Winter survival of age-0 smallmouth bass, <Emphasis Type="Italic">Micropterus dolomieu</Emphasis>, in north eastern lakes

We examined the winter survival of age-0 smallmouth bass,Micropterus dolomieu, in lakes at their northern limit of distribution in New Brunswick, Canada. Pre- and post-winter collections over a 3 year period suggested the smallest individuals, <50 mm total length, died during winter under ice. Experiments with wild, age-0 smallmouth bass held in lakes demonstrated a size-dependent survival where smaller individuals had greater survival with an increasing temperature of exposure, but the largest individuals had reduced survival at warmer temperatures. Survivors lost 22–54% of pre-winter energy reserves measured as ash-free dry weight, which was similar to wild individuals captured in spring. Body size at the onset of winter affects survival, but it also appears that temperature interacting with a suite of environmental and biological factors affect changes in energy use and therefore survival of age-0 smallmouth bass under ice in winter.     

The effects of temperature, pH and water hardness on winter starvation of young-of-the-year smallmouth bass, Micropterus dolomieui Lacepede

Year-class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young-of-the-year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q₁₀ for starvation rate over the temperature range 2.5-8° C is 2.2. Starvation rate increases as pH declines from 7.0-4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl⁻¹ to 80mgl⁻¹: the rate at 80 mg Ca 1⁻¹ is ∼0.80 times the rate at 1 mgl⁻¹.     

Spatiotemporal patterns and habitat associations of smallmouth bass (Micropterus dolomieu) invading salmon‐rearing habitat

1. Smallmouth bass (Micropterus dolomieu) have been widely introduced to fresh waters throughout the world to promote recreational fishing opportunities. In the Pacific Northwest (U.S.A.), upstream range expansions of predatory bass, especially into subyearling salmon‐rearing grounds, are of increasing conservation concern, yet have received little scientific inquiry. Understanding the habitat characteristics that influence bass distribution and the timing and extent of bass and salmon overlap will facilitate the development of management strategies that mitigate potential ecological impacts of bass. 2. We employed a spatially continuous sampling design to determine the extent of bass and subyearling Chinook salmon (Oncorhynchus tshawytscha) sympatry in the North Fork John Day River (NFJDR), a free‐flowing river system in the Columbia River Basin that contains an upstream expanding population of non‐native bass. Extensive (i.e. 53 km) surveys were conducted over 2 years and during an early and late summer period of each year, because these seasons provide a strong contrast in the river’s water temperature and flow condition. Classification and regression trees were applied to determine the primary habitat correlates of bass abundance at reach and channel‐unit scales. 3. Our study revealed that bass seasonally occupy up to 22% of the length of the mainstem NFJDR where subyearling Chinook salmon occur, and the primary period of sympatry between these species was in the early summer and not during peak water temperatures in late summer. Where these species co‐occurred, bass occupied 60–76% of channel units used by subyearling Chinook salmon in the early summer and 28–46% of the channel units they occupied in the late summer. Because these rearing salmon were well below the gape limitation of bass, this overlap could result in either direct predation or sublethal effects of bass on subyearling Chinook salmon. The upstream extent of bass increased 10–23 km (2009 and 2010, respectively) as stream temperatures seasonally warmed, but subyearling Chinook salmon were also found farther upstream during this time. 4. Our multiscale analysis suggests that bass were selecting habitat based on antecedent thermal history at a broad scale, and if satisfactory temperature conditions were met, mesoscale habitat features (i.e. channel‐unit type and depth) played an additional role in determining bass abundance. The upstream extent of bass in the late summer corresponded to a high‐gradient geomorphic discontinuity in the NFJDR, which probably hindered further upstream movements of bass. The habitat determinants and upstream extent of bass were largely consistent across years, despite marked differences in the magnitude and timing of spring peak flows prior to bass spawning. 5. The overriding influence of water temperature on smallmouth bass distribution suggests that managers may be able limit future upstream range expansions of bass into salmon‐rearing habitat by concentrating on restoration activities that mitigate climate‐ or land‐use‐related stream warming. These management activities could be prioritised to capitalise on survival bottlenecks in the life history of bass and spatially focused on landscape knick points such as high‐gradient discontinuities to discourage further upstream movements of bass.     

