Japanese Abalone Research Articles

EFFECT OF THREE PHOTOPERIOD REGIMES ON THE GROWTH AND MORTALITY OF THE JAPANESE ABALONE HALIOTIS DISCUS HANNAI INO

Feeding activity of the Japanese abalone Haliotis discus hannai is clearly diurnal, with an increase in feeding between the onset of darkness and midnight. The feeding rate increases slowly in the afternoon, approaching sunset and becomes constant between sunset and midnight. The abalone remain within shaded refuges during the day, and only emerge from them at night. The present study evaluated some effects of varying the photoperiod on a group of these abalone to determine its potential effects on their feeding behavior. Three groups of juvenile abalone with an initial mean length near 14 mm were maintained in raceway cage culture systems with a continuous flow of fresh seawater and abundant food where each group was exposed to different photoperiods. Growth of the abalone in these systems was monitored for a period of 106 days. Treatment A, considered “natural,” included 12 h of light and 12 h of darkness. In Treatment B, the abalone were maintained in complete darkness, and Treatment C included four h of light and 20 h of darkness. The results showed that juveniles cultured in total darkness demonstrated some retardation in growth early in the experiment compared with abalone in a natural light regimen, and those with a partial light regimen. After 43 days, the abalone in the partial light regimen reached and surpassed sizes of the abalone maintained in the natural light regimen and in total darkness, although their feeding activity and growth patterns were erratic compared with abalone in the normal light and total darkness regimes. The results of the experiment were inconclusive as to which light regimen was most favorable when considering the growth patterns and comparative mortality rates within the systems.

Mass Mortality of Japanese Abalone Haliotis discus hannai Caused by Vibrio harveyi Infection

Sixty thousand of deaths among cultured Ezo abalone Haliotis discus hannai occurred within a few days at an abalone farm in Japan in the middle of August, 2002. Dead animals were characterized by a hemolymphatic edema around the major circulatory system. Vibrios showing swarming motility dominated in the edema. The pathogenic vibrios were identified as Vibrio harveyi based on a phylogenetic analysis and a phenotypic characterization. In both immersion and injection experiments, the swarming vibrios fulfilled Koch's postulates as a pathogen for Ezo abalone. Using a GFP-tagged V. harveyi S20, a clump of bacterium was detected on the gills of the abalone within 48 hours after contact with the bacterium. This is the first report of V. harveyi infection in Ezo abalone Haliotis discus hannai.

Segregation and Linkage Analysis of 75 Novel Microsatellite DNA Markers in Pair Crosses of Japanese Abalone (Haliotis discus hannai) Using the 5′-Tailed Primer Method

We present novel microsatellite markers of the Japanese abalone (Haliotis discus hannai) for general mapping studies in this species. A total of 75 microsatellite markers were developed, and the allele-transmission patterns of these markers were studied in three families generated by pair crosses. For allele scoring, we employed the 5'-tailed primer polymerase chain reaction (PCR) technique, which substantially reduces the cost for fluorescent labeling of primers. Of the 225 possible marker-family combinations (75 markers x 3 families), 18 cases of informative null-allele segregation were inferred. When such null-allele segregations were allowed, more than 70% of the 75 markers in the families turned out to be markers with an expected segregation ratio of 1:1:1:1, allowing maximal exploitation of the codominant nature of microsatellite markers. There were 16 instances of segregation distortion at the 5% significance level. The test for independence of segregation assigned the 75 markers into 17 linkage groups, which is in close agreement with the haploid chromosome number of H. discus hannai (n = 18). Six markers could not be placed into any linkage group. We suggest that these markers could help construct a H. discus hannai linkage map.

