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Focuses on the otolith microstructural analysis of reared larvae of the Japanese eel Anguilla japonica in Japan. Validation of the daily deposition of otolith increments; Problems with the rearing techniques used with eel larvae; Estimation of the early growth of artificially fertilized larvae in comparison with wild glass eels.

Investigates the biological indicator for stock identification of sandfish Arctoscopus japonicus in Japan. Role of the copepod Steindachner Acanthochondria priacanthi; Parasitic relationship between the sand fish and the crustacean; Percentage of infected hosts in a sample.

Focuses on the non-destructive determination of fat content in frozen and thawed mackerel by near infrared spectroscopy in Japan. Importance of fat content and freshness vis-a-vis fish quality; Analysis of the multiple linear regression based on second derivative spectra and fat content in frozen and thawed fish; Calibration equation with temperature compensation of fish samples.

Examines the effect of increased seawater temperature on Ecklonia cava population in Tosa Bay, southern Japan. Ecophysiology; Seasonal average surface water temperature; Photosynthetic rate of bladelets of Ecklonia cava.

Studies the impact of the water currents, temperature and salinity along the coastal areas of northern Japan on the occurrence of Dinophysis species, the causative plankton of diarrhetic shellfish poisoning. Collection of samples of the species and seawater along Kesennuma Bay; Determination and monitoring of inorganic concentration of nitrogen and phosphorus; Influences of salinity and the different environmental conditions to the appearance of the species.

Studies the potential smolting ability of stream-dwelling Dolly Varden, Salvelinus malma. Collection of samples of the species; Classification of the species into phenotypes according to body coloration characteristics; Observation of the phenotypes on their smolting abilities.

To understand and manage marine ecosystems for conservation, particle-tracking simulation based on a realistic ocean model is one of the most basic and essential scientific numerical techniques for a multidisciplinary approach. In Japanese waters, this technique was first used under somewhat simplified conditions in the 1980s, and then it continued to be developed, with the number of studies using this technique increasing drastically after the mid-2000s. At that time, mesoscale eddy-resolving ocean forecast systems moved into operational phase, and since then, those reanalysis or analysis products have been publicly shared among scientists. This article provides an overview of the history and current status of particle-tracking simulation for marine biology around Japan (e.g., target species, ocean models utilized, configurations and timescales of particle-tracking models, and related biological data) and summarizes the scientific resources to be maintained and some issues to be resolved in the next future step. [ABSTRACT FROM AUTHOR]

The paper compiles a catch history of Japanese eels Anguilla japonica in East Asia and some Japanese relative abundance series. Maximum likelihood estimates of stock abundance of eels have been obtained using the abundance series and various biological parameters, such as growth, maturity and natural mortality. Age- and sex-structured models have been used to express the dynamics of stock abundance, and the Beverton and Holt model has been used to express the relationship between stock and recruitment. Data for estimations are standardized catch per unit effort of commercial fishery for exploitable stock (1954-2006 and 1968-2008) and for glass eel (1954-2010, 1972-2004, and 1973-1997). From the results of the base case scenario of estimations, the estimated stock size of individuals aged ≥1 year was 18.7 thousand tons in 2010, which was 24 % of the carrying capacity. The estimated stock size has recovered since 1990. Maximum sustainable yield was 4,180 tons if only the exploitable stock were utilized, and 266 tons if only the glass eel were utilized. These results and issues relating to estimation and management for reducing the fishery impact on stock are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we examine the structure and change of the walleye pollock industry from a marketing and distribution perspective. Our focus is not only on industrial internationalisation, but also on local industry and community utilisation of walleye pollock. This is a subject of interest because its diverse utilisation has the potential to promote industrial management as well as the livelihood of local communities. We reason that Japan's weakness in marketing, distribution and price setting of walleye pollock is largely due to its lack of competitiveness in the world market. Given the rapid decline of walleye pollock utilisation by local industry and society, it is of critical importance to take steps towards a long-term solution considering the rapid decline of walleye pollock use by our local industry and society. Our analysis indicates that Japan's walleye pollock industry is inherently resilient, with diverse commodity chains, business flexibility and traditional food culture. However, as local industry and community have been reducing use of walleye pollock over time, there is a need to restore and reactivate the local society. [ABSTRACT FROM AUTHOR]

To validate the involvement of meiobenthos in cellulose breakdown in wetlands, meiobenthos were collected from sediments of Lake Furen and the Biwase River in Hokkaido Prefecture, the Kako River in Hyogo Prefecture, and the Chinai River in Shiga Prefecture. Cellulase activities of the meiobenthos were measured by cellulose zymographic analysis using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) gels containing 0.5% carboxymethyl cellulose. The results showed that most of the Turbellaria, Nematoda, Harpacticoida, and Oligochaeta species exhibited cellulase activity. The molecular sizes of the cellulase-active bands of the sediments in Lake Furen, the Biwase River, and the Chinai River coincided with those of meiobenthos. The findings suggest that meiobenthos might play a major function in cellulose breakdown in these wetlands. This paper is the first to report cellulase activity in meiobenthos and that they are possibly involved in the breakdown of cellulose in wetlands. [ABSTRACT FROM AUTHOR]

