Predicting introduction, establishment and potential impacts of smallmouth bass

Aim The introduction of non‐indigenous species has resulted in wide‐ranging ecological and economic impacts. Predictive modelling of the introduction and establishment of non‐indigenous species is imperative to identify areas at high risk of invasion to effectively manage non‐indigenous species and conserve native populations. Smallmouth bass (Micropterus dolomieu), a warm water fish species native to central North America has negatively impacted native fish communities, including cyprinids and salmonid populations, as a result of intentional introductions. We predicted the introduction risk; species establishment based on habitat suitability; identified lakes at high risk of invasion; and finally assessed the consequential impacts on native salmon, trout and cyprinid populations. Location Ontario and British Columbia, Canada. Methods Classification tree and logistic regression models were developed and validated to predict the introduction and establishment of smallmouth bass for thousands of lakes. Results Densely human populated areas and larger lake surface areas successfully identify lakes associated with the introduction of smallmouth bass (introduction model) in British Columbia. Climate, lake morphology and water chemistry variables were the driving environmental parameters to define suitable smallmouth bass habitat (establishment model). A combination of the introduction and establishment model identified 138 lakes that are currently at risk in British Columbia to the introduction and establishment of smallmouth bass. Of these 138 high‐risk lakes, 95% of them contain at least one species of salmon, trout or cyprinid, thereby increasing the potential impact of an invasion by smallmouth bass. Main conclusions Our framework can be applied to other terrestrial and aquatic species to obtain a better understanding of the potential risk posed by a non‐indigenous species to an ecosystem. Furthermore, our methodology can be used to focus management efforts on areas at higher risk (e.g. number of potential releases, more favourable habitats) to control future introductions of non‐indigenous species, thereby conserving native populations.     

Facilitation between herons and smallmouth bass foraging on common prey

Understanding how multiple predators affect one another and their shared prey is an increasingly important goal for ecologists examining predator–prey dynamics and food-web structure. In a field experiment, we examined the outcome of interactions between terrestrial and freshwater predators foraging for the same prey in two temperate North American streams. We used a factorial design to examine the combined foraging effects of herons and smallmouth bass on striped shiners and central stonerollers. We found that there was facilitation between the two predators, resulting in risk-enhancement for the prey species, with particularly pronounced effects on the smallest (<70 mm) size classes. Facilitation is the least well-documented predator–predator interaction and has not been quantitatively demonstrated for freshwater and terrestrial predators. Our results indicate that bass may gain a net benefit from the presence of wading birds such as herons and egrets, and that concerns about the negative effects of birds on fish stocks through competition may be unwarranted.     

Walleye Sander vitreus and smallmouth bass Micropterus dolomieu interactions: an historic stable-isotope analysis approach

The carbon (δ(13) C) and nitrogen (δ(15) N) values of Sander vitreus scales differed pre and post-introduction in treatment lakes among years following the introduction of Micropterus dolomieu. No difference of δ(13) C and δ(15) N in S. vitreus scales was found in control lakes where M. dolomieu were not introduced. In treatment lakes, S. vitreus δ(15) N increased and δ(13) C decreased. No relationship was found between S. vitreus and M. dolomieu abundance in the two treatment lakes. Size structure of S. vitreus and M. dolomieu was negatively correlated and condition of the two species was positively correlated. Although S. vitreus feeding habits may have changed in the treatment lakes after M. dolomieu introductions, evidence suggests that fitness-related factors (i.e. abundance and condition) of S. vitreus remained unchanged, indicating S. vitreus and M. dolomieu may coexist where M. dolomieu have been introduced.     

