Differentiation of striped bass, Morone saxatilis (Walbaum), from a hybrid: effectiveness of training

Abstract The ability of consumers and fishermen to distinguish-between wild striped bass, Morone saxatilis (Walbaum), and its hybrids may be important to marketing farm-raised fish and managing wild stocks. The ability of randomly selected persons to distinguish between wild and hybrid specimens was examined and it was found that a significant improvement in recognition occurred with only minimal training. Average correct response of 70% without training rose to nearly 90% after training. Moreover, the respondents' sex and age were important factors in determining successful identification.     

Physiology of seawater acclimation in the striped bass,Morone saxatilis (Walbaum)

Several experiments were performed to investigate the physiology of seawater acclimation in the striped bass, Morone saxatilis. Transfer of fish from fresh water (FW) to seawater (SW; 31–32 ppt) induced only a minimal disturbance of osmotic homeostasis. Ambient salinity did not affect plasma thyroxine, but plasma cortisol remained elevated for 24h after SW transfer. Gill and opercular membrane chloride cell density and Na⁺,K⁺-ATPase activity were relatively high and unaffected by salinity. Average chloride cell size, however, was slightly increased (16%) in SW-acclimated fish. Gill succinate dehydrogenase activity was higher in SW-acclimated fish than in FW fish. Kidney Na⁺, K⁺-ATPase activity was slightly lower (16%) in SW fish than in FW fish. Posterior intestinal Na⁺,K⁺-ATPase activity and water transport capacity (J_v) did not change upon SW transfer, whereas middle intestinal Na⁺,K⁺-ATPase activity increased 35% after transfer and was correlated with an increase in J_v (110%). As salinity induced only minor changes in the osmoregulatory organs examined, it is proposed that the intrinsic euryhalinity of the striped bass may be related to a high degree of “preparedness” for hypoosmoregulation that is uncommon among teleosts studied to data.     

Transmission of infectious pancreatic necrosis virus in striped bass, Morone saxatilis (Walbaum)

Abstract. Infectious pancreatic necrosis virus (IPNV) did not cause increased mortality in experimentally challenged striped bass, Morone saxatilis (Walbaum). Fry became transiently infected after waterborne challenge but fingerlings were resistant to that route. However, striped bass fingerlings readily became chronic virus carriers following ingestion of IPNV-contaminated food. Vertical transmission was not demonstrated using either IPNV-carrier striped bass adults or IPNV-exposed sex products.     

Reproduction of striped bass, Morone saxatilis (Walbaum), broodstock: monitoring maturation and hormonal induction of spawning

Abstract Levels of gonadal steroid hormones were quantified in an adult striped bass, Morone saxatilis (Walbaum), broodstock during their gametogenic cycle. Blood plasma concentrations of Estradiol (E₂) and testosterone in females, or 11-ketotestosterone(11-KT) and testosterone (T) in males, were used as indicators of maturation. In both sexes, hormone levels were low in summer but increased significantly by late October to intermediate levels which were then maintained until late January. They then increased again rapidly to maximum pre-spawning values attained in late February or March, and subsequently decreased during the spawning period (April and May) with an increased incidence of spent fish with low hormone levels. The changes in blood hormone concentrations coincided with annual changes in photoperiod and water temperature that may be useful landmarks for maturation in captive broodstock. Mature females were implanted with pellets containing a dose of approximately 20 μg/kg body weight of [D-Ala⁶-Pro⁹-Net]-LHRH (GnRHa) in a matrix of cholesterol (CH) and cellulose. In April, they had not yet begun final oocyte maturation (FOM) and were too immature for conventional induction of spawning by injection with human chorionic gonadotropin (hCG). In early April, females given two 95% CH (slow hormone-release) GnRHa pellets (95/95) or females given one 80% CH (fast hormone-release) GnRHa pellet and one 95% CH GnRHa pellet (80/95) spawned within 13 days treatment (n= 4) with good egg fertility (76 ± 7% of total) and hatch rates (62 ± 15% of fertile). Females given dual fast-release GnRHa pellets (80/80) or control (Sham) pellets did not spawn or show evidence of increased oocyte diameter or development. In late April, four of six females given the 80/95 GnRHa pellet combination spawned within 9 days. Three fish produced fertile eggs (54 ± 18%). one spawned overripe eggs, and the remaining two increased oocyte diameter and maturation. Three corresponding controls did not spawn, and two of these showed clear signs of atresia within 11 days. In early May, some females were undergoing early FOM and were mature enough to be spawned by hCG injection. Three were given a single 80% CH GnRHa pellet and spawned within 6 days of treatment to produce fertile eggs (44 ± 6%). Of two other females given dual 80% CH GnRHa pellets, one spawned infertile eggs and the other failed to spawn within 9 days. GnRHa implants show promise as a technique for inducing spawning of captive striped bass broodstock although the optimum hormone delivery systems, dosages and release rates should be verified for fish at specific maturational stages.     