Toxic heavy metals such as cadmium (Cd) accumulate in cultured fish from solid-form feed mixtures. In this paper, two natural ingredients, supposed to inhibit accumulation of heavy metals in the fish body, were investigated to develop a functional feed mixture for healthy fish. Three test diets: (i) ♯1, regular diet as negative control; (ii) ♯2, ♯1 + 2% lyophilized Chinese parsley Coriandrum sativum (CP); and (iii) ♯3, ♯1 + 3% chitosan (CT), were each fed to 50 rainbow trout Oncorhynchus mykiss once a day, at the constant rate of 1.0–1.2% of body weight for 12 weeks. No undesirable effect on fish growth was observed by an addition of either CP or CT to regular feed. Then, 10 mg Cd was added to 1 kg each of the three test diets and they were named as: (i) ♯4, ♯1 + Cd; (ii) ♯5, ♯2 + Cd; and (iii) ♯6, ♯3 + Cd, respectively. The fish given positive a control feed (diet ♯4) for 3 weeks accumulated Cd in the liver and kidney at approximately 0.52 mg/kg. However, Cd in ordinary muscle was found to be just above the detection limit. Upon accumulation of Cd, three groups of 50 fish were each fed test diets ♯4, ♯5, and ♯6 for 12 weeks at the same feed rate described above. The concentrations of Cd accumulated in the liver, kidney, and ordinary muscle of the fish were measured every 3 weeks. Contrary to the positive control fish fed diet ♯4, those fish fed test diets ♯5 and ♯6 accumulated 20–30% and 25–40% less Cd in the liver, respectively. Test diets were a little less effective for inhibition of Cd uptake in the kidney than that observed in the liver. These results suggest that addition of CP or CT to fish feed might be used to decrease toxic heavy metal accumulation in fish. [ABSTRACT FROM AUTHOR]

This paper investigates the relationship between sea-surface temperature (SST) and catch fluctuations in the Pacific stock of walleye pollock Theragra chalcogramma in Japan. Incorporating time lags between years of birth and harvest, the correlation coefficients between the catch and SST in two regions off the east coast of Hokkaido were calculated. The catch in year t had a high negative correlation with the SST during January–April and November–December of the years t-2 and t-3 in the spawning area. These results coincided well with the correlation observed in the northern ‘Sea of Japan’ stock. Both analyses suggested that the long-term catch fluctuations of the two stocks could be explained by the same mechanism, that is, the fluctuations would be explained by the SST in their spawning area during the spawning season using 2–3 or 3–5 years time lags, which corresponded to the dominant age of the catch within these two stocks. [ABSTRACT FROM AUTHOR]

The purpose of the present paper was to reveal the migration pattern of shirauo Salangichthys microdon Bleeker, in the Ishikari River system and its adjacent coastal sea areas. To this end, the strontium–calcium (Sr:Ca) ratios of the otoliths of 98 individuals were examined. Profiles of the Sr:Ca ratios during the life history after hatching in the estuary of the Ishikari River fell into two different patterns. One was characterized by a high (slightly fluctuating) Sr:Ca ratio throughout the life history; the other was characterized by an initial high Sr:Ca ratio followed by a lower value later in life. The former pattern was considered to be that of estuary–sea residents and the latter that of upstream migrants. Most upstream migrants migrated upstream once, although several did it twice. Back-calculated body lengths during the upstream and seaward migrations of the upstream migrants varied widely from 6.4 mm to 39.8 mm and from 13.5 mm to 79.4 mm, respectively. These findings suggest that estuary–sea residents and upstream migrants co-occurred spatiotemporally, and suggest a wide variation in migration patterns in the shirauo's life history. [ABSTRACT FROM AUTHOR]

The purpose of the present paper was to examine the genetic population structure of Buccinum tsubai in the Japan Sea. Mitochondrial 16SrRNA gene sequence analysis was performed with specimens from various stations in the Japan Sea. Mitochondrial lineages were clearly patterned geographically in four separate areas: the Hokkaido area, the Yamagata–Toyama area, the Yamato Bank area, and the San’in area. The main distribution depth range of B. tsubai is between 200 m and 1000 m isodepths, and the horizontal distance between the 200 m and 1000 m isodepth lines represents the specific spatial scale of the habitat (SSSH). These four areas were separated either by the complete discontinuity of the SSSH area or by its narrow spatial extension. Genetic distances between the main haplotypes of each area were calculated as Jukes–Cantor distances, the value of which ranged between 0.012 and 0.017. This value seemed to be unrelated to the geographic distance. There was no tendency for clustering according to depth. In future, the morphological characters of the four lineages of B. tsubai should be compared in detail in order to elucidate significant genetic differences among them. [ABSTRACT FROM AUTHOR]

SUMMARY:This paper proposes a method for estimating stock abundance for a fishery exploiting two stocks, using a model of stock dynamics incorporating effort allocation. We assume that the fishery selects a target stock every hour of operation from the two stocks with a certain probability (α), and that the spatial distribution of stock is either regular or aggregated. The parameters are estimated by the maximum likelihood procedure. Our model is applied to the data of the diving fishery from 1972 to 1976 which catches abalone and top shell along the coast of Toji in Shizuoka Prefecture. The minimum Akaike Information Criterion (AIC) supported the model that the α values were changed between- and within-year. The coefficients of variation of the abundance estimate for abalone ranged from 0.01 to 1.37, and for top shell from 0.01 to 0.03. The abundance estimates were compared with those by the DeLury’s method. The modifications of the model are discussed. [ABSTRACT FROM AUTHOR]

SUMMARY:This paper estimates the age and growth of the alfonsino Beryx splendens in the waters around the Izu Islands off the Pacific side of Japan. The samples consist of 250 fish of the landings of the offshore longliners from December 1995 to November 1996 and 10 fish of the coastal longliners in February of 1995. By the surface method using a microscope, a reader counted the number of hyaline and opaque zones on the sagittal otoliths, judged whether the edge was hyaline, and measured the radii from the focus to the outer edge of each hyaline zone. In order to estimate the parameters of the von Bertalanffy’s growth equation representing the overall ages, the age and fork length data and the mean length at 1 year old. In a previous study were used for the maximum likelihood approach. From the results, the rate of readability of the otolith from the offshore samples was 97.6% and that from the coastal samples was 100%. The monthly changes in the frequency of the opaque edge showed that the hyaline and opaque zones were laid down once a year. The hyaline zone began to form from May to July (peaking in August). The ages of the offshore samples for both the sexes ranged from 2 to 23 years, and those of the coastal samples 2 to 5, respectively. The estimated growth curves were expressed by l(t) = 44.4[1–exp{–0.132(t + 3.45)}] for males and l(t) = 45.0[1–exp{–0.150(t + 2.08)}] for females, where l(t) and t denote the fork length (cm) and the age in years, respectively. The issues to be resolved in the future were discussed. [ABSTRACT FROM AUTHOR]

