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Among the strategies that can be used to improve fish welfare in a rearing environment, domestication and/or selective breeding was proposed to minimize fish responsiveness to husbandry practices. To verify this hypothesis on a recently domesticated species, the sea bass Dicentrarchus labrax, two experiments were realized, each using two populations differing according to their level of domestication or selection. For the first experiment, we used one population produced from wild parents (Wild; initial body mass: 106 ± 3 g), and one population from parents selected for growth for one generation (Selected 1; initial body mass: 129 ± 4 g). For the second experiment, we used one population produced from parents domesticated for two generations (Domesticated; initial body mass: 72 ± 3 g), and one produced from parents selected for growth for two generations (Selected 2; initial body mass: 89 ± 4 g). The first experiment was carried out over 112 days with 240 fish (60 fish per tank, 120 fish per population), and the second one over 84 days with 200 fish (50 fish per tank, 100 fish per population). Two variables, self-feeding behavior and growth performance, were measured over the time of the experiments. After a control period, the fish were submitted twice, at three-week intervals, to an acute stress treatment consisting of draining the tank and leaving the fish out of water for one minute. Both self-feeding behavior and growth performance were altered by the acute stress treatment. During the first post-stress period, the Domesticated and Selected (1 and 2) groups showed more pronounced post-stress exposure responses than the Wild fish: they modified their feeding rhythm, their feed intake, and their growth rate. During the second post-stress period, feeding rhythm was still affected (being more diurnal with a well defined peak), but the feed intake and growth rate results showed that the Domesticated and Wild groups seemed less affected than the Selected (1 and 2) populations, which continued to express a high post-stress response. According to these results, it can be concluded that: (1) an application of two acute stress treatments, at three-week intervals, modified fish feeding behavior and growth performance; (2) the domestication process seemed to improve fish adaptation abilities to this kind of stress; and (3) the process of selection for growth led to a final, better growth, but did not seem to improve fish acute stress tolerance. [ABSTRACT FROM PUBLISHER]

This article discusses a study which examined Gramma dejongi species, a Basslet from Cuba. The species was found from deep reefs off the town of Trinidad. The study showed the relationship of the species to the common and widespread Royal Gramma, G. loreto. It also identified the species' uniform yellow coloration on the head and body without stripes through the eye. The study conducted the barcode COI mitochondrial (mt) DNA sequence and suggested that the species represent an interesting case of speciation within the Caribbean.

Vibriosis caused by the pathogenic bacterium Vibrio (Listonella) anguillarum leads to serious losses in European sea bass, Dicentrarchus labrax. Because of its pleiotropic activity in controlling immune and inflammatory responses against various pathogens, interleukin-1β (IL-1β) is an attractive candidate for resistance to bacterial vibriosis. Four polymorphisms c.76 + 52C>T, c.76 + 157A>G, c.76 + 215A>and c76 + 310A>G of IL1B were genotyped in progeny of four families of wild sea bass captured in geographically distinct regions of the Black Sea and Sea of Azov and challenged with V. anguillarum. In the transmission disequilibrium test, the TGGG haplotype of IL1B showed significant overtransmission from parents to surviving progeny, thereby suggesting an association with higher resistance to V. anguillarum infection (Odds Ratio 0.38, P < 10−7). Using a luciferase reporter assay, we found a 1.4-fold increase in transcription activity of the protective IL1B TGGG variant compared to the susceptible CAAA variant of IL1B. The higher transcriptional activity of IL1B TGGG may arise from the functional effects of c.76 + 157A>G and c.76 + 215A>G polymorphisms disrupting potential binding sites for glucocorticoid receptor and YY1, both are negative transcription regulators. [ABSTRACT FROM AUTHOR]

A method of geometric morphometrics was used to characterize body shape variation in meiotic gynogenetic and triploid sea bass in comparison with diploid controls. A total of 13 coordinate landmark data were recorded on the profile of 34-month-old control (n = 81), gynogenetic (n = 117) and triploid (n = 131) siblings generated from two females (A and B). Three main axes of morphometric variation were consistent, and these accounted for 60.8 and 57.6% of the total variability in females A and B, respectively. There were significant shape deviations of triploid and gynogenetic fish relative to the controls, and differences were particularly evident in the progeny of one female. Overall, triploids displayed a more slender shape than diploids, whereas gynogenetic fish were deeper bodied and had flexed caudal peduncles and cranial features. The results are discussed especially in relation to the characterization of triploid fish for commercial purposes. [ABSTRACT FROM PUBLISHER]

Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were particularly abundant in areas with aquatic vegetation in the freshwater zone. This distribution pattern suggests that the early life history of the temperate seabass depends more intensively on the river (freshwater) than previously considered. Small juveniles in the freshwater zone fed on copepods and chironomid larvae and upon reaching a standard length (SL) of approximately 20 mm did they fed on mysids. In contrast, juveniles (approx. 17–80 mm SL) in the surf zone fed mainly on mysids. [ABSTRACT FROM AUTHOR]

Strong genetic change over short spatial scales is surprising among marine species with high dispersal potential. Concordant breaks among several species signals a role for geographic barriers to dispersal. Along the coast of California, such breaks have not been seen across the biogeographic barrier of Point Conception, but other potential geographic boundaries have been surveyed less often. We tested for strong-population structure in 11 species of Sebastes sampled across two regions containing potential dispersal barriers, and conducted a meta-analysis including four additional species. We show two strong breaks north of Monterey Bay, spanning an oceanographic gradient and an upwelling jet. Moderate genetic structure is just as common in the north as it is in the south, across the biogeographic break at Point Conception. Gene flow is generally higher among deep-water species, but these conclusions are confounded by phylogeny. Species in the subgenus Sebastosomus have higher structure than those in the subgenus Pteropodus, despite having larvae with longer pelagic phases. Differences in settlement behavior in the face of ocean currents might help explain these differences. Across similar species across the same coastal environment, we document a wide variety of patterns in gene flow, suggesting that interaction of individual species traits such as settlement behavior with environmental factors such as oceanography can strongly impact population structure. [ABSTRACT FROM AUTHOR]

A nucleotide sequence analysis of a fragment of a Morone MHC class Ia gene detected high levels of polymorphism in striped bass Morone saxatilis, white perch Morone americana and yellow bass Morone mississippiensis. Extremely low levels of MHC diversity, however, were detected in white bass Morone chrysops, suggesting the possibility of a severe population bottleneck for this species. [ABSTRACT FROM AUTHOR]

Fish eggs collected in the West Mariana region of the western North Pacific (7°–18°N, 137°–144°E) were identified using mitochondrial 16S ribosomal RNA (16S rRNA) gene sequences, and their morphology and distribution were analyzed. Of the 5,321 eggs collected, 2,698 live eggs were morphologically divided into 108 types based on the character of shape, diameter, chorion, oil globule, pigmentation, yolk segmentation and perivitelline space. Excluding 20 types of formalin preserved eggs, partial sequences of 16S rRNA gene (1,019–1,190 base pairs) obtained for all remaining 88 types of ethanol preserved eggs were compared with sequences deposited in the DDBJ/EMBL/GenBank using Basic Local Alignment Search Tool. This resulted in 16 species being genetically identified and their morphological characters were observed including the first description of the eggs of three species, Ventrifossa garmani, Diodon hystrix, and Scopelogadus mizolepis. Distribution analysis showed that 52–100% eggs of eight species, Katsuwonus pelamis, D. hystrix, S. mizolepis, Thunnus spp., Xiphias gladius, Cepalopholis spp., Naso spp. and V. garmani were collected around seamounts of the West Mariana region, whereas the other eight species, Lampris guttatus, Oxyporhamphus micropterus, Ranzania laevis, Istiophorus platypterus, Exocoetidae spp., Lactoria diaphana, Tetrapturus angustirostris and Regalecus glesne showed no tendency to be concentrated around the seamounts and were widely distributed through the study area. These distributional patterns of eggs appeared to correspond well with the life histories of each species. The present study suggests that DNA species identification can provide a significant new tool for ecological studies on fish eggs. [ABSTRACT FROM AUTHOR]

