Optimum temperature for growth of Australian abalone: preferred temperature and critical thermal maximum for blacklip abalone, Haliotis rubra (Leach), and greenlip abalone, Haliotis laevigata (Leach)

The preferred temperature and critical thermal maximum of Australian blacklip abalone, Haliotis rubra (Leach), and greenlip abalone, Haliotis laevigata (Leach), were found to differ only slightly; the blacklip abalone exhibited lower temperature tolerance and preference, as expected from its habitat distribution. Preferred temperatures were 16.9 and 18.9°C, and 50% critical thermal maxima were 26.9 and 2 7.5°C for blacklip and greenlip abalone, respectively. The optimum temperatures for growth calculated from each of these indices and averaged were 17.0 and 18.3°C, respectively.     

Effects of oxygen supersaturation and temperature on juvenile greenlip, Haliotis laevigata Donovan, and blacklip, Haliotis rubra Leach, abalone

Growth and survival of juvenile greenlip (39.03 (SD 3.80) mm (n=524)) and blacklip (31.92 (SD 4.19) mm (n=531) abalone were investigated at high dissolved oxygen levels (95–120% saturation) between 17 and 19°C. Abalone were fed the same artificial diet and each species was contained in groups of approximately 30 individuals within triplicate tanks for each of six treatments and were exposed to flow through water adjusted to give experimental conditions for up to 75 days. Blacklip abalone held at 16.9°C and 97% oxygen saturation grew in shell length significantly faster than all other treatments of blacklip abalone held at 19°C, and significantly faster than blacklip abalone maintained at 111% oxygen saturation and 17.5°C. Both temperature and oxygen saturation significantly affected the survival of this species. Blacklip abalone held at 19°C had significantly lower survival for both 96% oxygen saturation and 120% oxygen saturation, compared with blacklip abalone maintained at either 110% oxygen saturation and 19°C, or for any 17°C treatment. No significant differences were noted for greenlip abalone within the range tested in terms of growth rate, food consumption rate or survival, indicating that greenlip abalone tolerated these conditions better than did blacklip abalone.     

Assessment of the physiological effect of altered salinity on greenlip (Haliotis laevigata) and blacklip (Haliotis rubra) abalone using respirometry

The early physiological response (3 days) of greenlip (Haliotis laevigata Leach) and blacklip (H. rubra Leach) abalone to a single abrupt change in salinity was monitored using a multi‐channel open‐circuit respirometer. The range of salinity tolerance for both species in this trial was 25–40 ppt. Indications from other trials were that a margin of 2 ppt outside this range will cause mortality. Serum volume was increased by reduced salinity as much as 25% in the short term, with equilibration of the concomitant whole body weight increase (9.2±0.5%) occurring within 1 h. The serum volume appeared to be decreased at high salinity. There was little underlying change in basal oxygen usage levels, but significant behavioural changes that affected overall oxygen consumption. Both high and low salinity appeared to reduce activity. Animals in low salinity exhibit partial recovery of activity levels after 1 day in a manner similar to other stress responses. Animals at high salinity (40 ppt) did not show recovery of activity levels over 3 days. Overall, these results suggest that greenlip and blacklip abalone will have little trouble tolerating moderately low‐salinity environments.     

Triploidy induction in Australian greenlip abalone Haliotis laevigata (Donovan) with cytochalasin B

Triploid induction in Australian greenlip abalone, Haliotis laevigata (Donovan), was conducted by blocking the formation of the second polar body using cytochalasin B (CB). Twenty minutes after fertilization, the zygotes of greenlip abalone were treated with four CB concentrations (0, 0.25, 0.5 and 0.75 mg L⁻¹) for 10, 15 and 20 min. The ploidy of resultant larvae was determined using flow cytometry at 72-h post fertilization. Our study showed that fertilization, hatching, survival and induced triploidy of abalone larvae were significantly affected by the CB concentration and treatment duration. The effective range of CB concentration for triploid induction on greenlip abalone was 0.5–0.75 mg L⁻¹ with an induction duration of 10–15 min. The results indicate that the most effective treatment combination for triploid induction in greenlip abalone is 0.5 mg CB L⁻¹ for 15 min starting at 20-min post fertilization.     

