Trachurus Japonicus Research Articles

Codend selectivity for jack mackerel and whitefin jack and unequal split parameter estimates observed in trouser trawl experiments

Codend selectivity for the jack mackerel Trachurus japonicus and the whitefin jack Kaiwarinus equula were evaluated based on data from trouser trawl experiments carried out in the East China Sea, using a test codend of 60 mm diamond mesh and a control codend made of minnow net with a square mesh of 9 mm bar length. Between-haul variations in parameters and the mean selection curves were tested with the catch data in the SELECT approach, and then the model of between-haul variation in the split parameter with the mean selection curve was chosen as the best fit using Akaike’s information criterion model selection. The 50% retention lengths and the selection ranges were 11.4 and 3.36 cm for jack mackerel and 8.83 and 0.93 cm for whitefin jack, respectively. The selection curve for whitefin jack was sharp, whereas that for jack mackerel was relatively wide. As the estimated split parameters indicated, about 80% of the whitefin jack entered the control codend, but 85 and 90% of the jack mackerel entered the control codend in the second and third hauls, respectively. The inequality in the split parameter is discussed from the viewpoint of the animal’s swimming behavior and water movement based on underwater video observations.

口腔・咽頭の異物としての魚骨に関する研究（２）

In recent years, seafood consumption has been declining nationwide. One of the suggested reasons for this downtrend, known as flight from fish, is the problem with throat lodgement of fish bone from seafood dish. The Pacific saury, Japanese jack mackerel, sardine, mackerel, and Japanese eel are commonly consumed fish, but their small bones tend to lodge in the throat. Here, we report the morphological characteristics of small bones of these types of fish. Twenty samples of each of the Pacific saury, Japanese jack mackerel, sardine, mackerel, and Japanese eel were purchased from fish markets during the period from January to December 2009. Abdomens of raw or cooked fish were dissected to recover small bones (ribs, epipleural, epicentral, epineural and pteygiophore). The bone samples were first subjected to softex radiography and then stained with alizarin red S. The length and diameter of these bone specimens were measured and their form were observed under a microscope. Decalcification of small bones immersed in acetic acid was observed in a similar manner. It was found that the tips of the small bones of the Pacific saury, sardine, and Japanese jack mackerel were very pointed, suggesting that these can easily damage the tonsilla palatina and lodge in the pharynx. Formation of hook-shaped lumps in their base parts were also observed, and this was considered to cause frequent deep lodgement of bones in the larynx leading to difficulties in their removal. The small bones of the Pacific saury and sardine were finer, denser and more elastic than those of the Japanese jack mackerel and mackerel, and that the small bones of the Japanese eel were sharply pointed at both ends and finer than those of the other types of fish. These results suggest that the sites, forms, and incidence of lodgement of small fish bones in the throat vary depending on the types of fish.

3Pa6-4 Developments of a New Discrimination Method between Japanese Jack Mackerel and Chub Mackerel by Using the relation between incident angle and reflect ratio(Poster Session)

3Pa6-4 Developments of a New Discrimination Method between Japanese Jack Mackerel and Chub Mackerel by Using the relation between incident angle and reflect ratio(Poster Session)

Studies on the Benefits for Human Health on Fermented Seafood and the Development of Freshness Maintenance Technique of Fish

I and my students have developed some fish sauces made from puffer, whale and sea urchin gonad as the local specialties of Shimonoseki city in west Japan. These sauces were commercialized. Antioxidant actives of these sauces were measured by using chemiluminescence, ESR (electron spin resonance), ORAC (oxygen radical absorbance capacity) and HORAC (hydroxyl radical averting capacity) methods. As the results, these sauces indicated the high antioxidant activities. Furthermore, these sauces were researched by the next-generation food functional estimation method, i.e., the new simultaneous measurement method using cellular signal transduction mechanisms. This method means the simultaneous measurement of chemiluminescence and fluorescence by LED light indicating superoxide anion radical generation and intracellular calcium ion concentration, respectively, of neutrophil-like HL60 culture cells. It was found that some sauces indicated the anti-inflammatory activity in addition to antioxidant activity. On the other hand, I and co-researchers investigated the supply of high quality frozen raw fish by a quick freezing method using alcohol brine. The whole body of Japanese horse mackerel was used. Alcohol brine freezing at -25°C was compared with air freezing at -20°C. Quality of fish meat was analyzed using K value as an indicator of freshness by HPLC, pH, TBARS value as an indicator of lipid oxidation, remaining ethanol by GC/MS and sensory test. As the results, it was indicated that the fish meat frozen quickly by alcohol brine method was superior to that by air freezing.