The horizontal distributions of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the surface sediments where complex aquaculture is conducted in Shido Bay, Seto Inland Sea, Japan, were determined to investigate the impact of fish and oyster farming. We also determined five fractions of phosphorus in the surface sediments. Relatively high phosphorus contents (P/C ratios) were observed in fish farming areas, likely due to the waste feed and fecal matter. Moreover, relatively high abundances of the Ca-bound P (Ca-P) and detrital P (Ref-P) fractions were observed in fish farming areas, likely due to bones of small fish used as feed. Our results strongly suggest that the P/C ratio and the Ca-P and Ref-P fractions in the surface sediments are good indicators of the effects of fish farming and allow its characterization, and are particularly valuable in the area of complex aquaculture. [ABSTRACT FROM AUTHOR]

Fish appetite is modulated in a complex manner by orexigenic hormones. To investigate appetite regulation, the fasting response of appetite-related hormone genes in eight brain regions was observed in yellowtail Seriola quinqueradiata, the most important aquaculture species in Japan. Gene expression of appetite-related hormones, neuropeptide Y (NPY), two agouti-related proteins (AgRP1 and AgRP2), two melanin-concentrating hormones (MCH1 and MCH2), and five cocaine- and amphetamine-regulated transcripts (CART1b, CART2a, CART2b, CART3a, and CART3b) was measured in the olfactory bulb, telencephalon, optic tectum, hypothalamus, pituitary gland, corpus cerebellum, crista cerebellum, and medulla oblongata and compared between 7-day-fasted fish and 3-h post-fed fish. Except that of cart2b, the gene expression of all appetite-related hormones was detected in all brain regions. The expression of optic tectum agrp1, mch1, mch2, and cart1b; hypothalamic agrp1; pituitary cart1b and cart3a; and corpus cerebellar npy, agrp1, and agrp2 was significantly increased after fasting. Fasting significantly reduced olfactory bulb cart1b and cart2b, optic tectum cart2b, hypothalamic cart1b, pituitary cart2a and cart3b, corpus cerebellar cart2a, and medulla oblongata agrp2 and mch2 expressions. These results suggest that brain regions other than the hypothalamus—the center of appetite—might also be involved in appetite regulation. [ABSTRACT FROM AUTHOR]

We examined specimens from the winter–spring cohort of the neon flying squid Ommastrephes bartramii caught off the coast of northeastern Japan in early summer and the following winter for mantle length, sex, maturity, and age to determine their hatching dates as well as their growth and migration patterns. Squid specimens were collected with a research driftnet in July 2018 in the northwestern Pacific and by squid jigging off the coast of northeastern Japan in November 2018 and January 2019. The ages of 300 specimens were estimated from statolith increment counts and used to back-calculate hatching dates. Hatching dates ranged from September 2017 to July 2018. The peak hatching dates varied with the survey season, even for the same winter–spring cohort. Squid caught in July 2018 hatched mainly from February to April, while those caught in November 2018 hatched mostly during April and May and those caught in January 2019 hatched principally during May and June. This pattern indicates that squid migrate among fishing grounds and that stocks are gradually replaced by late-hatching squid. [ABSTRACT FROM AUTHOR]

Sustainable conservation management of chum salmon in Japan requires ecological information on wild fish. This study investigated the spawning timing in a nonstocked river and the occurrence of wild fry in a surf zone in Niigata Prefecture. Most redds were observed from mid-October to mid-December on riverbeds having stream water of variable but cold temperatures above 5.4 °C. Chum salmon fry (< 41 mm), identified as wild based on comparison with the expected minimum size of hatchery fish (> 41.2 mm), were collected at the surf zone generally from early March to early May when the sea surface temperature (SST) was 7.4−17.5 °C. This period largely matched the predicted time of emergence based on the surveyed river cumulative water temperature. A generalized linear model predicted that the probability of occurrence would decrease as SST increased, being 42.5% even when SST was 15 °C. Hatchery fish are stocked by late March in Niigata Prefecture. Our results reveal that wild chum salmon fry at the southern limits of their distribution, which is affected by the Tsushima Warm Current, enter the sea when SST is relatively high, mainly from March to April, and even in May, 2 months after the end of hatchery stocking. [ABSTRACT FROM AUTHOR]

Seasonal variations of extractive components in mussels cultured in Hiroshima Bay were investigated. Meat yield was maintained at approximately 30%, except for in December and January. Glycogen content from June to August was significantly higher than that from November to January. Glutamic acid and aspartic acid showed no seasonal variation. Taurine and glycine indicated different seasonal changes from most of the other free amino acids. AMP was significantly higher from July to October than from November to June. Seasonal variations in succinic acid were not observed throughout the year. Taste-active values (TAVs) of glutamic acid, glycine, and alanine were over one throughout the year, except for a part of the month. In addition, TAVs of AMP and IMP were over one from July to October, and the values of succinic acid were more than two throughout the year. The equivalent umami concentrations from July to October were 2–3 times higher than those from November to April. Based on these results, it has been clarified that the best season to eat mussels in Japan is from summer to early autumn, and especially from August to October. These results coincided with the empirical best season for eating mussels. [ABSTRACT FROM AUTHOR]