First record of Emetha audouini, a cymothoid isopod parasite, from cultured sea bass Dicentrarchus labrax in Greece

For the first time, Emetha audouini (Milne Edwards, 1840), a cymothoid isopod, is reported parasitising cage cultured sea bass Dicentrarchus labrax L., 1758 in Greece. The specimens observed are larvae (Pulli II). They were found in great numbers in the buccal and branchial cavity of young (3.5 m.o. old) sea bass, in an intensive cage farm facility. This parasite is certainly transferred to sea bass from wild populations of Sparidae or Centracanthidae. Serious lesions were visible and typical of a crustacean infection, with extensive and deep skin damage in the head area. The cumulative mortality, over a 2 wk period, was 10.75%. The parasitic problem was successfully dealt with by optimization of management practices rather than use of costly and dangerous chemotherapeutants.     

Introgressive hybridization and species turnover in reservoirs: a case study involving endemic and invasive basses (Centrarchidae: <Emphasis Type="Italic">Micropterus</Emphasis>) in southeastern North America

Invasive species threaten native taxa with extirpation and extinction via several biological mechanisms. One such mechanism, hybridization and subsequent introgression of invasive alleles into native genomes is a serious concern, especially for taxa displaying weak reproductive barriers, as is the case for black basses. Black basses introduced outside of their native ranges thus pose elevated threats to endemic congeners, particularly in the southern United States where restricted ranges preclude refuge from introgression. The recently delineated Bartram’s bass (M. sp. cf M. coosae) is endemic to the upper regions of the Savannah River basin, throughout which anthropogenic modification, including impoundment, has been extensive. Non-native Alabama bass (M. henshalli) and smallmouth bass (M. dolomieu) have been introduced into this system on multiple occasions and now threaten Bartram’s bass via introgression. In this study we sampled four reservoirs (Jocassee, Keowee, Hartwell, and Russell) in the upper Savannah River during 2004 and 2010. Results from three codominant nuclear loci and one mitochondrial locus revealed extensive introgression between Alabama and Bartram’s bass. Results show that Alabama bass have replaced Bartram’s bass in lakes Keowee and Russell, where they were first introduced, while the frequencies of hybrids in lakes Jocassee and Hartwell are increasing. Hybridization involving Bartram’s bass with native largemouth bass and introduced smallmouth bass was detected in very low frequencies. Results highlight the importance of continual study over geographic and temporal scales to inform management and conservation of rare fishes threatened with extinction via interspecific hybridization.     

Patterns of gastric evacuation, digesta characteristics and pH changes along the gastrointestinal tract of gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.)

A comparative study of gastric evacuation rates (GERs) and digesta content, moisture and pH values along the gastrointestinal tract was performed between gilthead sea bream and European sea bass. In order to distinguish species-specific differences from diet-elicited effects, all parameters were determined under either a fishmeal diet or a carob seed germ meal diet that contained high levels of total and soluble non-starch polysaccharides. GERs were significantly different between species and they were not affected by diet. Similarly, species-specific patterns were revealed in the distribution of digesta and water content along the gastrointestinal tract. In sea bream, stomach digesta and water content decreased with time, whereas in sea bass stomach retained the highest digesta and water content throughout the sampling period. The anterior and distal intestine exhibited the lowest accommodating capacities of digesta and water in either species. Overall, sea bream performed stomach digestion at lower hydration levels and higher pH compared with sea bass. Diet affected stomach moisture in both species and pH of stomach digesta in sea bass and of all intestinal sections in sea bream. The results obtained indicated that water and inorganic ion exchanges through the gut may differentiate between the species and warrant further investigation.     

