Description of two new gill myxozoans from smallmouth (Micropterus dolomieu) and largemouth (Micropterus salmoides) bass

Two previously undescribed species of myxozoan parasites were observed in the gills of bass inhabiting the Potomac and James River basins. They are described using morphological characteristics and small-subunit (SSU) rDNA gene sequences. Both were taxonomically identified as new species of Myxobolus; Myxobolus branchiarum n. sp. was found exclusively in smallmouth bass, and Myxobolus micropterii n. sp. was found in largemouth and smallmouth bass. Small, spherical, white plasmodia of M. branchiarum from smallmouth bass were observed grossly in the gills; these plasmodia had an average length of 320.3 μm and width of 246.1 μm. The development of the plasmodia is intralamellar in the secondary lamellae of the gills. Mature spores were pyriform in shape with a length of 12.8 ± 1.4 (8.1-15.1) μm and width of 6.9 ± 1.1 (4.0-9.0) μm. Analysis of SSU rDNA identified M. branchiarum in a sister-group to 3 species of Henneguya , although morphologically caudal appendages were absent. Myxobolus micropterii observed in the gills of largemouth and smallmouth bass had larger, ovoid, cream-colored plasmodia with an average length of 568.1 μm and width of 148.1 μm. The cysts developed at the distal end of the gill filament within the primary lamellae. The mature spores were ovoid in shape with a length of 10.8 ± 0.7 (9.2-12.2) μm and width of 10.6 ± 0.6 (9.0-11.8) μm. SSU rDNA analysis placed M. micropterii in a sister group with Henneguya lobosa and Myxobolus oliveirai . The highest prevalence of M. branchiarum was observed in the gills of bass collected from the Cowpasture River (50.9%). Prevalence was 44.6% in bass from the Potomac River and only 4.3% in bass collected from the Shenandoah River. A seasonal study of M. branchiarum , which included both infected and uninfected smallmouth bass, determined that a significantly higher intensity was observed in the spring than in the summer (P < 0.001) or fall (P = 0.004). In an analysis excluding uninfected bass, a higher intensity was observed in the spring than in the summer (P = 0.001) or fall (P = 0.008). Prevalence and seasonal differences were not determined for M. micropterii .     

Predation of Japanese dace, Tribolodon hakonensis, by largemouth bass, Micropterus salmoides, in experimental aquaria

 To test the size range of prey fish that largemouth bass, Micropterus salmoides, can successfully consume, live Japanese dace, Tribolodon hakonensis, were given as prey fish to individual largemouth bass in aquaria. The ratio of maximum standard length (SL) of the Japanese dace consumed by largemouth bass was 46–69% of bass SL. The maximum length of Japanese dace consumed did not differ significantly between largemouth bass and smallmouth bass (M. dolomieu) previously studied, although largemouth bass have relatively larger mouth sizes than smallmouth bass. Largemouth bass occasionally injured and killed Japanese dace larger than the limit that could be consumed.     

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.     

First record of Neoergasilus japonicus (Poecilostomatoida: Ergasilidae), a parasitic copepod new to the Laurentian Great Lakes

The parasitic copepod Neoergasilus japonicus, native to eastern Asia, was first collected from 4 species of fish (fathead minnow, Pimephales promelas; largemouth bass, Micropterus salmoides; pumpkinseed sunfish, Lepomis gibbosus; and yellow perch, Perca flavescens) in July 1994 in Saginaw Bay, Lake Huron, Michigan. Further sampling in the bay in 2001 revealed infections on 7 additional species (bluegill, Lepomis macrochirus; carp, Cyprinus carpio; channel catfish, Ictalurus punctatus; goldfish, Carassius auratus; green sunfish, Lepomis cyanellus; rock bass, Ambloplites rupestris; and smallmouth bass, Micropterus dolomieu). An additional 21 species examined in 2001 were devoid of the parasite. A limited collection of fish from Lake Superior (n = 8) and Lake Michigan (n = 46) in 1994 showed no infection. Neoergasilus japonicus is most frequently found attached to the dorsal fin and, in decreasing frequency, on the anal, tail, pelvic, and pectoral fins. Prevalence generally ranged from 15 to 70 and intensity from 1 to 10. The greatest number of copepods on a single host was 44. The copepod Neoergasilus japonicus appears to disperse over long distances rather quickly, spreading across Europe in 20 yr and then moving on to North America over a span of 10 yr. Its main vehicle of transport and introduction into the Great Lakes is probably exotic fish hosts associated with the fish-culture industry.     