Sepioteuthis lessoniana is a crucial squid species in fisheries and plays a critical role in marine ecosystems. At least two taxa of the squid species have been identified in the waters around Japan; however, the basic biological information of these taxa is limited. In this study, the taxa composition of Sepioteuthis was examined using molecular evidence, and the life-history traits and statolith shape of these taxa were analyzed to elucidate the potential population structure. A total of 142 squid samples were collected from six locations around Nagasaki (southwestern Japan) where high taxonomic diversity has been found previously. Three taxa (Sepioteuthis sp. 1, sp. 2, and sp. 2A) were identified based on the mitochondrial cytochrome oxidase c subunit I (COI) gene, among which Sepioteuthis sp. 2A was defined for the first time. Sepioteuthis sp. 2 was predominant in the region (average occurrence rate 84%), whereas Sepioteuthis sp. 1 was rare, with only two individuals found near Goto Islands. The mantle length composition, mantle length–body weight relationship, age structure, and average growth rates were similar between Sepioteuthis sp. 2 and sp. 2A. However, Sepioteuthis sp. 2 mainly hatched during summer (June–July), whereas Sepioteuthis sp. 2A hatched during winter (December–February). The statolith shapes of the squids were similar between the taxa, although slight differences were noted in the wing regions. The three taxa largely overlapped in a principal component analysis bi-plot based on variations extracted from five life-history traits. These results suggest that at least three taxa of Sepioteuthis inhabited the region, although few differences were found between them in life-history traits or statolith shapes that might be substantially influenced by regional oceanographic conditions. This study provides essential information on the population structure and connectivity of the squid, which is crucial in the context of conservation and management measures for fisheries. [ABSTRACT FROM AUTHOR]

The solitary European sea squirt Ascidiella aspersa was introduced to northern Japan, causing dense coverage of the aquacultured Japanese scallop Mizuhopecten yessoensis. There are concerns that allelopathy by the sea squirt will suppress the growth of the scallop. Herein, we studied the allelopathic and defensive potential of A. aspersa using hemolytic assay. An alkyl sulfate, viz. 3,7,11,15-tetramethyl-hexadecan-1,19-disulfate (1), was isolated as a hemolytic compound, and 1 showed mild toxicity against the Japanese scallop and brine shrimp. [ABSTRACT FROM AUTHOR]

Describes the purification and properties of chitinase isozyme from the liver of Japanese common squid Todarodes pacificus. Purification steps; Hydrolization of chitin to N-acetylchitooligosaccharides; Chitinase activity; Hydrolysis of chitosan.

We investigated the compositions of free amino acids (FAAs), organic acids (OAs), and nucleotides and their related compounds (NAs) in the gonads of edible sea urchins in Japan. In Hemicentrotus pulcherrimus and Pseudocentrotus depressus, glycine, alanine, lysine, and arginine were abundant FAAs in both sexes before gametogenesis. As gametogenesis proceeded, glycine and threonine showed increasing trends while arginine and histidine showed decreasing trends in both species regardless of sex. Alanine and serine in H. pulcherrimus and isoleucine in P. depressus showed increasing trends regardless of sex. Some other FAAs showed different trends between the sexes. Among the OAs and NAs, adenosine monophosphate, inosine monophosphate, and acetic acid were relatively abundant in H. pulcherrimus testes and ovaries before gametogenesis. In Heliocidaris crassispina, Strongylocentrotus intermedius, and Mesocentrotus nudus, glycine was commonly the most abundant FAA followed by alanine and arginine in the testes and ovaries during early gametogenesis. Compared to the other species, testes and ovaries of Tripneustes gratilla contained lower amounts of arginine and higher amounts of serine and proline. The results of this study could contribute to the development of the aquaculture and seafood industry for sea urchins by accounting for the variation in gonad taste among species, sexes, and according to their maturational status. [ABSTRACT FROM AUTHOR]

The effects of temperature and prey density on the recent growth rate (RGR) of chub mackerel, Scomber japonicus, were examined. Scomber spp. larvae and juveniles were collected along the Boso–Kashimanada Pacific coast in Japan between March and July in 2015 and 2016. Larvae and juveniles identified as S. japonicus using DNA were subjected to stomach-content and otolith-increment analyses. The effects of temperature and prey density on RGR were analyzed using a generalized linear mixed model (GLMM), which showed that temperature positively affected the RGR of larvae in the body length (BL) classes < 5 mm, 5–7 mm, 7–9 mm and 9–11 mm. Prey density also affected growth in the < 5 mm, 5–7 mm, 7–9 mm and > 11 mm classes and effects of prey density on RGR for larger (> 11 mm) larvae and juveniles were stronger than those for smaller (< 9 mm) larvae. S. japonicus larvae transform into juveniles at around 12 mm BL, and the increased feed demands of juveniles likely lead to prey-density-dependent growth. The otolith increment widths of larvae and juveniles were significantly narrower than those during the same stages in 1-year-old S. japonicus collected from purse seine fisheries operated in the Joban or Kashimanada areas, suggesting growth-dependent mortality. [ABSTRACT FROM AUTHOR]

The USA and Japan differ in their approaches to managing inland recreational fisheries. The USA uses a public property rights regime whereby access rights are assigned to the states, which manage the fishery resource for the public good. Japan uses a common property rights regime whereby access rights for waterways are assigned to fishery unions, which manage the resource for the benefit of their members. Members of fishery unions are likely to develop an emotional attachment to the fishery that results in few regulation violations or illegal fish introductions. The USA would benefit from actions that promote such a caretaker attitude toward the environment. Habitat improvement is a major activity in the USA but is less prevalent in Japan where stocking is the dominant management activity. Catch-and-release angling, size restrictions, and employment of professional fisheries biologists are more prevalent in the USA compared to Japan. The USA has a tax on fishing equipment that funds management activities whereas such a funding source is lacking in Japan. Despite differences in management regimes, both countries face similar challenges in recruiting new anglers and meeting the conflicting mandates to enhance sport fisheries while conserving native species. [ABSTRACT FROM AUTHOR]

