Tissue essential fatty acid composition and competitive response to dietary manipulations in white bass (Morone chrysops), striped bass (M. saxatilis) and hybrid striped bass (M. chrysopsxM. saxatilis)

The effects of wide changes in dietary levels of docosahexaenoic (DHA) or arachidonic (ArA) acids on growth, survival and fatty acid composition in body tissues of Morone larvae were examined. White bass (WB, Morone chrysops), striped bass (SB, Morone saxatilis) and sunshine hybrid bass (HSB, M. chrysopsxM. saxatilis) larvae (day 24-46) were fed Artemia nauplii enriched with algal sources of varying proportions of DHA and ArA (from 0 to over 20% of total fatty acids). WB larvae fed DHA-deficient Artemia diet retarded over 50% of their potential growth, however, increasing dietary DHA/ArA ratios were associated with a significant growth improvement. The highest proportion of polyunsaturated fatty acids was found in WB neural tissue (approx. 50% of total fatty acids), while HSB neural tissue contained the highest proportion of saturated fatty acids (approx. 35% of total fatty acids). Within the neural tissues of all Morone larvae, both DHA and ArA were generally the most dominant as well as the most responding fatty acids to dietary manipulations (except in WB fed DHA or ArA deficient diets). HSB neural tissue was particularly efficient in retaining a significant amount of DHA in the face of dietary deficiency. However, WB neural tissue was the most responsive to dietary increase in DHA, accumulating a significantly higher amount of DHA (P<0.05) than SB or HSB. Results demonstrate significant differences in fatty acid composition and growth responsiveness to dietary manipulations between Morone larvae species and within specific tissues. WB weight gain and neural tissue composition was affected most by dietary changes in both DHA and ArA whereas SB and HSB tissue compositions were generally less affected by dietary manipulations.     

Comparative severity of experimentally induced mycobacteriosis in striped bass Morone saxatilis and hybrid tilapia Oreochromis spp

Twenty striped bass Morone saxatilis and 20 hybrid tilapia Oreochromis niloticus x O. mossambicus x O. aureus each received a single intramuscular injection of 1.6 x 10(6) colony forming units per gram body weight of Mycobacterium marinum. Striped bass manifested significantly greater clinical and microscopic disease compared to tilapia. Whereas all the striped bass had died or were clinically ill by Day 8 post-infection, there was no apparent disruption of normal behaviour, physical appearance, or growth in any of the sacrificed or surviving tilapia. Histologically, granulomas in striped bass were generally larger and less discrete, with a higher proportion of heavily vacuolated macrophages, and large cores of necrotic cells. Visceral granulomas in tilapia were smaller, with a higher proportion of epithelioid macrophages, more pigment-containing cells, more peripheral lymphocytes, and virtually no central necrosis. Visceral granulomas were 18-fold more numerous in striped bass than in tilapia. Based upon histomorphometric data, mean proportions of acid-fast bacteria within pronephros granulomas were 4-fold greater in striped bass than tilapia, and striped bass granulomas averaged more than twice as large as tilapia granulomas. In the anterior kidney of striped bass, a positive correlation existed between mean mycobacterial proportions and mean necrosis scores. In tilapia, mean mycobacterial proportions correlated negatively with mean granuloma numbers, whereas there was no correlation between these parameters in striped bass. Results suggest that intrinsic functional differences in the immunologic systems of striped bass and hybrid tilapia may contribute to inter-species variation in mycobacteriosis susceptibility.     