Ecomorphological dimorphism of juvenile Trachurus japonicus in Wakasa Bay, Japan

Morphometric analyses of marine pelagic fishes have generally been conducted for stock identification rather than for ecomorphological understanding. Many papers on stock identification of Trachurus japonicus reported polymorphisms in the Japanese Islands waters. However, none of them has found polymorphism in fish less than 100 mm standard length (SL), despite the environmental differences experienced by juvenile cohorts. The objective of this study was to detect ecomorphological polymorphism of juvenile T. japonicus (<100 mm SL) in Wakasa Bay, Japan, where multiple juvenile cohorts appear. From analyses of size frequency distributions and otolith microstructure, five cohorts were recognized in the bay from September 2003 to August 2004. We then compared 17 morphometric characters on body, fin, and otolith morphology, and found cohort-specific and roughly dimorphic pattern (a streamlined morph and a compressed morph). The dimorphism was markedly observed in 50–70 mm SL, and was regarded as specific to the juvenile stage by comparison with the senior dimorphisms (≥100 mm SL). Referring to the literatures on functional morphology, the streamlined morph and the compressed morph were considered to be suitable to body and caudal fin (BCF) periodic propulsion and BCF transient propulsion, respectively. The juvenile dimorphism was interpreted as adaptive in its developmental environments (i.e., ecomorphological dimorphism) by relating the functional differences to the inferred ecological differences: the streamlined morph is adaptive to feed on larval Engraulis japonicus in coastal waters, whereas the compressed morph is adaptive to associate with jellyfishes in offshore waters.

Ontogenetic changes in the spatial learning capability of jack mackerel Trachurus japonicus

Ontogenetic changes in learning capability were studied in jack mackerel Trachurus japonicus juveniles ranging from 20 to 95 mm standard length (L(S)) collected from either pelagic or coastal habitats. Simple spatial and reversal learning tasks were used to estimate learning capability. There was no size dependence in the scores of simple reward conditioning using a Y-maze, whereas the scores of reversal learning tasks showed a clear sigmoidal curve of increase with an inflexion point at 51·7 mm L(S). The increase in this learning capability coincided with the size at which juveniles recruit from offshore pelagic to coastal rocky habitats.

Kudoa iwatai and two novel Kudoa spp., K. trachuri n. sp. and K. thunni n. sp. (Myxosporea: Multivalvulida), from daily consumed marine fish in western Japan

Infection of marine fish by certain myxosporean species of the genus Kudoa results in unsightly cyst formation in the trunk muscle or post-mortem myoliquefaction, causing a great economic loss to aquaculture industries, capture fisheries, and fish dealers. In addition, consumers encountering unsightly Kudoa cysts in fish fillets believe them to be unknown foreign materials acquired during processing. To identify prevalent Kudoa spp. encountered in daily life by the Japanese population, fresh fish slices (sashimi) or fish fillets with whitish spots were collected during a 7-month period (May to December 2008) at local markets in the city of Yamaguchi, western Japan. Kudoa cysts were found in three Japanese seaperches (Lateolabrax japonicus), two black sea bream (Acanthopagrus schlegelii), two Japanese jack mackerel (Trachurus japonicus), and one albacore (Thunnus alalunga). Kudoa iwatai was identified in all the examined Japanese seaperch and black sea bream from Japan's Inland Sea, as assessed by morphology and genetic analysis of the 18S and 28S ribosomal RNA gene (rDNA). Kudoa trachuri n. sp. from two Japanese jack mackerel fished in the Japanese Sea off Nagasaki and Kudoa thunni n. sp. from one albacore fished in the Pacific Ocean had a spore, which was semiquadrate in shape in apical views and ovoid in lateral views, with four equal shell valves and drop-like polar capsules. Scanning electron microscopy revealed that these three Kudoa species had different types of small projections at the apex of each valve. The 18S and 28S rDNA sequences of K. trachuri n. sp. and K. thunni n. sp. were found to be closely related to those of Kudoa crumena; however, these sequences were distinct in each of the species, which additionally exhibited different morphological features.

