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Striped bass (Morone saxatilis) are anadromous fish that support an important fishery along the east coast of North America. In Chesapeake Bay, strong juvenile recruitment of striped bass can occur when larvae overlap with high concentrations of their zooplankton prey, but the mechanisms fostering the temporal overlap are unknown. Here, the influence of winter temperature on the peak abundances of a key prey, Eurytemora carolleeae, was estimated with a temperature-dependent developmental model. The role of these peaks in regulating striped bass recruitment was explored in three nursery areas: upper Chesapeake Bay, Choptank River, and Patuxent River. Model results indicated that cold winters delay the timing and increase the size of peak E. carolleeae spring abundance. When the model output was used in regression relationships with striped bass juvenile recruitment and freshwater discharge, the regression models explained up to 78% of annual recruitment variability. Results suggests that cold, wet winters could increase the chance of a match between striped bass larvae and high concentrations of their prey. This mechanistic link between winter temperatures and striped bass production, acting through prey dynamics, could further understanding of fish recruitment variability and indicates that warmer winters could negatively affect some striped bass populations.

After being extirpated from the St. Lawrence Estuary (SLE), striped bass (Morone saxatilis) were reintroduced in 2002, and by 2008 they were naturally reproducing. The increase of this reintroduced population prompted the need to document its nursery habitats utilization, which contribute to species recruitment. We analysed mortality-dispersion rates and the growth of larvae and juveniles in relation to their occurrence and migration patterns. From June to September 2014, we collected striped bass distributed in four estuarine habitats: the upstream freshwater section (UP), the oligohaline (O-ETM) and the mesohaline (M-ETM) estuarine turbidity maximum zone, and the downstream polyhaline section (DOWN). Based on otolith microstructure and microchemistry, 305 back-calculated growth and 36 migration trajectories have been reconstructed. The UP and the O-ETM provided optimal conditions wherein which larvae and juveniles exhibited fastest growth. In the SLE, we emphasized the co-existence of a freshwater resident contingent and two migrant contingents to the M-ETM and DOWN. We propose that migrants adopt an adaptive migration behaviour to avoid suboptimal conditions and strong intraspecific competition from resident in the upstream habitats. The potential advantage of a downstream migration later in the season might be an adaptative strategy to promote their survival during the early life stages.

After being extirpated from the St. Lawrence River in the 1960s, striped bass (Morone saxatilis) were reintroduced to the estuary in 2002 and by 2008, they were naturally reproducing. To document the habitat use and feeding ecology of this reintroduced population, we examined the gut contents of 333 larvae and juveniles. Samples were collected in four estuarine habitats in 2014: the upstream freshwater section (UP), the oligohaline (O-ETM) and the mesohaline (M-ETM) estuarine turbidity maximum zones, and the downstream polyhaline section (DOWN). In June, pelagic larvae developed in the UP and the O-ETM, feeding mainly on copepods such as Eurytemora affinis. The O-ETM exhibited better suitable feeding conditions compared to the UP, likely due to the presence of Bosmina sp. as a primary prey. After July, striped bass shifted to larger prey items, consuming mainly dipteran pupa in upstream littoral habitats and gammarids and mysids in downstream habitats. In the early summer, the UP provided a high-quality nursery habitat and as the season progressed, the smallest juveniles dispersed downstream and improved their feeding success by exploiting a new feeding niche. This observation suggests that being distributed throughout the estuary may increase the potential survival of striped bass early life stages.

Suction feeding is a powerful and complex process of prey ingestion that relies on contributions from both head and body muscles in fishes. Whereas the cranial and hypobranchial muscles in the head region might intuitively be seen as the main drivers behind suction feeding, the axial muscles of the body have long been understood as necessary contributors to the process as well (Muller and Osse 1984; Westneat 1990; Van Wassenbergh et al. 2007). In many fishes, epaxial muscles contract to rotate and lift the neurocranium while the hypaxial muscles contribute to hyoid depression via pectoral girdle retraction (Lauder 1979, 1982; Liem 1980; Camp and Brainerd 2014). The sternohyoideus (SH) muscle serves as a bridge between the body and the head, transmitting hypaxial muscle power to the hyobranchial elements of the head yet still retaining the potential to act on these elements itself. Recent studies have shown that axial musculature provides a majority of the power for strikes in largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus; Camp et al. 2015; Camp et al. 2018). In both species, the SH muscle is the only muscle in the head that is large enough to contribute more than negligible power. In largemouth bass, however, the SH function has been found to vary, as the muscle sometimes shortens and other times lengthens around the time of peak gape (Carroll 2004). Peak suction power production occurs just before peak gape, and the SH was later determined to show little to no shortening during periods of peak power production in M. salmoides (Camp et al. 2015). This lack of shortening during peak power indicates that the largemouth bass SH contributes little to no positive work and power. In contrast, bluegill sunfish rapidly shorten the SH during suction feeding, contributing power for both hyoid depression and, by extension, suction expansion (Camp et al. 2018). However, the contribution of the SH is still small, likely providing less than 10% of overall power, though the constant shortening of the bluegill sternohyoid for all studied strikes suggest that 10% may be crucial to generating a successful strike in the bluegill. These muscle strain patterns indicate that in largemouth bass, the SH is active isometrically at the time of peak power production, effectively serving to transmit pectoral girdle rotation and hypaxial muscle power for hyoid depression (Carroll 2004; Carroll et al. 2004; Camp and Brainerd 2014; Camp et al. 2015), whereas in bluegill it serves a dual function both transmitting hypaxial power and contributing its own additional power for hyoid depression. In bluegill, the SH muscle is nearly twice the size of the SH in bass, when measured as a fraction of axial muscle mass (Camp et al. 2015; Camp et al. 2018). Clariid catfishes display this same relationship between SH muscle size and function. Of four species studied, the SH is largest in Gymnallabes typus, and this is the only species that showed SH shortening during suction feeding (Van Wassenbergh et al. 2007). In other studied clariid species, SH muscles were about half the size of G. typus and contracted isometrically during the first half of hyoid depression and then lengthened during the second half (Van Wassenbergh et al. 2007). The clariid catfish and centrarchid results together suggest that the SH may be more likely to shorten and contribute power to suction expansion when the SH is relatively large, whereas, in species in which it is smaller, the SH does not shorten but instead acts much like a stiff ligament to transmit force and power from the hypaxial musculature to the hyoid. If muscle size is to be considered an indicator of sternohyoid bifunctionality, as both a transmitter and contributor to suction power, then studies focused on testing this prediction in species that fit this emerging size-specific criterion are necessary. This study focuses on the suction feeding mechanism of the striped surfperch, Embiotoca lateralis, a species with a large SH muscle relative to M. salmoides and L. macrochirus (the mass of the SH is 8.8% of axial muscle mass in E. lateralis relative to 4.0% in L. macrochirus and 1.7% in M. salmoides; see “Materials and methods” and “Results” sections for more information on these masses). Does the surfperch SH shorten during suction expansion? We use a relatively new method, Video Reconstruction of Moving Morphology (VROMM) (Jimenez et al. 2018; Hoffmann et al. 2019) to track and animate the neurocranium, cleithrum, and a reference body plane, as well as a new method that employs external 3D marker tracking to estimate epaxial and SH muscle strain. As this particular application of external marker tracking is previously undescribed, we additionally present an experimental evaluation of the new method.