Seasonal pattern of depth selection in smallmouth bass

The current study used a stationary acoustic telemetry array to monitor the depth selection of adult smallmouth bass Micropterus dolomieu in a large, oligotrophic lake in Ontario, Canada. At an annual scale, smallmouth bass demonstrated regular, seasonal changes in inhabited depths: fish occupied shallow water during the summer (2–5 m depth) and descended to deeper water (12–15 m depth) during winter under ice. Smallmouth bass remained above the thermocline in the summer, seasonal depth patterns did not vary across fish size and movements to and from seasonal depths were closely linked to the development and degradation of the thermocline. At finer time scales, smallmouth bass exhibited diel vertical migrations in summer, with fish moving to <2 m at night, and then descending to 3–5 m during the day. This pattern remained constant during the summer period examined, and varied with size such that larger fish remained deeper than smaller fish. During winter, depth did not vary across the 3-month monitoring period ( c . 14 m), but small (<2 m) changes in depth were observed periodically, suggesting limited movements were occurring. Results are further discussed in the context of climate change and reproductive success for this species.     

Genetic mating system and mate selection in smallmouth bass

Mating systems are an important factor influencing the variance in reproductive success among individuals within natural populations and thus have important ecological and evolutionary implications. We used molecular pedigree reconstruction techniques with microsatellite DNA data to characterize the genetic mating system and mate selection in adult smallmouth bass spawning in Lake Opeongo. The genetic mating system of smallmouth bass in this system can be characterized as predominantly monogamous with a low rate of polygynandry particularly among larger individuals. Iteroparous individuals showed a complete absence of interannual mate fidelity, presumably due to the low annual return rate of spawning adults. Within a season, individuals from both sexes pursued additional mating opportunities with males showing greater variance in mate number than females. Female mate selection appeared to be largely random with little evidence for elevated levels of inbreeding in this population. Multiple mating females pursued additional males to whom they were less related than the first male with which they spawned within a given season, however, this pattern varied among years. The mating pattern observed in this population would likely limit the strength of sexual selection and thus could account for the lack of sexual dimorphism and the absence of alternative reproductive tactics in this species.     

Occurrence of acanthocephalans in largemouth bass and smallmouth bass (Centrarchidae) from Gull Lake, Michigan

A total of 65 largemouth bass, Micropterus salmoides, and 27 smallmouth bass, M. dolomieu, collected in April-September 2000 and April-July 2001 from Gull Lake, Michigan, were examined for acanthocephalans. Leptorhynchoides thecatus and Neoechinorhynchus cylindratus infected all the bass examined. Leptorhynchoides thecatus had the highest mean intensity (258.2 +/- 185.4 in 2000 and 145.0 +/- 61.0 in 2001) of the species infecting smallmouth bass. Although N. cylindratus had higher mean intensities (42.1 +/- 37.9 in 2000 and 68.9 +/- 70.5 in 2001) than did L. thecatus in largemouth bass, the values were not significantly different between bass species. The prevalence, mean intensity, and mean abundance of Pomphorhynchus bulbocolli in the bass species were below the values for the other acanthocephalan species. Leptorhynchoides thecatus and N. cylindratus are the most abundant intestinal helminths in bass from Gull Lake.     

Reproductive success and the energetic cost of parental care in male smallmouth bass

Direct field measurements of the energetic expenditure on parental care and within-nest reproductive success of individual male smallmouth bass Micropterus dolomieui were determined by measuring the change in total body mass as well as by total body electroconductivity analysis (TOBEC™). With TOBEC, the change in total body lean mass of the same live individual was measured non-destructively at the beginning and end of the parental care period. Lean mass was the primary source of energy utilized during parental care indicating starvation and potential loss of future reproduction. Individual loss in lean mass was related positively to reproductive success suggesting that the energy expended during parental care does affect individual fitness.     