The activities of several digestive enzymes during larval development of the spotted sand bass ( Paralabrax maculatofasciatus) were evaluated using electrophoretic techniques. The results show the presence of three isoforms of alkaline protease from day 2 after hatching (ah) and the early appearance of one pepsin-like band from day 12 ah onwards. In addition, two lipase bands first appeared on day 2 ah, and there was a change in the molecular weight of one band from day 15 ah onwards. Several α-amylase isoforms were observed from hatching up to day 5 ah. These results indicate that the important digestive enzymes develop rapidly in these larvae, supporting the possibility of early weaning at day 12 ah using artificial diets. [ABSTRACT FROM AUTHOR]

We evaluated the response of Minnesota populations of largemouth bass Micropterus salmoides to implementation of 305-mm maximum total length (TL) limits (three lakes) and mandatory catch-and-release regulations (six lakes). Responses were compared with population trends observed in nine reference populations where largemouth bass harvest was regulated by prevailing statewide regulations. Increased harvest regulation generally improved largemouth bass size structure, but statistically significant improvements in size structure indices were detected in only a few individual lakes. Increased regulation of harvest did not appear to influence electrofishing catch per unit effort (CPUE; fish/h) of largemouth bass less than 381 mm TL. Electrofishing CPUE of fish greater than or equal to 381 mm TL (CPUE-381) generally improved after more stringent harvest regulations were in place, but improvements were only significant for two of the three lakes where a 305-mm maximum length limit was implemented. With the exception of one lake, increased harvest regulation did not appear to reduce largemouth bass growth rates. Improvements in size structure and CPUE-381 were rarely observed in reference lakes. Our results suggest that despite increases in voluntary catch and release of largemouth bass, angler exploitation is still an important factor regulating size structure in some Minnesota lakes, and more intensive harvest regulations can improve size structure in some populations. [ABSTRACT FROM AUTHOR]

The Guadalupe bass Micropterus treculii is endemic to Texas and is threatened by introgression with introduced smallmouth bass M. dolomieu as well as habitat degradation. This study described and quantified the movements and habitat associations of Guadalupe bass to assess the factors that may influence current populations. Radio-tagged adult Guadalupe bass were tracked in the Pedernales River (n = 12) and South Llano River (n = 12) from January through August 2008. Available microhabitats were measured and modeled in terms of depth, velocity, substrate, and cover for about 1.5 km in the Pedernales River and 1.2 km in the South Llano River. Rates of movement were greatest during the reproductive season, ranging from less than 1 to 9 m/d. Instream cover (such as undercut banks and woody debris) was preferred during daylight hours throughout the study period, although the distances from cover increased from January to August. Habitat shifts from cover to open water occurred at night and from woody structures to boulders and ledges during a large flood pulse. The habitats most suitable for adult Guadalupe bass had a depth of 1.0 m and a current velocity of 0.05 m/s, and habitat selection was strongest for eddy mesohabitats with smaller substrates. By July, the Guadalupe bass in the South Llano River were associated with runs with greater current velocities, whereas those in the Pedernales River were associated with pools with greater depths, largely owing to the low flows and reduced habitat availability in the Pedernales River. Environmental factors, including the availability and suitability of instream cover, are probably the strongest influences on the distribution and abundance of Guadalupe bass. [ABSTRACT FROM AUTHOR]

The effect of feeding three commercial diets on production characteristics and body composition of juvenile cobia Rachycentron canadum reared using recirculating aquaculture systems (RASs) was assessed in a 56-d growth trial. Juvenile cobia (mean weight ± SE, 29.2 ± 0.7 g) were stocked into three 8-m³ tanks in each of four RASs at an initial density of 1.2 kg/m³. After stocking, fish were fed one of three commercial diets: Hybrid Striped Bass diet (HSB; 44% protein, 12% lipid), Finfish Gold diet (GOLD; 42% protein, 16% lipid), or Marine Grower diet (MG; 50% protein, 15% lipid), all at a targeted feed rate of 3-5% of body weight per day. At 2-week intervals, 10% of the population of each tank was collected to determine mean weight, weight gain, specific growth rate (SGR), feed conversion efficiency (FCE), and biomass. At the end of the rearing trial, the entire population of each tank was harvested to determine production characteristics and survival. In addition, fish were sampled to determine whole-body composition, hepatosomatic index, intraperitoneal fat ratio, energy retention (ER), protein efficiency ratio (PER), and protein productive value (PPV). Final weight (311.0 g), weight gain (281.8 g), SGR (4.23% per day), FCE (85.7%), biomass (11.20 kg/m³), and ER (32.7%) of fish fed the MG diet were significantly greater than those of fish fed the HSB and GOLD diets. No differences in survival, gross energy, ash, or crude lipid content existed among fish fed the three diets. Lowest dry matter content, lowest PPV, and highest protein content were observed in fish fed the HSB diet. Highest PER was observed in fish fed the GOLD diet. Although the cost of production per kilogram for rearing juvenile cobia with the MG diet would be greater, this cost could be offset by the 15% reduction in rearing time required as compared with the HSB and GOLD diets. [ABSTRACT FROM AUTHOR]

Fishery biologists have documented small home ranges, relative to available habitat, for many littoral freshwater fishes. Home ranges for pelagic species, such as white bass Morone chrysops, are generally not well described, yet are thought to be large. We studied white bass movement using acoustic telemetry in two irrigation reservoirs of the Republican River basin in south-western Nebraska. Acoustic transmitters were implanted in fall of the previous year and tracking occurred a minimum of once per week throughout spring (mid-March to May) 2007 and 2008. Linear home ranges were calculated from observed locations of individual fish. Twelve of the twenty-seven tagged fish with at least five locations exhibited localised home ranges throughout the spring whereas the remaining fish exhibited home ranges extending across large portions of each reservoir. Home range size was not correlated with fish size or condition. [ABSTRACT FROM AUTHOR]

Monosex populations can be a valuable management tool in culture of larger size largemouth bass (>400 g). In this study, we investigated the effective mode and duration of oestrogen and androgen administrations to produce monosex largemouth bass populations. The experiment consisted of nine treatments. In oral administration groups, we fed 40-day-old fry either 200 mg of an oestradiol-17β (E2) kg−1 diet or 60 mg of a 17α-methyltestosterone (MT) kg−1 diet for 30, 45 or 60 days. In bath treatments, we immersed fry in a 1 mg MT L−1 solution for 5 h a day on three or six occasions. For control treatment, we fed fry an ethanol-treated diet for 45 days. The frequency of females in the control group was 53.1%. Oral administration of E2 at all durations resulted in slight increases in the frequency of females (59.8–70.5%). Both modes of androgen administration at all durations were ineffective in altering phenotypic sex. The experimental results of our study indicated that male differentiation passed the point of being completely and functionally influenced by exogenous oestrogens, while female differentiation had already taken place and was no longer responsive to exogenous androgens in 40-day-old (33.5 mm) largemouth bass fry. [ABSTRACT FROM AUTHOR]