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 sulphuric acid exposure on the behaviour of largemouth bass,Micropterus salmoides

Synopsis Young-of-the-year largemouth bass,Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at pH 6.1 and at pH 4.8 performed the two feeding acts, bites and orientations, more often, and spent more time feeding than bass at pH 7.2. Bass at pH 3.7, however, reduced feeding, and spent a significantly larger portion of their time hovering in the water column. Frequencies of comfort and agonistic acts increased with a decline in pH. Alterations of behavioural repertoires of young-of-the-year largemouth bass were useful indicators of sulphuric acid exposure.     

Age‐0 striped bass,Morone saxatilis (Walbaum, 1792), response to immunostimulation

Young‐of‐the‐year (age‐0) striped bass, Morone saxatilis, were studied to characterize their responses to inflammatory stimuli. There were two studies, with the hypotheses that (i) <5 g striped bass would respond to inflammatory insult within 6 h, and (ii) response to antigens would be maintained for >24 h in larger fish. Study I was conducted to understand the cytokine expression pattern (IL‐1β, TNF‐α, Nramp and TGF‐β) in response to lipopolysaccharide (LPS) or Freund's complete adjuvant (FCA) stimulation in age‐0 striped bass (3.44 ± 1.68 g, 70.6 ± 10.3 mm fork length) up to 24 h post injection (hpi). Study II was similar to Study I, but striped bass were sampled over a longer time frame (by 48 hpi) and larger age‐0 striped bass were used (20.6 ± 5.9 g, 129.2 ± 10.9 mm fork length). It was confirmed that immunostimulants such as LPS and FCA induce production of inflammatory cytokines and Nramp, which are important in innate immune response to bacterial infection. The responses were rapidly stimulated with LPS (IL‐1β, TNF‐α, TGF‐β >3‐fold increase, compared to PBS) or FCA (IL‐1β >3‐fold and TGF‐β >2‐fold, compared to PBS) within 6 hpi and maintained in most cases 48 hpi (spleen Nramp and TGF‐β 2‐fold >PBS, at 24 and 48 h), similar to other teleosts. Intraperitoneal injection with PBS also simulated inflammatory gene expression, but was delayed (IL‐1β, TNF‐α, TGF‐β and Nramp, FCA and LPS< at 6 h; 24 h >LPS and PBS) in comparison to LPS and FCA, suggesting that this procedure and possibly the volume used can be stimulatory and potentially harmful in age‐0 fish. Therefore, this study suggests that age‐0 striped bass are capable of strong cytokine induction in response to immunological stimulation within a very short period of time.     

Annual cycles of growth and reproduction in hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus, raised on forage or pelleted diets

Annual cycles of growth and reproduction of hatchery–reared Florida largemouth bass, Micropterus salmoides floridanus , were investigated. Animals were raised on either forage (goldfish, Carassius auratus ) or a pelleted salmon feed. Male and female year–class 1 largemouth bass were sampled throughout one complete yearly cycle (January–December). A biphasic growth cycle was observed in both forage–fed and pellet–fed fish. No increase in body length or weight was observed until approximately midway through the spawning period (May), after which fish grew at a consistent rate for the remainder of the study. The reproductive cycle of forage–fed fish was characterized by a rapid increase in gonadosomatic index (GS1) between January and April, followed by a prolonged spawning period (April–July) during which GSI progressively declined. Fully regressed gonads were observed in September and October, and a resumption of gonadal recrudescence was observed between October and December. Visceral adipose deposits (expressed as mesenteric fat index; MFI) were resorbed during gonadal growth and the initial stages of the spawning period, and restored during the post–spawning phase. Fish raised on pelleted feed had growth and reproductive cycles that parallelled those of forage–fed fish, but several significant differences were observed between the two diet groups. During the growth phase of the cycle, pellet–fed largemouth bass grew significantly faster than forage–fed largemouth bass, and had significantly larger MFIs than forage–fed largemouth bass at all times of the year. Pellet–fed fish also had significantly larger GSIs than forage–fed fish. These data indicate that diet composition may be an important determinant of growth and reproductive function in this species.     