Effects of acidic water on young-of-the-year smallmouth bass (Micropterus dolomieui)

Synopsis Smallmouth bass (Micropterus dolomieui) populations are declining in areas vulnerable to anthropogenic acidification. To determine if populations may be lost directly from acid effects (i.e., in isolation from synergists), we performed a laboratory study on the effects of acid exposure on growth, survival and histology of young smallmouth bass (3 to 36 d post swimup). We exposed them to declining, then fluctuating acid levels averaging pH 7.4 (control), 5.7 and 5.0. Substantial decreases in survival were observed, as well as damage to tissues. Survival declined with increasing acidity to 43% of that in controls at pH 5.7 and to 4% at pH 5.0. Histological analysis revealed severe changes in the most acidic treatment, with damage to blood, gill, and epithelial tissue. In contrast, growth was less useful as an indicator of response to acidity. Growth in both length and dry weight was greater at the lower pH levels than in controls. This was probably a reflection of lower survival at the lower pH levels, reduced density, and hence less competition for food. Our results suggest that an increase in environmental acidity is sufficient to cause losses in this species, even in the absence of synergists such as heavy metals.School of Forest Resources, University of Georgia, Athens, GA 30602, U.S.A.     

Quantifying the potential effects of climate change and the invasion of smallmouth bass on native lake trout populations across Canadian lakes

Climate change and invasive species are two stressors that should have large impacts on native species in aquatic and terrestrial ecosystems. We quantify and integrate the effects of climate change and the establishment of an invasive species (smallmouth bass Micropterus dolomieu ) on native lake trout Salvelinus namaycush populations. We assembled a dataset of almost 22 000 Canadian lakes that contained information on fish communities, lake morphologies, and geography. We examined the pelagic-benthic and littoral forage fish community available to lake trout populations across three lake size classes in these aquatic ecosystems. Due to the decreased presence of alternate prey resources, lake trout populations residing in smaller lakes are more vulnerable to the effects of smallmouth bass establishment. A detailed spatially and temporally explicit approach to assess smallmouth bass invasion risk in Ontario lakes suggests that the number of Ontario lakes with vulnerable lake trout populations could increase from 118 (~1%) to 1612 (~20%) by 2050 following projected climate warming. In addition, we identified nearly 9700 lake trout populations in Canada threatened by 2100, by the potential range expansion of smallmouth bass. Our study provides an integration of two major stressors of ecosystems, namely climate change and invasive species, by considering climate-change scenarios, dispersal rates of invasive species, and inter-specific biotic interactions.     

The effects of supplemental food on reproduction in parental male smallmouth bass

Synopsis We provided supplemental food for parental male smallmouth bass,Micropterus dolomieu, to determine if food supply limits the reproductive performance of nesting males as measured by care duration, reproductive success and survival of adult males. Although supplementing the diet of parental males had a positive effect on all three reproductive measures, the experiment generated contrasting results in different years. In the first year, supplemental feeding only improved the survival of fed males versus unfed males. In the second year, supplemental feeding increased care duration and reproductive success of fed males but reduced their survival relative to unfed males. Our supplemental feeding improved current or future measures of reproductive performance, but not both simultaneously. The results appear to demonstrate phenotypic plasticity in the extent to which energy from supplemental feeding can be allocated to present or future reproduction.     

Intraguild predation between spawning smallmouth bass (Micropterus dolomieu) and nest‐raiding crayfish (Orconectes rusticus): implications for bass nesting success

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Spatial and annual variation in the diets of juvenile smallmouth bass, Micropterus dolomieu

Synopsis We measured macroinvertebrate densities and abundance, size, and diet of juvenile smallmouth bass, Micropterus dolomieu, at five sites located at varying distances from a metalimnetic release dam. We used these data to determine the influence of high prey abundances on stomach fullness and age-0 year-class strength. Summer diets of juvenile smallmouth bass (27.7–107.7 mm total length) were dominated by Ephemeroptera (primarily Baetidae) but diet composition was highly variable among years and sites. A linear index of prey selection showed that Ephemeroptera were preferred and Trichoptera were avoided at all sites in all years; but, selection indices were not consistent for Chironomidae or Amphipoda and Isopoda. In two of three years, stomach fullness (gut content mass relative to predicted maximum) of juvenile smallmouth bass decreased with distance downstream of the dam, which reflected patterns observed in benthic macroinvertebrate densities. However, in 1989 when flooding and increased turbidity reduced abundances of juvenile smallmouth bass, no differences in stomach fullness were found among sites. High stomach fullness of juvenile smallmouth bass was attributed to high prey abundances near the dam in years of low or normal streamflow. However, patterns in juvenile smallmouth bass abundances in mid-summer could not be attributed to longitudinal variation in prey abundance.     