Harvest restrictions (e.g. size, sex or species limitations) that are implemented to maintain sustainable fisheries often result in by-catch, e.g. unwanted non-target catch. By-catch is frequently discarded back into the ocean and assumed to survive. However, discarded fishes can succumb to delayed mortality resulting from accumulated stress from fishing activity, and such mortality can impede sustainability efforts. Quantifying reflex and behavioural impairments is a quick and cost-effective method to predict discard-related mortality in some species. We developed and evaluated the effectiveness of a release condition index, based on a reflex-action mortality prediction (RAMP) model, for predicting delayed mortality of black sea bass (Centropristis striata) caught and discarded by the commercial trap fishery in the Mid-Atlantic Bight. Accumulation of impairments, and therefore release condition index, was strongly correlated with delayed mortality of black sea bass discarded and held in sea cages. This is the first release condition index validation study to predict mortality in black sea bass and could be a useful approach for predicting delayed mortality in the commercial fishery.

Understanding the dynamic processes that contribute to reproductive output is vital to determine appropriate harvest controls and sustain marine fisheries. For sequential hermaphrodites, the process of reproduction is complicated by sex transition within the life history. We examined the reproductive dynamics of black sea bass (Centropristis striata), a protogynous serranid, within a major fishing region of the Northwest Atlantic during two consecutive spawning seasons to quantify the strength of size-dependence and the magnitude of temporal variation in several key traits. Specifically, we estimated the size-dependence of sex ratio, maturity, spawning capability, batch fecundity, and spawning frequency at both fine (weeks/months) and broad (years) temporal scales. We observed fecundity to be highest in females of intermediate body size, which was entirely a function of reduced spawning frequency among the largest females. Female fecundity peaked at sizes well below the estimated size at sex transition, and contrary to the pattern typically observed for gonochoristic fishes in which the largest females yield the greatest number of eggs. Among protogynous fishes, females may decrease egg production prior to sex change and instead allocate energy to somatic growth, benefitting from larger body size during the subsequent male phase. The production of fewer batches of eggs by larger females directly impacted estimates of annual fecundity. In addition, we detected large interannual differences in the proportion of spawning capable females, and also spawning frequency, which resulted in considerable variation between annual fecundity estimates. The inclusion of temporal and size-dependent variation in female egg production should produce more robust estimates of stock reproductive potential and its response to changing harvest scenarios.

Mark-recapture experiments were conducted in the tidal Nanticoke River (Chesapeake Bay) to determine how the salt front retains striped bass larvae and controls nursery production. During two spring spawning seasons, 25.1 million hatchery-produced, first-feeding larvae (5–12 days post-hatch) were released with chemically marked otoliths at selected locations and times. Surveys tracked the spatial and demographic fates of released and naturally spawned larvae. Released larvae dispersed rapidly within the freshwater tidal portion of the estuary and were retained above the salt front. Their distributions overlapped with natural larvae. Growth and mortality rates did not differ with respect to release location, but did vary with day of release, influenced by storm events and seasonal changes in temperature. In 1993, a group released during a storm event did not yield any recaptured larvae. Zooplankton concentrations in both years were likely sufficient for successful larval feeding. In spring 1993, a season of relatively high freshwater flow, nursery volume was 2.1-fold larger and juvenile production from larval releases was fourfold higher than in 1992. We propose that increased nursery volume reduces variance in water quality, enhances retention of larvae within the nursery, thus increasing production of larval striped bass.

Because of growing interest in producing Largemouth bass (HMB) as a source of high-quality protein for human consumption worldwide, it is imperative to understand the metabolism of nutrients (including amino acids and carbohydrate) in this aquatic animal. The present study tested the hypothesis that amino acids are oxidized at a higher rate than carbohydrates (e.g., glucose) and fatty acids (e.g., palmitate) to provide ATP for tissues of LMB fed a 45%-crude protein diet. The liver, intestine, kidney, and skeletal muscle were isolated from juvenile LMB and incubated at 26 °C (the body temperature of LMB) for 2 h in 1 ml of oxygenated Krebs–Henseleit bicarbonate buffer (pH 7.4) containing a mixture of nutrients (2 mM glutamate, 2 mM glutamine, 2 mM aspartate, 2 mM alanine, 2 mM leucine, 5 mM glucose, and 2 mM palmitate). The rate of oxidation of each energy substrate was determined by using [U-14C]-labeled glutamate, glutamine, aspartate, alanine, leucine, glucose, or palmitate and collecting 14CO2 from each tracer. Results indicated that aspartate, glutamate and glutamine were extensively oxidized in all the four tissues and contributed to 67% of total ATP production. Glutamate contributed to more ATP than glutamine in the intestine, whereas similar amounts of ATP were produced from glutamate and glutamine in the liver, kidneys and skeletal muscle. In all the four tissues, rates of oxidation of alanine, leucine, palmitate and glucose were low and each of those nutrients contributed to < 10% of total ATP production. Together, the oxidation of aspartate, glutamate, glutamine, alanine plus leucine provided 82–85% of total ATP for the liver, intestine, kidney, and skeletal muscle. We conclude that amino acids, rather than glucose and long-chain fatty acids, are the primary energy substrates in the major tissues of Largemouth bass.