Comparative analysis of mycobacterial infections in wild striped bass Morone saxatilis from Chesapeake Bay

During an ongoing epizootic of mycobacteriosis, wild striped bass Morone saxatilis from Chesapeake Bay were analyzed using 3 methods for detection of either mycobacterial infection or associated granulomatous pathology. The specific detection techniques, which utilized aseptically collected splenic tissue, were histology, quantitative culture and nested PCR. Based on analysis of 118 samples, detection of infection differed significantly between the 3 methods (chi-square, p = 0.0007). Quantitative culture and nested PCR detected similar, higher rates of infection (69 and 75%, respectively) than the histological method (52%). Although primary PCR assays for a 924 to 940 bp segment of the mycobacterial 16S rRNA gene were positive for genomic DNA from mycobacterial cultures, a secondary, nested PCR reaction for an internal 300 bp gene segment was required in order to detect mycobacteria within splenic tissue. A similar rate of mycobacterial infection was present in fish collected from all sites tested. Although all detection methods found that striped bass age 4.0 to 4.9 yr had the highest positive incidence, nested PCR detected a higher frequency of mycobacterial infection in fish > or = 6.0 yr of age than the other 2 methods. Quantitative bacteriology was a more sensitive detection technique when the fish tissue contained < or = 10(3) mycobacteria g(-1).     

The glutathione-dependent system of antioxidant defense is not modulated by temperature acclimation in muscle tissues from striped bass,Morone saxatilis

Cold temperature generally induces an enhancement of oxidative capacities, a greater content of intracellular lipids, and a remodeling of lipids in biological membranes. These physiological responses may pose a heightened risk of lipid peroxidation (LPO), while warm temperature could result in greater risk of LPO since rates involving reactive oxygen species and LPO will be elevated. The current study examines responses of the glutathione system of antioxidant defense after temperature acclimation. We measured total glutathione (tGSH), and protein levels of GPx1, GPx4, and GST (cardiac and skeletal muscles), and enzymatic activity (skeletal muscle) of glutathione-dependent antioxidants (GPx, GPx4, and GST) in tissues from striped bass (Morone saxatilis) acclimated for six weeks to 7 °C or 25 °C. tGSH of cardiac muscle from cold-acclimated animals was 1.2-times higher than in warm-bodied counterparts, but unchanged with temperature acclimation in skeletal muscle. A second low molecular weight antioxidant, ascorbate was 1.4- and 1.5-times higher in cardiac and skeletal muscle, respectively in warm- than cold-acclimated animals. Despite 1.2-times higher oxidative capacities (as indicated by citrate synthase activity), in skeletal muscle from cold- versus warm-acclimated fish, levels and activities of antioxidant enzymes were similar between acclimation groups. Lipid peroxidation products (as indicated by TBARS), normalized to tissue wet weight, were more than 2-times higher in skeletal muscle from cold- than warm-acclimated animals, however, when normalized to phospholipid content there was no statistical difference between acclimation groups. Our results demonstrate that the physiological changes, associated with acclimation to low temperature in the eurythermal striped bass, are not accompanied by an enhanced antioxidant defense in the glutathione-dependent system.     

Maturation and fecundity of a stock-enhanced population of striped bass in the Savannah River Estuary, U.S.A

The striped bass Morone saxatilis population in the Savannah River (south-eastern U.S.A.) collapsed in the 1980s, and recent eorts to restore the population have resulted in increased catch-per-unit-eort (CPUE) of striped bass in the Savannah River Estuary (SRE). The abundance of eggs and larvae, however, remain well below historic levels. The primary cause of the population decline was remedied, and environmental conditions seem suitable for striped bass spawning. Regression analysis of data derived from ultrasonic imaging of 31 striped bass resulted in a statistical model that predicted ovary volume well (r²=0.95). The enumeration of oocytes from ovarian tissue samples and the prediction of ovary volume allowed fecundity to be estimated without sacrificing the fish. Oocyte maturation in Savannah River striped bass seemed to progress normally, with oocytes developing to final stages of maturity in larger fish (>750 mm L _T). Additionally, fecundity estimates were comparable to a neighbouring striped bass population. The environmental cues needed to trigger development and release of striped bass oocytes into the SRE appeared to be present. If most of the striped bass females in the SRE are still young (<7 years), the ability to produce large numbers of eggs will be limited. As these young fish mature, egg production probably will increase and the density of striped bass eggs eventually will approach historic levels, provided suitable habitat and water quality are maintained.     