Interactions between the Japanese abalone Haliotis discus hannai (Ino 1953) and Chilean species: Consumption, competition, and predation

The Japanese abalone, Haliotis discus hannai (Ino, 1953) is produced in Land-based culture on the coast of Chile. The high costs involved in such culture systems generated the interest to evaluate the possibility to culture the abalone confined to cages in the sea. Introduction of this species into the natural environment may pose risks to local flora and fauna, particularly the establishment of populations arising from escaped specimens or larval settlement. Laboratory experiments were carried out to evaluate interactions between this abalone and local species in order to determine rates of consumption of local algae by these molluscs, competition with other organisms occupying the same feeding niche, and predation on the abalone by some local carnivores. The experiments demonstrated consumption of all offered algae by the abalone, particularly Rhodymenia howeana at rates of 1.3% to 5% of their body weight per day. In competition with other species of herbivores it was observed that with some there was a decline in consumption rate both by the abalone and the competitors when they were together, suggesting occurrence of competitive interference. The abalone readily attracted and were consumed by a variety of predators, particularly Meyenaster gelatinosus and Cancer setosus. It was concluded that if H. discus hannai escapes from the cages or produces larvae which settle on rocky reefs, this species might become established as an additional component of the natural communities. However, due to competitive interactions, predation pressure, and an opportunistic fishery, the development of substantial populations, let alone population explosions, with serious negative environmental impacts is improbable.

EFFECTS OF MACROALGAL TYPE AND WATER TEMPERATURE ON MACROALGAL CONSUMPTION RATES OF THE ABALONE HALIOTIS DIVERSICOLOR REEVE

The Japanese abalone “tokobushi” (Haliotis diversicolor Reeve) supports a valuable fishery off Tanegashima Island, southern Japan. However, catches have been declining, probably caused by over harvesting and other factors. Understanding the effects of macroalgal type and water temperature on the consumption rates of tokobushi has applications for the management of its population such as to identify sites with appropriate quality and quantity of macroalgae and the favorable water temperature during stock enhancement. Under controlled conditions, the effects of macroalgal type and water temperature on the macroalgal consumption rates of tokobushi were evaluated. On a short-term basis (24-h feeding), consumption rates were higher on leathery brown algae (Sargassum fusiforme, Sargassum patens, Sargassum duplicatum, Sargassum alternato-pinnatum, Undaria pinnatifida and Laminaria japonica), corticated red algae (Acanthophora spicifera, Gracilaria gigas, Carpopeltis affinis and Ceramium sp.) and foliose green algae (Ulva pertusa and Enteromorpha intestinales) than on siphonous green algae (Codium spp.) and filamentous green algae (Chaetomorpha crassa and Cladophoropsis zollingeri). Averaged across 20 species of macroalgae, the mean consumption rate was 4.96 ± 0.27%wet-TW.d−1 (wet alga and wet abalone; TW = total weight) or 1.37 ± 0.19%dryTW.d−1 (dry alga and dry abalone). On a long-term basis (20 days feeding), tokobushi had higher consumption rates on the green alga Ulva pertusa and the brown alga Sargassum fusiforme than on the red alga Meristotheca papulosa. When presented with a choice of species (3 days feeding), tokobushi ate more of the brown alga Sargassum fusiforme and the red alga Gracilaria gigas than the green alga Codium cylindricum. Consumption rates generally increased with temperature. Generally, tokobushi prefer macroalgae with high percent dry weight composition, most of which are brown and red algae, and eat more at water temperatures around spring/fall (17°C, 21°C) and summer (27°C) in Kagoshima, Japan.

Transfer of a foreign gene to Japanese abalone ( Haliotis diversicolor supertexta) by direct testis-injection