We report population genetic structure and fine-scale recruitment processes for the scallop beds (Pecten fumatus) in Bass Strait and the eastern coastline of Tasmania in southern Australia. Conventional population pairwise FST analyses are compared with novel discriminant analysis of principal components (DAPC) to assess population genetic structure using allelic variation in 11 microsatellite loci. Fine-scale population connectivity was compared with oceanic features of the sampled area. Disjunct scallop beds were genetically distinct, but there was little population genetic structure between beds connected by tides and oceanic currents. To identify recruitment patterns among and within beds, pedigree analyses determined the distribution of parent–offspring and sibling relationships in the sampled populations. Beds in northeastern Bass Strait were genetically distinct to adjacent beds (FST 0.003–0.005) and may not contribute to wider recruitment based on biophysical models of larval movement. Unfortunately, pedigree analyses lacked power to further dissect fine-scale recruitment processes including self-recruitment. Our results support the management of disjunct populations as separate stocks and the protection of source populations among open water beds. The application of DAPC and parentage analyses in the current study provided valuable insight into their potential power to determine population connectivity in marine species with larval dispersal.

Bacheler, N. M., Schobernd, Z. H., Berrane, D. J., Schobernd, C. M., Mitchell, W. A., and Geraldi, N. R. 2013. When a trap is not a trap: converging entry and exit rates and their effect on trap saturation of black sea bass (Centropristis striata) – ICES Journal of Marine Science, 70: 873–882. Catch rates are often used to index the abundance of marine organisms, but catch saturation (i.e. declining catch rate as fishing time increases) can decouple catch and abundance. Researchers have struggled to account for saturation when using trap catch to infer population dynamics. We used the underwater video to document entries and exits of black sea bass (Centropristis striata) from chevron traps (n = 26) to quantify catch saturation. Black sea bass catch varied between 3 and 188 individuals for soak times of ∼90 min. Overall, 3564 black sea bass entered the traps and 1826 exited; therefore, over half (51%) of black sea bass entering traps exited before traps were retrieved. Black sea bass catch rates were non-linear and asymptotic for most (81%) trap samples, despite short soak times. Moreover, catch saturation occurred at 50 min, when the entry rate declined and the exit rate increased to a point where their confidence intervals overlapped. Several lines of evidence suggest that the level of black sea bass catch once saturation occurred may be positively related to true abundance, but additional research is needed to more fully test this hypothesis.

Aquaculture of carnivorous species has strongly relied on fish meal and fish oil for feed formulation; however, greater replacement by terrestrial plant-based products is occurring now. This rapid change in dietary environment has been a major revolution and has to be taken into consideration in breeding programs. The present study analyzes potential consequences of this nutritional tendency for selective breeding by estimating genetic parameters of BW and growth rates estimated by the thermal growth coefficient (TGC) over different periods with extremely different diets. European sea bass (Dicentrarchus labrax L.) from a factorial cross (1,526 fish) between 25 sires and 9 dams were used to estimate heritabilities and genotype by diet interaction. Starting 87 d after fertilization (2.5 g), one-half of the sea bass were fed a diet containing marine products (M), and the other one-half were fed a totally plant-based (PB) diet (without any fish meal or fish oil). The fish were individually tagged, reared in a recirculated system, and genotyped at 13 microsatellites to rebuild parentage of individuals. Body weight and TGC were measured for 335 d until fish fed the M diet reached 108.3 g of BW. These traits were significantly less in fish fed the PB diet (P 0.1). Survival was significantly less in fish fed the PB diet (PB=64.7%, M=93.7% after 418 d, P

Genetic population structure of anadromous striped bass along the US Atlantic coast was analyzed using 14 neutral nuclear DNA microsatellites. Young-of-the-year and adult striped bass (n = 1114) were sampled from Hudson River, Delaware River, Chesapeake Bay, North Carolina, and South Carolina. Analyses indicated clear population structure with significant genetic differentiation between all regions. Global multilocus FST was estimated at 0.028 (P < 0.001). Population structure followed an isolation-by-distance model and temporal sampling indicated a stable population structure more than 2 years at all locations. Significant structure was absent within Hudson River, whereas weak but significant genetic differences were observed between northern and southern samples in Chesapeake Bay. The largest and smallest effective striped bass population sizes were found in Chesapeake Bay and South Carolina, respectively. Coalescence analysis indicated that the highest historical gene flow has been between Chesapeake Bay and Hudson River populations, and that exchange has not been unidirectional. Bayesian analysis of contemporary migration indicated that Chesapeake Bay serves as a major source of migrants for Atlantic coastal regions from Albemarle Sound northward. In addition to examining population genetic structure, the data acquired during this project were capable of serving as a baseline for assigning fish with unknown origin to source region.