Apolipoprotein A-I from striped bass (Morone saxatilis) demonstrates antibacterial activity in vitro

HDL and apolipoprotein A-I from teleostean fishes demonstrate in vitro activity against gram-positive and gram-negative bacteria. In this study, we purified ApoA-1 from striped bass (Morone saxatilis) plasma and examined its in vitro antibacterial activity against Streptococcus sp., Escherichia coli, and Mycobacterium marinum. In addition, we obtained sequence for a putative striped bass ApoA-1 gene, which when translated contained the identical sequence generated from N-terminal sequencing of the purified ApoA-1. The predicted secondary and tertiary structures contained the characteristic proline residues and high alpha-helical content conserved between mammals and fishes. Purified ApoA-1 exhibited antibacterial activity against the bacteria assayed. Concentrations of 125 microg/mL for E. coli, 250 microg/mL for Streptococcus sp., and 250 microg/mL for M. marinum, inhibited bacterial growth by 50% compared to control. ApoA-1 plasma concentrations in experimental and wild fish ranged from undetectable levels to greater than 5 mg/mL, indicating that striped bass ApoA-1 is an effective antibacterial agent at concentrations below the range of physiological concentrations in striped bass plasma. We therefore conclude that ApoA-1 could play a role in innate defense against bacterial pathogens in striped bass.     

Responses of hybrid striped bass to waterborne and dietary copper in freshwater and saltwater

Mechanisms of copper toxicity and consequences of exposure vary due to uptake route and ionoregulatory status. The goal of this research was to develop a model fish system to assess the influence of different Cu exposure routes (waterborne or dietary) on bioavailability, uptake, and effects in hybrid striped bass (Morone chrysops x Morone saxatilis) acclimated to fresh- or saltwater. Initially, hybrid striped bass were exposed to dietary Cu concentrations of 571, 785, and 1013 mug Cu/g, along with a control (approximately 5 microg Cu/g), for 14 days in saltwater. Intestinal and liver Cu accumulated in a dose-dependent manner in fish exposed to increasing levels of dietary Cu. Chronic (42 days) experiments were then conducted to determine sub-lethal effects of aqueous, dietary, and combined aqueous and dietary Cu exposures to both freshwater- and saltwater-acclimated hybrid striped bass. Growth and Cu accumulation in the gill, intestine, and liver were measured. Although no significant effects were observed in fish exposed to waterborne Cu, those exposed through the diet accumulated significant liver and intestinal Cu but showed no significant change in growth. Overall, these results suggest that at the levels tested, exposure to elevated waterborne Cu did not cause significant long-term tissue Cu accumulation, whereas dietary Cu exposure caused significant liver and intestinal Cu accumulation in hybrid striped bass which was comparable in both freshwater and saltwater (15 g/L).     

Lipid and fatty acid composition of striped bass (Morone saxatilis) larvae during development

Changes in lipid class, fatty acid composition, protein, and dry and wet weights of fertilized eggs and developing larvae of striped bass (Morone saxatilis) fed with the live food, Artemia, were investigated. A decrease of wet and dry weights and moisture was observed at the beginning of the larval stage. Larvae regained the original moisture level, and wet and dry weights increased steadily after feeding. Total lipids decreased from 190 μg/egg in fertilized eggs to 151 μg/egg during hatching and increased after feeding. When total lipid contents were expressed as a percentage of larval dry weight, a decline of lipid did not occur until after feeding. Total protein, on the other hand, increased right after feeding, but there was some variation between days. Polar lipids increased significantly from 20 μg/egg at the egg stage to 199 μg/larva at 26 days post-hatching (DPH), 2 days before the onset of metamorphosis, while neutral lipids declined from 175 μg/egg to 80 μg/larva during the same time period. Wax/steryl esters decreased from 150 μg/egg in fertilized eggs to 32 μg/larva at 26 DPH. Triacylglycerols dropped from 21 μg/egg to 15 μg/larva before feeding and increased gradually after feeding. In contrast, the level of cholesterol increased 2–3-fold. There was a significant increase of phospholipids, particularly phosphatidylcholine in larvae after feeding. The fatty acid composition of fish larvae was significantly influenced by the diet, Artemia. There was an indication of catabolism of endogenous eicosapentaenoic and docosahexaenoic acids during metamorphosis.     

