor until temperatures outside the harbor approached 18.5°C, at which time they left the harbor. Frequent temperature fluctuations of >3°C occurred outside the harbor within 24-hour periods. Sudden reductions in water temperature were associated with smallmouth bass temporarily returning to the harbor until the temperature outside the harbor again approached 18.5°C. As water cooled during fall, smallmouth bass again returned to the harbor. Largemouth bass exhibited comparatively restricted movements during this time and rarely ranged outside the harbor. Thus, home range estimates for smallmouth bass (142.6ha) were an order of magnitude greater than those of largemouth bass (12.9ha). Both water temperature and species played a role in determining the degree of movement outside the harbor but both black basses used the harbor as a thermal refuge.

Fish Assemblage Shifts and Population Dynamics of Smallmouth Bass in the Beaver Archipelago, Northern Lake Michigan: A Comparison between Historical and Recent Time Periods amidst Ecosystem Changes

AbstractThe ecological and economic importance of Great Lakes nearshore areas and the paucity of information on nearshore Lake Michigan fish assemblages prompted us to document changes that occurred from a historical time period (1969–1972, 1975, 1977, and 1984) to a recent period (2005–2008) in a nearshore northern Lake Michigan (Beaver Archipelago) fish assemblage, with an emphasis on smallmouth bass Micropterus dolomieu. From historical to recent periods, the Beaver Archipelago fish assemblage shifted from predominantly brown bullheads Ameiurus nebulosus to predominantly smallmouth bass. Relative abundance of brown bullheads and white suckers Catostomus commersonii declined from historical to recent time periods, as did overall species richness. The relative abundance, recruitment variability, and mortality rates of smallmouth bass have not significantly changed since the historical time period, whereas both condition (ages 5–7) and growth (ages 2–7) of this species have significantly increased. Our results suggest that the smallmouth bass population in the Beaver Archipelago area has not been negatively affected by recent ecological changes (i.e., declining primary productivity, increasing benthic invertebrate densities, increasing numbers of double‐crested cormorants Phalacrocorax auritus, and increasing introductions of nonnative species). The smallmouth bass is currently the dominant nearshore species and remains a critical component of the nearshore fish assemblage in northern Lake Michigan.

ポンプを用いたコクチバスの産卵床駆除技術の開発

ポンプを用いたコクチバスの産卵床駆除技術の開発

Effects of Smallmouth Bass on Atlantic Salmon Habitat Use and Diel Movements in an Artificial Stream

AbstractInvasive smallmouth bass Micropterus dolomieu have been introduced to some of the last remaining watersheds that contain wild anadromous Atlantic salmon Salmo salar, yet little is known about the interactions between these species. We used an artificial stream equipped with passive integrated transponder tag antenna arrays to monitor habitat use and movements of age‐0 Atlantic salmon and age‐0 smallmouth bass in sympatry and allopatry. We used additive and substitutive designs to test for changes in habitat use, diel movements, and diel activity patterns of prior‐resident Atlantic salmon or smallmouth bass resulting from the addition of conspecifics or heterospecifics. Atlantic salmon prior residents did not change their habitat use in the presence of conspecific or heterospecific invaders. However, Atlantic salmon invaders did lessen riffle habitat use by smallmouth bass prior residents during daytime. Atlantic salmon and smallmouth bass displayed different diel activity patterns of movement (Atlantic salmon were more nocturnal; smallmouth bass were more diurnal), which were affected by heterospecific introductions. Because the two species tended to favor different habitat types and displayed different diel activity patterns, we suggest that under the conditions tested, the level of interspecific competition for habitat was low. Age‐0 Atlantic salmon and smallmouth bass may be able to avoid intense interspecific competition through spatial and temporal habitat partitioning. These data do not, however, predict the potential for competition under different seasonal or ontogenetic circumstances.