The effects of dissolved gas supersaturation on larval striped bass, Morone saxatilis (Walbaum)

Abstract. Gas bubble disease in larval striped bass, Morone saxatilis (Walbaum), was characterized by overinflation of the swimbladder and the formation of intestinal bubbles. This accumulation of gas hindered normal swimming of the fish and in extreme cases resulted in floating fish. As gas accumulated in the gut, the inner mucosal lining was compressed down into a cuboidal epithelium and in more advanced cases nearly the entire digestive tract was reduced to a squamous inner epithelium surrounded by a thin serosa. A significant increase in swimbladder volume was observed at total gas pressures as low as 102.9% and mortality was increased at 105.6-106.0%. The older larvae (30-day-old) were less sensitive to gas supersaturation than 10- to 19-day-old larvae.     

The culture, zooplankton dynamics and predator-prey interactions of Chesapeake Bay striped bass, Morone saxatilis (Walbaum), in estuarine ponds

Abstract. Four 0.05-ha research ponds were filled with brackish water (12 ppt) for the purpose of evaluating zooplankion dynamics and predator-prey interactions. Three of the ponds were stocked with Chesapeake striped bass, Morone saxatilis (Walbaum). All ponds were fertilized to stimulate zooplankton blooms using a protocol that has been successful in freshwater systems. Zooplankton was dominated by four major groups: rotifers, copepod nauplii, Eurytemora adults and Eurytemora copepedites with rotifers and the nauplii being the most abundant organisms found. Rotifer populations peaked 15-20 days after filling while the copepods peaked 17-22 days after filling. Fish production was very similar to that found in freshwater ponds with an average yield of 84.4 kg/ha (2.0 kg/ha/day) for phase 1 fish (=45mm). Food selectivity indices indicated striped bass avoided both rotifers and copepod nauplii and preferred adult and copepedite Eurytemora as a food item. However, due to various problems associated with sampling, these selectivity results should be considered with caution. The findings of this study reveal fertilization regimes used successfully in freshwater production systems can be applied in an estuarine environment.     

Survival of juvenile striped bass (Morone saxatilis) and Morone hybrid bass (Morone chrysops × Morone saxatilis) increased by addition of calcium to soft water

CaCl₂ was used to increase the total hardness of water in three ponds from 20 to 45–100 mg/l as CaCO₃ 5 days before harvest. CaCl₂ was also used to increase hardness from 10 to 70–200 mg/l as CaCO₃ in water used for holding and transporting fish after they were harvested from ponds. All groups of fish in water containing additional calcium had 80–99% survival compared with 16% survival for a group of fish without additional calcium in the water before or after harvest. Addition of 1% NaCl to the water did not increase survival.     

Infections with Philometra sp. associated with mortalities in wild-hatched captive-raised striped bass, Morone saxatilis (Walbaum)

The striped bass, Morone saxatilis (Walbaum), once represented an important resource for fisheries in the St Lawrence River (Quebec, Canada). A restoration programme, involving captive propagation, was implemented with the objective of restocking the population, which had disappeared in the late 1960s. An unusually high rate of mortality was observed during the winter of 2006 in captive-raised fingerlings that were originally collected from the Miramichi River (New Brunswick, Canada) the previous summer. Post-mortem examinations revealed extensive granulomatous and hyperplastic peritonitis associated with numerous nematodes of the genus Philometra. Given the severity of the lesions, high intensity of infection by Philometra sp. was presumed to be the primary factor in the unusual mortalities reported that winter. Observations suggest that this nematode, which was acquired in the wild, cannot establish itself in a captive environment, most likely because of the absence of the obligate intermediate host. Examination of archived specimens of striped bass showed that this parasite was probably present in the St Lawrence River population prior to its extirpation. Consequently, the introduction of infected fish into this ecosystem should not be a concern. Nevertheless, infection-related mortalities of fingerlings might affect dynamics of wild striped bass populations.     