Radioactive contamination from the Fukushima disaster has undermined the seafood caught around the area. Approximately 20 % of general consumers are reported to avoid seafood from Fukushima, even though it has not been found to exceed the Japanese criteria of radioactivity since April 2015. Based on a survey of more than 2000 domestic consumers in Japan, this study investigated the characteristics of those who boycotted safe marine products from the devastated region, using conjoint analysis with a latent class model. The attributes (levels) included price, three prefectural origins (including Fukushima and adjacent prefectures), six local origins, and two ecolabels targeting white fish meat. The latent class model divided participants into three classes: boycotters (27.5 %), consumers devaluing cod (41.0 %), and ordinary consumers (31.5 %). Boycotters neither believed the radioactive test results from any entity nor bought seafood frequently. Furthermore, they tended not to recognize the Marine Stewardship Council, earned more, and were relatively older than the average. [ABSTRACT FROM AUTHOR]

Evaluates the influence of interposition of pink muscle fiber into dorsal ordinary muscle on degrading activity in various fish species in Japan. Relationship between the interposition percentage of pink muscle fibers; Code number of each sample fish species; Increase in the rate of K-value in dorsal ordinary muscle.

Examines the existence of chitosanase-like enzyme in the ovary of sea urchin in Japan. Measurement of enzyme activity; Identification of protein bands; Examination on the molecular weights of the enzyme.

We estimated the demands of Japan's cod and pollock markets, taking into account unknown structural changes. We used monthly wholesale price and quantity data between January 2004 and July 2013 at the Tsukiji market in Tokyo, Japan. Structural break tests detected multiple structural changes in the targeted period. A price-dependent demand model with detected structural changes successfully cleaned up the effects of the structural changes and estimated an accurate demand and elasticities. When structural changes were taken into account, the model fits improved by up to 17 points. The results indicated the one-way influence of cod on the pollock market. Also, the pollock market was sensitive to an economic recession, but household income did not affect pollock as well as cod, presumably because both goods are necessary goods for Japanese consumers. These results are helpful for policy makers in devising marketing strategies. Since fresh cod is an inelastic good, cod fisheries can reduce their cost by reducing their days at sea, which would increase the cod price due to its inelastic characteristics. As such, they can expect some profit via cost reduction and an increase in the price. [ABSTRACT FROM AUTHOR]

The Japanese spiny lobster Panulirus japonicus is an important marine resource in Japan. In order to manage its stock, an effective methodology for population assessments is needed. In this study, we focused on the stridulating sounds produced by spiny lobsters. The stridulating sounds are widely accepted to function as an anti-predator signaling, for potential use in monitoring lobster stocks remotely. An underwater sound recorder was attached on gill nets or lobster pots around Izu Oshima and Niijima islands, within the Izu archipelago, Tokyo, Japan, where lobster fishing is common. Stridulating sounds were manually extracted from each data file. The frequency of stridulating sounds tended to increase on nights with a large tidal change. There was a positive correlation between the frequency of stridulating sounds and the number of lobsters caught in the net or lobster pot. Even in trials where no lobsters were caught, several stridulating sounds could be detected and increased at night. In this study, we describe the sound characteristics of the stridulation, and the trend of nocturnal call productions of this species. This study is the first step towards passive acoustic resource monitoring of Japanese spiny lobsters, which were quite difficult to estimate the density of remotely. [ABSTRACT FROM AUTHOR]

This study analyzed the existence of imperfect competition, and the time period for which it existed in the supply chain of fisheries products in Japan from 1976 to 2009. An empirical analysis of the imperfect competition using a structural model robust to nonstationary time series revealed that sellers of horse mackerel, Japanese flying squid, and sardines in wholesale markets located in consumption areas had market power before 1993 in upstream markets. In downstream markets, retailers of horse mackerel and sardines had market power not only before 1993 but also after 1992, and retailers of Pacific saury and red seabream had market power before 1993. However, there were a number of periods when the detected imperfect competition was mostly less than that in upstream markets. The findings of this study are consistent with those of a previous study, which pointed out that sellers in wholesale markets lost negotiation power due to the emergence of large retailers, such as supermarkets, who buy directly from producers, trading companies, wholesalers at production sites, etc., especially after 1992. A comparison with another previous study indicates that market power and asymmetric price transmission are closely related. [ABSTRACT FROM AUTHOR]

This study examined the effect of warm temperature on the survival of paralarvae of Japanese common squid Todarodes pacificus and on their swimming behavior as they ascended to the surface. Observations were conducted on paralarvae in Petri dishes and in 85-cm-tall, cylindrical tanks that had a warmer upper layer and cooler lower layer separated by a small thermocline. Paralarvae were obtained through artificial fertilization and reared in Petri dishes at six experimental temperatures between 20.9 and 30.4 °C. Paralarvae reared at lower temperatures survived longer than those reared at warmer temperatures, and survival decreased at temperatures above 24 °C. When the mean temperatures in the upper layer of the tanks were 24.4-26.0 °C, the paralarvae ascended through the thermocline to the surface, but when the mean temperatures in the upper layer were 29.7-29.8 °C, paralarvae stopped ascending at the thermocline. These results show that paralarvae have a temperature preference but ascend to the surface in the unfavorable temperature range. The results suggest that increasing surface temperatures at spawning grounds will negatively affect both the survival and behavior of T. pacificus paralarvae. [ABSTRACT FROM AUTHOR]