We developed a technique that easily transfers exogenous DNA fragments into the genome of Japanese abalone ( Haliotis diversicolor supertexta), an important aquaculture shellfish. From 0.1 to 10 μg/μl of the linearized plasmid pOBA–YPGHc, containing the yellowfin porgy ( Acanthopagrus latus) growth hormone cDNA driven by the medaka β-actin promoter, was directly injected into abalone testis with a microsyringe in a total volume of 10 μl. The sperm activity, fertility, and hatchability of fertilized eggs from testis-injected abalone did not differ ( P < 0.05) from those of abalone in the untreated control group. From extracted genomic DNA from sperm, larvae at the trochophore stage (9 h after fertilization), juveniles (3 weeks after fertilization), and adults (1-year-old) of testis-injected abalone, a product with a molecular weight of 954-bp was amplified using polymerase chain reaction (PCR). Southern blot analysis showed that the amplified PCR product hybridized to the pOBA–YPGHc probe. The gene-transfer efficiency of G 0 in larvae, juveniles, and 1-year-old adults was 90%, 92.5%, and 60%, respectively. Around 20% of G 0 mature abalone contained the transgene in their gonads. Genomic Southern blot analysis of 1-year-old abalone derived from DNA-injected group revealed that the transgene was integrated in the genome of the transgenic abalone. The mean shell lengths and body weights were significantly greater ( P < 0.05) than those of control group. We conclude that direct testis injection is a simple, high-throughput, minimally invasive, non-viral based, and efficient approach for producing transgenic abalone.

MOLECULAR PHYLOGENY AND THE GEOGRAPHIC ORIGIN OF HALIOTIDAE TRACED BY HAEMOCYANIN SEQUENCES

Phylogenetic relationships of 12 species of the vetigastropod family Haliotidae were analysed on the basis of partial haemocyanin coding genes. Both protein-coding and genomic sequence data, of which the latter includes one ancient intron, were analysed. We were able to distinguish two genetically different monophyletic groups with high bootstrap support: (i) the abalones from Europe, South Africa, Australia, Taiwan and Japan group together and are separated from (ii) five California and two Japanese abalones. The usefulness of haemocyanin as a phylogenetic character and the origin of the Haliotidae are discussed.

Genetic difference between Ezo-awabi Haliotis discus hannai and Kuro-awabi H. discus discus populations: Microsatellite-based population analysis in Japanese abalone

This study documents the genetic population relationships between Ezo-awabi Haliotis discus hannai and Kuro-awabi H. discus discus by means of the microsatellite technique with an emphasis on the extent of genetic difference between Ezo-and Kuro-awabi populations. Eight markers were employed to screen five populations each collected from Ezo-and Kuro-awabi habitats. All eight loci showed polymorphisms in all populations (number of alleles per locus, 11.1–14.1; averaged expected heterozygosity, 0.64–0.70). The number of loci that yielded significant genetic heterogeneities (allele frequency distribution and/or pairwise θ) between Ezo- and Kuro-awabi populations was larger than that generated in comparisons between populations within Ezo- and Kuro-awabi habitats. According to the bootstrap neighbor-joining trees constructed on the basis of two genetic distance measures (D A and D ST), the 10 populations fell into two clusters of populations (Ezo-awabi and Kuro-awabi habitat groups), and the results of hierarchical AMOVA testing also supported the neighborjoining clustering. The outcomes presented here suggest that the microsatellite markers used in this study are potentially an efficient means to differentiate Ezo- and Kuro-awabi populations.

Preparation and Characterization of Monoclonal Antibody Against Abalone Allergen Tropomyosin

Muscle protein tropomyosin is a major and common allergen of mollusks. In order to develop immunoassays based on monoclonal antibody (MAb) for allergen characterization, a MAb against Japanese abalone (Haliotis discus) was prepared and characterized in the present study. In comparison with the IgE reactivities of sera from crustacean allergic individuals, the selected MAb AE9F9 showed specific reaction to the abalone allergenic tropomyosin. The MAb AE9F9 reacted to the crustaceans including lobster, crab, and shrimp, but not to the mollusks other than abalone. It was surprising that the MAb AE9F9 was also reactive to the vertebrate chicken tropomyosin and smooth muscle tropomyosin of chicken gizzard. Comparison of amino acid sequences of tropomyosins among abalone, other mollusks, crustaceans, and chicken showed that two regions (90-105 and 147-165) have a high identity among abalone, crustaceans, and chicken, but are polymorphic among mollusks. In the two regions, substitutions at residues 99-Leu, 149-Lys, and 160-Arg of abalone tropomyosin are observed only in mollusks, suggesting that these residues might be important for determining the abalone tropomyosin structure recognized by the AE9F9 antibody. Because of the distinct binding site, the MAb AE9F9 might be useful for abalone allergen detection and epitope mapping of allergen tropomyosin.