Differences in bold and shy personality on sea bass Dicentrarchus labrax were investigated between a population (wild) produced from wild-brood fish and a population (selected) produced from selected-brood fish. During the experiment (112 days), fish were reared under self-feeding condition to characterize the feeding behaviour of each individual fish. Three risk-taking tests (T1, T2 and T3 of 24 h with day–night alternation) were carried out at > 1 month intervals on 180 fish of each strain in order to monitor D. labrax behaviour over time and in relation to the light:dark period. A risk-taking score was evaluated via a preference choice between a safe zone (without food) and a risky zone (potentially with food) by recording the number and the duration of individual passages through an opening in an opaque divider. Results showed that fish performed passages preferentially during the night period and that wild fish were generally bolder than selected fish during T1 and T2 but showed a decrease in risk taking during T3, contrary to selected fish which showed a constant increase in their risk-taking behaviour. The phenotypic characteristics of the bold fish were different in the two strains: wild bold fish were the smallest within the wild strain and selected bold fish presented the higher growth rate within the selected strain. For both strains, these bold fish were also generally characterized by a high feed-demand activity. Fish hunger state thus seemed to be the highest motivation for risk-taking behaviour under the present conditions. Furthermore, behavioural variations over tests such as higher risk taking (number of passages) and faster exploratory responses (higher score emergence) could be interpreted as relevant indicators of the learning process and habituation. According to the results, however, no real difference in coping strategy between strains could be observed at this first stage of domestication and selection. [ABSTRACT FROM AUTHOR]

1. Hyper-successful exotic species can both displace the native prey that formerly made up a native predator’s diet and represent an abundant potential prey resource for native predators. Little is known about how this drastic change affects native predators, or their short- and long term potential to regulate the exotic species. 2. We compared zebra mussel consumption by pumpkinseed sunfish ( Lepomis gibbosus), redbreast sunfish ( Lepomis auritus) and rock bass ( Ambloplites rupestris) from populations that were either previously exposed to zebra mussels or naive to them. 3. Fish from populations with longer exposure to zebra mussels consumed many more zebra mussels than fish from populations with shorter or no previous exposure to zebra mussels. 4. Our experiment does not allow us to identify the mechanisms that underlie the patterns we found, but we discuss several plausible scenarios and their ecological implications. 5. Predator adaptation to exotic prey may be an important but overlooked factor in invasion biology. The initial response to exotic prey by a native predator may be a poor estimate of its ability to present biotic resistance to the invasion over the long term. [ABSTRACT FROM AUTHOR]

Feeds rich in saturated (SFAs) and monounsaturated fatty acids (MUFA) appear to maximize the retention of long-chain polyunsaturated fatty acids (LC-PUFA) in the fillets of sunshine bass (female white bass Morone chrysops x male striped bass M. saxatilis). To determine whether different sources of SFA and MUFA have equivalent effects on tissue fatty acid (FA) profile change, coconut (CO) and paire oils(PO) were evaluated as partial and complete substitutes for fish oil (FO) in feeds for juvenile sunshine bass. After 8 weeks of culture, the production performance of ail groups was within the acceptable range for sunshine bass; however, weight gain was significantly reduced within the 100%-CO group. Partial replacement of FO with CO or PO resulted in significant alteration of fillet FA profiles, and these changes were exacerbated in the complete-FO-replacement groups. The LC-PUFA were disproportionately enriched in the fillets of fish fed the reduced or FO-free feeds, whereas dietary surpluses of 12:0 and 14:0 (CO-based feeds) and 16:0 (PO-based feeds) were not reflected in any of the tissues analyzed. Rather, the levels of the SFA elongation-desaturation products (i.e., 18:0 and 18:1[n-9]) were elevated, particularly within liver lipid, suggesting enhanced FA biotransformation activity among fish fed higher levels of either alternative lipid source. Based on tissue FA composition, PO and CO appear to be approximately equivalent in terres of fillet LC-PUFA retention. However, the digestibility and utilization of these feedstuffs must be further investigated to maximize the ability of PO and CO to (partially or completely) replace FO in sunshine bass feeds. [ABSTRACT FROM AUTHOR]

For organisms with great fecundity and high mortality in early life stages, such as shellfish or fishes, the need to match reproductive activity with environmental conditions conducive to spawning, fertilization, larval development and recruitment may result in extreme variance in reproductive success among individuals. The main objective of this study was to investigate evidence of large variance in the reproductive success of the striped bass Morone saxatilis in the Santee–Cooper system, South Carolina, USA. Seven microsatellite loci were analysed in 603 recruits representing three yearly cohorts from 1992 to 1994, and a group analysis was performed to identify full-sib families. Large variance in reproductive success was detected, with a few large, full-sib families contributing disproportionately to each of the cohorts. The severity of sweepstakes reproductive success varied among cohorts depending on environmentally imposed mortality. Estimations of the effective number of breeders in these long-lived fish ranged from 24 in 1992 to 44 in 1994. Furthermore, the estimated genetic effective population size ( Ne = 93) is approximately four orders of magnitude lower than estimates of adult census size ( N = 362 000). Furthermore, the presence of large full-sib families indicates that striped bass engage in pair mating in the wild. Heterogeneity in genetic composition was also observed among cohorts, suggesting that genetically different adults contribute to different cohorts and that chance rather than fitness variation determines reproductive success. [ABSTRACT FROM AUTHOR]

The article offers information on a research conducted to ascertain the cause of Eustrongylides ignotus infection among commercial bass, Morone chrysops female X Morone saxatilis male, and other fish in the southeastern U.S. As reported, this strain causes mortality among commercially produced fish. Species of Eustrongylides have complex life cycles involving a definitive host. It was inferred that bass has acquired the infections of E. ignotus in ponds directly from oligochaetes.

Data from entrainment survival sampling programs conducted in 1979, 1980, and 1988 at the Indian Point generating stations and in 1977, 1978, and 1980 at the Roseton generating station, both located on the tidal Hudson River estuary, were reanalyzed using a series of failure time models to estimate the survival of entrained striped bass Morone saxatilis based on sampling stress, mechanical entrainment stress, and thermal stress. The model with the lowest Akaike information criterion value was the most complex model examined, with year- and station-specific parameters for both sampling and entrainment. However, the lowest Bayesian information criterion was achieved with a model that had year- and station-specific sampling parameters but only station-specific entrainment parameters. The models indicated that survival was positively related to fish length and salinity and negatively related to discharge temperatures above 30°. Parameter uncertainty was addressed via a bootstrap resampling procedure to estimate parameters for the station-specific model, and the results were applied to entrainment abundance data from each facility from 1983 to 1987. The distribution of the estimated mean annual entrainment survival after 1 d for Indian Point had modes at 0.48, 0.60, 0.70, and 0.81. For Roseton, the distribution of mean annual entrainment survival was normal, with a mean of 0.41 and a variance of 0.0028. Survival differences between the two stations were due to inherent differences in entrainment stresses, as indicated by differences in the parameters for the model as well as differences in the length of entrained striped bass, discharge temperature, and salinity. [ABSTRACT FROM AUTHOR]