The rise and fall of Japan's marine fisheries have been well documented and are clearly evident in official landings statistics. However, the extent of illegal, unreported and unregulated fisheries, including recreational fisheries, and the discarding of unwanted catch in Japanese waters, both of which may have significant implications on the success of management regimes, have yet to be closely examined. This study reassessed the impact of fisheries on the marine ecosystems of Japan's Exclusive Economic Zones (EEZ) by estimating the total marine biomass removed through the use of an established catch reconstruction approach. Since 1950, 368 million t of marine biomass have been extracted from the Japanese EEZ as commercial catch, recreational catch, illegal catch and discards. Commercial catch accounted for 87 % of the total, while discards accounted for an additional 8 %. The disparity between the estimated biomass removals and the reported commercial catch is 48 million t, or 15 % of the reported catch. The difference is not as large as observed in similar studies of other regions. Nonetheless, the reconstructed biomass removals represent a better baseline for the management of fisheries in the Japanese EEZ, particularly if Japan is to move forward with implementation of output control management. [ABSTRACT FROM AUTHOR]

The life history of the leopard coralgrouper Plectropomus leopardus was examined for the purpose of stock evaluation and to help maintain populations in the Okinawa Islands, southwestern Japan. Age was estimated from cut and burnt otoliths, and gonads were observed histologically to reveal the growth, spawning period and relationships between age and both sexual development and sexual maturation for P. leopardus in waters north of Okinawa Island. The three parameters in the von Bertalanffy growth equation, L∞, k, and t0, were estimated at 61.2 cm fork length, 0.289, and 0.41, respectively. The oldest individual obtained among the specimens was 18.8 years. The spawning period started in May and lasted until July. During this period, 50 % of females reached maturity at 43.3 cm fork length and at 5 years of age. Due to the sexual transition from female to male, the sex ratio decreased to 50 % at 59.8 cm fork length and at 10.3 years of age. [ABSTRACT FROM AUTHOR]

The relationship between release date and migration speed was examined for hatchery chum salmon Oncorhynchus keta fry exiting the Nishibetsu River in eastern Hokkaido, northern Japan so that future releases might be scheduled so that fry arrive at the ocean during periods favoring high survival. Separate marked groups of chum salmon released in early April, mid-April, and early May in 2008, late March and mid-April in 2009, and mid-April in 2010 were recaptured with a rotary screw trap 12 km above the river mouth. Chum salmon in later release groups tended to migrate downstream faster than fish in earlier release groups. Those released after mid-April arrived in the lower river on average 9 days after release, while those released before mid-April arrived on average 26-28 days after release. Most marked fish arrived in the lower river during late April to mid-May. These results suggest that chum salmon are adapted to adjust their migratory speed so as to arrive at the ocean during a relatively discrete period, presumably during a time of high productivity favoring good survival. [ABSTRACT FROM AUTHOR]

One important component in determining the market value of fish is freshness, essentially the time period from capture to consumer. By shortening the time from harvest to landing, freshness can be improved and thus the market value may increase. The opportunistic nature of the marine capture fisheries sector, however, can encourage fishers to extend their time at sea to catch additional fish, while retaining already harvested fish. Here, fishers face a tradeoff: extending the duration of their operations, but compromising their ability to maintain product freshness. This study estimates the freshness premium for two fish species, swordfish and blue shark, landed at Kesennuma, Japan. Swordfish is generally destined for the raw market, while blue shark is first processed into several products. Our results suggest substantial heterogeneity in the freshness premium, depending on the likelihood of a product being consumed fresh or after processing. This work is an important investigation in the Kesennuma region, which suffered devastating damage from the tsunami following the Tohoku Earthquake. [ABSTRACT FROM AUTHOR]

The diversity of cyanobacteria and diazotrophs in the Japan Sea was investigated by analyzing sequences of cyanobacterial 16S rRNA genes and nitrogen fixation genes ( nifH) from seawater sampled at depths ranging from the surface to 100 m at two stations. Of the 107 cyanobacterial 16S rRNA gene sequences obtained, 97 and three sequences were assigned to Synechococcus sub-cluster 5.1 and Prochlorococcus HL (II), respectively. Unlike other oceanic regions, at our two sampling stations the composition ratio of the sequences assignable to Synechococcus sub-cluster 5.3 was relatively high (8 %). No sequences of diazotrophic cyanobacteria were found in the cyanobacterial 16S rRNA genes. In the nifH clone library (36 sequences), ten sequences were identified as a UCYN-A group of diazotrophic cyanobacteria; the other 26 sequences (72 %) were assigned to proteobacteria. These results suggest that heterotrophic bacteria, including UCYN-A, dominate the diazotrophic community in the Japan Sea. Our study reveals the dominance of Synechococcus in cyanobacterial community and (photo)heterotrophic diazotrophs in the diazotrophic community in the Japan Sea, suggesting its unique characteristics. [ABSTRACT FROM AUTHOR]

Lighting systems combining light-emitting diodes (LEDs) and metal halide lamps (MHs) are expected to be energy-saving tools in Japan's squid jigging fishery. Previous research has shown the need for light stronger than LEDs (9 kW) and 36 MHs (108 kW) to catch the Japanese common squid Todarodes pacificus. We tested a stepwise lighting method termed 'stage reduced lighting' in the Tsushima Strait in January and February 2010 using nine fishing boats. LEDs (9 kW) and 50 MHs (150 kW) were lit for 3.9 h on average, and then the number of MHs was reduced to either 30 or 36 until the end of fishing (7.3 h on average). This method reduced fuel consumption by 22-25 % compared to the continuous use of all fishing lamps (159 kW). We carried out a catch analysis of nine experimental boats and 21 commercial boats during the experimental period. Generalized linear modeling analysis suggested that the squid catch can be explained by the illuminated fraction of the moon and monthly changes in squid abundance, and the lighting method. The stage reduced lighting using LEDs and MHs has the potential to reduce fuel consumption while maintaining the squid catch. [ABSTRACT FROM AUTHOR]