Evaluating Two Observational Sampling Techniques for Determining the Distribution and Detection Probability of Age‐0 Smallmouth Bass in Clear, Warmwater Streams

AbstractAccurate determination of the distribution and abundance of age‐0 sport fish, such as smallmouth bass Micropterus dolomieu, is an important aspect of successful species management (e.g., characterizing nursery habitats for protection or enhancement; identifying reproductive dynamics and influences of environmental variables). Two observational techniques—snorkeling and above‐water (AW) observation—were evaluated in several Missouri Ozark streams to determine (1) accuracy of identifying age‐0 smallmouth bass with each technique, (2) detection probabilities under a variety of channel unit (CU) conditions (i.e., discrete morphological features such as riffles or pools) and the relations between detection probability and hydraulic variables, and (3) behavioral responses (fright response, return response, or no response) of fish to the observers using each technique. Identification of age‐0 smallmouth bass was over 90% accurate when using AW observation in shallow water and when snorkeling in deep water. In both streams, detection probabilities differed depending on the CU sampled and the method used. In deep pools, detection probabilities when snorkeling were two to three times those obtained from AW observation; however, AW observation was more efficient for sampling most shallow‐water (<0.5‐m) CUs. Velocity had no significant relation to detection probability, whereas depth was significantly related to detection probability for both sampling methods (the relationship was positive for snorkeling and negative for AW observation). The percentage of age‐0 smallmouth bass that exhibited a fright response was greatest for fish observed by snorkeling in shallow‐water CUs. On average, approximately 20% of fish showed a fright response, but a large proportion of these fish exhibited a return response. Our results indicate that multiple sampling methods may be necessary to achieve high accuracy when sampling small fish in a variety of CUs, and snorkeling and AW observation may be viable methods for selecting CUs in many warmwater streams. Additional work is recommended to address knowledge gaps, especially those related to the influence of biotic and abiotic variables that were not measured in this study.Received November 9, 2010; accepted May 12, 2011

GROUNDWATER INFLUENCES ON THE DISTRIBUTION AND ABUNDANCE OF RIVERINE SMALLMOUTH BASS, MICROPTERUS DOLOMIEU, IN PASTURE LANDSCAPES OF THE MIDWESTERN USA

ABSTRACTThis study examined how spring‐flow (SF) contributions to streams related to the distribution and abundance of smallmouth bass Micropterus dolomieu in a predominately pasture landscape in Missouri, USA. Stream segments (N = 13) with similar landscape characters were classified by SF volume into high SF (HSF) or low SF (LSF) groups. The densities of smallmouth bass, channel unit (CU) use and temperature‐selection patterns were assessed for several life stages and frequency distributions for age 0 fish. More smallmouth bass were present in stream segments with HSF influence. Age 0 fish were twice as likely to be present in HSF stream segments. Older age classes were present in stream reaches independent of SF contribution. For all age classes, the use of particular CUs did not depend on SF influence. All age classes were more likely to be present in pools than other CUs. Microhabitat temperature selection differed among age classes. Age 0 fish selected warmer temperatures with a gradual shift towards cooler temperatures for older age classes. The length frequency of age 0 fish was skewed towards larger individuals in streams with limited SF influence, whereas the length frequency in HSF stream segments was skewed towards smaller individuals. The benefits of significant groundwater via SF influence seem to be related to increased hatch or survival of age 0 fish and the availability of optimal temperatures for adult smallmouth bass growth. Thermal refugia and stable flows provided by springs should be recognised for their biological potential to provide suitable habitat as climate change and other land‐use alterations increase temperature regimes and alter flow patterns. Published in 2011 by John Wiley & Sons, Ltd.

Competitive interactions between walleye (Sander vitreus) and smallmouth bass (Micropterus dolomieu) under various controlled conditions

The range of smallmouth bass (Micropterus dolomieu) is expanding northward, creating new interactions with native predators, including walleye (Sander vitreus). We used a series of experiments to investigate competition between walleye (WAE) and smallmouth bass (SMB) at different life stages and light conditions, identified behaviors that allowed one fish to outcompete another, and evaluated whether prey switching mitigated competitive interactions. Juvenile and adult SMB appeared to outcompete WAE when fed during the daytime; neither species dominated when fed near dusk. Attack rates and capture efficiencies of both species were similar with an intra- or interspecific competitor, but SMB often exploited prey before the competitor had a chance to feed (exploitative competition) or displayed agonistic behaviors toward a potential competitor (interference competition). Prey selectivity of WAE or SMB did not differ when by themselves or with a potential competitor. These results indicate that SMB could outcompete WAE under limiting prey conditions due to the aggressive nature of SMB, but resources may be partitioned at least along a temporal scale.