Modelling selective breeding in protandrous,batch‐reared Asian sea bass (Lates calcarifer,Bloch) using walkback selection

A bioeconomic simulation model for Lates calcarifer predicted that a strategy involving crossing current generation males with previous generation females would be a practical, effective and profitable way of dealing with protandry when batch rearing for selective breeding to improve the growth rate. The strategy allowed earlier initialization and more frequent ongoing rounds of selection, and resulted in a 16–19% higher overall response, than an alternative where each generation's males were crossed with the same generation's females. The strategy also yielded the highest short‐term benefit–cost ratio (13:1 versus 7:1 after 8 years of selective breeding) and the highest short‐ and long‐term value for participants in a breeding cooperative (a net present value of AU$28 million and an internal rate of return of 144% over 10 years), due to higher yields per fixed costs of production per unit area and due to savings in feed costs per kilogram of production. Breeding facilities of scale producing 50 full‐sibling families per generation were found to be more profitable than those producing 100 families.     

Implications of the dichotomy between the spatial scales at which abalone are managed and harvested

Commercial abalone divers make decisions about the location of their harvesting activities at a relatively fine scale. Management of these abalone fisheries, however, is normally conducted at a larger scale. To gauge the implications of this dichotomy, the following question was asked: Would it be worthwhile managing the fishery at a finer scale that corresponds with the harvesters' spatial preferences? To answer this, an existing abalone model was applied to a population of blacklip abalone, Haliotis rubra Leach. The model simulates both the existing practice of large scale spatial management combined with smaller scale spatial harvest and an alternative practice, whereby management and harvest are synchronised at a similarly small scale. It was concluded that the costs and effort associated with managing at a finer scale would unlikely yield benefits substantial enough to justify its implementation.     

Spatial abundance patterns and recruitment of a virus‐affected commercial mollusc fishery

Infectious pathogens figure prominently among those factors threatening marine wildlife. Mass mortality events caused by pathogens can fundamentally alter the structure of wild fish stocks and depress recruitment rates and yield. In the most severe instances, this can precipitate stock collapses resulting in dramatic economic losses to once valuable commercial fisheries. An outbreak of a herpes‐like virus among commercially fished abalone populations in the south‐west fishery of Victoria, Australia, during 2006–2007, has been associated with high mortality rates among all cohorts. Long‐term records from fishery‐independent surveys of blacklip abalone Haliotis rubra (Leach) enabled abundance from pre‐ and post‐viral periods to be analysed to estimate stock density and biomass. The spatial distribution of abundance in relation to physical habitat variables derived from high‐resolution bathymetric LiDAR data was investigated. Significant differences were observed in both measures between pre‐ and post‐viral periods. Although there was some limited evidence of gradual stock improvement in recent years, disease‐affected reefs have remained below productivity rates prior to the disease outbreak suggesting a reduction in larval availability or settlement success. This was corroborated by trends in sublegal sized blacklip abalone abundance that has yet to show substantial recovery post‐disease. Abundance data were modelled as a function of habitat variables using a generalised additive model (GAM) and indicated that high abundance was associated with complex reef structures of coastal waters (<15 m). This study highlights the importance of long‐term surveys to understand abalone recovery following mass mortality and the links between stock abundance and seafloor variability.     

Pharmacological and histological assessment of gut muscle movement in blacklip abalone, Haliotis rubra (Leach)

We examined the basic pharmacology of abalone gut tissues for adrenergic and peptide receptors using ligand binding and by determining the pharmacological effectors of abalone gut motility in a number of gut regions. Contractile responses could not be elicited, even though we could show the existence of α‐adrenergic and peptide receptors. Responses to any muscle contractile agents, including carbachol and potassium chloride, could not be found in blacklip abalone, Haliotis rubra (Leach). Histology confirmed the relative absence of muscular layers in all the tissues of the gut, indicating that previous literature reports of muscular involvement in contractile movement of gut contents did not appear to apply to this species.     