To evaluate potential effects of lakeshore development on nest site selection, we compared locations of black crappie Pomoxis nigromaculatus and largemouth bass Micropterus salmoides nests in three Minnesota lakes with available habitat in the littoral and riparian zones and the presence or absence of developed shoreline. We used binomial logistic regression to determine how the frequency of nest sites varied among lakes and with the presence or absence of five habitat variables. Black crappies in all three lakes were more likely to nest adjacent to undeveloped shoreline. Black crappies were also more likely to nest in stands of emergent vegetation, particularly hardstem bulrush Scirpus acutus. Largemouth bass were more likely to nest near undeveloped shoreline but were less dependent on hardstem bulrush. Shoreline development has the potential to alter nest site selection by largemouth bass and, particularly, by black crappies. [ABSTRACT FROM AUTHOR]

The value of using characters from multiple sources – chromosomes, ecology, gene sequences, and morphology – to evaluate the species status of closely related black flies is demonstrated for three European members of the Simulium vernum group: Simulium crenobium (Knoz, 1961), Simulium juxtacrenobium Bass & Brockhouse, 1990, and Simulium vernum s.s. Macquart, 1826. Simulium juxtacrenobium is a chromosomally, molecularly, and morphologically distinct species that diverged from S. crenobium and S. vernum s.s. about 2 Mya. It is specialized for intermittent streams, is univoltine, and is recorded for the first time from northern Europe, based on collections from Finland and Sweden, representing a range extension of about 1800 km. In contrast, S. crenobium, although confirmed as a distinct species, differs from S. vernum s.s. by only a few larval and chromosomal characters, and by a breeding habitat restricted to mountain spring brooks. Whereas all four character sets independently support the specific distinctness of S. juxtacrenobium and S. vernum s.s., multiple character sets are required to establish the specific validity of S. crenobium. [ABSTRACT FROM AUTHOR]

This paper interprets and discusses the usefulness of otolith microstructure for ageing Japanese sea bass ( Lateolabrax japonicus) larvae and juveniles. Samples were collected from the Tango Sea along the Japan Sea coast, January–March 2007. Known-age (0-day and 10-day-old) larvae were obtained from the Ibaragi Prefectural Hatchery, Japan. Sagittal and lapillar otolith were processed and read using an otolith reading system. Clearly discernible hatch- and first-feeding marks were evident on sagitta, and development of accessory premordia (AP) appeared to be associated with larva-juvenile transition; however, no other marks indicating metamorphosis or settlement were evident. In lapillus, no discernible check mark was found. Known-age larvae showed that deposition of the first daily increment (DI) corresponded to first-feeding, which occurred at day-4 post-hatch. However, mean increment counts were significantly lower in lapillus than in sagitta, caused by poorly expressed increments around the centrum as well as relatively unclear centrum of the lapillus. The authors suggest that the use of lapillus can cause significant underestimation of age. Therefore, the sagitta is recommended for age and growth estimations of larvae and juveniles, although the presence of numerous subdaily increments warrants careful preparation and interpretation of the microstructure. A test for asymmetry showed the right and left otoliths to be quite symmetrical and their DI counts not significantly different, suggesting that either otolith can be used for studying age and growth of Japanese sea bass larvae and juveniles. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the historical presence of mycobacteriosis in Chesapeake Bay striped bass Morone saxatilis from 1975 to 1985. For the stud, researchers analyzed paraffin-embedded tissue samples of age 1+ wild-captured striped bass taken from the Oxford Laboratory archives. Researchers found that of 37 cases available from the study period, two fish were positive according to histopathology and genus-specific polymerase chain reaction (PCR). Results showed that mycobacteriosis is not a new condition of Chesapeake Bay striped bass.

Pop-up satellite archival tags (PSATs) have been used to study movements, habitat use, and postrelease survival of large pelagic vertebrates, but the size of these tags has historically precluded their use on smaller coastal species. To evaluate a new generation of smaller PSATs for the study of postrelease survival and habitat use of coastal species, we attached Microwave Telemetry, Inc., X-tags to ten striped bass (Morone saxatilis) 94-112 cm total length (TL) caught on J hooks and circle hooks during the winter recreational fishery in Virginia. Tags collected temperature and depth information every five minutes and detached from the fish after 30 days. Nine of the ten tags released on schedule and eight transmitted 30% to 96% (mean 78.6%) of the archived data. Three tags were physically recovered during or after the transmission period, allowing retrieval of all archived data. All eight striped bass whose tags transmitted data survived for 30 days after release, including two fish that were hooked deeply with J hooks. The eight fish spent more than 90% of their time at depths less than 10 m and in temperatures of 6-9°C, demonstrated no significant diel differences in depth or temperature utilization (P>0.05), and exhibited weak periodicities in vertical movements consistent with daily and tidal cycles. [ABSTRACT FROM AUTHOR]

Determining the optimum conditions for tank culture of sunshine bass (female white bass Morone chrysops X male striped bass M. saxatilis) fingerlings will facilitate a year-round supply of seed for the production cycle of this increasingly popular food fish. This study determined the relationship between temperature and larval sunshine bass growth and survival to the time when fish were trained to accept commercial feeds. At 4 d posthatch (dph), larvae were stocked at five temperatures from 20°C to 32°C at 3°C increments. There were two replicates for each temperature. The larvae were fed rotifers through 8 dph. Conversion to a diet of brine shrimp Artemia spp. nauplii began at 6 dph, and training for acceptance of dry starter feed began at 20 dph. At harvest, average total length and average weight of the fish increased in a linear relationship with temperature, while relative survival and number of fish harvested decreased linearly with temperature. Tank yield had a curvilinear relationship with temperature. The temperature that provided maximum yield was 23.1°C. Although growth was faster at warmer temperatures, relative survival and yield were not. These relationships between tank culture conditions and production characteristics support optimization of tank culture to meet specific production goals. This should eliminate some of the logistical constraints to expanded tank culture of sunshine bass fingerlings. [ABSTRACT FROM AUTHOR]

Water temperature could be an important factor during the feed training phase of largemouth bass Micropterus salmoides production, as it could affect appetite and starvation time. We evaluated three water temperatures during largemouth bass feed training. Pond-reared largemouth bass fingerlings (weight = 2.1 ± 0.6 g [mean ± SE]) were randomly stocked into twelve 0.5-m³ polyethylene cages to achieve a stocking density of 350 fish per cage. ]'he cages were suspended in six 3,800-L polyethylene tanks with a common water source housed in a greenhouse with four replicate cages per water temperature treatment (20, 24, and 28°C). Each tank contained two cages, and there were two tanks per treatment temperature, In each cage, fingerlings were initially fed freeze-dried krill, then gradually weaned onto a commercial pellet (floating trout feed; 1.5 ram) over a 24-d period according to an established training protocol. At harvest, the average weight and the percentage of fish successfully trained to commercial teed were significantly different among temperatures (P ≤ 0.05), increasing as water temperature increased (weights averaged 5.4, 6.8, and 7.8 g and percent trained averaged 70, 82, and 90% for fish feed-trained at 20, 24, and 28°C, respectively). The results from this experiment indicate that water temperature has a significant effect on feed training success and the average weight of feed trained largemouth bass. [ABSTRACT FROM AUTHOR]