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

Numerous studies on smallmouth bass (Micropterus dolomieu) have focused on movements, diets, and capture rates among habitat types, but we are aware of no study that has documented capture rates and size structure by month to aid in assessment and management of this fish. The objective of this study was to determine monthly sampling dynamics and population size structure of smallmouth bass in four northeastern South Dakota glacial lakes. Smallmouth bass were collected monthly (May–September) from Enemy Swim Lake and Roy Lake in 2007 and Clear Lake and Pickerel Lake in 2008 using modified-fyke nets and night electrofishing in rocky habitats. Monthly mean catch-per-unit-effort (CPUE) values for smallmouth bass collected with fyke nets were variable but generally low (0.2–4.7 fish/net night) across months and lakes. Monthly mean CPUE values for smallmouth bass collected by electrofishing were variable in all four lakes (99.7–771.8 fish/h); however, in Clear Lake and Enemy Swim Lake CPUE significantly increased from May through September, primarily due to age-0 bass becoming vulnerable to electrofishing. For all lakes except Clear Lake, there were no significant differences in monthly mean CPUE values of 180 mm and longer smallmouth bass. Length distributions varied by month, but in general May and June samples contained a higher proportion of larger individuals than later sampling months. Overall mean relative weight (Wr) values were greater than 80, but relative weight varied among lakes and months. Our results suggest that spring (May to June) sampling of smallmouth bass using night electrofishing in rocky habitats will result in the broadest length range of captured bass.

Habitat Selection and Overlap of Atlantic Salmon and Smallmouth Bass Juveniles in Nursery Streams

AbstractIntroduced smallmouth bass Micropterus dolomieu have invaded much of the historic freshwater habitat of Atlantic salmon Salmo salar in North America, yet little is known about the ecological interactions between the two species. We investigated the possibility of competition for habitat between age‐0 Atlantic salmon and age‐0 and age‐1 smallmouth bass by means of in situ observations and a mesocosm experiment. We used snorkel observation to identify the degree and timing of overlap in habitat use in our in situ observations and to describe habitat shifts by Atlantic salmon in the presence of smallmouth bass in our mesocosm experiments. In late July 2008, we observed substantial overlap in the depths and mean water column velocities used by both species in sympatric in situ conditions and an apparent shift by age‐0 Atlantic salmon to shallower water that coincided with the period of high overlap. In the mesocosm experiments, we detected no overlap or habitat shifts by age‐0 Atlantic salmon in the presence age‐1 smallmouth bass and low overlap and no habitat shifts of Atlantic salmon and age‐0 smallmouth bass in fall 2009. In 2009, summer floods with sustained high flows and low temperatures resulted in the nearly complete reproductive failure of the smallmouth bass in our study streams, and we did not observe a midsummer habitat shift by Atlantic salmon similar to that seen in 2008. Although this prevented us from replicating our 2008 experiments under similar conditions, the virtual year‐class failure of smallmouth bass itself is enlightening. We suggest that future studies incorporate the effects of varying temperature and discharge to determine how abiotic factors affect the interactions between these species and thus mediate the outcomes of potential competition.

Empirical assessment of potential interactions between walleye and smallmouth bass

Summary The expansion of smallmouth bass Micropterus dolomieu throughout North America has created substantial changes in some food webs and created novel interactions with native predators in many systems through competition and predation, causing declines in native predator populations. In this study, we examined potential interactions between smallmouth bass (introduced) and walleye Sander vitreus (a native predator) in two Missouri River reservoirs and four natural lakes in South Dakota, USA, using historical standardized sampling data, which indexed four fitness-related factors (relative abundance, size structure, condition, and growth) of both species. Of the 24 total relationships tested among all water bodies, three (13%) were determined to be significant (size structure in Pickerel Lake: P = 0.06; condition in Lake Kampeska: P = 0.06, and growth at Brant Lake: P = 0.02). Of these three, two relationships were negative as would be expected if negative interactions exist between these two species (size structure in Pickerel Lake: r = )0.61; condition in Lake Kampeska: r = )0.61); the remaining relationship was positive (growth at Brant Lake: r = 0.75). Further, no water body consistently demonstrated significant negative interactions in all relationships tested. The results of our study did not support the concept that introduced smallmouth bass interfere with walleye populations in South Dakota waters. Rather, it is more likely that other environmental factors influence the observed variability in walleye demographics and dynamics observed in this study. At this time, we believe that both fisheries will continue to co-exist. However, continuous monitoring of both species is warranted as changing environmental conditions in the future could allow these interspecific relationships to shift toward the dominance of smallmouth bass over walleye.