Postexercise physiology and repeat performance behaviour of free-swimming smallmouth bass in an experimental raceway

We studied postexercise physiology and behaviour of smallmouth bass (Micropterus dolomieu) that voluntarily ascended experimental raceways of varying length (20-50 m) against water velocities ranging from 8 to 120 cm/s. Our first objective was to link mean swimming speed to metabolism using patterns in postexercise muscle glycogen, muscle lactate, and plasma lactate. Our second objective was to examine several behavioural indices (attempt rate, success rate, and recovery time between an ascent and a subsequent attempt) and determine whether patterns in these data reflected those from the physiological measurements. Postexercise muscle glycogen and plasma lactate data suggest that smallmouth bass powered swimming speeds up to 70-80 cm/s using energy from aerobic processes. However, lactate did not begin to accumulate in the white muscle until speeds in excess of 120-130 cm/s were reached. The behavioural parameters measured did not indicate the presence of a physiological threshold at 70-80 cm/s; however, patterns in all factors changed appreciably when fish maintained speeds in excess of 120-130 cm/s. Therefore, it is clear that behaviour and physiology are tightly linked in this species and that maximum aerobic swimming capacity may not limit performance (or re-performance) during short-duration swims.     

Impact of indigenous egg eaters on the early survival of exotic smallmouth bass

Exotic species become invasive aliens when they have an adverse effect on the community of the recipient ecosystem, and their spread among closed water systems is of recent concern for the conservation of native biodiversity in Japan. Smallmouth bass (Micropterus dolomieu Lacepède) is recognized as one of the worst 100 alien species, being undesirable because of its trophic level as a top predator. Smallmouth bass that have been illegally introduced into Lake Aoki, central Japan, in the 1990s for the purpose of sports fishing have seriously affected the lower trophic levels in the lake including fisheries resources, while a strong effort to remove them has proved to be limited in usefulness. We intended to identify indigenous agents that have a potential to control smallmouth bass in the lake. Snorkeling observations in the daytime revealed that Japanese dace (Tribolodon hakonensis Günther) intruded into smallmouth bass spawning nest as a school and were able to consume the eggs while the male bass was guarding the nest. Consequently, the proportion of lost eggs owing to the predation reached 92.4% per clutch on average, proving that native cyprinids are able to function as an efficient egg predator that reduces the survival of smallmouth bass. We consider that employing the indigenous egg predator can be a practical means to eradicate exotic smallmouth bass, combined with the removal of stones on the nest as a subsidiary step to expose smallmouth bass eggs to predation by Japanese dace.     

Biochemical and toxicopathic biomarkers assessed in smallmouth bass recovered from a polychlorinated biphenyl-contaminated river

Smallmouth bass (Micropterus dolomieu) were collected to quantify the nature and prevalence of biomarker responses, including biochemical indices, toxicopathic lesions and general health indices, among fish collected from polychlorinated biphenyl (PCB)-contaminated and nearby uncontaminated reaches of the Kalamazoo River, Michigan, USA. Blood and tissue samples (gill, liver, spleen, head kidney, trunk kidney, thyroid and gonads) were collected and preserved at necropsy for biochemical and histological analyses. The body condition factor and liver somatic index were significantly lower in fish collected from the downstream, contaminated site. Plasma vitellogenin was not detected in male fish collected from either site. Liver ethoxyresorufin-O-deethylase activity and liver and spleen superoxide dismutase activity were significantly depressed in fish collected from the downstream site. Significant toxicopathic lesions such as glycogen depletion, enhanced macrophage aggregates, hepatic foci of cellular alteration (i.e. preneoplastic lesions) and neoplasia were also detected in the liver of fish collected from the downstream site. This study indicates that many of the biochemical and histopathological biomarker responses were associated with liver and body tissue PCB concentrations. Taken together, the biomarkers of exposure and effect strongly suggest that fish within the downstream site are adversely affected by PCBs and other chemical stressors.     

