Effect of the squid viscera hydrolysate on growth performance and digestion in the red sea bream <Emphasis Type="Italic">Pagrus major</Emphasis>

The improvement in feed efficiency is one of the most important subjects in fish culture. The development of feed, in terms of good intake, high growth performance, and high feed efficiency is needed. Squid viscera are one of the candidates for alternative material in improving feed efficiency in fish culture. In the present study, we described the dietary effect of the squid viscera hydrolysate (SVH) on the growth performance of the red sea bream. The addition of SVH to feed caused significant increases in feed intake, fork length, and body weight and produced a marked improvement in feed conversion after 4 weeks of feeding. Furthermore, the results of this feeding revealed that low dietary levels of SVH promote growth performance in the red sea bream. We physiologically analyzed digestion and appetite in fish fed diet containing SVH. SVH promoted the activity of hepatic trypsin and lipase, gene expression of stomach pepsin, hepatic lipase, and pyloric caeca trypsin, thereby improving the nutrient availability in red sea bream. Moreover, the mRNA expression of appetite regulating factor, such as brain NPY and stomach ghrelin was significantly improved by dietary SVH. Our current results indicate that dietary SVH as alternative material produced excellent effects on growth performance, which is dependent on the promoting effect on digestion and appetite in red sea bream.     

Protective immunity of sevenband grouper, Epinephelus septemfasciatus Thunberg, against experimental viral nervous necrosis

This paper describes the protective immune responses of sevenband grouper, Epinephelus septemfasciatus Thunberg, immunized with live piscine nodavirus, the causative agent of viral nervous necrosis (VNN), or the Escherichia coli – expressed recombinant coat protein. Nodavirus-neutralizing antibodies were detected at titres ranging from 1:158 to 1:1257 in serum of sevenband grouper which survived intramuscular injection with the virus, by a cell culture assay system. The virus-neutralizing ability of immune serum was also confirmed by injecting virus previously treated with serum into fish. This indicates establishment of acquired immunity in survivors and thus explains why survivors from natural infection are resistant to recurrence of the disease. Young sevenband grouper were immunized twice by intramuscular injections with the recombinant coat protein. Immunized fish produced neutralizing antibodies at high titres for at least 110 days and showed significantly lower mortalities in virus challenge tests. These results suggest the potential for vaccination against VNN in sevenband grouper, which is susceptible to piscine nodavirus at all life-stages.     

Evaluation of stock management procedures for walleye pollock in northern waters of the Sea of Japan using a simulation

To evaluate walleye pollock stock management procedures in the northern waters of the Sea of Japan, 30-year population dynamics, including uncertainties, were forecast. Errors in current stock size estimation, variability in future recruitment and changes in future fishing mortalities were incorporated. Results of virtual population analysis (VPA) from resampled catch-at-age data with bootstrap methods was used as the current stock size estimation with uncertainty. Performances of each scenario were evaluated using conservation, utilization, stability and reliability factors. Twenty-two management scenarios and continuing the current fishing mortality were evaluated. Scenarios with minor regulation changes and continuing the current fishing mortality showed poor stock conservation performances. Scenarios with minor regulation changes produced good short-term but poor long-term utilization. Stabilities were poor in continuing the current fishing mortality and fishing ban scenarios. Reliability in all scenarios after 30 years was smaller than in continuing the current fishing mortality; however, small differences among scenarios were observed. The simulation results indicated that multilateral assessment is needed to evaluate the management candidates. Uncertainty caused by recruitment variability mostly affected future population dynamics. The role of simulations in the production of effective scientific advice is discussed.     

Age estimation of the wild population of Japanese mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> (Crustacea: Stomatopoda) in Tokyo Bay,Japan, using lipofuscin as an age marker

ABSTRACT:   In this study, the age composition of the Japanese mantis shrimp, Oratosquilla oratoria , in Tokyo Bay, central Japan, was investigated using lipofuscin, an autofluorescent pigment, as an age marker. Lipofuscin in a histological section of protocerebral bridge cell mass (PBCM) in the brain was identified by confocal microscopy, and its concentration was quantified by image analysis. Modal analysis of the lipofuscin concentration showed four regularly-spaced modes that could each be regarded as a distinct age group. This implied a constant lipofuscin accumulation in PBCM at a 6.5 × 10⁻²% volume fraction per year; it also implied the existence of individuals that are at least 4 years old. The lipofuscin concentration was found to be a more appropriate index than body length for estimating the age of O. oratoria , because the modal analysis on the body–length histogram failed to detect apparent age groups. This was probably a result of the declining growth rate with age and the individual variations in growth through molting leading to considerable overlap in the size between different age groups. The lipofuscin analysis suggested that fast-growing individuals in each cohort are recruited to the fishery, and most individuals attain the exploitable size between 2 and 3 years of age.     

