Modelling the dispersal of larval Japanese sardine, Sardinops melanostictus, by the Kuroshio Current in 1993 and 1994

Acoustic Doppler current profiler (ADCP) data collected during routine monitoring surveys of the distribution and abundance of Japanese sardine larvae ( Sardinops melanostictus ) off the Pacific coast of Japan in February 1993 and 1994 were used to construct stationary average flowfields for three levels in the upper 100 m in each year. No large-scale meanders in the path of the Kuroshio Current were present in either year, but the axis of the current was closer to the coast in 1993 than in 1994. The flowfields were used to drive a particle-tracking model representing the dispersal of sardine eggs and larvae. Particles were released in accordance with the observed distribution of eggs, and their positions tracked for up to 40 days. In 1993, the model indicated that ≈ 50% of the egg production was carried north-eastwards out of the survey area into the area of the NW Pacific referred to as the Kuroshio Extension Zone. In contrast, only 5% of the egg production was exported to the Extension Zone in 1994, the remainder being retained in Japanese coastal waters. The consequences of the different dispersal patterns are discussed in relation to subsequent recruitment to the sardine stock. Based on commercial catch data, survival of the 1993 year class was 15% of that for the 1994 class. Hence, the results indicate that export of larvae to the Kuroshio Extension cannot in itself lead to successful recruitment.     

Application of microparticle diets for Japanese flounder Paralichthys olivaceus larvae

ABSTRACT:   A feeding trial was conducted with two newly developed microparticle diets (MD-Q and MD-V), which differed in the mixing ratios of two types of casein hydrolysates (C700 and C800) as the protein source. The ratio of C700 and C800 were adjusted to 7:3 in MD-Q and 6:4 in MD-V, respectively. Japanese flounder larvae were fed from 7 days after hatching (d.a.h.) to 32 d.a.h. on live food (LF), MD solely, MD + 1/3 LF (either of the MD and one-third quantity of the live food) and 1/3 LF (one-third quantity of live food alone), respectively. They were then switched to Kyowa diet B from 33 d.a.h. until 40 d.a.h. The larvae fed on MD-Q exclusively had a higher survival rate (36.4%) than those fed on MD-V (24.2%) by 22 d.a.h. Unfed larvae could survive up to only 12 d.a.h. Larvae fed on MD-Q + 1/3 LF also had a significantly higher survival rate (34.2%) than those on MD-V + 1/3 LF (16.3%) and 1/3 LF solely (15.4%) at 32 d.a.h. These results suggest the potential of MD-Q as a part replacement for LF from the early developmental stage in the seed production of Japanese flounder.     

Environmental effects on recruitment and productivity of Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus with recommendations for management

We compared a wide range of environmental data with measures of recruitment and stock production for Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus to examine factors potentially responsible for fishery regimes (periods of high or low recruitment and productivity). Environmental factors fall into two groups based on principal component analyses. The first principal component group was determined by the Pacific Decadal Oscillation Index and was dominated by variables associated with the Southern Oscillation Index and Kuroshio Sverdrup transport. The second was led by the Arctic Oscillation and dominated by variables associated with Kuroshio geostrophic transport. Instantaneous surplus production rates (ISPR) and log recruitment residuals (LNRR) changed within several years of environmental regime shifts and then stabilized due, we hypothesize, to rapid changes in carrying capacity and relaxation of density dependent effects. Like ISPR, LNRR appears more useful than fluctuation in commercial catch data for identifying the onset of fishery regime shifts. The extended Ricker models indicate spawning stock biomass and sea surface temperatures (SST) affect recruitment of sardine while spawning stock biomass, SST and sardine biomass affect recruitment of chub mackerel. Environmental conditions were favorable for sardine during 1969–87 and unfavorable during 1951–67 and after 1988. There were apparent shifts from favorable to unfavorable conditions for chub mackerel during 1976–77 and 1985–88, and from unfavorable to favorable during 1969–70 and 1988–92. Environmental effects on recruitment and surplus production are important but fishing effects are also influential. For example, chub mackerel may have shifted into a new favorable fishery regime in 1992 if fishing mortality had been lower. We suggest that managers consider to shift fishing effort in response to the changing stock productivity, and protect strong year classes by which we may detect new favorable regimes.     