A liquid chromatographic method was developed for the determination of albendazole and its metabolites albendazole sulfoxide, albendazole sulfone, and albendazole-2-aminosulfone from largemouth and hybrid striped bass muscle tissue with adhering skin. The muscle tissue samples were made alkaline with potassium carbonate and extracted with ethyl acetate. The extracts were further subjected to cleanup by using a series of liquidliquid extractions. After solvent evaporation, the residue was reconstituted in mobile phase and chromatographed. The chromatography was carried out on a reversed-phase Luna C18 column, using acetonitrilemethanol buffer as the mobile phase. The analytes were detected by fluorescence with excitation and emission wavelengths of 290 and 330 nm, respectively. The average recoveries from the fortified muscle tissue of the 2 fish species for albendazole (25100 ppb), albendazole sulfoxide (8.7552.5 ppb), albendazole sulfone (110 ppb), and albendazole-2-aminosulfone (10100 ppb) were 89, 82, 99, and 74, respectively. The coefficient of variation for each compound was 20 in all cases. The procedure was applied to the determination of albendazole and its 3 metabolites in the muscle tissue of the 2 fish species after orally dosing them with albendazole.

Despite almost 50 years of research on the functional morphology and biomechanics of suction feeding, no consensus has emerged on how to characterize suction-feeding performance, or its morphological basis. We argue that this lack of unity in the literature is due to an unusually indirect and complex linkage between the muscle contractions that power suction feeding, the skeletal movements that underlie buccal expansion, the sharp drop in buccal suction pressure that occurs during expansion, the flow of water that enters the mouth to eliminate the pressure gradient, and the forces that are ultimately exerted on the prey by this flow. This complexity has led various researchers to focus individually on suction pressure, flow velocity, or the distance the prey moves as metrics of suction-feeding performance. We attempt to integrate a mechanistic view of the ability of fish to perform these components of suction feeding. We first discuss a model that successfully relates aspects of cranial morphology to the capacity to generate suction pressure in the buccal cavity. This model is a particularly valuable tool for studying the evolution of the feeding mechanism. Second, we illustrate the multidimensional nature of suction-feeding performance in a comparison of bluegill, Lepomis macrochirus, and largemouth bass, Micropterus salmoides, two species that represent opposite ends of the spectrum of performance in suction feeding. As anticipated, bluegills had greater accuracy, lower peak flux into the mouth, and higher flow velocity and acceleration of flow than did bass. While the differences between species in accuracy of strike and peak water flux were substantial, peak suction velocity and acceleration were only about 50% higher in bluegill, a relatively modest difference. However, a hydrodynamic model of the forces that suction feeders exert on their prey shows that this difference in velocity is amplified by a positive effect of the smaller mouth aperture of bluegill on force exerted on the prey. Our model indicates that the pressure gradient in front of a fish that is feeding by suction, associated with the gradient in water velocity, results in a force on the prey that is larger than drag or acceleration reaction. A smaller mouth aperture results in a steeper pressure gradient that exerts a greater force on the prey, even when other features of the suction flow are held constant. Our work shows that some aspects of suction-feeding performance can be determined from morphology, but that the complexity of the behavior requires a diversity of perspectives to be used in order to adequately characterize performance.

Pawson, M. G., Pickett, G. D., Leballeur, J. Brown, M., and Fritsch, M. 2007. Migrations, fishery interactions, and management units of sea bass (Dicentrarchus labrax) in Northwest Europe. – ICES Journal of Marine Science, 64: 332–345. A total of 4959 sea bass was tagged between 2000 and 2005 around the coasts of England, Wales, southern Ireland, and the Channel Isles to investigate whether movement patterns documented in 1987 have changed and to estimate the level of competition for sea bass between inshore and offshore fisheries. Most (54%) of the recaptures of adult bass (fish >40 cm) tagged inshore and made between May and October were within 16 km of the release positions. From November on, an increasing proportion was recaptured at least 80 km south or southwest of tagging sites. Bass tagged on offshore spawning grounds in March and April showed reciprocal movement, 75% of recaptures between May and October being at least 80 km from the release site. These observations reaffirm the hypothesis that adult sea bass may move considerable distances to offshore winter spawning areas, but there was little evidence of the spawning migrations between the North Sea and the western Channel that were observed in the early 1980s. Just 3% of the recaptures of bass >36 cm tagged in UK inshore fisheries were reported from the offshore pairtrawl fishery, whereas half the recaptures of bass tagged in that fishery were made inshore along the UK coast. When weighted by the respective catches, this suggests that the effects of management measures implemented in the UK inshore fishery are largely restricted to that fishery. A proposal for stock units for assessment and management of NW European sea bass fisheries is presented.

Some teleost species, including European sea bass, harbor two different kisspeptin coding genes: kiss1 and kiss2. Both genes are expressed in the brain, but their differential roles in the central control of fish reproduction are only beginning to be elucidated. In this study, we have examined the effects of intracerebroventricular injections of the highly active sea bass peptides Kiss1-15 and Kiss2-12 on spermiating male sea bass. Physiological saline, Kiss1-15, or Kiss2-12 was injected into the third ventricle. To establish the gene expression cascade involved in the action of kisspeptins, the expression of the two sea bass kisspeptin receptor genes (kiss1r and kiss2r) and the three sea bass Gnrh genes (gnrh1, gnrh2, and gnrh3) were analyzed in the forebrain-midbrain and the hypothalamus. In addition, the protein levels of hypothalamic and pituitary Gnrh1 were measured. Blood samples were collected at different times after injection to analyze the effects of kisspeptins on the release of gonadotropins (Lh and Fsh) and androgens (testosterone and 11-ketotestosterone). The present results provide the first evidence that the effects of Kiss2 on central regulation of reproductive function involve the neuroendocrine areas of the forebrain-midbrain in teleost fish. The marked effect of Kiss2 on kiss2r and gnrh1 expression in the forebrain-midbrain and on Gnrh1 release suggest that this neuronal system is involved in the neuroendocrine regulation of gonadotroph activity. This hypothesis was confirmed by a surge of plasma Lh in response to Kiss2, which presumably has a strong stimulatory effect on testosterone release, and thus on sperm quality parameters.