Nearshore fish assemblages associated with introduced predatory fishes in lakes

Changes to native fish assemblages in lakes are commonly associated with introduced predatory fishes. How fish assemblages change as multiple predatory species are introduced is not well understood. This study investigated the relationship between the presence of introduced large-bodied predatory fishes (largemouth bass Micropterus salmoides, pike Esox lucius, rock bass Ambloplites rupestris, smallmouth bass Micropterus dolomieu, walleye Sander vitreus) and the composition of native fish assemblages in littoral areas of 40 lakes in Algonquin Provincial Park, Ontario, Canada. Fish assemblages were compared across lakes of different predator composition, and within lakes before and after recent predator invasions. The presence of an introduced predator was associated with significantly different native fish assemblages across lakes, after controlling for environmental and spatial variables. Native fish assemblages did not significantly vary across lakes with more than one predator species. Furthermore, while declines in native species richness over time were observed in a number of lakes, these were not associated with introductions of additional predators. Several small-bodied species (brook stickleback Culea inconstans, fathead minnow Pimephales promelas, finescale dace Chrosomus neogaeus, and northern redbelly dace Chrosomus eos) consistently showed strong negative correlations with predator presence. The results suggest that predatory fish introductions alter native fish assemblages and that this impact is consistent regardless of the number of predatory species introduced. Copyright © 2011 John Wiley & Sons, Ltd and Her Majesty the Queen in Right of Canada.

Temporal Variation in Prevalence of Viral Hemorrhagic Septicemia Virus Type IVb among Upper St. Lawrence River Smallmouth Bass

AbstractWe investigated a newly introduced pathogen in a wild population of smallmouth bass Micropterus dolomieu in the St. Lawrence River to illuminate unknown temporal and demographic prevalence patterns. We used real‐time quantitative reverse‐transcription polymerase chain reaction to assess viral hemorrhagic septicemia virus (VHSV) genotype IVb (VHSV‐IVb) viral N‐gene levels. Our objectives were to characterize the distribution and abundance of this newly introduced pathogen within a naïve population of economically valuable sport fish through an annual cycle. We also sought to describe VHSV‐IVb levels across demographic groups (males and females; adults and subadults). Strong temporal variation in prevalence of VHSV‐IVb was evident through the annual cycle; peaks in prevalence corresponded to the smallmouth bass spawning period and a temperature range of 10–14°C. No difference in VHSV‐IVb prevalence between male and female smallmouth bass was detected. However, a markedly higher prevalence was observed in subadult fish than in adult fish. Owing to the observed temporal patterns in prevalence, surveillance programs for VHSV‐IVb in smallmouth bass should concentrate effort on springtime sampling and should include subadult fish.

Development of a Riverine Index Netting Protocol: Comparisons of Net Orientation, Height, Panel Order, and Line Diameter

We developed a gillnetting protocol by sampling 17 nonwadeable rivers across northern Ontario over the course of four summers from 2005 to 2008. The rivers represented a range of habitats; however, all had a coolwater to warmwater fish community characterized by walleyes Sander vitreus, northern pike Esox lucius, white suckers Catostomus commersonii, yellow perch Perca flavescens, and smallmouth bass Micropterus dolomieu. During the study, three net designs were used. Each net had one to four configurations that varied in height, length, monofilament diameter, and sequence of the mesh sizes. We found that most fish (87%) were captured in the lower half of 1.8-m-high gill nets and that there was no difference in catch between gill nets with serial panels (i.e., sequentially increasing mesh sizes) and those with randomly organized panels. Net that were set perpendicular to shore or angled to shore caught approximately twice as many fish as nets that were set parallel to shore. Contrary to expectations, there were no differences in net durability and catch between thick- and thin-diameter monofilament nets. Based on the results of these experiments, we propose an improved net design that we call the large-mesh riverine index net for use in rivers; it is more versatile, reduces net drag, and fishes more effectively than the traditional gill nets that are used in lakes. The large-mesh riverine index net has eight panels (3.1 m long × 0.9 m high) and totals 24.8 m in length. Panel stretch measures (and the random order used) for this design are 127, 76, 178, 25, 102, 203, 51, and 152 mm. The nets are set perpendicular to shore in rivers from July 1 to October 1 and should be fished in areas where water velocity is less than 0.1 m/s. Received January 12, 2010; accepted November 2, 2010