Purification,characterization and immunoassay of striped bass (Morone saxatilis) vitellogenin

The egg yolk precursor, vitellogenin (VTG), was purified from blood plasma of striped bass by chromatography on hydroxylapatite or DEAE-agarose. The fish were first implanted with estradiol-17β (E₂), which induced vitellogenesis. A rabbit antiserum (a-FSPP) raised against plasma from mature female striped bass, and then adsorbed with mature male plasma, was used to detect female-specific plasma protein (FSPP) in the chromatography fractions. Striped bass VTG (s-VTG) was collected from the peak fraction that was induced by E₂, reacted with a-FSPP, and contained all detectable phosphoprotein. It appeared as a single band (M_r ≂ 170,000) in SDS-PAGE or Western blots using a-FSPP, and as a pair of closely-spaced phospholipoprotein bands in native gradient-PAGE, suggesting that there is more than one circulating form of s-VTG. The relationship of s-VTG to the yolk proteins was verified using a-FSPP. The antiserum reacted with the main peak from gel filtration of saline ovary extracts, and it specifically immunostained the two main bands in Western blots of the extracts and the yolk granules of mature oocytes. The amino acid composition of s-VTG was similar to that of VTG from other fish and Xenopus. A radial immunodiffusion assay for s-VTG was developed using a-FSPP and purified s-VTG as standard. The s-VTG was not detected in blood plasma of males, immature females, or regressed adult females, but plasma s-VTG levels were highly correlated with plasma E₂ and testosterone levels, and oocyte growth, in maturing females. The results indicate that the maturational status of female striped bass can be identified by s-VTG immunoassay.     

Induced maturation and spawning of domestic and wild striped bass, Morone saxatilis (Walbaum), broodstock with implanted GnRH analogue and injected hCG

Abstract. A domestic striped bass. Morone saxatilis (Walbaum), broodstock was established by rearing fish to sexual maturity in ponds. A method was developed to reproduce the domestic females, and also wild females too immature to be successfully induced to spawn with injected human chorionic gonadotropin (hCG). The fish were implanted with pellets containing 100–150μg of a synthetic analogue of mammalian gonadotropin reieasing-hormone, [D-Ala⁶- Pro⁹-NEt]-LHRH (mGnRHa), in a matrix of cholesterol (CH) and cellulose. They were implanted with one fast hormone-release (80% CH) pellet and one slow hormone-release (95% CH) pellet and allowed to mature for 1–3 days, until they entered the process of final oocyte maturation and were induced to ovulate or spawn with an hCG injection. The secondary hCG injection was found to be necessary to speed the maturation of the wild fish; they otherwise would succumb to the stresses of capture, handling and confinement before they could be spawned. The total mGnRHa dosages used ranged from 33 to 111μg mGnRHa/kg body weight, and the hCG doses were either 165 or 330 IU hCG/kg body weight. Using the combined mGnRHa implant-hCG injection technique, fry production rates were comparable to those obtained using fully mature wild females taken directly from their spawning grounds.     

Quantitative dietary lysine requirement of juvenile striped bass Morone saxatilis

Two feeding trials of 8 and 10 weeks each were conducted to quantify the dietary lysine requirement of juvenile striped bass, Morone saxatilis. Diets in both experiments contained approximately 420 g crude protein kg^–1 and 13.4 MJ digestible energy (DE) kg^?1. L ‐Lysine‐HCl was added to the basal diet to yield five and six treatments in the two experiments. Diets in the first experiment were determined to contain 9.2, 14.1, 14.6, 19.9 and 21.0 g available lysine kg^?1 on a dry‐matter basis. Diets in the second experiment were determined to contain 14.8, 18.1, 21.3, 24.5, 27.6 and 30.9 g available lysine kg^?1 on a dry‐matter basis. Weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and apparent nitrogen utilization (ANU) were significantly (P < 0.05) improved by increasing dietary lysine concentrations to approximately 20 g kg^?1 of diet. Least‐squares regression analysis of weight gain and SGR in the first experiment indicated a minimum dietary lysine requirement of 20.1 ± 2 g kg^?1 dry diet. Least‐squares regression analysis of the same criteria measured in the second experiment yielded the following estimates of dietary lysine requirements (g kg^?1 dry diet): 19.8 ± 2.3 for weight gain, 21.7 ± 1.5 for SGR, 23.7 ± 3.5 for FCR and 18.6 ± 1.3 for ANU. From these results the minimum recommended dietary lysine requirement for optimal growth of juvenile striped bass is approximately 21 g kg^?1 dry diet which equates to 49 g kg^?1 dietary protein or 1.57 mg kJ^?1 DE. Although higher than that reported for hybrid striped bass, this requirement level is similar to those reported for many other fish species.     