Vibrio neonatus sp. nov. and Vibrio ezurae sp. nov. Isolated from the Gut of Japanese Abalones

Five alginolytic, facultative anaerobic, non-motile bacteria were isolated from the gut of Japanese abalones (Haliotis discus discus, H. diversicolor diversicolor and H. diversicolor aquatilis). Phylogenetic analyses based on 16S rRNA gene and gap gene sequences indicated that these strains are closely related to V. halioticoli. DNA-DNA hybridizations, FAFLP fingerprintings, and phylogenies of gap and 16S rRNA gene sequences showed that the five strains represent two species different from all currently described vibrios. The names Vibrio neonatus sp. nov. (IAM 15060T = LMG 19973T = HDD3-1T; mol% G+C of DNA is 42.1-43.9), and Vibrio ezurae sp. nov. (IAM 15061T = LMG 19970T = HDS1-1T; mol% G+C of DNA is 43.6-44.8) are proposed to encompass these new taxa. The two new species can be differentiated from V. halioticoli on the basis of several features, including beta-galactosidase activity, assimilation of glycerol, D-mannose and D-gluconate.

Pacific dulse (Palmaria mollis) as a food and biofilter in recirculated, land-based abalone culture systems

Palmaria mollis (Pacific dulse) is increasingly being used as an in situ biofilter and feed in land-based abalone culture. This work reviews physical and nutrient requirements for P. mollis culture and its nutritional value for three abalone species, the Japanese abalone Haliotis discus hannai, the red abalone Haliotis rufescens, and the U.S. Federally endangered white abalone Haliotis sorenseni.P. mollis growth was positively correlated with light over specific light densities (SLD) ranging from 0.0048 to 0.036molphotonsg−1fresh weightd−1, under tumble culture conditions. Under low light conditions, growth was greatest at a temperature of 12°C (SGR=8.69±0.29%d−1), while under high light conditions growth was greatest at a temperature of 14–18°C (SGR=10.5±0.12%d−1). Addition of Guillard's f nutrient medium [Guillard, R.R.L., Ryther, J.H., 1962. Studies on marine plankton diatoms. I. Cyclothella nana Huntedt and Detonula confercacae (Cleve). Gran. Can. J. Microbiol. 8, 229–239] significantly increased Pacific dulse growth in cultures receiving one seawater exchange per day; furthermore, growth was significantly improved by addition of trace metals. The use of NaNO3 as an N source in the f medium resulted in better growth compared with NH4NO3. The use of phosphorus additions above 83.3μMPd−1 depressed P. mollis growth rates. P. mollis growth was positively correlated with concentrations of dissolved inorganic carbon, including HCO3−. Growth rates were not significantly different over a pH range of 8.3–8.9.There were no significant toxic effects on Japanese abalone, H. discus hannai cultured in seawater supplemented with (0.75f+1.37μM Zn) trace metals d−1. H. discus hannai showed the highest growth rates when fed on P. mollis fertilized with f medium and nitrate (NO3−-N) loads ranging from 1176 to 2353μMd−1 while red abalone, H. rufescens, grew best when fed on P. mollis fertilized with f medium and nitrate loads of 2353–2942μMd−1. Both abalone species grew better on P. mollis fertilized with (0.75f+1.37μM Zn) d−1 trace metal solution compared with P. mollis without trace metal additions. H. sorenseni, grew well when fed on P. mollis, showing higher linear shell growth rates and higher survival rates compared with those of abalone fed on commercially harvested and abundant giant kelp, Macrocystis pyrifera.