The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35°N and west of 170°E) were studied using a quantitative echosounder. This is the first attempt at such a study in this region. Data were collected in summer from 2004 to 2007. The biomass was estimated using data collected at 38 kHz. Species compositions in the backscatterings from pelagic fish were assigned based on the results of trawl hauls taking account of sea surface temperature (SST). Japanese anchovy tended to be high density to the west of 153°E and were distributed in an SST range of 9-24 °C. Although the temporal and spatial coverage of the survey differed each year, at least 1.5-3.4 million tons of Japanese anchovy were present in the survey area between 2004 and 2007. To take account of the spatial coverage of the survey each year, the most reliable biomass estimate for this region in the time period was 3.4 million tons (coefficient of variation 0.22). [ABSTRACT FROM AUTHOR]

The recruitment patterns of black-spot tuskfish Choerodon schoenleinii were compared with those of orange-dotted tuskfish (OT) C. ancholago. Individuals at the settlement and juvenile stages were collected using a push net in the intertidal zone and a seine net in seagrass beds. Relative values of standard length to total length (TL) for the two Choerodon species indicated an inflection point at approximately 10-20 mm TL, suggesting that both species complete metamorphosis at a similar size. However, their temporal and spatial occurrence patterns were distinct. Newly settled individuals (postflexion stage) of black-spot tuskfish were collected mainly within foliage of Sargassum plants of the intertidal zone around March-April, while those of OT occurred in both the intertidal zone and seagrass beds mainly in May and June. In seagrass beds, the abundances of both species increased from May or June; however, the TL of black-spot tuskfish was bigger than that of OT. Therefore, black-spot tuskfish progressively migrate to seagrass beds after settling and completing metamorphosis in the intertidal zone, indicating that they utilize two different habitats as nursery grounds. Early spawning and migration from the intertidal zone by this species contributed to the occurrence of relatively large individuals in seagrass beds. [ABSTRACT FROM AUTHOR]

In order to analyze the genes related to histamine production in halophilic lactic acid bacteria, 16 strains of histamine-producing bacteria were isolated from three fermented seafoods produced in the Hokuriku region of Japan. Phenotypic and 16S rRNA gene sequence analyses identified all of the strains as those of Tetragenococcus muriaticus. Pyruvoyl-dependent histidine decarboxylase gene ( hdcA) was determined from all strains using the PCR method with an hdcA-specific detection primer set. Genetic analyses (Southern blot and restriction fragment length polymorphism analysis) of hdcA and genes related to histamine production (the hdc cluster) confirmed that all of the strains harbored 21-23 kbp plasmids encoding a single copy of hdcA. The four representative strains were selected based on isolation source and genetic analysis, and subsequently full sequences of plasmids harbored in these strains were determined. hdc cluster sequences from the plasmids showed very high similarity (>99 %) to known hdc clusters of T. halophilus, Lactobacillus hilgardii 0006, and other lactic acid bacteria. The structures of the plasmids, the replication region, the hdc cluster, and the plasmid maintenance system were conserved between the plasmids present in new isolates and the T. halophilus strains. These results indicate that plasmids encoding hdcA are widely distributed among T. halophilus and T. muriaticus and function in both species. [ABSTRACT FROM AUTHOR]

Microbiological profiles during the processing of heshiko, produced by aging salted mackerel with rice bran for over seven months, were investigated in connection with the production of organic acids and volatile basic nitrogen (VBN). Viable counts in commercial heshiko samples were in the range of 10-10 cfu/g in 2.5% NaCl-GYP agar medium, and over 80% of them were identified as Tetragenococcus halophilus via 16S rRNA gene sequence analysis. When experimentally processing heshiko using conventional practices, viable counts in fish flesh increased to 10 cfu/g during the aging process with rice bran, which was accompanied by a marked increase in lactic acid but only slight production of VBN. Although the dominant species among the microflora in raw mackerel was identified as a Staphylococcus sp., the microflora diversified during the salting process. T. halophilus was prominent during the early stage of aging. The microflora gradually simplified with aging, and eventually consisted of only T. halophilus after five months of aging. These results suggest that a simple microflora consisting of T. halophilus forms when processing heshiko using conventional practices because of the stable environment present, which contains carbohydrates as fermentation materials in rice bran, along with high salinity (around 10%). [ABSTRACT FROM AUTHOR]

The present study examined whether the elemental compositions of whole otoliths and chronological transect profiles of otoliths covering the complete life history are useful for evaluating the population structure of Pacific herring. Eight elemental ratios, Li:Ca, Na:Ca, Mg:Ca, K:Ca, Mn:Ca, Cu:Ca, Sr:Ca, and Ba:Ca, were measured in whole otoliths and in a series of ablations across the life-history transects by laser ablation inductively coupled plasma mass spectrometry. We studied fish from three sample groups collected from Lake Obuchinuma, Miyako Bay, and Akkeshi Bay of northern Japan from March to May 2008. Significant differences were found in the Na:Ca, Mg:Ca, P:Ca, K:Ca, Mn:Ca, and Ba:Ca ratios of the whole otoliths and in the Li:Ca, Na:Ca, K:Ca, Mn:Ca, Sr:Ca, and Ba:Ca ratios of the otolith core among the three sample groups. Therefore, the present study showed clear differences in elemental composition among the three sample groups from different locations, suggesting that otolith elemental compositions reflect the habitats experienced by individual fish. [ABSTRACT FROM AUTHOR]