A study was undertaken to determine whether stress responses and associated mortality in hybrid striped bass (white bass Morone chrysops X striped bass M. saxatilis) during and after transport could be mitigated by use of anesthesia with low concentrations of clove oil (10 µL/L of water) during transport. Stress indicators, including plasma cortisol, glucose, chloride (CI-), sodium (Na+), potassium (K+), and calcium (Ca++) concentrations, were determined for hybrid striped bass sampled (l) initially from ponds, (2) after seining (45 min), (3) immediately after a 3-h transport, and (4) at 24 h posttransport (recovery); these values were compared with those of captive control fish. Fish anesthetized with clove oil during transport exhibited prolonged elevation of cortisol concentrations (124.3 ± 13.2 ng/mL, mean ± SE) at 24 h posttransport, while fish not exposed to anesthetic during transport recovered rapidly (to 34.1 ± 13.3 ng/mL) within 24 h. Plasma glucose concentrations in hybrid striped bass exposed to clove oil during transport were significantly (α = 0.05, P < 0.05) elevated (135.1 ± 5.6 mg/dL) immediately after transport and then decreased by 24 h posttransport (84.3 ± 3.4 mg/dL) compared with the 24-h posttransport level for fish transported without anesthetic (101.0 ± 5.0 mg/dL). Plasma electrolyte (Na+ CI-, and K+) concentrations indicated that osmoregulatory distress occurred after transport in hybrid striped bass transported with clove oil, while electrolyte changes were less severe in fish transported without anesthesia. No hydromineral imbalance occurred based upon plasma Ca-H- concentrations in either treatment. High mortality occurred within 7 d posttransport in both treatment groups but was not significantly different (P < 0.05) between the treatments. Observed mortality was primarily, if not entirely, due to Flavobacterium columnare infection. Hybrid striped bass transported during light clove oil sedation took longer to recover and exhibited no improved survival or disease resistance compared with fish transported without anesthesia. No potential benefit of transporting hybrid striped bass under anesthesia induced by clove oil is evident. [ABSTRACT FROM AUTHOR]

A previously reported protocol for culture of larval sunshine bass (female white bass Morone chrysops X male striped bass M. saxatilis) to fingerling size in tanks involved an initial feeding of rotifers for several days before the larvae were weaned to nauplii of brine shrimp Artemia spp. and prepared feed. Maintaining rotifer cultures requires space, time, equipment, supplies, and trained culturists. The rotifer cultures are often unstable, which increases risk of poor sunshine bass fingerling production in tanks. Elimination of the use of rotifers would greatly enhance the feasibility of reliable tank culture of fingerlings and should reduce production cost. This experiment compared three treatments with three replicates per treatment. In one treatment, larvae were initially fed rotifers Brachionus plicatilis and then were weaned to brine shrimp nauplii (0.48 X 0.19 mm). In a second treatment, larvae were fed brine shrimp nauplii throughout the experiment. In a third treatment, larvae were fed microcyst brine shrimp nauplii (0.43 X 0.18 mm) for the entire experiment. At 4 d posthatch (dph), sunshine bass larvae were stocked into 100-L tanks at 75 larvae/L. Larvae were fed according to the three treatments to 14 dph. Survival was significantly higher for larvae fed rotifers plus brine shrimp nauplii and for larvae fed microcyst brine shrimp nauplii (93.6% and 37.9%, respectively) than for larvae fed only brine shrimp nauplii (4.3%). Larvae (7.13 mm standard length [SL]) that were fed rotifers plus brine shrimp nauplii and larvae (7.26 mm SL) that were fed microcyst nauplii were significantly longer than those (6.86 mm SL) fed brine shrimp nauplii. This experiment is the first time that sunshine bass have been cultured to 14 dph on brine shrimp nauplii without rotifers at first feeding. [ABSTRACT FROM AUTHOR]

From February through August of 2006, a team of two researchers visited 130 ethnic live seafood markets in the northeastern USA that sell live seafood. Operators of 27% of these locations completed a survey asking basic information about their businesses with respect to live seafood. This study provides interesting baseline information on these markets directly from market managers and operators. The markets surveyed have been in business for median of nine years. Sixty-three percent receive more than one live fish shipment per week. Fifty-five percent of markets sell over 227 kg of live seafood per month. Asians are the predominant clientele in most of these locations. Most market operators stated they prefer freshness and quality over price and availability. About the same number of markets identified strong sales during the winter months as those that indicated constant live seafood sales. Live tilapia and hybrid striped bass are the two most common products. Sixty-two percent of market operators view the live seafood section as very important to overall sales in their store and roughly one-quarter of those surveyed are considering expansion. [ABSTRACT FROM AUTHOR]

Variation in life-history traits (growth, condition, mortality and recruitment) and relative abundance of 11 large-bodied fish species was investigated among three water-management regimes (unimpounded, run-of-the-river and winter reservoirs) in the large regulated Ottawa River, Canada. If waterpower management had an effect on fishes, then (1) would be expected community structuring among water-management regimes and (2) species with similar life-history traits should be affected in a similar manner. Large-bodied fish communities were assessed using two different standard index-netting techniques, one using trap nets and the other gillnets. Community structure could be discriminated based on species caught in nets using holographic neural networks (78·8% correct overall classification rate using trap nets and 76·0% using gillnets); therefore, water-management regimes affected community structure in the Ottawa River. Littoral zone benthivores were significantly lower in abundance ( P < 0·001) or absent in winter reservoirs, whereas the abundance of planktivores or species that were planktivorous at young ages were significantly greater than in unimpounded river reaches. Growth, condition and mortality did not vary among reach types except smallmouth bass Micropterus dolomieu were in better condition in winter reservoirs than unimpounded reaches. Lake sturgeon Acipenser fulvescens recruitment was impaired in run-of-the-river reaches, whereas recruitment for other species that spawn in fast water was not affected. [ABSTRACT FROM AUTHOR]

The aim of this study was to monitor erythrocyte nuclear abnormalities (NA) including micronuclei (MN) in cultured and wild sea bass Dicentrarchus labrax and wild mullet Mugil spp. Seasonal sampling was performed at seven locations along the eastern coast of the Adriatic Sea. The frequency of NA and MN was positively correlated to temperature (NA: P < 0·05, r = 0·11; MN P < 0·05, r = 0·10), and there was also a positive correlation between NA and MN frequency ( P < 0·001, r = 0·43). The lowest NA and MN values for both fish species were recorded in spring, while the highest were recorded in autumn. Significantly higher frequency of NA was seen in D. labrax compared to Mugil spp., while MN frequency was low in both species and not significantly different. There was no significant difference in NA and MN frequency between cultured and wild D. labrax sampled in the same month, and there was no difference between wild Mugil spp. sampled near or far from fish farms. In view of sampling sites, the highest values were detected in fishes from the Limski Channel, the lowest from the Janjina location. [ABSTRACT FROM AUTHOR]