Size-Based Variation in Somatic Energy Reserves and Parental Expenditure by Male Smallmouth Bass, Micropterus dolomieu

Male smallmouth bass show size-based variation in both probability and timing of reproduction. The objective of this research was to determine seasonal and size-based patterns of depletion of energy reserves and determine if parental defense is related to males' energy reserves. We sampled male smallmouth bass in the spring, during the parental care period and in the fall to measure energy reserves (lipid stores in muscle and viscera tissue) over a two year period. Energy stores, which were not built up before nesting, declined to a minimum level by the end of the parental care period. Small males had consistently lower energy reserves than larger males and did not utilize these reserves at the same rate during the parental care period. All parental males complimented endogenous energy reserves by feeding during parental care, however, small males appear to rely proportionately more on exogenous energy intake than do larger males. Parental defense by all sizes of males declined over the parental care period, the decline being the most obvious by small males. Small males' lower energy budget may make them less effective parents and decrease their probability of survival over the following winter relative to larger males.     

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.     

Complete mitochondrial DNA sequences of two haplotypes of the smallmouth bass, <Emphasis Type="Italic">Micropterus dolomieu</Emphasis>, collected from nonindigenous populations in Japan

We determined the complete mitochondrial genome sequences of two haplotypes of the smallmouth bass, Micropterus dolomieu; individuals used in the analysis were collected from nonindigenous populations in Japan. Both genomes comprised 16,488 bp, with genome contents and gene orders being identical to those of other teleost fishes. A previous study revealed that the Japanese smallmouth bass had only two haplotypes, and the present study revealed that the complete mitochondrial DNA (mtDNA) sequences of the haplotypes differed in only one nucleotide difference. The low genetic diversity in the mtDNA of the smallmouth bass individuals in our study and the results of the mtDNA sequence comparison between the Japanese and the North American individuals suggested that the fish had been transplanted from a fish farm with a low-diversity stock.     

Changes in Diet and Food Consumption of Largemouth Bass Following Large-scale Hydrilla Reduction in Lake Seminole, Georgia

Largemouth bass Micropterus salmoides Lacepède growth (in length) increased an average of 14% and bioenergetics modeling predicted a 38% increase in total annual food consumption following a large-scale reduction of hydrilla Hydrilla verticillata L.f. Royle in Spring Creek, a 2,343-ha embayment of Lake Seminole, Georgia. Coverage of submersed aquatic vegetation (SAV) declined from 76% to 22% in 1 year due to a drip-delivery fluridone treatment. In contrast, largemouth bass growth only increased an average of 4% and bioenegetics modeling predicted a 13% increase in total food consumption over the same time period in the Chattahoochee River embyament, where SAV coverage naturally declined from 26% to 15%. Diets were collected from a total of 4,409 largemouth bass over a 2.5-year period in the two embayments; the primary diet item (by weight) for largemouth bass in both embayments was sunfish (mostly Lepomis spp.). Diets before and after SAV reduction were generally similar for fish greater than stock-size (≥203 mm) in the Spring Creek arm; however, fewer invertebrates were consumed after SAV reduction. Low diet similarity was observed in smaller fish, caused by a decline in consumption of grass shrimp and sunfishes and an increase in use of damselflies, shiners Notropis spp., and topminnows Fundulus spp. after SAV reduction. Diets were similar between the same time periods for all sizes of fish in the Chattahoochee River arm. These results agreed with many laboratory results describing the effects of aquatic plant density on largemouth bass food consumption and growth, and demonstrated that increased predation efficiency resulting from decreased plant abundance was likely a stronger factor determining growth rates than any potential diet shift that may occur as a result in vegetation decline.     

Environmental influences on annual variation in nest success of smallmouth bass,Micropterus dolomieui,in Long Point Bay,Lake Erie

Synopsis Successful production of young in smallmouth bass,Micropterus dolomieui, nests varied between 33 and 88 percent over two years. Six variables were measured at each successful smallmouth bass nest. Discriminant analysis indicated that the combined influences of these variables differed between years. Canonical coefficients determined that hours of strong wind followed by degree-days contributed to the observed difference. Nest success was higher when the total hours of wind stronger than Beaufort force 4 was low during offspring development. Higher degree-day values during offspring development were recorded in the more successful year.     