Growth and feeding in juvenile triploid and diploid blacklip abalone, Haliotis rubra (Leach, 1814), at two temperatures

Growth and feeding of juvenile triploid and diploid blacklip abalone Haliotis rubra (Leach, 1814) were investigated at two temperatures of 17 and 21 °C over a 50‐day period. There were no differences in growth between triploid and diploid abalone as measured by shell length and body weight. Both triploid and diploid abalone increased in length but not in weight at 21 °C. Condition indices were similar for triploid abalone maintained at both temperatures; however, those for diploid abalone were significantly higher at 17 °C than at 21 °C. Food intake was significantly greater yet feed conversion efficiency was significantly lower in triploid than in diploid abalone. Both the feeding variables were independent of temperature. On average, diploid abalone were able to convert 1 g of dry food ingested to 0.58 g of body weight, but triploid abalone only 0.44 g.     

Identification of a microsatellite marker that is completely linked to shell colour in small abalone,Haliotis diversicolor

A novel orange shell colour has been discovered in small abalone, Haliotis diversicolor (Reeve, 1846). To facilitate and accelerate a selective breeding programme for orange shell colour, a microsatellite marker that was completely linked to the shell colour gene was identified using a selective DNA pool approach and was verified in 448 individuals. Two DNA pools were constructed by pooling equal amounts of genomic DNA from 74 individuals with dark‐brown shells and 87 individuals with orange shells. Approximately 12 of 308 microsatellite markers that were linked to the shell colour gene were isolated using the selective DNA pooling method. After verification in 32 individuals with dark shells and 32 individuals with orange shells, only the Hdi3‐119 locus remained tightly linked to the shell colour gene. Finally, four families were used to verify the accuracy of the Hdi3‐119 locus. All of the individuals with orange shells in the four families harboured a unique 381‐bp allele in marker Hdi3‐119. This marker could be used for selective breeding of orange small abalone.     

Divergent selection for shell length in two stocks of small abalone Haliotis diversicolor

To determine whether genetic improvement can be attained through a selective breeding programme, divergent selection for shell length was applied to two stocks of Haliotis diversicolor. Stock A was descended from the cross between males from a Japanese wild population and females from a Taiwan aquacultured population and Stock B was from the Taiwan cultured population, which had been successively cultured in mainland China for about 10 generations. The 10% largest and 10% smallest abalones for each of these two stocks were selected as parents for the large‐selected and small‐selected lines respectively. Equal numbers of abalone were randomly chosen from the two stocks to serve as parents for the control lines before the selection. The selected and control lines were reared under the same conditions at early juvenile, later juvenile and grow‐out stages. Stock A showed a significantly higher response to selection and realized heritability than Stock B (P<0.01). The large‐selected line of Stock A and Stock B grew 12.79% and 4.58% faster than their control lines on shell length respectively. The average realized heritability for shell length was 0.441±0.064 for Stock A and 0.113±0.013 for Stock B. Responses to selection were different at different ages in each stock and the body weights of the selected lines were significantly different from the control lines in both stocks at the grow‐out stage. Asymmetric responses to selection in the two directions were also observed in both stocks. Differences in response to selection and realized heritability between the two stocks are presumably due to genetic variability.     