Proteocephalus ambloplitis and Contracaecum sp. from largemouth bass (Micropterus salmoides) stocked into Boundary Reservoir, Saskatchewan

Nonresident (introduced) largemouth bass (Micropterus salmoides) from Boundary Reservoir, Saskatchewan were examined for helminths. Four species of parasites were found (Diplostomum sp., Proteocephalus ambloplitis, Pomphorhynchus bulbocolli, and Contracaecum sp.). Contracaecum sp. larvae were absent in age-0 and age-1 bass, but prevalence and mean intensity increased with age for bass age-2 or older. Similarly, the prevalence and mean intensity of P. ambloplitis plerocercoids in bass were low until age-2; older bass harbored significantly more plerocercoids. Analysis of stomach contents indicates that this pattern of recruitment for Contracaecum sp. and P. ambloplitis is probably due to increased feeding by largemouth bass on aquatic insects and cannibalism after age-2, respectively. Although Contracaecum sp. may have been established in the reservoir prior to the introduction of bass, we are certain that P. ambloplitis was introduced via stocking with infected fingerlings.     

Empirical assessment of potential interactions between walleye and smallmouth bass

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.     

Geographic analysis of host use, development, and habitat use of an acanthocephalan species, Leptorhynchoides thecatus

Leptorhynchoides thecatus (Linton, 1891), an acanthocephalan parasite of freshwater fishes, varies in host use, development, and habitat use throughout North America. Spatial structure of these characteristics was examined from data extracted from the literature. Geographic patterns were inferred from point comparisons using correllograms and then tested with Moran's I statistic for global and local significance, and visually from regional means within major river drainages. Species of Micropterus Lacepède, 1802 (black basses) were common hosts in most regions, except the Lower Mississippi and South Atlantic regions where species of Lepomis Rafinesque, 1819 (sunfishes) were common hosts. Development, described as the proportions of adults relative to cystacanths (extraintestinal juveniles), decreased with latitude. Habitat use of L. thecatus showed marked geographic patterns. Leptorhynchoides thecatus occurred in the intestine of sunfishes in the South Atlantic and Lower Mississippi regions, in the ceca in fish of all species included in the study in the Missouri and Texas-Gulf regions, and both in ceca and intestines in fish of all species in northern regions. Leptorhynchoides thecatus showed geographic patterning within the variable traits across the range of the species. These patterns may be the result of ecological factors or of genetic differences that might indicate L. thecatus comprises multiple cryptic species.     

Experimental trophic ecology of juvenile largemouth bass,Micropterus salmoides,and blue tilapia,Oreochromis aureus

Synopsis The potential for feeding competition between largemouth bass, Micropterus salmoides, and blue tilapia, Oreochromis areus, in Lake Fairfield, Texas was evaluated experimentally. Largemouth bass and blue tilapia were grown in cages alone and in combination with each other. The fish were allowed to feed on the natural food within the lake. Largemouth bass grown in combination with blue tilapia were significantly shorter and weighed less than largemouth bass grown alone. Blue tilapia grown in combination with largemouth bass were statistically significantly longer and heavier than blue tilapia grown alone. Largemouth bass grown alone had diets (volume and number of food items) significantly different than the largemouth bass grown with the blue tilapia. Largemouth bass fed primarily on chironomid larvae and pupae, and odonates, whereas blue tilapia consumed vegetable matter, detritus, and chironomid larvae. Length and weight differences between large-mouth bass grown alone and in combination with blue tilapia, in conjunction with the largemouth bass diet shift, support the theory that these two species compete for food resources.     

Phylogenetics of Freshwater Black Basses (Centrarchidae: Micropterus) Inferred from Restriction Endonuclease Analysis of Mitochondrial DNA

Geographic isolation and habitat specialization has aided in the evolution and genetic integrity of the micropterid bass species of North America. Members of the genus Micropterus form a close natural unit with little morphologic and meristic variation. Our goals were to measure the genetic characteristics of and distances between six black bass species by using mitochondrial DNA analysis. Mitochondrial DNA restriction fragment length polymorphisms were examined in Guadalupe bass (M. treculi), largemouth bass (M. salmoides), shoal bass (M. cataractae), smallmouth bass (M. dolomieu), spotted bass (M. punctulatus), and Suwannee bass (M. notius), using 15 restriction endonucleases. The bluegill (Lepomis macrochirus) was used as an outgroup. The phylogeny inferred from Dollo parsimony cladistic analysis concurred with published results from allozyme analyses, yet it was inconsistent with published meristic analyses. Genetic distances between species ranged from 0.0659 to 0.2145, with the largemouth and Suwannee basses showing the greatest divergence from the other black basses. The Guadalupe, smallmouth, and spotted basses were most diverged from the bluegill. The black basses diverged over a broad time frame, with estimated black bass speciation occurring during late Miocene-early Pliocene (3.30-10.73 MYA).     