Sub-lethal ammonia toxicity in largemouth bass

Guidelines for ammonia toxicity in fish are often determined using static exposure tests with immature fish over a 96-h period. These results may not be relevant to aquaculture, hauling or angling tournament scenarios where mature fish can be exposed to ammonia for shorter durations, often following additional stressors such as handling. The current study sought to quantify (1) the impact of ambient ammonia on the ability of largemouth bass to recover from exercise, (2) the behavioural response of largemouth bass to elevated ambient ammonia and (3) the concentration of ammonia that can accumulate in a live-release vessel at an angling tournament. After approximately 3 h, total ammonia (T(amm)) concentrations in a live-release vessel at an angling tournament were almost 200 muM. Exposure of fish to 1000 microM T(amm) (a value approximately 80% below the criteria maximum concentration for largemouth bass) caused significant reductions in ventilation rates, and increases in erratic swimming and irregular ventilation. Exposure to 100 microM T(amm) impaired the ability of largemouth bass to recover from exercise relative to fish recovering in fresh water. Therefore, sub-lethal ambient ammonia concentrations cause physiological disturbances that can impair the recovery of largemouth bass from exercise.     

Bioremoval of an azo textile dye,Reactive Red 198, by <Emphasis Type="Italic">Aspergillus flavus</Emphasis>

The objective of this paper was to study the potential for bioremoval of a textile dye, Reactive Red 198 (RR198), by a fungus isolated from soil collected from an effluent disposal area near a textile company. The fungus was identified as Aspergillus flavus, and its use as a low-cost live-cell biomass for the biodegradation of RR198 from contaminated water was investigated using batch studies. The effects of time, dye concentration, and pH as variable factors were examined in the process. Results showed that bioremoval of RR198 by A. flavus increased to over 84.96% with increasing time until equilibrium was reached after a period of 24 h. A low pH was the most effective, as were lower levels of dye concentration. The decolorization was determined by the decrease in the absorption maximums of this dye by UV–visible spectroscopy. A. flavus was shown to be an efficient fungus for removal of RR198 from wastewater.     

Microsatellite DNA markers for parental assignment in hybrid striped bass (Morone saxatilis × Morone chrysops)

Development of nine polymorphic microsatellites from a genomic library of hybrid striped bass (female Morone chrysops × male Morone saxatilus) DNA is described. Breeding of hybrid striped bass for aquaculture is based largely on breeding wild fish. Molecular markers such as microsatellites will be useful tools for developing broodstock, estimating heritability for production traits, and selective breeding via marker‐assisted selection. The nine polymorphic microsatellites include six dinucleotide and three complex repeat motifs. The number of alleles detected among a sample of 10 individuals of each species was relatively low. All polymerase chain reaction primer pairs also amplified products in the sea bass Dicentrarchus labrax.     

Direct and indirect effects of an introduced piscivore, <Emphasis Type="Italic">Cichla kelberi</Emphasis> and their modification by aquatic plants

The non-native peacock bass (Cichla kelberi) is causing freshwater fish extinctions in the tropical regions around the world, but there are very few studies on its interaction with native species. This study, based on a mesocosm experiment, examined direct and indirect effects of a non-native peacock bass on the native prey in Paraná River, Brazil, and tested whether these effects were mitigated by aquatic vegetation. Feeding activity of most prey was unaffected by the presence of peacock bass. All prey were consumed in the absence of vegetation; whereas a marginally significant decrease in mortality was observed in the vegetated habitats. Overall, peacock bass had minor indirect effects on prey foraging, but very significant direct effects on prey survival. As aquatic plants provide very limited protection to native prey, vegetated habitats are unlikely to slow down the decline in biodiversity resulting from this invasive species and conservation measures may need to consider other ways to ensure survival of the source populations.