<Superscript>1</Superscript>H-NMR metabolite profiling of abalone digestive gland in response to short-term starvation

The effect of a short-term feeding and starvation experiment on juvenile abalone (Haliotis rubra × H. laevigata) was investigated (average length = 67 mm; average weight = 48 g). All aquaculture experiments were conducted at The University of Melbourne, Australia. Artificial feed was supplied ad libitum to the fed group, and no feed was supplied to the starved group. A modified metabolite extraction protocol using deuterated solvents was developed for ¹H-NMR-based metabolite profiling of digestive gland in response to the short-term feeding/starvation experiment, to avoid lyophilisation prior to biochemical analysis. PLS-DA revealed that fed and starved abalone are metabolically distinct from each other after 28 and 56 days. After 28 days, the fed group was defined by an increase in arginine, glucose, glutamate, glycine, inosine and uracil (P < 0.05), and the starved group was defined by an increase in N,N-dimethylglycine. After 56 days, the fed group still displayed increased glucose (P < 0.05), while N,N-dimethylglycine remained elevated in the starved group (P < 0.05). Arginine and glycogen were all higher at 28 days compared to 56 days, suggesting decreased anaerobic energy production at the later time point. Only glucose and N,N-dimethylglycine were significantly different between the fed and starved groups after 56 days, suggesting that abalone had not acclimatised to the starvation treatment after 28 days. These results infer N,N-dimethylglycine is a robust marker for short-term starvation in abalone. ¹H-NMR was also conducted on the artificial feed and starved abalone faecal matter, revealing the biochemical differences between them and digestive gland tissue. These methodology and results will facilitate a deeper understanding of the nutritional and physiological requirements of abalone in an aquaculture setting.     

Effects of cooling rate on post-thaw motility and fertility of Japanese pearl oyster <Emphasis Type="Italic">Pinctada fucata martensii</Emphasis> spermatozoa

The post-thaw motility and fertility of Japanese pearl oyster sperm show large variances, even among sperm samples obtained from the same individuals. This study aimed to clarify the factors that cause such differences. Spermatozoa were diluted 50 times with diluent comprising 10 % methanol, 18 % fetal bovine serum, and 72 % seawater, and dispensed into 0.25 ml straws. A total of 59 straws were cooled, one by one, at 11 different heights from the surface of liquid nitrogen (LN) to −50 °C, and then immediately immersed in LN. After thawing the straws, the relationships between the cooling rate and the post-thaw motility and post-thaw fertility of the spermatozoa were examined. Both the post-thaw motility and the post-thaw fertility showed a sharp peak when the straws were cooled at around −20 °C/min. There was a strong correlation between post-thaw motility and fertility (P < 0.001). There was a large difference in the cooling rates and the post-thaw motilities and fertilities of the spermatozoa, even between straws cooled at the same height. These results indicate that the optimum range for the cooling rate of oyster spermatozoa is quite narrow, and the method of cooling straws at a fixed distance from the LN surface is unsuitable for the cryopreservation of Japanese pearl oyster spermatozoa.     

新时期保障中国粮食安全的对策研究

"民以食为天",粮食安全是国家经济安全和社会稳定的基础,保障粮食安全已经成为中国重要的国家发展战略。通过对当前中国粮食生产现状与特征进行深入分析,剖析了中国粮食增产背后农业科技的重要支撑作用,明确了未来发展阶段保障中国粮食安全的总体目标,并从大力提升粮食科技创新能力、加快农业经营体制机制创新和不断完善粮食政策等方面提出了保障中国粮食安全的对策建议。     

Paralytic shellfish poison as an attractant for toxic snails

The attracting effect of paralytic shell poison (PSP) on eight toxic snail species (Polinices didyma, Natica lineata, N. vitellus, Zeuxis sufflatus, Niotha clathrata, Oliva miniacea, O. mustelina, O. hirasei) and two non-toxic species (Pomacea canaliculata, Satsuma bairdi) was investigated. Eight toxic species were reported to contain tetrodotoxin, and three out of these contained minor PSP. The minimum lethal dose of PSP in most toxic gastropods was estimated to be more than 150 MU PSP/20 g body weight, but in non-toxic gastropods was less than 15 MU PSP/20 g body weight. After the attracting test, all toxic gastropods showed significant positive linear relationship (Y=3.716X+0.363, r=0.8427) between comparative attracting variation and the toxicity reported. The relationship between PSP resistance ability and the toxicity also had a positive correlation (Y=0.91X+210.090, r=0.6803). However, the non-toxic species showed a negative response. This indicates that PSP is an attractant for toxic snails.     