Role partitioning of swimming musculature of striped Bass Morone saxatilis Walbaum and Bluefish, Pomatomus saltatrix L.

Electromyography was used to determine the functional roles of the axial musculature in striped bass and bluefish at imposed swimming velocities. The lateral red muscle powers propulsive movements at all sustainable swimming speeds in both species. The amplitude and frequency of EMG's from the red muscle grade with increasing swimming velocity. The white muscle, forming the main mass of the myotome, is reserved for high-speed burst swimming above maximum sustainable speeds. The proportion of the myotome occupied by the red muscle at the level of the caudal peduncle is 10.9% and 18.6% for the striped bass and the bluefish respectively.     

Determination of factors influencing stomach content retention by striped bass captured using gillnets

The influence of mode of capture, season of capture and total body length ( L _T) on the probability of regurgitation for striped bass Morone saxatilis captured using gillnets in Smith Mountain Lake, Virginia, was examined. Overall, the mean rate of regurgitation for striped bass which contained food contents in their stomach was 8·3%. Striped bass captured by wedging had a higher mean regurgitation rate (17%) than individuals that were either entangled (5%) or gilled (2%). Striped bass caught during the autumn had approximately the same frequency of regurgitation as individuals captured during the summer (10 v . 9%), but these regurgitation rates were higher than those observed for fish during the spring sampling periods (4%). Larger striped bass were more likely to regurgitate their stomach contents than smaller individuals, with the frequency of regurgitation increasing by 0·7% for every 50 mm increase in L _T. The results of this study demonstrate the importance of identifying factors that influence regurgitation of stomach contents to minimize and account for biases associated with diet data collected from striped bass captured in gillnets. Using this information, sampling recommendations for food‐habit and feeding‐rate studies involving the collection of piscivorous fishes using gillnets are made.     

Lesion induction by the plerocercoid Lacistorhynchus tenuis (Cestoda) and wound healing in the striped bass Morone saxatilis (Walbaum)

San Francisco Bay-Delta striped bass, Morone saxatilis (Walbaum), form open lesions in response to a plerocercoid infection of Lacistorhynchus tenuis (Van Beneden, 1858) (Cestoda: Trypanorhyncha). Laboratory infection experiments showed that striped bass can be infected with the plerocercoids by ingesting infected copepods. Histological sections indicated that a cellular host response was mounted early in the infection period, and that despite the leucocytic infiltration the parasites continued to develop. However, at 3 months post-infection some of the plerocercoids began to degenerate, and lesions formed at this time and 14 months post-infection. Open lesions in adult striped bass collected from the field took 2 months to heal and were detectable for at least 22 months. Regeneration of the muscle tissue did not occur although the wound completely healed externally.     

Development and use of striped bass-specific RFLP probes

We sought to develop nuclear DNA (nDNA) probes which could be used to complement mtDNA and DNA fingerprinting markers in distinguishing striped bass, Morone saxatilis (Walbaum), from discrete spawning systems. Restriction endonuclease-generated single copy, 10–20-kb striped bass nuclear nDNA fragments were cloned into the bacteriophage vector Lambda Dash II and tested in Southern blot analyses for their abilities to reveal population-specific polymorphisms. Three of the I7 nDNA sequences tested exhibited polymorphisms which potentially could be used to delineate striped bass populations. One probe, DSB 22, revealed significant genotypic frequency differences between Gulf of Mexico and Atlantic striped bass and among striped bass representative of some Atlantic systems. These preliminary results suggest that single copy nDNA sequences may provide sufficient polymorphisms to aid in stock identification of species which proved genetically monomorphic using other approaches.     