Variations in otolith patterns, sizes and body morphometrics of jack mackerel Trachurus japonicus juveniles

Variations in otolith patterns, sizes and body morphometrics of jack mackerel Trachurus japonicus juveniles were investigated. Under transmitted light, translucent (W(t)) and opaque otoliths (W(o)) were detected in juveniles collected from Wakasa Bay between July 2005 and April 2006, whereas only opaque otoliths (G(o)) were detected in Goto-nada Sea individuals between May and June 2006. Three groups of juveniles were distinguished based on differences in hatch season, otolith size and growth history, and body morphometrics. As T. japonicus has different spawning seasons according to spawning grounds, each group was estimated to hatch in different waters. Juveniles with W(t) otoliths were considered to have stayed in coastal habitat longer, as the hatch area was estimated to be near Wakasa Bay. Juveniles with W(o) and G(o) otoliths appear to recruit to coastal waters at larger size, since their hatch areas were estimated to be far from each collection area. Larger otoliths of W(t) were attributed to otolith accretion after the second growth flexion, which was observed only for W(t) . Standard length of W(t) fish at the second otolith growth flexion was estimated to correspond to recruitment size to coastal rocky reefs in Wakasa Bay. Body morphometrics were correlated with otolith size after removing body size effect, suggesting that morphological variations of T. japonicus juveniles were also associated with the timing of recruitment to coastal habitat.

Food habits of fishes on an exposed sandy beach at Fukiagehama, South-West Kyushu Island, Japan

To clarify the feeding habits and major food sources of sandy beach fishes, the gut contents of 55 fish species collected on a sandy beach at Fukiagehama, South-West Kyushu Island, Japan, were examined. Ontogenetic changes in food preference were recognized in nine species (Hypoatherina valenciennei, Lateolabrax japonicus, Trachurus japonicus, Sillago japonica, Sphyraena japonica, Paralichthys olivaceus, Heteromycteris japonica, Paraplagusia japonica, and Takifugu niphobles). A cluster analysis based on dietary overlaps showed that the sandy beach fish assemblage comprised six trophic groups (mysid, amphipod, zooplankton, juvenile fish, terrestrial insect, and mollusk feeders). Of these, the first three groups were the most abundantly represented, whereas the last two were represented by only a single species. These results indicated that epibenthic macrofauna, such as mysids and gammaridean amphipods, and zooplankton, were important food resources for the fish assemblage at the study site, but infaunal macrobenthos, such as polychaetes and bivalves, being relatively unimportant.

Quantitative Risk Assessment of Vibrio parahaemolyticus in Finfish: A Model of Raw Horse Mackerel Consumption in Japan

The aim of this study was to evaluate the effects of implemented control measures to reduce illness induced by Vibrio parahaemolyticus (V. parahaemolyticus) in horse mackerel (Trachurus japonicus), seafood that is commonly consumed raw in Japan. On the basis of currently available experimental and survey data, we constructed a quantitative risk model of V. parahaemolyticus in horse mackerel from harvest to consumption. In particular, the following factors were evaluated: bacterial growth at all stages, effects of washing the fish body and storage water, and bacterial transfer from the fish surface, gills, and intestine to fillets during preparation. New parameters of the beta-Poisson dose-response model were determined from all human feeding trials, some of which have been used for risk assessment by the U.S. Food and Drug Administration (USFDA). The probability of illness caused by V. parahaemolyticus was estimated using both the USFDA dose-response parameters and our parameters for each selected pathway of scenario alternatives: washing whole fish at landing, storage in contaminated water, high temperature during transportation, and washing fish during preparation. The last scenario (washing fish during preparation) was the most effective for reducing the risk of illness by about a factor of 10 compared to no washing at this stage. Risk of illness increased by 50% by exposure to increased temperature during transportation, according to our assumptions of duration and temperature. The other two scenarios did not significantly affect risk. The choice of dose-response parameters was not critical for evaluation of control measures.