Pawson, M. G., Kupschus, S., and Pickett, G. D. 2007. The status of sea bass (Dicentrarchus labrax) stocks around England and Wales, derived using a separable catch-at-age model, and implications for fisheries management. – ICES Journal of Marine Science, 64: 346–356. The commercial fishery for sea bass (Dicentrarchus labrax) around the coasts of England and Wales developed rapidly in the late 1970s and 1980s and, by 1986, involved some 3000 fishers using more than 2000 boats to make landings worth £3–4 million. The estimated annual catch of sea bass by sport-anglers was similar to the level recorded from the commercial fishery. Sampling of landings showed strong evidence of growth-overfishing in many areas, and a package of technical measures was introduced in 1990 aimed at improving the exploitation pattern and yield per recruit. This paper describes how data collected through a fishery and biological sampling programme around England and Wales over the period 1985–2004 have been utilized in a separable catch numbers-at-age model to assess the dynamics of sea bass stocks in English and Welsh coastal waters. The model output shows that recruitment improved during the 1990s and that moderate levels of fishing mortality allied to an exploitation pattern that largely avoids juvenile fish have enabled the bass population and its fishery to develop sustainably. Results are discussed in relation to model development and management of the bass fishery.

A new, rapid, and reproducible reversed-phased liquid chromatography (LC) method with ultraviolet (UV) absorption and/or mass spectrometry (MS) detection has been developed and validated for quantitation of cichoric acid, a major constituent of Echinacea spp. The method involves the use of a short Phenomenex Hydro-RP C18 column (4 μm, 50 × mm 3.0 mm id) and a simple isocratic mobile phase profile. Both UV (diode array detector) and selective-ion monitoring (SIM) at m/z 472.8 were used for quantitation of cichoric acid. The limit of detection was 0.75 ng for UV and 0.15 ng for MSSIM, and the limit of quantitation was is 2.5 ng for UV and 0.5 ng for MSSIM. Watermethanol (1 + 1) soluble extracts of 6 commercially available Echinacea purpurea aerial parts-based dietary supplements (EPADS). EPADS were first profiled using a traditional HPLC-UV method. Their UV chromatograms were compared, and cichoric acid was identified to be a key biomarker for EPADS. Then the samples were analyzed by the fast LC-UV/MS method. The turnaround time for a single analysiswas 3 min, compared to 15 to 60 min needed for traditional reported LC methods. The high-throughput method was able to separate the cichoric acid peak from peaks of other components in extracts of complex matrixes of EPADS.

A rapid and sensitive immuno-based screening method was developed to detect domoic acid (DA) present in extracts of shellfish species using a surface plasmon resonance-based optical biosensor. A rabbit polyclonal antibody raised against DA was mixed with standard or sample extracts and allowed to interact with DA immobilized onto a sensor chip surface. The characterization of the antibody strongly suggested high cross-reactivity with DA and important isomers of the toxin. The binding of this antibody to the sensor chip surface was inhibited in the presence of DA in either standard solutions or sample extracts. The DA chip surface proved to be highly stable, achieving approximately 800 analyses per chip without any loss of surface activity. A single analytical cycle (sample injection, chip regeneration, and system wash) took 10 min to complete. Sample analysis (scallops, mussels, cockles, oysters) was achieved by simple extraction with methanol. These extracts were then filtered and diluted before analysis. Detection limits in the ng/g range were achieved by the assay; however, the assay parameters chosen allowed the test to be performed most accurately at the Euopean Union's official action limit for DA of 20 g/g. At this concentration, intra- and interassay variations were measured for a range of shellfish species and ranged from 4.5 to 7.4% and 2.3 to 9.7%, respectively.

Anadromous populations of striped bass occur along the Atlantic coast of the US from Maine to North Carolina. Recruitment overfishing and declining water quality led to substantial reductions in striped bass abundance during the 1970s and 1980s. Cooperative interstate fishery management of striped bass began in 1981, with the development of a fishery management plan by the Atlantic States Marine Fisheries Commission, an organization of Atlantic coastal states. Effective fishery management and additional research and monitoring contributed to a tenfold increase in abundance of striped bass stocks by the late 1990s. This dramatic increase resulted in increased predation on a variety of anadromous fish species including American shad, blueback herring, and alewives. Predation by striped bass on Atlantic salmon smolts in North America has been documented, but the impact of this predation has not been quantified. Moderate to strong correlations were found between estimates of striped bass abundance and the return of Atlantic salmon to three of the four major New England salmon rivers. Further research is required to quantify the proportion of smolt production consumed by striped bass, particularly for salmon populations listed as endangered under the US Endangered Species Act.

Quantifying the degree of density-dependence in stock–recruit relationships is critical to understanding fish population dynamics. The Shepherd and Cushing (1980) model couples a simple model of density-dependent larval growth with a constant rate of mortality to predict numbers surviving to recruitment. The model has not been evaluated using field data, nor have its predictions been compared with those from other models. Here, the S&C model, an individual-based model (IBM), and a regression model are applied to 8 years of field data for striped bass larvae in the Potomac River, Maryland, USA, to predict larval carrying capacity (K) and percentage of recruitment lost as a consequence of density-dependent growth. The IBM and the regression model were corroborated by comparing their predictions of average growth rates of larvae and relative recruitment strengths to observed values for the 8 years of field data. Although the IBM and the regression model differed in their predictions of several important intermediate variables, both models predicted higher values of K and lower values of density-dependent growth than did the S&C model. Over the 8 years, the IBM and the regression model predicted an average of 0.3 and 1.8% recruitment lost as a result of density-dependent growth, respectively. In contrast, the S&C model predicted much higher recruitment lost (average of 27%). Slight differences in the assumed rate of mortality used in the S&C model resulted in values of carrying capacity similar to those predicted by the IBM and the regression model. Difficulties in estimating parameters of the S&C model from field data are discussed.