The effects of temperature change on the hatching success and larval survival of largemouth bass Micropterus salmoides and smallmouth bass Micropterus dolomieu

In this study, the effects of abrupt temperature change on the hatching success and larval survival of eggs, yolk-sac larvae (YSL) and larvae above nest (LAN), for both largemouth bass Micropterus salmoides and smallmouth bass Micropterus dolomieu were quantified. Temperature had a significant effect on hatching success and time to 50% mortality, with large heat shocks causing accelerated mortality. The temperature changes shown to influence survival of all life stages, however, were beyond what is typically experienced in the wild. Micropterus salmoides had greater egg hatching success rates and increased survival rates at YSL and LAN stages, relative to M. dolomieu. Additionally, egg hatching success and survival of LAN varied across nests within the study. These findings suggest that temperature alone may not account for variations in year-class strength and may emphasize the need for protection of the nest-guarding male Micropterus spp. to ensure recruitment.

Distribution and Population Characteristics of Shadow Bass in Two Arkansas Ozark Streams

AbstractWe examined the longitudinal distribution and population characteristics of shadow bass Ambloplites ariommus in the Spring River and lower Eleven Point River of Arkansas to determine potential length limit regulations for this species. Shadow bass were the second most abundant sport fish species collected in both streams (most abundant sport fish was the smallmouth bass Micropterus dolomieu). Abundances (catch per effort) of shadow bass were greatest upstream and declined significantly downstream (Spring River: 32.6 fish/h upstream versus 3.4 fish/h downstream; Eleven Point River: 13.4 versus 5.0 fish/h). Size distributions and relative weights (Wr) were also greatest upstream (Spring River: Wr = 109 upstream versus 99 downstream; Eleven Point River: Wr = 105 versus 95). Associated with this distribution trend was a downstream decline in stream slope and frequency of riffles. Catch rates and size distributions of shadow bass were greater for the Spring River (proportional size distribution mean = 83) than for the Eleven Point River (mean = 36). Stream differences in preferred size distributions were even greater. Total length at age for shadow bass indicated rapid growth rates compared with results of previous studies; age‐3 fish reached 183 mm total length. The von Bertalanffy equation yielded the following growth model for shadow bass: Lt = 250.8[1 − e−0.381(t−0.477)], where Lt is length at age t. Stomach contents of shadow bass in the Spring River comprised mostly crayfishes, which is consistent with feeding patterns of other rock basses Ambloplites spp. Relative weights were high for shadow bass in both rivers, although Wr was greater for Spring River fish (Wr = 107) than for Eleven Point River fish (Wr = 102). Based on abundance, diet, and condition of shadow bass, upstream reaches of both rivers contain sustainable populations of this species. Despite these positive population and growth features, length limits for shadow bass are not recommended for these streams.

The influence of changing climate on the ecology and management of selected Laurentian Great Lakes fisheries

The Laurentian Great Lakes Basin provides an ecological system to evaluate the potential effect of climate change on dynamics of fish populations and the management of their fisheries. This review describes the physical and biological mechanisms by which fish populations will be affected by changes in timing and duration of ice cover, precipitation events and temperature regimes associated with projected climate change in the Great Lakes Basin with a principal focus on the fish communities in shallower regions of the basin. Lake whitefish Coregonus clupeaformis, walleye Sander vitreus and smallmouth bass Micropterus dolomieu were examined to assess the potential effects of climate change on guilds of Great Lakes cold, cool and warm-water fishes, respectively. Overall, the projections for these fishes are for the increased thermally suitable habitat within the lakes, though in different regions than they currently inhabit. Colder-water fishes will seek refuge further north and deeper in the water column and warmer-water fishes will fill the vacated habitat space in the warmer regions of the lakes. While these projections can be modified by a number of other habitat elements (e.g. anoxia, ice cover, dispersal ability and trophic productivity), it is clear that climate-change drivers will challenge the nature, flexibility and public perception of current fisheries management programmes. Fisheries agencies should develop decision support tools to provide a systematic method for incorporating ecological responses to climate change and moderating public interests to ensure a sustainable future for Great Lakes fishes and fisheries.