Nutritional condition and physiology of paternal care in two congeneric species of black bass (<Emphasis Type="Italic">Micropterus</Emphasis> spp.) relative to stage of offspring development

Parental care requires a complex integration of physiology and behaviour, yet little is known about the physiological and energetic consequences or correlates of these behaviours. Using two species of male black bass (smallmouth bass, Micropterus dolomieu; largemouth bass, M. salmoides) as a model, the focus of this study was to determine the biochemical and hematological indicators of change in nutritional status and potential for chronic stress. This was accomplished by randomly sampling individuals at four stages across parental care. Additionally, a subset of individuals was repeatedly sampled at three brood development stages to track changes in biochemical factors within the individual. Though there were changes in physiological factors across parental care in randomly sampled fish of both species (declines in plasma glucose in largemouth bass; decreases in hematocrit and plasma chloride in smallmouth bass), repeated sampling of individuals was determined to be a more appropriate sampling technique due to natural variability in biochemical factors among individual fish. Repeated sampling of smallmouth bass did not adversely influence physiological metrics or brood abandonment. However, there were higher incidences of nest abandonment in repeatedly sampled largemouth bass. Amongst the repeatedly sampled smallmouth bass, nutritional indicators such as plasma triglyceride levels decreased indicating individual fasting across the majority of parental care. Increases in plasma calcium and magnesium towards the end of care indicated that feeding most likely resumed when the brood was close to independence after ~3 weeks of care. Lastly, several indicators of chronic stress, such as plasma glucose and chloride levels, increased throughout the parental care period. These sublethal stressors are indicative of decreasing body condition associated with prolonged activity and fasting which may have marked impacts on the ability of an individual to continue parental care for the current brood and impact subsequent individual fitness. Further research into the mechanistic relationships between behaviour, physiology, and energetics during the parental care period will provide a better understanding of the decisions by individuals facing multiple trade-offs that ultimately lead to differences in individual fitness.     

Predominance of cross-predation between lateral morphs in a largemouth bass and a freshwater goby

The predator-prey relationship between largemouth bass, Micropterus salmoides, and freshwater goby, Rhinogobius spp., in Lake Biwa, Japan, was examined with respect to their morphological antisymmetry (laterality). Largemouth bass and Rhinogobius gobies exhibited lateral dimorphism in the height of the mandible and the length of the dentary, respectively. Populations of both species were composed of both left-developed and right-developed individuals. Each predation event was categorized as either cross-predation (a predator caught prey of the opposite morph) or parallel-predation (a predator caught prey of the same morph). Stomach contents analysis revealed that cross-predation events predominated over parallel-predation. Annual sampling for eight years demonstrated that in both largemouth bass and Rhinogobius gobies, the ratio of right-developed individuals in the population fluctuated temporally around 0.5. As the predominance of cross-predation was found in the relationship between the exotic largemouth bass and an endemic goby, the predominance may be caused by a kinematical interplay at each predation event.     

Examination of the effects of largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) on the ecosystem attributes of lake Kawahara-oike,Nagasaki, Japan

The introduction of largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus) into the freshwater ecosystems of Japan has resulted in the suppression and/or replacement of native species, generating considerable concerns among resource managers. The impacts of largemouth bass and bluegill on native fauna have been examined in aquaria and isolated farm ponds, but there is limited work examining the likelihood to fundamentally modifying Japan's lakes. The objective of the present study is to examine the direct and synergistic ecological effects of largemouth bass and bluegill on the biotic communities of Lake Kawahara-oike, Nagasaki, Japan, using an ecosystem (Ecopath) modeling approach. Specifically, we examine whether the two fish species have played a critical role in shaping the trophodynamics of the lake. We attempt to shed light on the trophic interactions between largemouth bass and bluegill and subsequently evaluate to what extent these interactions facilitate their establishment at the expense of native species. We also examine how these changes propagate through the Lake Kawahara-oike food web. Our study suggests that the introduction of bluegill has induced a range of changes at multiple trophic levels. The present analysis also provides evidence that largemouth bass was unable to exert significant top-down control on the growth rates of the bluegill population. Largemouth bass and bluegill appear to prevail over the native fish species populations and can apparently coexist in large numbers in invaded lakes. Future management strategies controlling invasive species are urgently required, if the integrity of native Japanese fish communities is to be protected.     

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.     