Fluctuations in several environmental variables, such as salinity, can influence the interactions between organisms and pollutants in aquatic organisms, and, therefore, affect the toxicity of xenobiotics. In this study, after 2 species of fish, rainbow trout (Oncorhynchus mykiss) and hybrid striped bass (Morone saxatilis x chrysops) were acclimated to 4 salinity regimens of 1.5, 7, 14, and 21 ppt for 1 week and then exposed to 0.5 mg/l aldicarb. Mortality, brain, and muscle cholinesterase levels were measured after 96 h. Rates of (14)C-aldicarb sulfoxide formation were determined in kidney (trout only), liver, and gill microsomes from each species acclimated to the 4 salinity regimens. Salinity significantly enhanced aldicarb toxicity, cholinesterase inhibition, and (14)C-aldicarb sulfoxide formation in rainbow trout but not in striped bass. In vitro incubations with (14)C-aldicarb and the cytochrome P450 (CYP) inhibitor, N-benzylimidazole, did not significantly alter aldicarb sulfoxide formation in tissue microsomes from either species of fish, indicating CYP did not contribute to aldicarb sulfoxidation. Salinity increased flavin-containing monooxygenase (FMO) mRNA expression and catalytic activities in microsomes of liver, gill, and kidney of rainbow trout, which was consistent with the salinity-induced enhancement of aldicarb toxicity. Salinity did not alter FMO mRNA expression and catalytic activities in striped bass, which was also consistent with the lack of an effect of salinity on aldicarb toxicity in this species. These results suggest that salinity-mediated enhancement of aldicarb toxicity is species-dependent, and at least partially due to the salinity-related upregulation of FMOs, which, in turn, increases the bioactivation of aldicarb to aldicarb sulfoxide, which is a more potent inhibitor of cholinesterase than aldicarb.

Since the early 1960s, the Chesapeake Bay striped bass population has undergone a large cycle of abundance, recovering to record levels during the 1990s. Changes in age structure over this period were examined to determine contributions of old females (>13 yr) to the recovery. In 1992, in a sample of large female striped bass, 10 yr of absent year classes (1972-1981) were observed corresponding to a period of recruitment overfishing. Fishery-independent stock assessments conducted 1985-1990 by Maryland Department of Natural Resources indicated that old females, while present in small numbers, made relatively small contributions to annual egg production during the period of recovery. Abundances, weighted for age-specific fecundity, indicated that older fish were probably the most important contributors to recruitment throughout the 1970s and early 1980s. Egg production after 1986 was principally contributed by young females, those produced after 1981. Demographic analysis also supports the view that a Maryland fishing moratorium designed to protect year classes after 1981 stimulated recovery. Longevities of >30 yr documented in this study suggest that striped bass populations can persist during long periods of poor recruitment due to a long reproductive lifespan. Longevity may have also conferred resiliency against an extended period of recruitment overfishing in the Chesapeake Bay

Net avoidance rate increases as a function of larval striped bass size. This causes underestimation of abundance and overestimation of mortality rate. We modeled net avoidance by assuming that fish avoid the net by swimming a radial distance at a right angle to the net axis. This distance, the evasion radius, was estimated by comparing the calculated densities of striped bass larvae from a series of paired tows involving a large and a small net. Iteration and solution models were used to estimate the evasion radius for each millimeter size group of fish in order to estimate the actual density in the environment. Avoidance of the nets increased with fish length. The ratio of actual density in the environment to the measured density in the small net was used to adjust abundances measured in our ichthyoplankton surveys. After adjusting for net avoidance, mortality rates of striped bass larvae from the Sacramento–San Joaquin Estuary were reduced by 10% compared to the unadjusted rates.

In fish, both gonadotropin (GtH)-I and -II are involved in the spermatogenic process, but the differential regulation of these hormones by GnRH is still poorly understood. To gain further insight into the GnRH regulation of GtH-I and -II gene expression in the male striped bass, we have developed and optimized a ribonuclease protection assay for the simultaneous measurement of all GtH subunit mRNAs in a single pituitary gland. The RNA extraction protocol enables the determination of GtH protein content in the same sample, thus enhancing the power of the method. Maturing striped bass males were injected intramuscularly with [D-Ala6,Pro9Net]-LHRH (GnRHa) and sampled at 6 and 24 h postinjection. The mRNA levels of the alpha subunit and GtH-IIbeta increased after 6 h (4- and 6-fold, respectively), while the GtH-Ibeta mRNA levels increased only 2-fold after 24 h. Interestingly, GnRHa stimulation caused a significant increase in beta-actin mRNA levels. GnRHa treatment also resulted in a 2-fold decrease in pituitary GtH-II content, associated with a dramatic increase of plasma GtH-II levels from undetectable levels (< 0.2 ng/ml) to 13+/-2 ng/ml after 6 h. These results demonstrate that both GtH-Ibeta and -Ilbeta are expressed during striped bass spermatogenesis and that the two genes are subjected to differential regulation by GnRHa.

Spermiating striped bass, a perciform fish, were treated with two controlled-release gonadotropin-releasing hormone agonist (GnRHa)-delivery systems, and the resulting changes in plasma gonadotropin II (GTH II), testosterone (T), 11-ketotestosterone (11-KT), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (17,20beta,21-P) were correlated with changes in milt production and sperm density. GnRHa-delivery systems induced a sustained elevation of plasma GnRHa and GTH II for 14 days. Plasma T levels were unchanged after GnRHa treatment, while 11-KT levels increased significantly. Plasma 17,20beta-P also increased after GnRHa treatment and remained elevated compared to levels in controls, while plasma 17,20beta,21-P levels were unaffected. Both GnRHa-delivery systems induced many-fold increases in total expressible milt, lasting throughout the 14 days of the study. Sperm density decreased 2 days after GnRHa treatment, with a subsequent increase by Day 7. This study demonstrates that GnRHa-delivery systems induce a sustained elevation of plasma GTH II levels in striped bass, resulting in a long-term enhancement of milt production. The endocrine changes observed suggest that 11-KT and 17,20beta-P, but not 17,20beta,21 -P, are mediating the effects of GTH II on spermiation.