Effects of nutrient enrichment and biochemical composition of diets of Palmaria mollis on growth and condition of Japanese abalone, Haliotis discus hannai and red abalone, Haliotis rufescens

Two growth experiments were conducted with juvenile red abalone, Haliotis rufescens and Japanese abalone, Haliotis discus hannai. The first experiment was set up to determine if nutrient levels used for co-culture of the Rhodophyte, Pacific dulse ( Palmaria mollis) directly affected abalone growth. No significant differences (ANOVA; P=0.117) were found in growth of abalone cultured in either ambient seawater alone or seawater supplemented with different NaNO 3 loads (1176, 1765, 2353, and 2942 μM day −1 NO 3–N), NaH 2PO 4 (83.3 μM day −1 PO 4 −), and a modified version of Guillard and Ryther's [Gran. Can. J. Microbiol. 8, (1962) 229] f medium containing Fe, Zn, Mn, Cu, Mo, and Co. The second experiment was designed to determine the effect of different nutrient levels on the nutritional value of P. mollis when fed to abalone. P. mollis was cultured with different NaNO 3 loads (1176, 1765, 2353, and 2942 μM day −1 NO 3–N) and NaH 2PO 4 (83.3 μM day −1 PO 4 −) in the presence or absence of f medium trace metals (Fe, Zn, Mn, Cu, Mo, and Co). H. discus hannai showed the highest LGR and SGR when fed on P. mollis supplemented with nitrate loads ranging from 1176 to 2353 μM day −1 NO 3–N. In contrast, H. rufescens showed the highest linear growth rate (LGR) when fed on P. mollis supplemented with higher nitrate loads of 2353 to 2942 μM day −1 NO 3–N, while nitrate load had no significant effect on specific growth rate (SGR). Both abalone species grew better on P. mollis supplied with 0.75 f+Zn (day −1) metal solution [Gran. Can. J. Microbiol. 8 (1962) 229] compared to those without trace metal additions, with H. discus hannai showing a further improvement in food conversion efficiencies (FCE). The present work shows that understanding and manipulating the culture environment of P. mollis can significantly affect growth, FCE, and daily food consumption (DFC) of H. discus hannai and H. rufescens.

Enhanced production of Pacific dulse ( Palmaria mollis) for co-culture with abalone in a land-based system: nitrogen, phosphorus, and trace metal nutrition

Pacific dulse ( Palmaria mollis) is a high-quality algal feed for both red abalone ( Haliotis rufescens) and Japanese abalone ( Haliotis discus hannai); however, culture techniques capable of producing commercial quantities of P. mollis are still in development. This study was undertaken to improve our understanding of nutrient requirements and management strategies for P. mollis production in intensive, land-based systems. All experiments were conducted under moderate to high artificial light of 24–52 mol photons m −2 day −1 and low seawater exchange (1 vol day −1), in order to minimize seawater pumping costs. Application of nutrients every 5–7 days resulted in no significant difference in P. mollis growth compared with daily applications. Nutrient additions during the dark cycle compared with the light cycle were found to be effective in controlling epiphytes. The addition of f medium trace metals (Gran. Can. J. Microbiol. 8 (1962) 229) significantly increased growth rates compared with those of cultures supplied with just nitrate and phosphate alone. The concentration of Zn was increased to equal that of Mn (1.37 μM day −1), with resulting improvement in yields. NaNO 3 as a source of nitrogen was found to be superior for long-term growth (9 weeks) compared with NH 4NO 3, although NH 4NO 3 was superior on a short-term basis (first 2–5 weeks). This was likely due to NH 4 +–N toxicity resulting from the experimental design. While P. mollis growth was not significantly different between additions of 1176–2942 μM day −1 NO 3 −–N (average daily N load), an increasing trend in growth was observed with increasing N loads up to 2942 μM day −1 NO 3 −–N. P. mollis showed a sharp decline in growth with P additions above 83.3 μM day −1 (average daily P load). Tissue nutrient concentrations and molar ratios (N, P, trace metals, N/P and C/N) can be used in the development of optimal nutrient management strategies to ensure maximum dulse growth rates.