Abstract  Rockfishes (Sebastes spp.) represent a speciose and ecologically important group of marine fishes found in both the Pacific and Atlantic oceans, with approximately 105 species found world-wide (Hyde and Vetter 2007). They also comprise the majority of species found in the Pacific groundfish fishery. Thorough species assessments in terms of harvest management have been done for only 11 species, and of the 11 species, seven have been declared overfished. Having accurate genetic information is critical to the continuing effort at stock assessments, but sampling is often difficult in marine fishes. Genetic techniques are a powerful tool in the effort to better characterize the ecology of these species. These techniques can be used to investigate multiple biological traits, including species identity, intra- and interspecific genetic variation, migration patterns, and effective population size. There are important caveats and limitations when applying specific genetic methods, especially in marine species that lack discrete spawning aggregates. Nevertheless, it is clear from a review of recent literature that genetic tools have already provided very specific insight regarding rockfish population dynamics. The results are diverse and difficult to synthesize; however, existing studies show five primary patterns to population groupings in rockfishes: no obvious pattern of structure, structure consistent with isolation by distance, structure evident but inconsistent with isolation by distance, structure that correlates to oceanographic features, and potential genetic introgression. Clearly the study of rockfish population genetics is poised for rapid expansion that will unquestionably aid management of the rockfish fisheries and general understanding of rockfish evolutionary systematics. A principle challenge at this point is to derive generalized inferences from such a diverse array of study results across the vast North Pacific range of Sebastes. This review summarizes existing genetic studies in Sebastes spp. in the North Pacific to assist in identifying knowledge gaps for this ecologically important and diverse group. [ABSTRACT FROM AUTHOR]

The seasonal occurrence of organic contaminants, many of which are potential endocrine disruptors, entering the Potomac River, USA, watershed was investigated using a two-pronged approach during the fall of 2005 and spring of 2006. Passive samplers (semipermeable membrane device and polar organic chemical integrative sampler [POCIS]) were deployed in tandem at sites above and below wastewater treatment plant discharges within the watershed. Analysis of the samplers resulted in detection of 84 of 138 targeted chemicals. The agricultural pesticides atrazine and metolachlor had the greatest seasonal changes in water concentrations, with a 3.1- to 91-fold increase in the spring compared with the level in the previous fall. Coinciding with the elevated concentrations of atrazine in the spring were increasing concentrations of the atrazine degradation products desethylatrazine and desisopropylatrazine in the fall following spring and summer application of the parent compound. Other targeted chemicals (organochlorine pesticides, polycyclic aromatic hydrocarbons, and organic wastewater chemicals) did not indicate seasonal changes in occurrence or concentration; however, the overall concentrations and number of chemicals present were greater at the sites downstream of wastewater treatment plant discharges. Several fragrances and flame retardants were identified in these downstream sites, which are characteristic of wastewater effluent and human activities. The bioluminescent yeast estrogen screen in vitro assay of the POCIS extracts indicated the presence of chemicals that were capable of producing an estrogenic response at all sampling sites. [ABSTRACT FROM AUTHOR]

Intersex (specifically, testicular oocytes) has been observed in male smallmouth bass (SMB; Micropterus dolomieu) and other centrarchids in the South Branch of the Potomac River, USA, and forks of the Shenandoah River, USA, during the past five years. This condition often is associated with exposure to estrogenic endocrine-disrupting chemicals in some fish species, but such chemicals and their sources have yet to be identified in the Potomac. In an attempt to better understand the plausible causes of this condition, we investigated the reproductive health of bass sampled up- and downstream of wastewater treatment plant (WWTP) effluent point sources on the Potomac River in Maryland, USA. Smallmouth bass were sampled from the Conococheague Creek and the Monocacy River, and largemouth bass (LMB; Micropterus salmoides) were collected near the Blue Plains WWTP on the mainstem of the Potomac River. Chemical analyses of compounds captured in passive samplers at these locations also were conducted. A high prevalence of intersex (82-100%) was identified in male SMB at all sites regardless of collection area. A lower prevalence of intersex (23%) was identified in male LMB collected at the Blue Plains site. When up- and downstream fish were compared, significant differences were noted only in fish from the Conococheague. Differences included condition factor, gonadosomatic index, plasma vitellogenin concentration, and estrogen to testosterone ratio. In general, chemicals associated with wastewater effluent, storm-water runoff, and agriculture were more prevalent at the downstream sampling sites. An exception was atrazine and its associated metabolites, which were present in greater concentrations at the upstream sites. It appears that proximity to effluent from WWTPs may influence the reproductive health of bass in the Potomac watershed, but inputs from other sources likely contribute to the widespread, high incidence of testicular oocytes. [ABSTRACT FROM AUTHOR]

We evaluated tag-induced mortality (7 d), predation, and tag visibility (365 d) for age-0 largemouth bass (LMB) Micropterus salmoides (27-112 mm total length [TL]), age-0 channel catfish (CCF) Ictalurus punctatus (42-101 mm TL), and adult blacktail shiners (BTS) Cyprinella venusta (34-98 mm TL) tagged with three visible implant elastomer (VIE) tags. Tagging mortality after 7 d was 14.7% for age-0 LMB and 29.5% for BTS, whereas there was almost no mortality for CCF. Mortality for tagged age-0 LMB and BTS was size dependent; the smallest size-groups exhibited the greatest mortality rates. Visible implant elastomer tags, did not significantly increase predation of recently tagged fish by adult LMB, flathead catfish Pylodictis olivaris, or white bass Morone chrysops. Tag visibility (which reflects tag shedding and loss of visibility due to tissue thickening over the tag) varied greatly by species and tag location. In LMB, tag visibility decreased to 5% or less within 90 d for VIE tags in the dorsal head area and along the base of the anal fin, whereas visibility decreased gradually to 63% after 365 d for tags in the operculum. In CCF, tag visibility decreased to 5% or less within 90 d for tags in the dorsal head area and along the jaw, whereas visibility decreased to 46% after 365 d for tags along the base of the anal fin. Tags in BTS had the highest visibility: 100% visibility was recorded at all three tagging locations after 30 d, then visibility gradually decreased to 56% along the base of the anal fin, 72% in the dorsal portion of the caudal peduncle, and 78% in the ventral port on of the caudal peduncle after 365 d. Visible implant elastomer tags can be used without increasing risk of predation for tagged fish; however, VIE tag utility may be limited due to increased mortality for small age-0 fish and variable tag visibility among anatomical locations. [ABSTRACT FROM AUTHOR]

Copyright of Aquatic Living Resources is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Insulin-like growth factor I (IGF-1) plays an important role in fish growth and development. As the promoter of IGF-I regulates the expression of IGF-I, polymorphisms in the promoter region could be functionally important to differences in IGF-I expression and function. In this study, the 5′ flanking region (1,770 bp) of the largemouth bass IGF-I gene was cloned, sequenced and characterized. Several putative liver-enriched transcriptional factor binding sites, including HNF-1α, HNF-3β and C/EBP, were found to have multiple copies in the promoter sequence of the largemouth bass IGF-I gene. It did not contain consensus TATA, CCAAT-like or GAGA sequences. Sequencing of 5′ flanking sequences from individual fish revealed the presence of a deletion (GTTT) and two single-nucleotide substitutions, causing two different haplotypes: AT TTTT GTTTTT(A) and AT AATT—TT(B). The haplotypes were tested for their association with growth traits in a population of 91 largemouth bass individuals using polymerase chain reaction. The association analysis was carried out using a general linear model. Results showed the haplotypes had significant effects on body weight and body width ( P < 0.05). The individuals with the AA genotype had significantly higher body weight and body width than those with the AB and BB genotypes ( P < 0.05). Moreover, the effect of the genotypes on IGF-I mRNA expression in the liver was evaluated through the use of a semiquantitative RT-PCR method. The results showed that the IGF-I mRNA expression levels were affected by the promoter polymorphisms ( P < 0.01), and that levels of IGF-I mRNA of the AA genotype in liver were greater than those of both the AB and the BB genotypes ( P < 0.05 and P < 0.01). Our results implied that the IGF-I gene could be a potential quantitative trait nucleotide that affects growth traits in largemouth bass. [ABSTRACT FROM AUTHOR]