Author(s): Avise, JC; Pierce, PC; Van Den Avyle, MJ; Smith, MH; Nelson, WS; Asmussen, MA | Abstract: Species-specific RFLP markers from mitochondrial DNA (mtDNA) were identified and employed in conjunction with previously reported data for nuclear allozyme markers to examine the genetic consequences of an artificial introduction of spotted bass (Micropterus punctulatus) into a north Georgia reservoir originally occupied by native small mouth bass (M. dolomieui). The cytonuclear genetic data indicate that within 10-15 years following the unauthorized introduction, a reversal in these species' abundances has occurred and that more than 99% of the population sample analyzed here consists of spotted bass or products of interspecific hybridization. This demographic shift, perhaps ecologically or environmentally mediated, has been accompanied by introgressive swamping; more than 95% of the remaining small mouth bass nuclear and cytoplasmic alleles are present in individuals of hybrid ancestry. Dilocus cytonuclear disequilibria were significantly different from zero, with patterns indicative of an excess of homospecific genetic combinations (relative to expectations from single-locus allelic frequencies) and a disproportionate contribution of small mouth bass mothers to the hybrid gene pool. Results document dramatic genetic and demographic changes following the human-mediated introduction of a nonnative species.

Previous studies have shown that blood plasma levels of 17a, 20,B-dihydroxy-4-pregnen-3-one (DHP) and 1 7a, 20, 21-trihydroxy-4-pregnen-3-one (20-S) increase in striped bass (Morone saxatilis) undergoing final oocyte maturation (FOM). Both hormones are produced by ovarian fragments undergoing hCGinduced germinal vesicle breakdown (GVBD) in vitro. In the present study, we investigated binding of DHP and 20B-S to ovarian membranes from striped bass undergoing FOM. Saturable binding sites for DHP were not detected. Saturation of 2013-S binding sites with 5 nM [ 3 H]203-S occurred within 40 min at 0°C (at 3 min, half of the maximum specific binding of steroid was calculated to have occurred), and the binding was pH-dependent. Scatchard analyses revealed the presence of a single class of high-affinity (dissociation constant [Kd] = 1.4 + 0.2 nM), limited-capacity (estimated concentration [Bmax] = 2.7 ± 0.3 pmol/g ovary) 2013-S binding sites on membranes from striped bass ovaries undergoing FOM. In contrast, only low levels of specific binding (Bmx, < 0.04 pmol/g tissue) were detected on membranes from testes, liver, brain, and muscle. Ovarian membranes prepared from vitellogenic females also had low levels (Bmax < 0.1 pmol/g ovary) of specific 2001-S binding, less than 5% of that found during FOM. Results of competition assays showed that DHP was approximately 250 times less effective than 2001-S for displacing 20,1-S from ovarian membranes. In contrast, 2013, 21-dihydroxy-4-pregnen-3-one was a very effective competitor, although it is only a weak inducer of oocyte GVBD in vitro. Of several other steroids tested, only progesterone showed affinity for the 2001-S binding site within a physiological range of concentrations. Taken together with previous studies of striped bass FOM, these findings indicate that 20,1-S is the oocyte maturation-inducing steroid hormone in striped bass.

Receptors for white perch vitellogenin (wVTG) were characterized using wVTG, labeled in vivo with [3H]leucine or in vitro with 1251, and semipurified ovarian membranes. Specific binding of wVTG to the membranes was temperature-dependent, proportional to the amount of membrane, and saturable. Scatchard analyses revealed a single class of binding sites of low maximum binding capacity (MBC; -35 pmol VTG/mg membrane protein) and high affinity (Kd -400 nM), consistent with wVTG levels (540-2700 nM) circulating in maturing females. Ligand blotting revealed a receptor protein of Mr -157 000 and a smaller protein, possibly its degradation product. Striped bass vitellogenin, chicken egg yolk very low density lipoprotein, and suramin displaced wVTG from its receptor, but BSA did not. No change in Kd was noted over the course of vitellogenesis in maturing perch, and MBC increased only slightly very late in the gametogenic cycle. The wVTG bound specifically to membranes prepared from liver, muscle, and mesenteric fat, but not to erythrocyte membranes. The Kd for ovary (394 nM) and liver (345 nM) were similar, but the Kd for muscle (1440 nM) was much higher.

The Bacillus stearothermophilus disk assay for penicillin in milk (AOAC official method) was adapted for the determination of ampicillin in fish muscle. The method was evaluated in 2 species of cultured fish: channel catfish and striped bass. Recoveries of ampicillin ranged from 99 to 104% when muscle specimens from both species were spiked at concentrations of 0.025-1.00 μg/g. The lower limit of determination (LOD) was 0.025 μg/g. The assay was applied to monitor the elimination of ampicillin from the muscle of striped bass after intravascular administration (dosage of 10 mg/kg body weight). The mean concentrations in the muscle declined from 1.160 μg/g at 2 h to 0.063 μg/g at 18 h. The half-life of ampicillin in the muscle was 3.6 h. Ampicillin concentrations were below LOD at 24 h. No inhibitory activity was observed in the muscle of control fish.