Mycobacteriosis in cultured striped bass from California

Striped bass (Morone saxatilis) juveniles raised in an intensive culture system had chronic mortality resulting from infections with Mycobacterium marinum. Approximately one-half of a population of 900 yearlings succumbed to the disease and 80% of those remaining were infected. The bacteria were isolated on Petrignani's medium after 7 days at 25 C and subcultures grew at temperatures from 20 to 37 C. The disease was characterized by systemic nodular lesions in all major organs. Older tubercles contained numerous acid-fast bacilli. Chemotherapy by feeding rifampin (6 mg/100 g of food for 60 days) was not an effective treatment. Subclinical mycobacteriosis in adult striped bass may be the source for vertical transmission to their progeny.     

Interactions between bluefish and striped bass: Behavior of bluefish under size- and number-impaired conditions and overlap in resource use

A decline in bluefish (Pomatomus saltatrix L.) recreational landings during the 1990s and the early 2000s led to multiple theories on the ultimate cause. One theory was that a large portion of the bluefish population moved offshore and was unavailable to nearshore recreational fishers; one reason given for the movement offshore was increased competition with striped bass (Morone saxatilis W.). We conducted laboratory experiments (feeding and non-feeding) to examine behavioral interactions between adult bluefish and sub-adult striped bass in a large (121,000 L) research aquarium. Additionally, we examined diet and habitat overlap of bluefish and striped bass from the fall and spring bottom trawl surveys conducted by the National Marine Fisheries Service. Observations of feeding trials for the following treatments were made: non-impaired (i.e., same number and size of bluefish and striped bass), size-impaired (i.e., large striped bass/small bluefish), number-impaired (i.e.,10 striped bass/3bluefish), and single-species controls. Within a species, there was no difference in a variety of behavioral measures (e.g., attack rate, capture success, ingestion rate, and activity) between mixed- and control treatments under non-impaired or size-impaired conditions. However, behavior of number-impaired bluefish differed from control and size-impaired fish suggesting that striped bass may have a negative influence on bluefish foraging when bluefish are “out-numbered”. Feeding had a strong effect on swimming speeds for both species. Diet and habitat overlap between bluefish and striped bass in continental shelf waters was low. Overall, foraging behavior in mixed-species treatments and field observations suggest no competitive interactions between adult bluefish and sub-adult striped bass.     

Metabolic responses to acute handling by fingerling inland and anadromous striped bass

Fed and 3-day fasted inland (average mass: 6.97 g) and anadromous (average mass: 6.54 g) striped bass Morone saxatilis fingerlings were held in dipnets above water for 5 min in groups of six. Severity of the response to this handling was measured by whole-body glucose, glycogen, and lactic acid in non-handled bass (considered control level), and then at 30 min, 1, 6, 12, 24 and 48 h recovery. At resting levels, both fed and fasted inland bass showed significantly higher concentrations of the whole body variables than anadromous bass. All four groups of bass showed an increase in lactic acid and glucose immediately after handling, with a concomitant decrease in glycogen. Peak levels of glucose and lactic acid were similar in the four groups. Fasting did not have an effect on the glucose and lactic acid responses, but did affect the glycogen response. The two fasted groups did not return to control glycogen concentrations during the 48-h recovery period. By 48 h, both glucose and lactic acid had returned to control levels. It is concluded that inland and anadromous strains of fingerling striped bass do not differ in their sensitivity to an acute handling stress. Recovery of glycogen energy stores following handling is much better if fish are not fasted before handling.     