Mechanism of body cavity temperature regulation of chum salmon (Oncorhynchus keta) during homing migration in the North Pacific Ocean

Vertical movement patterns of five chum salmon (Oncorhynchus keta) during homing migration were examined using archival tags. The standard deviation of the depth and ambient and body cavity temperatures during daytime were larger than those during night‐time. Vertical movements through the thermocline with a periodicity of less than 1 h were observed during daytime in addition to the diel vertical movement patterns in the open ocean. During these periods of frequent short‐term vertical movements, the difference between the body cavity temperature and ambient temperature was large while the variance of the body cavity temperature was less than that of the ambient temperature. From the results of a random simulation, the variation of the body cavity temperature was shown to decrease due to these periodic high frequency movements in comparison with random vertical movements. The whole‐body heat‐transfer coefficient k (s^?1), which was estimated by a heat budget model, was 1.48 × 10^?3. The k of chum salmon was larger than that of bigeye tuna (Thunnus obesus) by about one order of magnitude for the cooling of the body. The k of chum salmon did not change like tuna, which are physiologically adapted to conserve body cavity temperature. This indicates that the regulation of body cavity temperature by chum salmon is dependent on the vertical movements only. The maintenance of the body cavity temperature is concluded to be advantageous for their maturation and growth from the relationship between energy input and output during their homing migration.     

Proposal of screening method for intestinal mucus adhesive lactobacilli using the enzymatic activity of glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH)

Adhesion tests are complex, time‐consuming and expensive, while the most important criterion for a probiotic lactobacilli is the ability to adhere to the human intestine. Thirty lactobacilli isolates from human intestinal tissues were measured for cell surface glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) activity using a microtiter plate screening method. GAPDH activities were detected in 21 out of 30 samples from 12 h cultures and in all samples from 18 h cultures. This suggests GAPDH is universally expressed on the bacterial cell surfaces from many lactobacilli. A statistically significant positive correlation was shown between GAPDH activity and adhesion using the BIACORE adhesion assay (P < 0.01). The new screening method using GAPDH enzymatic activity without an adhesion test may be possible due to the significant positive correlation of GAPDH activity with adhesion of lactobacilli derived from the human intestine.     

The effects of concentrations of lysine in media on differentiation of 3T3‐L1 preadipocytes

Intramuscular fat content is increased by feeding of low lysine diets in pigs. Reduction in dietary lysine intake results in low plasma lysine concentration and low cytosolic lysine concentration in skeletal muscles. From these observations, we hypothesized that low plasma lysine concentration in pigs fed on low lysine diets reduced supply of lysine from blood circulation to preadipocytes, and this limited supply of lysine might promote adipocyte differentiation in porcine muscles. In order to verify the hypothesis, we investigated the effects of low concentrations of lysine in culture medium on differentiation of 3T3‐L1 preadipocytes. Low concentration of lysine suppressed lipid accumulation and messenger RNA (mRNA) expression and enzyme activity of fatty acid synthase. mRNA expressions of peroxisome proliferator‐activated receptor γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα) were lower in cells cultured in low lysine medium. On the other hand, mRNA and protein expressions of C/EBPβ and C/EBPδ were not inhibited by low concentrations of lysine in culture medium. These results indicate that low lysine concentrations in culture medium inhibit differentiation of 3T3‐L1 preadipocytes through inhibiting the mRNA expressions of PPARγ and C/EBPα.     

Effect of conjugated linolenic acid (cis-9, trans-11, cis-13–18:3) on growth performance and lipid composition of fingerling rainbow trout Oncorhynchus mykiss

ABSTRACT:   This study investigated the effect of conjugated linolenic acid (CLNA) on the growth and lipid composition of fingerling rainbow trout Oncorhynchus mykiss . Thirty individuals in each tank with three dietary treatments and duplicate groups were subjected to three dietary levels (0:4, 2:2, 4:0) of CLNA and linolenic acid (LNA) at 16°C in the laboratory for a period of 9 weeks. Punicic acid ( cis -9, trans -11, cis -13–18:3) and linseed oil were used as sources of CLNA and LNA, respectively. The hepatosomatic index and body lipid content of the 2% CLNA dietary treatment increased significantly ( P  < 0.05) with respect to the control (LNA treatment). But the specific growth rate and percent gain did not improve significantly. After 6 weeks' observation, the 4% CLNA dietary treatment exhibited higher mortality and liver weight but lower weight gains (1.1–1.9 g). No significant differences were observed in the results of the feed efficiency and moisture as well as the protein content of the whole body among the treatments. Incorporation of CLNA into fish tissues was at a distinctly higher level in neutral lipids than in polar lipids. Increased levels of 22:6n-3 were found in the 4% CLNA treatment but decreased levels were found in the 2% CLNA treatment in both neutral and polar fractions. In the CLNA treatments, saturated fatty acid was relatively unaffected, the level of 18:1 was increased and the level of 18:2n-6 was decreased. These results indicate that the lower level (2%) of CLNA had no significant effect on the growth and the higher level (4%) of CLNA caused higher mortality as well as attenuating the growth of the fish. Dietary CLNA accumulated in a greater amount in the neutral lipids and modulated the fatty acid composition in the whole body of rainbow trout fingerlings.     