On the fishing condition and size of horse mackerel, Trachurus japonicus, taken in the Pacific coast of Tokushima Prefecture

On the fishing condition and size of horse mackerel, Trachurus japonicus, taken in the Pacific coast of Tokushima Prefecture

Abnormal development of the cranial bones of “Jack-Mackerel” Trachurus japonicus TEMMINCK & SCHLEGEL with the growth

Abnormal development of the cranial bones of “Jack-Mackerel” Trachurus japonicus TEMMINCK & SCHLEGEL with the growth

Colour preference of five marine fishes: bias for natural and yellow-dyed krill in laboratory tanks, sea cages and an earthen pond

In this study, the colour preference during feeding was determined in three members of the family Sparidae: girella (Girella punctata Gray), the black porgy (Acanthopagrus schlegeli Bleeker) and the Japanese silver bream (Acanthopagrus latus Houttuyn); and in two members of the family Scombridae: the Japanese horse mackerel (Trachurus japonicus Temminck et Schlegel) and the spotted mackerel (Scomber australasicus Cuvier). The three sparids are omnivorous and are confined to neritic habitats and the two scombrids are schooling planktivores and open-ocean forms. The experiments were conducted under three different holding conditions: grey and white tanks in the laboratory, sea cages and an earthen pond. The prey used in the tests was the Antarctic krill, in its natural colour (control) and in artificial colours of yellow, red, green, blue (produced with food dyes) and black (Chinese ink). These prey were offered in different two-colour pairs to groups of fish, and the colour of the krill attacked first was recorded. The frequencies of first attacks against each colour of the different pairs were analysed by the paired-preference test and Thurstone's law of comparative judgment. The data were converted into mean z-scores and significant biases from zero were noted. The five species took without hesitation all the krill of all colours, but preferred blue krill the least, and did not clearly distinguish red from black. The three sparids showed a strong bias for yellow krill under all holding conditions. The two scombrids preferred natural krill and showed poor colour preference. The observed colour preference was probably due to colour per se and may be an innate ability, rather than due to relative brightness (sensitivity of the fish eye), prey conspicuousness (pigmented eyes of the krill), or the associated taste of the dyes.

Trash fish can be a source of betanodaviruses for cultured marine fish

A total of 360 samples of trash fish/mollusk used for feeding cultured marine fish were collected from 4 stations of National Research Institute of Aquaculture, Fisheries Research Agency, Japan. The brain or eyes of the samples were examined by reverse transcription-polymerase chain reaction (RT-PCR) and nested PCR assays to detect the coat protein gene of betanodavirus. Two species of trash fish/mollusk samples: Japanese jack mackerel Trachrus japonicus and Japanese common squid Todarodes pacificus were positive for betanodavirus and the sequences of the nested PCR products (177 nucleotides) of these two species were closely related (98%) to the redspotted grouper nervous necrosis virus (RGNNV) genotype. Sevenband grouper Epinephelus septemfasciatus were intramuscularly injected (10 6 TCID 50/fish) with betanodavirus isolates from trash fish/mollusk samples. The fish displayed abnormalities typical of viral nervous necrosis (VNN) infection, and mortalities ranged from 90 to 100%. These results suggest that trash fish/mollusk can be a source of betanodaviruses for cultured fish and that they pose a serious risk for outbreaks of VNN in susceptible cultured fish.

Effects of Hypoxia on Respiration in the Jack Mackerel, Trachurus japonicus

Effects of Hypoxia on Respiration in the Jack Mackerel, Trachurus japonicus

Eleven new microsatellite markers in jack mackerel (Trachurus japonicus) derived from an enriched genomic library

Jack mackerel (Trachurus japonicus, Carangidae) are a commercially important fisheries resource in Korea. To understand patterns of genetic variation for conservation and management efforts, we developed microsatellite DNA markers fromT. japonicus. We report the isolation and characterization of eleven microsatellite loci isolated using an enrichment method based on magnetic/biotin capture of microsatellite sequences from a size-selected genomic library. To characterize each locus, 50 individuals from a naturalT. japonicus population in southern Korea were genotyped. All loci except one, KTJ38, were polymorphic with an average of 14 alleles per locus (range 6–23). The mean observed and expected heterozygosities were 0.70 (range 0.46–0.92) and 0.81 (range 0.49–1.00), respectively. Significant deviation from Hardy-Weinberg equilibrium was observed at three loci, KTj3, KTJ20 and KTJ28. Such high variability indicates that these microsatellites are useful markers for high-resolution analysis for population gemetic studies.