Biochemical and toxicopathic biomarkers assessed in smallmouth bass recovered from a polychlorinated biphenyl-contaminated river

Smallmouth bass (Micropterus dolomieu) were collected to quantify the nature and prevalence of biomarker responses, including biochemical indices, toxicopathic lesions and general health indices, among fish collected from polychlorinated biphenyl (PCB)-contaminated and nearby uncontaminated reaches of the Kalamazoo River, Michigan, USA. Blood and tissue samples (gill, liver, spleen, head kidney, trunk kidney, thyroid and gonads) were collected and preserved at necropsy for biochemical and histological analyses. The body condition factor and liver somatic index were significantly lower in fish collected from the downstream, contaminated site. Plasma vitellogenin was not detected in male fish collected from either site. Liver ethoxyresorufin-O-deethylase activity and liver and spleen superoxide dismutase activity were significantly depressed in fish collected from the downstream site. Significant toxicopathic lesions such as glycogen depletion, enhanced macrophage aggregates, hepatic foci of cellular alteration (i.e. preneoplastic lesions) and neoplasia were also detected in the liver of fish collected from the downstream site. This study indicates that many of the biochemical and histopathological biomarker responses were associated with liver and body tissue PCB concentrations. Taken together, the biomarkers of exposure and effect strongly suggest that fish within the downstream site are adversely affected by PCBs and other chemical stressors.     

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.     

Comparison of several techniques for mobility and activity estimates of smallmouth bass in lentic environments

Mean daily mobility estimates for smallmouth bass Micropterus dolomieu from mark-recapture (47·5±12·5 m) were less than from conventional telemetry (77·1±10·6 m). The relationship developed in a respirometer between the activity transmitter and swimming speed ( r 2=0·99, P < 0·001, n =6) when applied to field activity data estimated mean daily movement at 27 408±4085 m, i.e. >100 times mark/recapture or telemetry estimates. Using these estimates in the activity parameter of a bioenergetics model resulted in different model outputs. These results highlight the potential underestimates in activity associated with using traditional mark-recapture and locational telemetry and reaffirm that fish expend a significant portion of their activity budgets undertaking localized movements.     

Differential effects of largemouth and smallmouth bass on habitat use by stoneroller minnows in stream pools

Previous investigations of within-reach distribution patterns of the stoneroller minnow, Campostoma anomalum Rafinesque, suggest that this species behavioural response to piscivorous bass differs among streams with different bass species. This study compares the responses of Camposloma to two common piscivorous fishes, largemouth bass, Micropterus salmoides Lacepede, and smallmouth bass, M. dolomieui Lacepede. Field experiments in Brier Creek, Oklahoma, U.S.A. showed that Campostoma responded to the presence of adult largemouth bass by shifting to shallow water habitats (commonly < 20 cm), but responded weakly or not at all to adult smallmouth bass. The magnitude of the response of Campostoma was positively related to activity level of the predators. Differences in behaviour between these two predator species may contribute to the differences in spatial distribution patterns of Micropterus and Campostoma observed in earlier investigations, but differences in stream channel morphology and temperature regimes among streams may also be important.     

A long-term view of density-dependent recruitment in smallmouth bass from Nebish Lake, Wisconsin

In a closed population of smallmouth bass Micropterus dolomieui during a 9-year period in Nebish Lake, Wisconsin, total egg production in spring, the percentage of constructed nests that receive eggs, and the mean number of eggs/nest were inversely related to spawning stock biomass. Yet, there was no relationship between total egg production or spawning stock biomass and total young-of-the-year production in autumn of the same year. Together, these results suggest that density-dependent processes regulate egg production, but not young-of-the year production, in smallmouth bass.