Effects of varying salinities on the toxicity of potassium permanganate to larval and juvenile striped bass, Morone saxatilis (Walbaum)

Abstract. Eight-day-old striped bass, Morone saxatilus (Walbaum) larvae, and one-month-old juveniles were held in varying salinities and exposed to a range of concentrations of potassium permanganate. Lethal concentrations of potassium permanganate for 50% of the larval fish exposed for96h (96h LC₅₀) were 1middot;02, 2 middot;11, 1 middot;41 and 1 middot;73mg/1 for salinities of 0, 3, 6and 9 g/l, respectively; The 96h LC₅₀S for juveniles were 0 middot;96, 3 middot;26, 1 middot;63 and 1 middot;48 mg/l for salinities of 0, 5, 10 and 15g/l, respectively. There were significant differences in 96h LC₅₀ values at different salinities for both life stages. The 96 h LC₅₀ values derived for both life stages revealed a decrease in toxicity as salinity increased from 0 to 3–5g/l. Results indicated potassium permanganate to be toxic in fresh water to striped bass larvae and fingerlings at recommended treatment levels (3 middot;0mg/l).     

Non-destructive measurement of sunshine bass, Morone chrysops (Rafinesque) ×Morone saxatilis (Walbaum), body composition using electrical conductivity

Abstract. We describe a rapid, non-destructive method for determining lean body mass (LBM; i.e. total body mass — total lipid mass) and lipid content in live fish. This method provides non-invasive determination of body composition by measuring the total body electrical conductivity (TOBEC) of an animal placed within a low-frequency electromagnetic field. This principle is governed by the different electrical properties of body fat and fat-free tissues. Relationships between TOBEC analysis and body composition were examined using juvenile sunshine bass (hybrid striped bass, Morone chrysops (Rafinesque) ♀× M. saxatilis (Walbaum) ♂) in a size range of 24–124g. Whole-body conductivity was significantly correlated to LBM, lipid, protein, water, and ash content. Analyses of an independent group of fish indicated TOBEC to be a reliable indicator of body composition. This method should prove useful for deriving body composition data at various phases of an experiment or a life cycle, rather than a single point in time as with destructive methods.     

杂交条纹鲈苗种培育及成鱼养殖技术

杂交条纹鲈目前有两种 ,一种为六十年代中期在美国南加州生产的“原始杂交”种即用条纹狼鲈的卵与金眼狼鲈的精子人工杂交而得 ,另一种为雌性的金眼狼鲈与雄性的条纹狼鲈杂交种“阳光鲈”。条纹鲈和杂交条纹鲈为目前美国的主要养殖鱼类之一 ,主要用于游钓业及餐饮业。杂交条纹鲈因其具有显著的杂交优势 :生长速度快、个体大、抗病力强并具有集群摄食习性 ,易驯化饲养、起捕率高 ,且肉质白嫩、无肌间刺、营养价值高等特点 ,目前己成为淡水养殖的优良品种。我国台湾、沿海省份及内陆地区都已相继引进了杂交条纹鲈。根据我省近年来养殖该鱼的经…     

Effects of light intensity, tank colour and photoperiod on swimbladder inflation success in larval striped bass, Morone saxatilis (Walbaum)

Striped bass, Morone saxatilis (Walbaum), larvae, although physoclistous as adults, initially need to inflate their swimbladders by passing ingested air through a pneumatic duct to the swimbladder. Failure to inflate the swimbladder results in swimbladder atrophy, dysfunctional buoyancy control, deformities, and poor larval survival and growth. The present investigation studied the effects of light intensity, tank colour and photoperiod on the initial swimbladder inflation success of striped bass. In the first experiment, newly hatched larvae were reared for 2 weeks in black or white 350-L circular tanks exposed to incandescent lighting at 163 or 10 lux. Larvae were fed Artemia from 6 days post-hatching (dph). The standard length, and oil globule and yolk areas were measured. Swimbladder condition and evidence of feeding were recorded. To study the effects of photoperiod on inflation, larvae were reared in black tanks exposed to either 8 h:16 h or 16 h:8 h light:dark photoperiods at 139 lux. Striped bass inflated their swimbladders between 6 and 9 dph at 17 ^oC. Inflation success was significantly higher in black tanks (65%) compared with white tanks (42%), but light intensity did not significantly affect swimbladder inflation. Larval growth and food consumption were better in black tanks, primarily because this treatment resulted in more larvae with inflated swimbladders, although larvae with uninflated swimbladders in black tanks were longer at 12 dph than larvae with inflated swimbladders in white tanks. Larvae that successfully inflated their swimbladders fed earlier and exhibited better growth than larvae with noninflated swimbladders. Larvae reared at higher light intensities used up yolk reserves faster. Exposing striped bass larvae to 8 h:16 h light:dark photoperiods resulted in higher inflation rates (55%) compared to larvae reared at 16 h:8 h light:dark photoperiods (30%). Therefore, black tanks and short photoperiods are preferable for early rearing of striped bass larvae to maximize swimbladder inflation success.