The efficacy of replacing fish meal with petfood-grade poultry by-product meal (PBM) on an ideal protein basis in commercial diets for hybrid striped bass (HSB) was evaluated under production conditions in pond culture. A generic production diet (GEN) for HSB was formulated to contain 45% protein, 12% lipid, and 3.7 kcal/kg. Protein in the generic diet was supplied by a mix of animal and plant sources typically used by the industry that included more than 20% select menhaden fish meal and less than 10% PBM. A positive control diet (GEN + AA) was formulated by supplementing the generic diet with feed-grade Met and Lys to match the level of those amino acids in HSB muscle at 40% digestible protein. Substitution diets were formulated by replacing 35, 70, or 100% of fish meal in the GEN diet with PBM on a digestible protein basis and then supplementing with Met and Lys (designated 35PBM, 70PBM, and 100PBM, respectively) as needed to maintain concentrations equal to those in the GEN + AA diet. Diet formulation and extrusion were conducted by a commercial mill, and all diets met or exceeded known nutritional requirements for HSB. Twenty 0.10-ha ponds (4 ponds/diet) were randomly stocked with juvenile HSB (76 ± 10 g; mean ± SD) at a density of 7400/ha and fed for 600 d (October 2004 to May 2006). Diets were fed once daily to apparent satiation to a maximum of 95 kg feed/ha. Total weight and number of fish in each pond were determined at harvest. Weight distributions in each pond were estimated by selecting every 15th fish during harvest. Subsets of ten fish from each of these samples were selected randomly for the determination of body composition and nutrient and energy retention. The availability of indispensable amino acids as well as ammonia production from the commercial test diets were determined in separate tank trials. Most production characteristics were not statistically different ( P > 0.10) among dietary treatments. Distributions of individual fish weights from each of the ponds were not affected by poultry by-product level in the diet. Multivariate analysis of body compositional indices grouped diets into two clusters composed of GEN, GEN + AA, 35PBM vs. 70PBM, and 100PBM mainly because fish fed the 70PBM and 100PBM diets had greater ( P = 0.001) body fat (visceral somatic indices) than fish fed the other diets. Ammonia production in tanks was not different among diets and peaked 6–8 h after feeding when fish were fed at 1.5% of body weight; ammonia-N excretion ranged from 197 to 212 mg/kg/d and 18.5–21.5% of nitrogen intake. Some imbalances in the levels and ratios of selected amino acids to Lys were found in the diets containing higher amounts of PBM and were attributed to a lack of accurate availability coefficients during formulation for some dietary proteins. These imbalances in essential amino acids may have been the predominant factor in the somewhat fattier fish observed fed diets containing the two highest levels of PBM. Nevertheless, these results from fish stocked at commercial densities and raised to market size in ponds suggest that formulating diets on an available amino acid basis for all protein sources while balancing limiting amino acids, particularly Met, Lys, Thr, and Trp, on an ideal protein basis will yield significant improvements in HSB performance when fed commercial diets in which all fish meal is replaced with PBM. [ABSTRACT FROM AUTHOR]

The article presents a study which examined the long-term effects of surgically implanted telemetry tags on nutritional physiology and condition of wild freshwater fish. Largemouth bass Micropterus salmoides was used as a model to evaluate the long-term impacts of telemetry devices on fish physiology and nutritional condition in a closed freshwater lake where recapture rates were reasonably high. Out of the 17 recaptured fish, three retained at least 1 of the absorbable monofilament sutures and showed localised signs of inflammation and infection despite an elapsed time. It concluded that transmitter implantation was not correlated with any long-term change in any of the physiological parameters investigated.

In this study, field biotelemetry and laboratory physiology approaches were coupled to allow understanding of the behavioral and physiological responses of fish to winter hypoxia. The biotelemetry study compared dissolved oxygen levels measured throughout the winter period with continually tracked locations of nine adult largemouth bass obtained from a whole-lake submerged telemetry array. Fish habitat usage was compared with habitat availability to assess whether fish were selecting for specific dissolved oxygen concentrations. The laboratory study examined behavioral and physiological responses to progressive hypoxia in juvenile largemouth bass acclimated to winter temperatures. Results from the dissolved oxygen measurements made during the biotelemetry study showed high variance in under-ice dissolved oxygen levels. Avoidance of water with dissolved oxygen <2.0 mg/L by telemetered fish was demonstrated, but significant use of water with intermediate dissolved oxygen levels was also found. Results from the lab experiments showed marked changes in behavior (i.e., yawning and vertical movement) at <2.0 mg/L of dissolved oxygen but no change in tissue lactate, an indicator of anaerobic metabolism. Combined results of the biotelemetry and laboratory studies demonstrate that a dissolved oxygen content of 2.0 mg/L may be a critical threshold that induces behavioral responses by largemouth bass during the winter. In addition, the use by fish of areas with intermediate levels of dissolved oxygen suggests that there are multiple environmental factors influencing winter behavior. [ABSTRACT FROM AUTHOR]

Centrarchids (sunfish and bass species) and Bullfrogs (Lithobates catesbeianus) have been introduced into aquatic systems around the world and have the potential to negatively impact native fish and anurans. We surveyed fish and anuran assemblages from 26 impoundments in the New Jersey Pinelands, USA. We excluded non-native species and used ordination analysis to generate four native-species community gradients based on native-fish and anuran presence-absence and abundance data. All four community gradients paralleled an increase in the percentage of upstream-altered land (development and upland agriculture) and an increase in either non-native-centrarchid richness or abundance. Based on presence-absence and abundance data, native-fish and native-anuran assemblages, including restricted species (those generally limited to the Pinelands region) and widespread species (those widely distributed in New Jersey), differed between impoundments with and without non-native centrarchids. Compared to widespread species, the greatest differences between impoundment types were found for restricted species. Three non-native-frog species, including Bullfrogs, were associated with degraded impoundments that supported non-native fish. Our results demonstrate that watershed conditions and native fish and anuran assemblages differ between impoundments with and without non-native centrarchids, and suggest that some restricted species may be especially vulnerable to impacts from watershed disturbance and non-native species. Our findings support the idea that the environmental resistance associated with intact water-quality conditions may help prevent the invasion of non-native fish and anurans. We recommend that land-use activities that degrade water quality and reduce invasion resistance be avoided in unaltered watersheds to conserve native-fish and native-anuran community integrity. [ABSTRACT FROM AUTHOR]

Water-level and associated variability are substantial influences on wetland and shallow aquatic communities. The Akwesasne Wetland Complex is an extensive St. Lawrence River system affected by water regulation. The responses of fish assemblages to short-term summer water-level variation were examined throughout this section of the St. Lawrence River and its tributaries. An influence of water-level variability was detected on abundance of three common species [bluntnose minnow (Pimephales notatus), rock bass (Amboplites rupestris), and white sucker (Catastomus commersonii)} and explained 30 - 44% of variation. This influence has implications for water regulation and natural resource management, and a larger scope evaluation may reveal more extensive effects. [ABSTRACT FROM AUTHOR]