Acetic acid production of Vibrio halioticoli from alginate: a possible role for establishment of abalone– V. halioticoli association

Acetic acid, which is converted from cellulose by means of the metabolism of their gut microbes, is an important oxidizable energy source and precursors of anabolism in ruminant animals and xylophagus insects. However, acetic acid production from algal polysaccharides by means of the metabolism of gut microbes of marine herbivorous invertebrates is not well studied. Abundance of Vibrio halioticoli, which is a dominant alginolytic gut microbe of abalone Haliotis discus hannai, in the gut of various marine herbivorous invertebrates and major fermentation products from alginate of these strains were investigated in this study. V. halioticoli strains were detected from the gut of three species of the Japanese abalone, Haliotis discus discus, Haliotis diversicolor aquatilis, and Haliotis diversicolor diversicolor, and a South African abalone, Haliotis midae, with a range of 40–65% amongst these microflora. The bacterium was also found in the gut of a turban shell, Turbo cornutus, of which occupation rate was 16%. Furthermore, acetic acid and formic acid were detected as major fermentation products of alginate in these V. halioticoli strains. It is suggested that the abundant populations of V. halioticoli in the gut of Haliotis abalone may have a great role for converting alginate to acetic acid.

Fluorescent amplified fragment length polymorphism and repetitive extragenic palindrome-PCR fingerprinting reveal host-specific genetic diversity of Vibrio halioticoli-like strains isolated from the gut of Japanese abalone.

When analyzed by fluorescent amplified fragment length polymorphism and repetitive extragenic palindrome-PCR fingerprinting, a total of 47 Vibrio halioticoli strains isolated from four Japanese abalone species and one turban shell species formed three clusters that roughly reflect the different species of host abalone from which they were isolated. The V. halioticoli isolates from turban shells were distributed evenly among the clusters. Representative isolates from two clusters were deemed separate species or subspecies by DNA-DNA hybridization.

Vibrio carchariae, a pathogen of the abalone Haliotis tuberculata.

Since 1997, mass mortality of the abalone Haliotis tuberculata L. has occurred in the natural environment along the French coast. The outbreak of disease started on the south coast of Brittany near Concarneau in 1997, then spread to the north of Brittany (in 1998) and the west coast of Normandy (Golfe de St. Malo in 1999). Between 60 and 80% of the abalone died. In 1999, mortality also affected a land-based abalone farm in Normandy during the summer. At this farm, a Vibrio sp. was isolated in abundance from abalone that had just died. The disease was experimentally reproduced by inoculation or by introducing the pathogen into the surrounding water. This vibrio, identified by genotypic and phenotypic characters, is related to V carchariae. It is similar to the V carchariae, responsible for mortality in the Japanese abalone Sulculus diversicolor supratexta, but some phenotypic characters differentiate both strains. In 2000, healthy abalone placed in 2 sites on the north and south coasts of Brittany died, and the pathogen V carchariae could be isolated from dead individuals, demonstrating that the pathogen was probably the cause of the abalone disease that has been occurring since 1997 in Brittany.

Ovo-testis and disturbed reproductive cycle in the giant abalone, Haliotis madaka: possible linkage with organotin contamination in a site of population decline