Protection conferred against viral nervous necrosis by simultaneous inoculation of aquabirnavirus and inactivated betanodavirus in the sevenband grouper, Epinephelus septemfasciatus (Thunberg)

An aquabirnavirus (ABV) and a formalin-inactivated betanodavirus [redspotted grouper nervous necrosis virus (RGNNV)] were investigated for their potential to prevent RGNNV-induced viral nervous necrosis (VNN) in the sevenband grouper, Epinephelus septemfasciatus (Thunberg). Three groups of fish were injected intramuscularly with ABV, intraperitoneally with inactivated RGNNV (iRGNNV) or with both ABV and iRGNNV. At 3, 7, 14, 21 and 28 days post-injection (p.i.), fish were challenged by intramuscular injection of RGNNV. Control fish, which received neither ABV nor iRGNNV, showed high mortalities in all RGNNV challenges. Fish that received only ABV exhibited relative percent survival (RPS) of >60 against RGNNV challenges at 3, 7, 14 and 21 days p.i., but not at 28 days p.i., while fish that received only iRGNNV showed significantly higher protection against RGNNV challenges only at 21 and 28 days p.i. In contrast, fish that received both ABV and iRGNNV showed 60 or higher RPS against all RGNNV challenges. Fish inoculated with iRGNNV with or without ABV exhibited similar high titres of neutralizing antibodies to RGNNV at 14, 21 and 28 days p.i. These results indicate that combined inoculation with iRGNNV and ABV conferred both rapid non-specific and delayed specific protection against VNN.     

Ceramide aminoethylphosphonate from jumbo flying squid Dosidicus gigas attenuates the toxicity of cyanotoxin microcystin-LR

We have previously established the method for isolation of ceramide aminoethylphosphonate (CAEP) from jumbo flying squid Dosidicus gigas. In this study, we performed a MTT assay to evaluate the safety of CAEP to the cell lines for the application to health food and supplements. The CAEP did not show any cytotoxicity to various HEK293-transfectant cells. Next, we elucidated the positive function of CAEP to the somatic cells. Recently, we have reported that hepatotoxin microcystin-LR was taken up into the hepatocytes mediated by hepatocellular uptake transporters OATP1B1 and OATP1B3, and the cells were induced cytotoxicity subsequently. Cytotoxicity of microcystin-LR to permanently OATP1B3-expressing HEK293-OATP1B3 cells rather than to HEK293-OATP1B1 cells was preferentially attenuated by CAEP in a concentration-dependent manner. In addition, the enzyme activity of serine/threonine phosphatase, which was inhibited by microcystin-LR, was recuperated by co-exposure to CAEP. Furthermore, microcystin-LR-induced cellular protein phosphorylation were disrupted by CAEP exposure. These results suggested that CAEP is a promising remedy and/or preventive medicine for liver damage with microcystin-LR.     

Dual effects of reversed winter–spring temperatures on year‐to‐year variation in the recruitment of chub mackerel (Scomber japonicus)

To clarify the effects of temperature on the recruitment of chub mackerel (Scomber japonicus) in the North Pacific, we investigated the influence of winter surface temperature (WST) on spawners at the time of maturity around the spawning grounds and the influence of ambient spring temperature on larvae using estimated temperature (ET) obtained from particle tracking experiments. We found a significant positive correlation between ET approximately 10 days following hatching and the recruitment per spawning stock biomass (RPS) after 2000. The closer (more meandering) the Kuroshio Current (KC) axis was in relation to the spawning ground, the higher (lower) the spring surface temperature and the higher (lower) RPS was in the spawning ground. In contrast, WST inside KC near the maturity/spawning ground was significantly negatively correlated with RPS. A significant negative correlation between the temperatures in winter and spring was detected in the area after 2000, when the conditions of the Pacific decadal oscillation index and the stability of the Kuroshio Extension were synchronous, indicating that KC shifted northward during this time. The reversed temperature pattern was consistent with the winter–spring movement of KC axis in the offshore direction and was correlated with the winter–spring difference in the intensity of the Aleutian low. These results suggest that the annual variation in chub mackerel recruitment after 2000 was strongly affected by the combined effects of ambient temperature because of the reversal of conditions that occurred between winter and spring around the maturity/spawning ground, which was related to the KC path.