Mortality of Centrarchid Fishes in the Potomac Drainage: Survey Results and Overview of Potential Contributing Factors

Skin lesions and spring mortality events of smallmouth bass Micropterus dolomieu and selected other species were first noted in the South Branch of the Potomac River in 2002. Since that year morbidity and mortality have also been observed in the Shenandoah and Monocacy rivers. Despite much research, no single pathogen, parasite, or chemical cause for the lesions and mortality has been identified. Numerous parasites, most commonly trematode metacercariae and myxozoans; the bacterial pathogens Aeromonas hydrophila, Aeromonas salmonicida, and Flavobacterium columnare; and largemouth bass virus have all been observed. None have been consistently isolated or observed at all sites, however, nor has any consistent microscopic pathology of the lesions been observed. A variety of histological changes associated with exposure to environmental contaminants or stressors, including intersex (testicular oocytes), high numbers of macrophage aggregates, oxidative damage, gill lesions, and epidermal papillomas, were observed. The findings indicate that selected sensitive species may be stressed by multiple factors and constantly close to the threshold between a sustainable (healthy) and nonsustainable (unhealthy) condition. Fish health is often used as an indicator of aquatic ecosystem health, and these findings raise concerns about environmental degradation within the Potomac River drainage. Unfortunately, while much information has been gained from the studies conducted to date, due to the multiple state jurisdictions involved, competing interests, and other issues, there has been no coordinated approach to identifying and mitigating the stressors. This synthesis emphasizes the need for multiyear, interdisciplinary, integrative research to identify the underlying stressors and possible management actions to enhance ecosystem health.

Dispersal of Smallmouth Bass from a Simulated Tournament Weigh‐In Site

AbstractSimulated smallmouth bass Micropterus dolomieu fishing tournaments were staged in Dale Hollow Lake, a 12,400‐ha reservoir in Tennessee, between March 2004 and February 2005 to investigate posttournament dispersal. Smallmouth bass (n = 54) were captured with conventional hook‐and‐line tackle and artificial lures, placed in live wells, and subjected to a weigh‐in procedure before being externally tagged with an ultrasonic transmitter and released. Water temperatures ranged from 7.4°C to 29.3°C (mean [SE] = 17.6°C [2.5]), fish ranged in total length from 330 to 572 mm (mean = 452 [8.3]), and no fish were dead at the weigh‐ins. Smallmouth bass dispersed rapidly away from the release site, which was located at the head of a 68‐ha embayment. After 3–5 d, survivors (n = 44) traversed an average distance of 1,475 m [213]. Most (72%) fish swam uplake and out of the 385‐ha study area after 6 d. The rapid dispersal of smallmouth bass may be relevant in systems that experience heavy tournament activity. The smallmouth bass caught and subjected to simulated tournament conditions on Dale Hollow Lake did not stockpile near the release site.

Habitat Selection and Abundance of Young‐of‐Year Smallmouth Bass in North Temperate Lakes

AbstractHabitat use during early life history plays an important role in the ecology of smallmouth bass Micropterus dolomieu in north temperate lakes. The highest levels of mortality occur during the first year of life, and the habitat selected probably affects mortality. We used resource selection functions and abundance data from two northern Wisconsin lakes to determine the habitats that influence the survival of smallmouth bass. Coarse substrates were consistently important to both nesting locations and young‐of‐year smallmouth bass. Young smallmouth bass used woody structure after swimming from their nests but disassociated themselves from habitats with more complex woody structure by August. Nonwoody cobble areas offer protection for young‐of‐year smallmouth bass without attracting predators, as woody habitats do. The decline in the abundance of young‐of‐year smallmouth bass was best fit to an exponential decay function in woody habitats, but in rock habitats it was linear. Habitat selection by young‐of‐year smallmouth bass shifts over time, and the shift is linked to predation risk: woody habitats initially offer them an advantage with respect to spawning but eventually provide their predators greater opportunities for ambush. This shift underscores the importance of having a diversity of littoral habitats. This study provides the first quantifiable analyses describing the habitat features selected by young‐of‐year smallmouth bass and links these descriptions to population dynamics.