Influences of feeding frequency of extruded pellet and moist pellet on growth and body composition of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> in suboptimal water temperatures

This study was carried out to investigate the influences of feeding frequency of extruded pellet and moist pellet on growth and body composition of juvenile flounder (initial mean weight 6.3 g) in sub optimal water temperatures. A 2 (diets: extruded pellet and moist pellet)×2 (feeding frequencies: two and three times daily)×2 (water temperatures: 12 and 17°C) factorial design with three replications was used. After 60 days of feeding, the feeding frequency did not significantly affect growth performance of fish. Weight gain, daily feed intake, feed efficiency and protein efficiency ratio were significantly (P<0.05) higher for fish reared at the higher water temperature. At the same water temperature, weight gain, feed efficiency, and protein efficiency ratio were significantly (P<0.05) higher for fish fed the extruded pellet than moist pellet. The results of this study indicate that feeding frequency of two times daily is sufficient for optimal growth of juvenile flounder when reared in suboptimal water temperatures, and an increase in water temperature from 12 to 17°C improved growth and feed efficiency.     

Growth changes in bighand thornyhead <Emphasis Type="Italic">Sebastolobus macrochir</Emphasis> off the Pacific coast of northern Honshu,Japan

ABSTRACT:     The biomass of bighand thornyhead Sebastolobus macrochir was increased by the high recruitment success of the 1999–2002 year classes off the Pacific coast of northern Honshu, Japan. In this study, the growth of bighand thornyhead was examined over a 9-year period from 1996 to 2004 in this area. The growth of the 1999 year class and the 2000–2002 year classes was reduced at 3 and 2 years old, respectively, while the 1999–2002 year classes were smaller than the 1993–1998 year classes. In 2-, 3- and 4-year-old fish, the relationship between abundance and mean standard length was expressed by negative linear regressions, while fish became smaller when abundance of the year class was larger. Mean bottom temperatures were stable at depths of 350–900 m; variations in water temperature were small in the main distribution area of bighand thornyhead. We discuss the factors affecting the growth of bighand thornyhead via changes in the demersal fish community and feeding habits.     

Consumer perception versus scientific evidence of farmed and wild fish: exploratory insights from Belgium

The increasing number of marketable fish being supplied from aquaculture is a response to the increasing demand for healthy food and is filling the gap left by depleting natural fish stocks. Little is known about the awareness and perception of the consumer in terms of farmed fish versus fish from capture fisheries. The consumer's subjective point of view is of overriding importance for the production system and product acceptance as well as for future market success. In this paper consumer perception in Belgium is explored and compared against scientific evidence of farmed versus wild fish. Primary data were collected through a consumer survey (April 2003) and focus group discussions (May 2004) with Belgian consumers. The majority of the consumer sample reported no perceived differences between farmed versus wild fish. However, mean perception scores were slightly in favour of wild fish on the attributes taste, health and nutritious value, in particular among consumers aged 55 years and older. The availability of farmed fish was perceived to be better than that of wild fish, while the consumer's perception of safety did not differ between farmed and wild fish. The focus group discussions indicated that consumers’ opinions and beliefs about farmed fish are mainly based on emotion and image transfer from intensive terrestrial livestock production rather than on awareness and factual knowledge of aquaculture.

<Emphasis Type="Italic">Streptococcus agalactiae</Emphasis> from tilapia (<Emphasis Type="Italic">Oreochromis</Emphasis> sp.) transmitted to a new host,bighead carp (<Emphasis Type="Italic">Aristichthys nobilis</Emphasis>), in China

Several outbreaks of Streptococcus agalactiae infection of bighead carp (Aristichthys nobilis) were observed in China. The molecular epidemiology and pathogenicity of S. agalactiae in bighead carp and tilapia (Oreochromis sp.) is poorly understood. In the present study, we identified S. agalactiae strains isolated from diseased bighead carp using the API 20 Strep kit and 16S rDNA sequencing and determined whether these strains came from tilapia. Of the 46 identified S. agalactiae strains, 24 strains were successfully isolated from diseased bighead carps, 20 S. agalactiae strains were isolated from tilapia, and two S. agalactiae strains were isolated from tiger frog (Hoplobatrachus chinensis). The results of molecular typing, including multilocus sequence typing, molecular serotyping, surface protein gene detection, and virulence-related gene detection showed that the 44 strains from bighead carp and tilapia were highly similar, whereas different from tiger frog GBS strains. Remarkably, the bighead carp strain Hn1404 showed high virulence in bighead carp and zebrafish. Moreover, this strain was pathogenic to Nile tilapia (Oreochromis niloticus). In addition, comparative genomic analysis showed that isolate Hn1404 had a close relationship with the bighead carp and tilapia S. agalactiae strains. All the analyses of the genetic characteristics of bighead carp and tilapia strains showed that tilapia S. agalactiae strains could be transmitted to other fish species such as bighead carp.