The interstices of coral rubble provide a good refuge for cryptic small crustaceans and molluscs, which are important prey items for reef fishes. In this study, we focused on the assemblage composition of cryptic mobile species along the depth gradient at an outer reef slope. Traps with coral rubble (22 × 18 × 6 cm) were set at three sites at different depths, and mobile animals that colonized the traps were sorted. In total, 117 species of larger animals (mainly Decapoda and Gastropoda) were recorded: 71 species at the 3 m point, 53 species at the 11 m point, and 37 species at the 22 m point. On average, 260.3 individuals were captured in the traps at 3 m, while 95.3 and 57.8 individuals were captured at 11 and 22 m, respectively. MDS ordination showed that assemblage composition differed among the three sites. The most abundant species at the 3 m was the galathean crab Galathea mauritiana, followed by the gastropod Diala albugo. At 11 and 22 m, the galathean crab Sadayoshia edwardsii was most abundant. Thus, at the reef slope, the benthic assemblage was most diverse at the shallow site, and specific communities occurred at the three sites. [ABSTRACT FROM AUTHOR]

Habitat utilization, feeding, and growth of a rare pleuronectid flatfish, spotted halibut Verasper variegatus, were examined in a brackish lagoon in northeastern Japan: Matsukawa-ura. The distribution and date-length data of spotted halibut collected mainly from beam-trawl samplings during 1983-2008 indicated that age-0 juveniles [ n = 25, 6.0-18.0 cm total length (TL)] and older spotted halibut ( n = 71, 13.8-43.0 cm TL) inhabited almost the entire northern part of Matsukawa-ura. Comparative distribution surveys of spotted halibut, stone flounder, and marbled flounder during 1985-1989 revealed similar distribution patterns of these flatfishes; the highest densities were found around the central part of Matsukawa-ura, although significantly lower abundance was detected for spotted halibut. Linear growth equations of age-0 juveniles demonstrated that spotted halibut were able to achieve high growth after June, probably because abundant prey (e.g., mysids and gammarids) and suitable physical conditions (warmer water temperature and lower salinity) were present. The main prey items shifted from various crustaceans including mysids, caridean shrimps, and anomurans to brachyura Hemigrapsus spp. (≥20 cm TL). Our study shows that spotted halibut use the shallow brackish lagoon as an important nursery for juveniles, and also as a feeding ground for young and adults. [ABSTRACT FROM AUTHOR]

The yield-per-recruit (YPR) analysis has been used to assess growth overfishing of exploited fish stocks. Since the ex-vessel price per weight widely depends on the size of the fish, the result of the YPR does not imply the revenue. The value-per-recruit (VPR) analysis, which is an economic expansion of the YPR analysis, was conducted for bighand thornyhead Sebastolobus macrochir caught off the Pacific coast of northern Honshu, Japan. The results showed that, for the current age at first capture ( t = 3), the current fishing mortality ( F = 0.12) was close to the optimum level. However, for the current F, optimum t in the VPR model was 8 years and would lead to a 47% increase compared to the current revenue. The maximum YPR was obtained at t = 6 years, but the revenue at t = 6 only gave a 20% increase in the maximum revenue. The difference was caused by the size dependency of the ex-vessel price per weight. The VPR model would generate fisheries management plans with both economical and biological consideration and would help in making general consensus of fisheries management strategies. [ABSTRACT FROM AUTHOR]

The Japanese type of set-net, Otoshi-ami, was introduced to Thailand in 2003 with the aim of assessing its feasibility as a sustainable coastal fisheries management tool for the empowerment of coastal fishers' communities. All preparations for constructing and installing the set-net in the coastal waters off Mae Rumpheung beach, Rayong Province, Thailand, were carried out by local fishers, with technical advice and support from national and international institutions. The gear was modified and developed to suit the conditions of the fishing ground and target species. Data on the catch and sales trends in Rayong using the set-net were collected for 7 years for statistical analysis; during this period, the gear design and marketing strategies were improved. Simulation analysis for evaluating the cost-profit bases was conducted to establish a model for set-net technology transfer in Southeast Asia, based on differing numbers of fishers and operation days. The simulation results show the required size of the average daily catch to cover the total cost according to the average unit price, where the economic return point is an average catch of 128 kg, based on a unit price of 25 Baht/kg (0.83 USD/kg), with ten fishermen and a daily operation cost of 3,200 Baht (USD 106.17). [ABSTRACT FROM AUTHOR]

We examined individual growth and fatness in the 1975-2002 year classes of Japanese sardine. Samples were collected at the feeding grounds in the Pacific waters off northern Japan during drastic fluctuations in the population in the 1970s to 2000s. Growth rates for ages 1-3 of the 1979-1988 year classes, which included low-recruitment year classes subsisting during the high population levels of the 1980s, were apparently slower than for other year classes. There was no obvious trend when comparing year classes, growth during the first year of life (age 0), and maximum body length (BL) at age ≥5. The condition factors (CF, indicating fatness) for adult sardines of BL ≥19 cm in the 1979-1983 year classes during the maximum population level of the mid-1980s were significantly lower than for other year classes. However, there were no apparent trends in CF variations for small sardines of BL <19 cm. The apparent decreases in growth rate and fatness were strongly related to the cumulative sum of population abundance that each year class experienced. It is thought that insufficient food owing to the density-dependent effect of an abundant population at feeding grounds resulted in a decrease in the growth rate for small-bodied sardines that are investing their energy intake in body growth, and a decrease in fatness for large-bodied adults that are accumulating fat for the next reproduction. [ABSTRACT FROM AUTHOR]