Effects of artificial selection practices on loss of genetic diversity in the Pacific abalone,Haliotis discus hannai

The Pacific abalone, Haliotis discus hannai Ino, is one of most important aquaculture species in China. Artificial selection has been the common and inevitable approach in breeding. In present study, the effect of artificial selection on the genetic structure of two abalone lines (JJ selection strain, three successive selection lines based on the fast‐growing trait, which was named JJF0, JJF1, JJF2, and JJF3; and R selection strain, the offspring of the red shell colored variants) were evaluated using 10 microsatellites. Loci showed from low to high polymorphism, with the number of alleles (A) ranging from 2 to 18 in each population. The mean observed (H_o) and expected heterozygosities (H_e) were 0.650 ± 0.022 and 0.711 ± 0.018, respectively. In selection strain JJ, the values for most diversity genetic indexes (A_e, the number of effective alleles, H_o and H_e) decreased from JJF0 to JJF3. Meanwhile, compared to JJ line, the genetic diversity estimates of R were close to those of JJF3. Nei's genetic distance ranged from 0.20357 to 0.51346. The unweighted pair group method with arithmetic mean tree based on Nei's genetic distance also showed that the control Japan population and JJF0 formed to a cluster firstly, which were subsequently grouped together with JJF1, JJF2, JJF3, whereas the R was isolated from the rest of the populations. Analysis of genetic information indicated that genetic diversity was lost with artificial selection practices. Mechanisms underlying the maintenance of an acceptable level of genetic diversity while pursuing economic interests should be conducted in future research studies.     

Greenlip abalone (Haliotis laevigata Donovan, 1808) sperm cryopreservation using a programmable freezing technique and testing the addition of amino acid and vitamin

This study investigated factors key to the development of sperm cryopreservation in the greenlip abalone Haliotis laevigata using a programmable freezing technique, including (1) permeable cryoprotectant agent (CPA) selection; (2) cooling rate; (3) endpoint temperature; (4) thawing temperature; (5) sperm to egg ratio and (6) sugar, vitamin and amino acid supplementation, using sperm motility, fertilization rate, plasma membrane integrity, mitochondrial membrane potential or acrosome integrity as quality assessment indicators. Results showed that among the permeable CPAs evaluated, 10% dimethyl sulfoxide was the most suitable for greenlip abalone sperm cryopreservation. The highest post‐thaw sperm motility was achieved with the sperm being frozen at a cooling rate of ?5°C min^?1 to ?30°C from 0°C and thawed and recovered in 40°C and 18°C seawater baths respectively. The addition of sugars in 10% dimethyl sulfoxide did not significantly improve the post‐thaw sperm motility and fertilization rate. The addition of 0.6% glycine, 0.2% taurine or 0.02% L‐ascorbic acid, on the other hand, significantly improved the post‐thaw sperm motility. However, only the addition of 0.6% glycine improved the post‐thaw sperm fertilization rate, which was further confirmed by the improvement of the post‐thaw sperm mitochondrial membrane potential and acrosome integrity through flow cytometry analysis.     

鲍遗传育种研究进展

Abalones are important farming species with a high economic value. They have already been farmed for more than 50 years. As problems and new requirements rose continuously in culture industry of abalone, studies on genetic and breeding techniques are needed to improve characteristics and to gain new traits. This review concentrates on advances in genetics and breeding techniques in abalone. As for genetic studies, karyological analyses, allozyme, DNA markers and genetic diversity were reviewed. So far, karyological analyses in abalone have been performed in 12 species that can be divided into three groups according to the chromosome number. In some economically important species, loci of allozymes and. microsatellites have been isolated and applied to investigate the genetic structure of natural and hatchery populations and to identify the result of chromosome set manipulation, but the related reports are only a few yet. The resultsof investigation with DNA markers and allozymes showed that the genetic structure of natural populations presents two characteristics: excessive homozygosity and subdivision. Advances of various breeding techniques, including introduction, selection,hybridization, polyploidy, gynogenesis and gene manipulation, were reviewed in the other part. Although Haliotis discus discus, introduced from Japan, has become one of the most important culture species in China, the economic, social and environmental effects of introduction have been rarely studied. Selection is one of the most important and basic breeding techniques, but the studies on selection are only a few and preliminary, referring to the relations between genetic characteristics and the traits of growth and resistance, genetic diversity and heritability of quantitative traits, and the effect of selection. Interspecific hybridization was the first breeding program carded out in abalone. Experimental hybridization have been carded out for about 20 crosses. Heterosis,such as faster growth and high survival rate, has been observed in some crosses. Triploids have been successfully induced in many species of abalone with physical or chemical shock, e.g.H, discus hannai, H. rufescens, H.diversicolor diversicolor and H. rnidae. Field experiments were conducted in some species of triploid abalone. In comparison with triploid, the research on tetraploid is still in quest stage. The progress of induction of gynogenesis in abalone is quite slow. Conditions of sperm inactivation, diploid restoration and nuclear behavior of gynogenetically activated eggs have been researched on in H. discus han nai. Notwithstanding the gene transfer technology in abalone is in the quest stage, the research have already involved preparation of exogenic DNA,means of gene transfer, identification integration and expression of target gene, etc. Three research directions in these topics were proposed : to investigate the germplasm resources of abalone deeply and widely, to make use of traditional breeding methods and modem biotechnique synthetically, and to combine the science research with production practice.     