Inhibition of post-mortem muscle softening following in situ perfusion of protease inhibitors in tilapia

ABSTRACT:     A method of introducing protease inhibitors into fish muscle through the bulbus arteriosus was developed using an in situ perfusion technique. Perfusion efficiency was initially tested using eosin and [³⁵S]-methionine. Visible fluorescence was observed in the gill, liver, intestine and dorsal muscle of the eosin-treated tilapia, and the occurrence of eosin in the blood vessels of the dorsal muscle was confirmed under a fluorescence stereoscopic microscope with ultraviolet light. The radioactivity of [³⁵S]-methionine was taken into the dorsal muscle and liver at a concentration of 7.8 Bq/g and 70.2 Bq/g, respectively, after perfusion with 1000 Bq/mL solution. Using the perfusion technique with four kinds of protease inhibitors dissolved in physiological saline, the type of proteases implicated in the post-mortem muscle softening in tilapia (867 ± 195 g, n  = 10/protease inhibitor) was investigated. After the perfusion of leupeptin (serine and cysteine protease inhibitor), benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk; caspase inhibitor), chymostatin (serine protease inhibitor) and ο -phenanthroline (metalloprotease inhibitor), the breaking strength of the perfused muscle was measured as a parameter of the meat toughness and compared with that of the control fish, which were perfused with physiological saline only. The reduction of breaking strength during storage was inhibited by the perfusion of leupeptin and Z-VAD-fmk.     

Estimation Models for the Morbidity of the Horses Infected with Equine Influenza Virus

Estimation formulas for the morbidity of horses infected with equine influenza virus by linear regression, logistic regression and probit transformation were developed, using data from the outbreak at the Sha Tin Racing Track in Hong Kong in 1992. Using these formulas, we estimated the equine influenza virus morbidity rates at training centers belonging to the Japan Racing Association (JRA) in October 1997 and in October 1998. In 1998 JRA started a new vaccination program, and every horse must now be vaccinated twice per year. At that time, the vaccine included two US lineage virus strains, the A/equine/Kentucky/81 strain and the A/equine/La Plata/93 (LP93) strain, against equine type-2 influenza viruses; it did not include any EU lineage virus strains, such as A/equine/Suffolk/89 (SF89). Comparing the geometric mean (GM) values of hemagglutination inhibition (HI) titers between the LP93 strain and the SF89 strain in 1997 and in 1998, they both rose significantly at every age (p<0.05) by Wilcoxon test. Calculations by the simulation models show the morbidity rates for LP93 diminished from 0.439 (linear), 0.423 (logistic) and 0.431 (probit) to 0.276 (linear), 0.265 (logistic) and 0.271 (probit), respectively. On the other hand, the estimated morbidity rates for SF89 diminished only slightly from 0.954 (linear), 0.932 (logistic) and 0.944 (probit) to 0.946 (linear), 0.914 (logistic) and 0.927 (probit), respectively. Our simulation models could estimate the effect of the vaccine on each of the equine virus strains represented by the morbidity of infected horses. Thus, they are useful for vaccine evaluation.     

Purification and characterization of sulfotransferase specific to O-22 of 11-hydroxy saxitoxin from the toxic dinoflagellate Gymnodinium catenatum (dinophyceae)

ABSTRACT: A novel sulfotransferase (O-ST), which transferred the sulfate group of 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to O-22 of 11-α,β-hydroxy saxitoxin (STX) and produced GTX2 + 3, was purified to homogeneity from the cytosolic fraction of clonal-axenic vegetative cells of the toxic dinoflagellate Gymnodinium catenatum GC21V. After four purification steps, including affinity chromatography and anion exchange chromatography, the enzyme was purified 500-fold and the yield was 4%. On affinity chromatography with a PAP-agarose column, O-ST was observed in the bound fraction, and N-ST specific to N-21 of STX and GTX2 + 3 was found in the unbound fraction. The molecular mass of the purified enzyme was determined by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) to be 65 kDa. Gel filtration chromatography showed a native molecular mass of 67 kDa, indicating that O-ST is a monomeric enzyme. The enzyme was optimally active at pH 6.0 and 35°C. O-ST did not require metal cations for its activity. O-ST required PAPS as the sole source of sulfate. O-ST transferred a sulfate group from PAPS to only O-22 of 11-α,β-hydroxy STX and not to N-21 of these toxins. These observations suggested that two ST, N-ST and O-ST, participate in the sulfation of PSP toxins.