한국 제주 인근해역에 서식하는 전갱이, Trachurus japonicus Temminck et Schlegel의 재생산 연구: 성숙과 산란

Maturation and spawning of the jack mackerel, Trachurus japonicus was investigated based on the samples captured in the coastal waters around Jeju Island from January 2007 to December 2008. Gonadosomatic index began to increase in March, and reached a maximum between April to June. After spawning it began to decrease from August. Reproductive season was estimated to March-July, with peak in April. Fecundity was proportional to the size of the female, with the clutch size varying from 33,493 eggs in the smallest female(FL=27.0cm) to 627,061 eggs in the largest(FL=40.6cm). Size at 50% sexual maturity(FL50), determined from mature females, was 26.6cm FL. Annual reproductive cycles of this species could be divided into six successive stages; immature stage(September-December), nucleolus stage(January-February), yolk vesicle stage(February-March), vitellogenic stage(March-April), ripe stage(April-July) and spent stage(July-September).

거제도 능포 정치망 어장의 어획물과 어획량 변동요인

The fisheries resources by a set net in the coastal waters off Neungpo, Goeje Island from 2003 to 2004 were studied to determine species composition and catch variation. The main fishing period by a set net were from April to December in 2003 and from May to December in 2004. A total weight of 48 species caught through the survey period was 540,688.0kg. Most of them were 44 species of fishes and a few were 4 species of cephalopods. Dominant species was Trachurus japonicus accounting to 57.5% in total catch. Subdominant species were Trichiurus lepturus(12.9%), Engraulis japonicus(10.6%), Scomber japonicus(6.9%), Clupea pallasii(4.5%), Todarodes pacificus(2.8%) and Parapristipoma trilineaturm (1.3%). The remnant species showed a low catch, indicating the catch had less than 1% in total, respectively. T. japonicus and T. lepturus were caught throughout the survey period, but C. pallasii, Gadus macro-cephalus, Oncorhynchus keta in low temperature season and Thunnus obesus in high temperature season. The fishing ground temperature was 11.7 24.0 in range and the catch by a set net was higher in autumn than in spring and in summer with the variation of fishing ground temperature. The annual catch by a set net was much higher in 2004 than in 2003 due to high temperature( 17 ) and the recruitment of T. japonicus from offshore seas. Therefore we concluded that the catch of Neungpo fishing ground by a set net was highly related to the variation of T. japonicus catch with fishing ground temperature.

Microbial and chemical properties of aji-no-susu, a traditional fermented fish with rice product in the Noto Peninsula, Japan

Aji-no-susu is a Japanese fermented fish product prepared from salted horse mackerel Trachurus japonicus, and cooked rice. We studied the organic acid and free amino acid contents and microflora in 12 aji-no-susu products to clarify their features as a lactic-acid-fermented food. Salinity of the samples was approximately 7.0% (rice portion) and 6.0% (fish portion) (w/w). Water activity was approximately 0.9, and pH was approximately 4.4 and lower. In the rice portions, lactic acid content was very high (57 mg/g sample). The predominant amino acids were alanine (2.3 mg/g rice portion) and lysine (2.1 mg/g). In the case of long-fermented (4 and 12 months) aji-no-susu, a high content of gamma-aminobutyric acid (GABA, 1.5 and 1.4 mg/g) was detected. Total viable counts in rice and fish portions were 7.7 and 7.4 log colony-forming units (cfu)/g, respectively. The number of lactobacilli in the rice and fish portions was 7.3 and 7.1 log cfu/g, respectively. Yeasts were detected in eight samples. Furthermore, acid-tolerant lactic acid bacteria (LAB) (Lactobacillus plantarum), GABA-producing LAB (Lactobacillus sp.), and halophilic or halo-tolerant yeast (Debaryomyces hansenii) were isolated and identified. Results in this study indicate that aji-no-susu is a typical traditional lactic-acid-fermented fish product.

Effect of temperature on the swimming endurance and post-exercise recovery of jack mackerel Trachurus japonicus as determined by ECG monitoring

The effect of temperature on the swimming performance of jack mackerel Trachurus japonicus was examined in a flume tank by measuring the swimming endurance time and heart rate. The lower swimming performance was observed at 10°C (the lowest temperature tested), manifesting as the shortest endurance time and the slowest maximum sustained speed. ECG measurements of the heart rate under free-swimming conditions at zero flow velocity revealed a temperature effect, with 25.3 beats/min observed at 10°C, 38.9 at 15°C, and 67.2 at 22°C. The heart rate also increased with swimming speed to maximum levels of 60, 125, and 208 beats/min, respectively, at these three temperatures. Heart rate recovery times measured after the fish had been swimming at prolonged speed tended to increase with temperature, while a negative correlation resulting in relatively short recovery times was observed after swimming at close to the burst swimming speed at each water temperature.