The effect of temperature and conditioning interval on the spawning success of wild-caught blacklip (Haliotis rubra, Leach 1814) and greenlip (H. laevigata, Donovan 1808) abalone

Wild‐caught blacklip (Haliotis rubra, Leach 1814) and greenlip (H. laevigata, Donovan 1808) abalone fed a formulated feed were held at 16 or 18°C for different conditioning intervals ranging from 114 to 235 days and induced to spawn using ultraviolet‐irradiated seawater. They were conditioned again for a second identical period before another induction. For H. rubra, mean spawning rate of both sexes was higher in groups held at 18°C than at 16°C, as was the repeat spawning rate. Conversely, animals held at 16°C produced significantly more gametes than those at 18°C. Egg production peaked in groups held at 16°C for ≥165 days. While both mean and total sperm production of H. rubra varied significantly, both figures were always high. Unlike H. rubra, the spawning rate, repeat spawning rate and gamete production of both sexes of H. laevigata were higher when cultured at 16°C than at 18°C. Egg production peaked in groups conditioned at 16°C for ≥212 days. Both mean and total sperm production by H. laevigata were much lower than for H. rubra. This study demonstrates that year‐round hatchery production of seedstock of both species is possible providing broodstock are held under favourable environmental conditions, preferably 16°C.     

Estimation of genetic parameters for growth traits in cultured clam Meretrix meretrix (Bivalvia: Veneridae) using the Bayesian method based on Gibbs sampling

The aim of this study was to estimate the genetic parameters of the growth performance of clam Meretrix meretrix. As part of the breeding programme, 25 full‐sib families nested within eight half‐sib families were produced, planted out and tested to assess the heritability of the total body weight (TW), shell length (SL), shell height (SH) and shell width (SW) at different growth stages. Method of analysis was implemented using the Bayesian method based on the Multiple Trait using Gibbs Sampling under Animal Model program, which was used to estimate the (co)variance components of the traits and conduct genetic analysis. A total of 25 full‐sib families, each with 30–35 individuals within family, were used for the analysis. Significant positive genetic and phenotypic correlations between SL, SW, SH and TW with each other were observed. The growth traits showed high‐magnitude heritabilities, with values ranging from 0.64 to 0.85, which indicates that these traits should respond to selection and therefore should be included in genetic improvement programmes.     

Supplementary oxygen and temperature management during live transportation of greenlip abalone, Haliotis laevigata (Donovan, 1808)