Histological examination of gonads as well as chemical analysis of organotin compounds in tissues of the giant abalone, Haliotis madaka, was conducted to evaluate possible endocrine disruption and to consider the causal factors for the decline of abalone stocks in Japan. Abalone specimens were collected from two different areas, Tsushima as a reference site and Jogashima as a site representative of declining abalone populations, each month from September 1995 to November 1996. Scores were given to the development stages of reproductive cells in the ovary and testis. The degree of sexual maturation was evaluated by calculating the mean value of a histogram of these scores for the reproductive cells of each abalone. The temporal variations in degree of sexual maturation showed that female and male abalone from Tsushima matured synchronously, while those from Jogashima did not. The observed maximum reproductive developmental score in abalone from Jogashima was much lower than that from Tsushima, because immature females were present at the former site throughout the spawning season. Approximately 20% of the abalone from Jogashima were masculinized females with an ovo-testis. The masculinization of female abalone was similar to the imposex, typically induced in other gastropod molluscs by tributyltin (TBT) and triphenyltin (TPhT) from antifouling paints. Concentrations of TBT and TPhT in the muscles of abalone from Jogashima ( n=83) of 4.9±4.4ng/g wet wt and 6.3±6.6 ng/g wet wt, respectively, were significantly higher than those from Tsushima ( n=125) ( P<0.01) of 0.8±0.8 ng/g wet wt and 0.6±1.3 ng/g wet wt, respectively. In situ exposure of abalone from Tsushima caged near a dockyard in Jogashima for 7 months (from the immature to the mature stage) resulted in spermatogenesis in the ovary of approximately 90% of females. Endocrine disruption may be caused in the giant abalone by organotin compounds from antifouling paints, which are possibly one of the causal factors for the decline of Japanese abalone stocks.

A sustainable integrated system for culture of fish, seaweed and abalone

A 3.3 m 2 experimental system for the intensive land-based culture of abalone, seaweed and fish was established using an integrated design. The goals were to achieve nutrient recycling, reduced water use, reduced nutrient discharge and high yields. Effluents from Japanese abalone ( Haliotis discus hannai) culture tanks drained into a pellet-fed fish ( Sparus aurata) culture tank. The fish effluent drained into macroalgal ( Ulva lactuca or Gracilaria conferta) culture, and biofilter tanks. Algal production fed the abalone. The system was monitored to assess productivity and nitrogen partitioning over a year. The fish grew at 0.67% day −1, yielding 28-kg m −2 year −1. The nutrients excreted by the fish supported high yields of U. lactuca (78-kg m −2 year −1) and efficient (80%) ammonia filtration. Gracilaria functioned poorly. Ulva supported an abalone growth rate of 0.9% day −1 and a length increase of 40–66 μm day −1 in juveniles, and 0.34% day −1 and 59 μm day −1 in young adults. Total abalone yield was 9.4 kg year −1. A surplus of seaweed was created in the system. Ammonia-N, as a fraction of total feed-N was reduced from 45% in the fish effluents to 10% in the post-seaweed discharge. Based on the results, a doubling of the abalone:fish yield ratio from 0.3 to 0.6 is feasible.

Vibrio carchariae Causes Mass Mortalities in Japanese Abalone, Sulculus diversicolor supratexta.

A new epizootic causing mass mortalities among cultured Japanese abalone, Sulculus diversicolor supratexta, occurred in Kanagawa Prefecture, Japan, during the period from June to October in 1997. Diseased abalone lost the ability to adhere and eventually died on the bottom of aquaria. White spots on the foot were a characteristic sign of the disease. In sections of tissues with lesions, there was necrotic degeneration in muscle fibers, and homogeneous bacterial cells were isolated from the infected tissue. Isolates of this bacterium were Gramnegative, facultatively anaerobic, rod shaped organisms that were motile by a single polar flagellum. They were identified as Vibrio carchariae on the basis of phenotypic characteristics, 16S rRNA gene sequences and DNA-DNA hybridization, although some phenotypic properties of the isolates differed from those of references. Infection experiments confirmed the pathogenicity of the bacterium to Japanese abalone. This is the first report of the isolation of V. carchariae from a diseased shellfish.

The Role of &amp;beta;, &amp;beta;-Carotene on Growth and Survival of Juvenile Japanese Abalone &lt;i&gt;Haliotis discus&lt;/i&gt;

The Role of &amp;beta;, &amp;beta;-Carotene on Growth and Survival of Juvenile Japanese Abalone &lt;i&gt;Haliotis discus&lt;/i&gt;