After the collapse of striped bass Morone saxatilis stocks in the late 1970s, hatchery programs and release experiments were instituted to evaluate the potential to restore striped bass in Chesapeake Bay. Because survival of striped bass larvae to first feeding (7 d after hatch) is low in Chesapeake tributaries, ranging from 0.2 to 5.2% of eggs spawned, it is possible to enhance survival through hatchery propagation of eggs and yolk-sac larvae, and it may be feasible to supplement recruitment by stocking post-yolk-sac larvae. During 1991-1993, otoliths of 31.7 million hatchery-produced striped bass larvae (5-13 d after hatch) were chemically marked and released into two tributaries of Chesapeake Bay. In years of moderate to poor natural larval production (1991, 1992), stocked larvae contributed 20 to 30% to overall juvenile abundance. In 1993, a year of high natural production, stocked larvae contributed only 5% to juvenile abundance, although numbers contributed were higher than in previous years. Using field and hatchery estimates of larval and juvenile growth and mortality, enhancement strategies were compared in which fish were released at three different ages: larvae (7 d post-hatch), summer-stocked juveniles (55 d post-hatch), or fall-stocked juveniles (220 d post-hatch). Based upon hatchery records, reared larvae and juveniles experienced substantially higher rates of growth and survival than did wild larvae and juveniles of similar age. In years of low natural egg production, cohort biomass at 220 d post-hatch was highest when juveniles were stocked in summer or fall. When approximate costs were incorporated into the analysis, the efficacy of stocking 7-d-old larvae was higher than summer and fall stocking of juveniles if stocked larvae encountered favourable conditions. In years of poor natural recruitment, stocking post yolk-sac larvae into estuarine tributaries could supplement stocks of striped bass and possibly other anadromous species which experience high embryo and yolk-sac larva mortality.

Fishes released from constraints of their previous thermal history tend to limit thermal exposure to a narrow range of temperatures. Thermoregulatory behavior (final preferendum) is a stable characteristic of each species studied, suggesting strong regulation by natural selection. However, the adaptive significance of the final preferendum has not been documented for most species. Species with wide geographic distributions, such as bluegill sunfish and largemouth bass exhibit constant laboratory final preferenda regardless of their geographic origin or thermal histories. This apparent evolutionary anomaly of the final preferendum requires further study. It is no longer adequate to describe responses of fish to thermal gradients, rather falsifiable hypotheses concerning adaptive relations between thermoselection, and physiological, biochemical, life-history and genetic correlates must be developed and tested experimentally.

1. 1. We have succeeded in cultivating Babesia (Piroplasma) canis in two out of four attempts, following the method of Bass , using blood and glucose, and incubating at 37° C. 2. 2. In one of these cultures, starting with heart blood containing corpuscles infected with one, two or, exceptionally, four piroplasmata, we succeeded in obtaining a maximum of 32 merozoites in a corpuscle. 3. 3. Various types of Babesia were seen in these cultures, namely, pyriform, amceboid, rounded and oval parasites. Division of rounded forms was observed following the method of gemination with chromatinic forking. There was evidence, in stained specimens, of direct binary fission. 4. 4. Haemolysis occurred in all the culture tubes. 5. 5. A puppy was successfully inoculated from a 41 hours' culture, and succumbed to piroplasmosis on the fifth day. 6. 6. B. canis is not so easily cultivated by Bass's method as the malarial parasites of man.

To study the efficacy of chemical larvicides; several materials were evaluated in two warm-water southern California artificial lakes, (Lake Calabasas and Westlake) and the residues of an effective larvicide (chlorpyrifos) in various components of one of the lakes were investigated. Abate® ( O,O' -(thiodi- p -phenylene) O,O,O',O' -tetramethyl phosphorothioate) gave excellent control of Chironomine midges ( Chironomus and Dicrotendipes spp.) but only mediocre or poor control of the smaller Tanypodine midges ( Cricotopus and Tanypus spp.). Carbaryl yielded poor control of both groups, and fenitrothion yielded good control of both groups at a higher rate of application. Chlorpyrifos gave excellent control of both groups of midges. It was more effective against the Chironomine larvae. This material at 0.2 lb active ingredients per acresurface yielded complete control of Chironomine midges for 12 weeks or longer, but suppressed the Tanypodine larvae for only 7–8 weeks. Residues of chlorpyrifos (used as 2% granules) were generally higher in the bottom water, even though maximum residues in both layers reached 0.6 ppb. Residues were much higher in the mud, reaching a mean maximum of 0.3 parts per million in the top 1-inch section of mud samples, but only traces were found in the remaining section of the mud. Maximum residues in water were obtained one day after treatment, declining to below 0.1 ppb within 4 weeks after treatment. The maximum residues in the mud were obtained one week after treatment, declining to below 0.1 ppm in 28 days. Slightly higher levels of residues were found in water and mud when the whole lake was treated. Bottom-dwelling and -frequenting fish, such as channel catfish ( Ictalurus punctatus Rafinesque) and, to some extent, black crappie ( Pomoxis nigromaculatus LeSueur), contained much higher quantities of chlorpyrifos than the nonbottom dwelling fish such as largemouth bass ( Micropterus salmoides Lacepede) and bluegill ( Lepomis microchirus Rafinesque). Mean maximum residues in channel catfish and black crappie were 0.8 and 0.5 ppm after 3 and 2 weeks posttreatment, respectively, declining to barely detectable levels 25 days after treatment. The residues in largemouth bass and bluegill were minimal, with maximum approaching 0.2 ppm but remaining 0.1 or below this level most of the time.

A little brown bat ( Myotis lucifugus lucifugus ) was found in the water of Western Lake Erie near Put-in-Bay on South Bass Island. When discovered it was approximately 200 feet from the shoreline of Gibraltar Island at the …

The effects (beneficial or detrimental) of insecticides on the morphology and physiology of crop plants are poorly understood. Plant growth has been shown to be inhibited by some insecticides (Arthur and Arant 1954) and plant yields have been increased by others (Wressell and Driscoll 1964). Wheeler and Bass (1971) reported that phorate, carbofuran, methomyl, and disulfoton, when applied to soybeans, did not affect germination, number of mature pods per plant, or yield. They did report, however, that soybean plants were taller in plots treated with methomyl and carbofuran. The following experiment was conducted in order to clarify some of the findings of Wheeler and Bass.