Live greenlip abalone, Haliotis laevigata , are highly valued in Australian export markets with demand increasingly being met with cultured stock. Live transportation of abalone requires the maintenance of favourable conditions within transport containers for periods exceeding 35 h. We examined the combined effects of temperature regulation (ice provision) and of supplemental oxygen (60% and 100% concentrations) on mortality rates of abalone over 7 days following a 35-h simulated live-transport experiment. We also examined the physiological condition of greenlip abalone (oxygen consumption rate, haemolymph pH and weight) during the simulation experiment. The provision of ice and supplementary oxygen reduced abalone mortalities. Omission of ice and supplementary oxygen during the transport simulation resulted in mortality rates ranging from 70% to 100%. The addition of ice to containers with ambient oxygen concentrations decreased average mortality rates by 50%. While supplementary oxygen further reduced these rates, the provision of both ice and 100% oxygen was by far the most effective combination, reducing mortalities to between 2% and 6%. Supplementary oxygen increased oxygen consumption rates of abalone above those transported at ambient oxygen concentrations. Live-transport decreased haemolymph pH in all treatments but was most pronounced in treatments without ice or supplementary oxygen. On average, abalone lost 7–13% of their weight during the simulation but this loss was independent of transport treatment.     

Genetic characterization and gonad development of artificially produced interspecific hybrids of the abalones, Haliotis discus discus Reeve, Haliotis gigantea Gmelin and Haliotis madaka Habe

Hybridization among abalone species has been suggested as a possible means to increase their growth rates for aquaculture. As a first step to test the usefulness of the hybrids of Japanese abalone species (Haliotis discus discus, Haliotis gigantea and Haliotis madaka) for aquaculture, we characterized the genetic background and gonad development of hybrids that were produced by artificial insemination. The hybrid status of the resulting offspring was confirmed by assaying 14 allozymes and by RFLP analysis of the 16s rRNA and cytochrome oxidase I (COI) regions of mtDNA using 13 restriction enzymes. Histological examination of the gonads of the hybrids was conducted in comparison with those of the parental species. Cross‐breeding among the three species was conducted successfully in all combinations although with lower fertilization rates (means of 1.3–60.8%) than the parental species (34.3–90%). Crosses between H. discus discus and H. madaka had higher fertilization rates (22.4–60.8%) than those involving H. gigantea (1.3–19.9%). The hybrids were ascertained by the presence of both parental genotypes at the LDH‐A, ME‐A, MDH‐A and GPI loci. The maternal origin of the hybrid mtDNA was confirmed by digestion with DdeI, TaqI, HpaII of the COI region. No polymorphism was observed in the 16S rRNA region. The hybrids had gonadal development and maturity stages similar to the parental species up to fully mature oocytes and sperm. They spawned upon stimulation and produced viable offspring with high fertilization rates and successful development to the juvenile stage in back‐ and homologous hybrid crosses.     

Genetic variability of cultured populations of the Pacific abalone (Haliotis discus hannai Ino) in China based on microsatellites

The genetic diversity of cultured populations of the Pacific abalone (Haliotis discus hannai Ino) from northern China was analysed using seven microsatellite markers. The microsatellite loci were polymorphic for all the populations, with an average of 8.7 alleles per locus (range 8.0–9.4). The mean observed and expected heterozygosities were 0.547 (range 0.500–0.596) and 0.774 (range 0.754–0.787) respectively. The allelic diversity in terms of number of alleles per locus was considerably lower than that previously found in wild populations (range 21.8–23.0), indicating that bottleneck effects occurred when each population was founded. Significant genetic differentiation among the five cultured populations was shown using F_st and R_st values, and pairwise comparison based on allelic distribution. A neighbour‐joining analysis of the genetic distance did not show a consistent relationship between the geographic and the genetic distances, suggesting the existence of exchanges of breeds and eggs between the hatcheries. The results obtained in this study are useful for a number of areas of interest for fisheries management and the aquaculture industry, especially with regard to breeding programmes.     

紫外线消毒海水培育九孔鲍苗的研究

2000年以来自福建省南部海域至广东、海南岛沿海，陆续发生九孔鲍人工培育种苗大量死亡现象一“脱板症”，造成九孔鲍苗的严重短缺。经研究初步认为“脱板症”是一种疑似病毒性疾病。本文针对九孔鲍人工培育种苗疑似病毒性疾病，利用紫外线发生装置消毒海水培育九孔鲍苗，取得了一定的成效，比较药物处理海水培育九孔鲍苗提高出苗率达50％以上。