The diet of largemouth bass, Micropterus salmoides, in Lake Naivasha, Kenya

Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. Of these, Oreochromis leucostictus, Tilapia zillii and Micropterus salmoides (largemouth black bass) support an important gillnet fishery with bass also being taken for sport. Until bass reached 260 mm f.l. they depended upon invertebrate food organisms. Thereafter crayfish, fish and frogs became increasingly important the larger the size of the bass. The most important invertebrate prey species was the water boatman, Micronecta scutellaris , followed by chironomid and culicid pupae. Zooplank-ton was consumed but only in large quantity by fish smaller than 80 mm. For bass over 260 mm the crayfish, Procambarus darkii , was the principal food. The largemouth bass in Lake Naivasha are generalized macro-predators, feeding principally on free-living animals of a kind most likely to be found in the littoral zones.     

Effects of coinfection with Pomphorhynchus bulbocolli on development of leptorhynchoides thecatus (Acanthocephala) in amphipods (Hyalella azteca)

The effect of the presence of Pomphorhynchus bulbocolli on the development of Leptorhynchoides thecatus (Acanthocephala) in amphipod intermediate hosts (Hyalella azteca) was examined. Two groups of amphipods were exposed either to eggs of both species (experimental) or only to L. thecatus eggs (control). Amphipods of both groups were dissected 39 days postexposure. The percentage of L. thecatus at the cystacanth stage and mean abundance of cystacanths and precystacanths per amphipod were determined. Contingency table analysis and Fisher's exact tests demonstrated that a significantly smaller proportion of L. thecatus reached the cystacanth stage in coinfected amphipods of the experimental group than either worms in the control group or worms in L. thecatus-only infections of the experimental group. Interspecific interaction between acanthocephalans in intermediate hosts has not been reported previously. Coinfection reduces the number of L. thecatus in amphipods available for transmission to definitive hosts. Habitat separation by eggs of L. thecatus and P. bulbocolli might reduce this effect if amphipods are less likely to become coinfected when eggs are in different microhabitats than when they are not.     

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.     

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.     

The influence of parental care behaviour on localized nest spacing in smallmouth bass, Micropterus dolomieu

Synopsis I examined the consequence of territorial behaviour on localized nest spacing by male smallmouth bass, Micropterus dolomieu in Jones Bay, Lake Opeongo, Ontario. I compared observed nest spacing to that predicted from (i) territory size and shape measured using sonic tracking procedures; and (ii) 1000 simulated, randomly established nesting stocks. The observed spacing between nests (17.52 ± 1.46 m; mean ± standard error) was not different from that predicted from measurements of territory size and shape (17.60 ± 3.20 m) but was significantly greater than that predicted for randomly established nests (9.53 ± 0.06 m). Parental care-associated territorial behaviour influences the spacing between smallmouth bass nests.     

Distribution and diet of Suwannee bass and largemouth bass in the lower Santa Fe River,Florida

Synopsis Suwannee bass,Micropterus notius, and largemouth bass,Micropterus salmoides, were collected by electrofishing in six habitats in the lower Santa Fe River, Florida during May 1981–March 1982. Both bass species were collected concomitantly in all habitats and habitat segregation was not evident. Crayfish (Procambarus spp.) were the primary food of Suwannee bass. Fish were the primary food of largemouth bass, but crayfish were common in the diet of largemouth bass ≥300 mm long. Suwannee bass have a greater throat width and consumed longer and wider forage than did largemouth bass of equal length. Available evidence suggests that Suwannee bass exhibit a positive selection for crayfish and a diverse forage resource, including abundant crayfish, is necessary for a Suwannee bass to coexist with a largemouth bass. This is Journal Series Number 6034 of the Florida Agricultural Experiment Station.     

Preliminary description of lesions in juvenile largemouth bass injected with largemouth bass virus

Juvenile largemouth bass Micropterus salmoides were intraperitoneally injected with largemouth bass virus (LMBV), a member of the genus Ranavirus, family Iridoviridae. Moribund fish which had been injected with 10(6.2) tissue culture infectious doses, 50% endpoint (TCID50), were sampled 4 d after injection; other largemouth bass injected with this dose died between 3 and 5 d after injection. Fish injected with 10(2.8) TCID50 of LMBV were also examined after 4 d and had lesions similar to those of fish injected with the high dose. Clinical signs included darker pigmentation, inflammation and necrosis at the site of injection, distended abdomen, corkscrew swimming, and lateral recumbency. Internally, fish had focally pale livers, bright red spleens and reddened intestinal ceca. Histologically acute fibrinous peritonitis affected the surface of all organs in the peritoneal cavity, but deeper portions of organs appeared normal. There was also necrosis of the gastrointestinal mucosa. Except for the injection site, lesions were confined to the peritoneal cavity.