Over 400 riprap grade control structures (GCSs) have been built in streams of western Iowa to reduce erosion and protect bridges, roads, and farmland. In conjunction with a companion study evaluating fish passage over GCSs in Turkey Creek, we evaluated the differences in fish assemblage and habitat characteristics in reaches immediately downstream from GCSs (GCS sites) and reaches at least 1 km from any GCS (non-GCS sites). The GCS sites were characterized by greater proportions of pool habitat, maximum depths, fish biomass, and abundance of juvenile largemouth bass Micropterus salmoides than were non-GCS sites. Index of biotic integrity (IBI) scores were poor or fair (<43 on a 0-100 scale) and not significantly different between the GCS and non-GCS sites. Additionally, we investigated both the longitudinal changes in fish assemblages in this GCS-fragmented stream and the changes in fish assemblages after slope modifications of three GCSs to facilitate fish passage. Thirteen fish species were present throughout the study area, whereas another 15 species exhibited truncated distributions not extending to the most upstream sampling location. After modification of the GCSs, IBI scores increased at seven of nine sites (mean increase = 4.6 points). Also, channel catfish Ictalurus punctatus were detected 7.3 km upstream at sites where, 2 years before GCS modification, they had been absent from collections. Given the number and distribution of GCSs in western Iowa streams, understanding the effects of these structures is vital to the conservation and management of fish assemblages in this and other regions where GCSs or similar structures are used. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electromyogram (EMG) radio transmitters have proven to be a useful tool to monitor activity levels in free swimming fish. Unfortunately, the availability of the EMG transmitter in only radio mode limited its use to the freshwater environment. Applications in the marine environment are numerous and include monitoring activity levels in both wild and cultured finfish. This study presents preliminary data from trials examining activity levels in free swimming sea bass, Dicentrarchus labrax, L., using an acoustic EMG transmitter. Three adult sea bass were surgically implanted with the newly created prototype EMG transmitters. Signals from the transmitter were calibrated to swimming speed using a Blažka-style chamber. Swimming trials showed a high correlation between EMG signal and swimming velocity ( r2 = 0.978) and were described using a sigmoid model. No significant differences ( P < 0.05) were found among the four swimming trials conducted on the same fish or among the trials of the three different fish, indicating minimum variation from the prototypes tested. [ABSTRACT FROM AUTHOR]

Compensatory growth (CG) is a period of growth acceleration that exceeds normal rates after animals are alleviated of certain growth-stunting conditions. In hybrid striped bass (HSB, Morone chrysopsxMorone saxatilis), 3 weeks of complete feed restriction results in a catabolic state that, when relieved, renders a subsequent phase of CG. The catabolic state was characterized by depressed levels of hepatic Type I and II GH receptor (ghr1, ghr2) and igf1 mRNA, along with considerable decreases in plasma Igf1. The state of catabolism also resulted in significant declines in hepatic igf2 mRNA and in circulating 40 kDa Igf-binding protein (Igfbp). Skeletal muscle expression of ghr2 mRNA was significantly increased. Upon realimentation, specific growth rates (SGRs) were significantly higher than sized-matched controls, indicating a period of CG. Hepatic ghr1, ghr2, igf1 and igf2 mRNA levels along with plasma Igf1 and 40 kDa Igfbp increased rapidly during realimentation. Plasma Igf1 and total hepatic igf2 mRNA were significantly correlated to SGR throughout the study. Skeletal muscle igf1 mRNA also increased tenfold during CG. These data suggest that endocrine and paracrine/autocrine components of the GH–Igf axis, namely igf1, igf2, and ghr1 and ghr2, may be involved in CG responses in HSB, with several of the gene expression variables exceeding normal levels during CG. We also demonstrate that normalization of hepatic mRNA as a function of total liver production, rather than as a fraction of total RNA, may be a more biologically appropriate method of quantifying hepatic gene expression when using real-time PCR. [ABSTRACT FROM AUTHOR]

Annual reproductive surveys monitored nesting location, reproductive success and the age and size of individually tagged male smallmouth bass Micropterus dolomieu that reproduced in Millers Lake, a 45 ha widening of the Mississippi River, Ontario, and in a 1·5 km pool and riffle section of the river directly upstream. The vast majority of males displayed fidelity to either the river or the lake as reproductive habitat throughout their lifetimes. Nearly, half of the males that reproduced in successive years exhibited strong nest-site fidelity by nesting within 20 m of their previous year’s nest site. In most years, when compared to those in the lake, reproductive males in the river differed significantly in reproductive characteristics including age and size at maturation and nesting success rates. A 3 year telemetry project identified two distinct habitat use patterns: lake-resident fish remained in the lake throughout the year and potamodromous individuals migrated from the lake to upriver spawning habitat in the spring and then returned to the lake prior to the onset of winter. Integration of habitat use and reproductive data suggests that there are significant differences in the life-history strategies of fish that reproduce in the river v. the lake. [ABSTRACT FROM AUTHOR]

Trophic adaptability is a term used to describe feeding flexibility in fishes. Though a useful conceptual starting point, fishes often face constraints on their ability to switch prey that could limit feeding success even when prey switching is observed. We compared striped bass diet compositions summarized from previously published studies in California’s Sacramento-San Joaquin Delta during two time periods (1963–1964 and 2001–2003), which allowed us to evaluate trophic adaptability in San Francisco Estuary striped bass at multiple time scales, ranging from intra-annual to multidecadal. The Delta is the landward region of the San Francisco Estuary; over time between the study periods, the Delta underwent substantial changes in potential prey availability for striped bass. We found evidence for trophic adaptability in San Francisco Estuary (SFE) striped bass at all temporal scales examined. Despite this ability to adapt to changes in prey availability, the relative abundance and carrying capacity of young striped bass have declined. This decline has previously been associated with substantial declines in their dominant historical prey—mysid shrimp. Our results, coupled with these previous findings, indicate that trophic adaptability may have limited usefulness as a conceptual model to predict foraging success when other food web constraints are not considered. We speculate that this is particularly true in highly invaded ecosystems like the San Francisco Estuary because invading species often introduce substantial and permanent changes into food webs, decreasing the likelihood that a predator will find prey assemblages that fully replace historical prey assemblages. [ABSTRACT FROM AUTHOR]

In trout and salmon, the metabolic costs of exercise and feeding are additive, which would suggest that gastrointestinal blood flow during exercise is maintained to preserve digestive and absorptive processes related to the specific dynamic action (SDA) of food. However, in most published studies, gastrointestinal blood flow drops during swimming, hypoxia, and general stress. To test whether gastrointestinal blood flow is spared during exercise after feeding, sea bass were instrumented with flow probes to measure cardiac output and celiacomesenteric blood flow while swimming in a respirometer before and after feeding. Swimming at 2 body lengths per second (bl s-1) increased metabolic rate considerably more than did feeding (208% vs. 32% increase, respectively, relative to resting), and a similar pattern was observed for cardiac output. In unfed fish, resting gastrointestinal blood flow was 13.8±0.5 mL min-1 kg-1. After feeding, resting gastrointestinal blood flow increased by 82% but then decreased progressively with increasing swimming speeds. At 2 bl s-1, gastrointestinal blood flow in fed fish was not significantly different compared with that in unfed swimming fish, and, therefore, the data do not support the gastrointestinal sparing hypothesis. The magnitude of the SDA was maintained despite the decrease in gastrointestinal blood flow and the consequent reduction in oxygen supply to the gut. An estimate of maximal oxygen flow to the gastrointestinal tract after feeding yielded 2.6 mmolO2 h-1 kg-1, but this amount is not able to cover the oxygen demand of 3.16 mmol O2 h-1 kg-1. Therefore, the SDA must reflect metabolic processes in tissues other than those directly perfused by the celiacomesenteric artery. [ABSTRACT FROM AUTHOR]