Osmoregulatory effects of hypophysectomy and homologous prolactin replacement in hybrid striped bass

The effects of ovine prolactin (oPRL) and striped bass prolactin (sbPRL; Morone saxatilis) on plasma osmolality, electrolyte balance, and gill Na(+),K(+)-ATPase activity were investigated in hypophysectomized (Hx), freshwater (FW)-acclimated, hybrid striped bass (M. saxatilisxMorone chrysops). They were kept in dilute (isoosmotic) seawater for about 10 days after surgery. Seven days after transfer to FW, Hx fish had lower plasma osmolality and lower levels of Na(+), Cl(-), and Ca(2+) than sham-operated and intact fish. Fish were injected four times with oPRL (1, 5, or 20 microg/g body mass), sbPRL (10 or 100 ng/g), or hormone vehicle (0.9% NaCl) at 48-h intervals (days 0, 2, 4, and 6) in FW and then sampled for blood plasma 24 h after the fourth injection (day 7). In Hx fish, oPRL (5 and 20 microg/g) and sbPRL (10 and 100 ng/g) were effective in maintaining plasma osmolality and levels of Na(+), Cl(-), and Ca(2+) above values seen in saline-injected controls. Hypophysectomy did not affect branchial Na(+),K(+)-ATPase activity, but enzyme activity was significantly reduced in Hx fish receiving oPRL (20 mug/g) or sbPRL (10 or 100 ng/g). These results indicate that PRL acts to maintain plasma osmotic and ionic balance in FW-adapted hybrid striped bass, and that this may involve downregulation of branchial Na(+),K(+)-ATPase activity.     

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

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

Chemical composition and oxidative stability of flax, safflower and poppy seed and seed oils

Three seeds of Turkish origin, flax, poppy and safflower were analyzed for their proximate, fatty acids, tocols (tocopherols and tocotrienols) and total phenolic composition, and oxidative stability of their oil. The major fatty acid in the flax oil was alpha-linolenic acid, comprising 58.3% of total fatty acids, whereas poppy and safflower oils were rich in linoleic acid at 74.5% and 70.5% level, respectively. The amount of total tocols was 14.6 mg/100g flax, 11.0mg/100g poppy and 12.1mg/100g safflower seed. Flax and poppy oil were rich in gamma-tocopherol as 79.4 mg/100g oil and 30.9 mg/100g oil, respectively, while alpha-tocopherol (44.1g/100g oil) was dominant in safflower oil. Only alpha- and gamma-tocotrienol were found in the oils. Oxidative stability of oils was measured at 110 degrees C at the rate of 20 L/h air flow rate, and poppy oil (5.56 h) was most stabile oil followed by safflower oil (2.87 h) and flax oil (1.57). There were no correlation between oxidative stability and unsaturation degree of fatty acids and tocol levels of the oils. All of the seeds investigated provide a healthy oil profile and may have potential as a source of specialty oils on a commercial scale.     

Comparison of lipid content and fatty acid composition in muscle and liver of two notothenioid fishes from Admiralty Bay (Antarctica): an eco-physiological perspective

During Antarctic summer, total lipids (g/100 g dry matter) in Notothenia coriiceps (n=18) and Lepidonotothen nudifrons (n=10) were low (6.1 and 4.7 in muscle), which is typical of Antarctic benthic species. The liver of female N. coriiceps was heavier and contained more lipids per dry weight than the liver of males. The fatty acid composition of N. coriiceps and L. nudifrons was dominated by polyunsaturated fatty acids (PUFA, respectively, 44 and 49% of total fatty acids in muscle, 31 and 46% in liver), which included primarily C20:5n-3 (18 and 19% in muscle, 13 and 18% in liver) and C22:6n-3 (15 and 19% in muscle, 12 and 20% in liver). In L. nudifrons, the levels of some unsaturated fatty acids increased with age and size. The high percent unsaturation (PUFA+MUFA, 78 and 80% in muscle, 82 and 80% in liver) is a response to low water temperature (-0.4°C). Fish fatty acid profiles reflect fatty acid profiles of the diet (amphipods, macroalgae and fish).